Modern Mechanix, April 1938

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—_< M A FAWCETT PUBLICATION TECA

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WAR MACHINES NEEDED BY U.S. See Page 35 SNOLLNAANI ONY SaISa0H XINWHI3W NYIN _ SIN39 a

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YOUR OWN — from the easy plans in the new 1938 edition of “HOW TO BUILD 20 BOATS” Boat bugs all over the country have eagerly awaited this collection of tested plans, drawn up at considerable expense. All sizes of boats from 7 to 27 feet, and a wealth of incidental information for the man who already owns one. This is a big 144-page book worth many times its modest price. a D S E a a o a o T e E a E a a e a y FAWCETT PUBLICATIONS, INC., Greenwich, Conn. Enclosed find 50 cents. Rush my copy of “How to Build 20 Boats.’’ 50 cents per copy On sale at newsstands everywhere, or sent postpaid for the same price. Use the convenient coupon, or merely write a short letter if you prefer not to cut the cover. Your book mailed out the day your order City and State arrives. (Please do not send coins through the mails, Remit by stamps or money order.) 4

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(lko gaid: Only College Men Can Get Good Jobs?” THESE MEN DID NOT GO TO COLLEGE Read about the jobs : they got and the money they make Many Radio Experts Make $30, $50, $75, a Week Do you want to make more money? Broad- casting stations employ engineers, operators, station managers and pay up to $5 pmo a year, Spare time Radio set serv. z as much as $200 ta $300 a) servicing jobs pay as much as week. Many Radio Experts operate or part time Radio businesses. Radio m facturers and jobbers employ testers, i tors, foremen, engineers, servicemen, up to $6,000 a year. Radio operat ships get good pay, see the world besides. Automobile, police, aviation, commercial Radio, and loud speaker systems offer good opportunities now and for the future. Tele- vision promises many good jobs soon. Men I trained at home have good jobs in all these branches of Radio. Many Make $5, $10, $15 a Week Extra in Spare Time While Learning Almost every neighborhood needs a good spare time serviceman. The day you enroll I start sending Extra Money Job Sheets showing how to do Radio repalr jobs. Throughout your training I send plans and ideas that made good spare time money for hundreds. I send J Iwill Train You at Hom time for a Good Job in RADIO Special Equipment to conduct build circuits, get practical e SET —SAVE TIME, MAKE MORE Find Out What Radio Offers You Mail the coupon now for “Rich Radio.’ It’s free to any years old, J. tunitie: NAME si R SERVICING INSTRU- T TO UELP SERVICE SETS QUICKER E. SMITH, President National Radio Institute, Dept. BDH, Washington, D. C. Dear Mr. Smith: Without obligaling me, send “Rich Rewards in which points out the spare time and full time oppor- 50-40 method of training men at home in spare time to become Radio Experts. Radio,” experiments, xperience, I in Television; tells aboul MONEY. Rewards in e fellow over 16 It points out Radio’s spare time s in Radio and explains your When Answering Advertisements Please Mention April Modern Mechanix my e in your spare J. E. SMITH, President National Radio Institute, Dept. 8DH, Washington, D. ©. and full time opportunities, also those coming training Radio and Television; shows you letters from men [I tralned, telling what they are doing, in earning; shows my Money Back Agreement. MAIL THE COUPON in an envelope or paste il on a penny postcard—NOW!

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re MOMERN ea 15 CENTS 1938 Volume XIX SAME PRICE Circulation over 250,000 Copyright 1938 by Fawcett Publications, Inc. A L 5 0 In This Issue Modern Photography SPECIAL FEATURES War Machines Needed By The United States - 35 Section By Robert W. Gordon Winners of Photo Awards - 103 How To Make Enlargements - 104 Water Treasure Hunting - - - - = «= 42 By John L. Coontz Trick Drawings From Photos 107 Tricks With Lenses - = - 108 Photo Short Cuts - - - - 110 Follow The Fleet - - - - - = = «= 50 . Kitchen Cabinet Becomes By Frederick C. Russell Photo Lab - - - - - 112 Handy Drawer For Enlarging : Paper - - - - How To Train Your Dog - - - =- - > 58 Build This Two-Purpose By Marty Soden Movie Projection Screen - 113 “Color” In Black and White - 114 The Flood Of New Stamps E Og e egy Amateur Photo Puzzlers - - 116 By Montgomery Mulford Each month MM offers cash awards for the best pictures sent in by amateur photo fans. By Don Murphy For full details see page 193. Fishing For Distant Earthquakes With A Home-Made Seismograph - - = 72 Documentary Evidence = = = = = = 8§ NEXT MONTH Progress means change and next month MM will announce several By Julian D. Corrington, Ph.D. innovations, including a change in name, which we believe will tend to make your favorite publication better than ever before. Reserve your copy NOW. (Continued on page 8) Published monthly by Fawcett Publications, Ine., 11th St., & Broadway, Louisville, Ky., U. S. A, Business office, 22 West Putnam Arve., Greenwich, Conn, Entered as second-class matter under the Act of March 3, 1879, at the ‘post office in Louisville, Ky., with additional entry at Greenwich, Conn, Editorial offices; 1501 Broadway, New York, N. Y. Not responsible for unsolicited manuscripts, In U. S- and Possessions and in Canada, lic a copy; $1.50 a year. Send subscriptions to Greenwich, Conn., address, Other Postal Unions, $2.00 a year. fast Indian Agent, P, C. Eranee ‘Sons, Bombay, India. Printed in U. S. A. Advertising forms glose the first of second month preceding date of issue. Advertising offices: New York, 1501 Broadway; Chicago, 360 N. Michigan Ave.; San Francisco, Simpson-Rellly, 1014 Russ Bldg.; Los Angeles, Simpson-Rellly. Garfield Tilde. Member ‘Audit Bureau of Circulation. 3 W. H. FAWCETT, Publisher RALPH DAIGH, Managing Editor ROBERT HERTZBERG, Editor AL ALLARD, Art Director JOHN L. SCHERER, CLIFFORD PETERS, Associate Editors S. S. RABL, Naval Consultant

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NGINEERING HA FUTURE ambitious men. mechani apprentices. and me to eam more money: Course is 4 real investment. eant tg course has me® Toren. blacksmiths. : 5 s— men z; a a alk find that enroliing ou, too. . en ds for trained m ities created sant industry. The opportunities a gia leading 3 ‘ ? repared by Almost in € decade radi 1 C. S. Radio Course: P FREE. ‘ en. ‘nati boo wilt be enjoyed by kained m ed man! A fascinating authorities. will help make you aq train’ WwW res]. F O UTi N A COMING AMERICA triumph an's supreme i bustion engine represents, great demand. ee The intemnal-com Diesel engineets are h spare-time study © jet of machine pow C onsarY knowledge raSi Send for free bookie sri e . ngi . are acquiring 5 Course on Diesel e RADIO holds great rewar o has become The modern + C. STRY oning — the NEX z : nditioning ite engineers must know ba Sate for informa- ea are en. 5 al zer aspects invites ambitious ved by the Internation 3 “enditioning Course oftere L ADVERTISING ecome an advertising man? knew if you possess the z Then here's your — today! ww ~ BOX 2325-P, SCRANTON, PENNA. % Without cost or obligation, ple opy of your booklet, “Who Wins and Why,” * and full particulars about the suti h I have marked X: CI MECHANICAL ENGINEERING _ RADIO [C] DIESEL POWER (J AIR CONDITIONING C] ADVERTISING TECHNICAL ANI INDUSTRIAL COURSES ical 4 een Steam Jlectric Engineer Marine Engineer Ee D Structural Draftsman O Structural Enginecr G Ilow to Invent and Patent D Electrical Engineer D Electric Lighting D Welding, Electric and Gas D Readirg Shop Blueprints D Boilermaker De D Surveying and Mapping D Coal Mining O Mine Foreman R. R, Locomotives D Navigation R, R. Section Foreman G Cotton Manufacturing Air Brakea O Woolen Manufacturing R. R. Sigaalmen C Agriculture C Ilighway Engineering C Fruit Growing Z Civil Engineering O Poultry Farming BUSINESS TRAINING COURSES D Business Management OC. P. Accountant T Service Station Salesmanship D Obice Management D Bookkeeping O First Year College D Industrial Managment O Secretarial Work G Business Correspondence O Iligh School Subjects D Traffic Management D Spanish O Lettering Show Cards 1 Signs G College Preparatory O Accountancy O french O Stenography and Typing O Miustrating O Cost Accountant D Salesmanship G Civil Service O Mail Carrier D Cartooning O Toolmaker O Patternmaker O Gas Engines D Aviation Jing D Automobile Me D Refrigeration LIH N C Railway Mail Clerk C Grade School Subjects Name... Present Position i 8 df you reside in Canada, send this coupon to the International Cerrespondence Schoors Canadian, Limited. Montrea Canada When Answering Advertisements Please Mention April Modern Mechanix

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To Determine The Patentability Of Your Invention Before you spend money in making a model, or spend weeks in its design, we advise you first to have a preliminary search made through U. S. Patents in the U. S. Patent Office to see if there are inventions like yours already on record; and, if so, let us give you our opinion as to the patent- ability of what vou nave. We employ experienced searchers to per- form this service for you. From the reports of our searchers we can quickly ‘form our opinion as to whether your invention is con- fronted with obstacles in the form of already granted patents. First get our FREE BOOK and read the chapter on “How Can I Know Whether My Idea Is Patentable?” How We Serve The I t We have secured patents for nventor inventors located in every state in the Union. Our organization is a large and efficient one. Our practice is confined en- tirely to Patents, Trade-Marks. and Copyrights. We have had years of experience in Patent Matters. When you place vour invention in our hands, we are in position to proceed at once to secure protection for you. Our fees are reasonable, and, if you desire, we can arrange convenient terms of payment.

What Help is the Patent Attorney? Your invention may provide your life’s greatest opportunity. If it is to bring income ic be legally yours. Upon your patent haw completely your patent ‘e points in your invention. lose money on his gle claimable point would not miss,

attorneys < re covers all the pr The

inventor invention by over! that a skilled patent at What The Inventor Must Know In order to pro- ceed successfully, the inventor must follow certain definite steps that precedent has established as the quickest way to reach his goal. Our FREE BOOK, “Patent Guide .. for the Inventor,” gives a concrete, logical, and thorough resume for the inventor to follow. It takes him, through 48 pages, from the crude first model to the finished commercial product. It shows _- the inventor how to avoid mistakes, how to shorten * the read in getting his invention ready for market; it also points out how to save money and avoid the errors of inexperience in applying for patent. Get- ting our FREE BOOK should be the first step in definitely declaring yourself an inventor. After you get this illustrated, clearly worded guide of carefully compiled patent knowledge you will know how to proceed without expensive mistakes and discouraging setbacks from “wrong-track” methods. or

CLARENCE A.OBRIEN & HYMAN BERMAN rea 317-B ADAMS BUILDING, WASHINGTON,D. C. Registered Patent Attorneys before U. S. Patent Office

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Keen competition in every form of industry FREE RECORD has put manufacturers feverishly at work try- OF INVENTION ing to speed up output, reduce overhead, save FORM fis, SPREE on materials, outsell trade opponents. The kapon Form enables you to inventor is the key-man in making advance- #keth, of your invention and have it witnessed in a man- ment possible to any business. Upon the in- pg of galue to you should the occasion for evidence ventor rests the success of many enterprises, ise, MAIL THE COUPON This does not mean that you must have some- eee On’ Boa eee thing gigantic to win commercial success. A new way to open a door or button up a shirt may be the very thing hundreds of manufacturers are looking for. If you have something novel—if it is practical to manufac- ture—no matter whether it be an improved rattle for a child or a whistle for a ~ mechanical automobile, there is likely a waiting market. Importance ~- Of Immediate Action In making application for patent it is important to be first. Even if TEAR OFF your application is delayed by a few AND a days you may be placed at a dis- MAIL a CLARENCE A. O'BRIEN & HYMAN BERMAN 317-B Adams Building Washington, D. C. Registered Patent Attorneys Before U. S. Patent Office advantage, The short time that NOW! Ù Beas seu naa! moe pour Bi Foge Pas ogh elapsed between Elisha Gray’s ap- D a or ene aoe Be eae plication for his telephone patent G and the application of Alexander a NAM Rasens | Graham Bell probably cost Gray the rights to the telephone. l | E E E E E / l

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Don’t send us a cent—just your name and address and we ship all of these books to you for ten days free examination. Look them over carefully, see how easy It is to find out the things you want to know, and then decide whether or not you want to keep them. The price and terms are so low that everyone should have them on hand for ready reference. Billions of dollars are being used to make jobs biggest chance to make money carpenters have ever known. Are YOU ready? Can you remodel from start to finish—do you know the tricks of estimating, laying out, etce.? Here’s your chance to get these facts—quickly—easily, without Study or work—just put your finger on what you want to know instantly. Carpenters, Architects, Contractors, Home | A gold mine of facts can_ often be converted into a gold Builders mine of dollars, for builders save money and learn how to make more money with the five big books on architecture, carpentry and building. Carpenters make themselves contractors by learning how to estimate correctly; contractors are able to handle bigger and more proktable jobs by learning how the big fellows do it. Men who want to ulld homes can save money by learning how it should be done. The new Jiffy Index puts before your eyes without wasted time, the things ye want to know. Nothing overlooked. Use of tools, building construc- lon, heating, lighting, plumbing, architectural drawing; ali covered. These Drawing Instruments (3129:20) Included = S Complete set of drawing instruments if 2 ou send for these building books NOW. hese instruments are made of the finest German silver, are absolutely accurate and are packed in velvet lined leatherette “ - 5 4 pockct case. Real $10 value, but free to Se zs you with these books. American Technical Society, 7 T A cn N E a Drexel Ave. at 58th St., Dept. G4320, Chicago, III. I would like to look at the five books ‘described above, Send them on your free offer. I will pay the few cents dellvery charges only and will examine them thoroughly and return them In ten days unless I like them, in which case I will send you $2.00 and after that $3.00 per month until the total price of only $19.80 Is paid. You are also to Bend me the drafting instruments and consulting membership certificate of the American Technical Society, without extra charge, Name-..-------+------------------ Address Please attach letter stating age, employer's of at least one business man as a reference. \ @ Now—a bantam- weight outboard motor ¥ with typical Sea-Horse refinements, including un- derwater exhaust and 360° steering and reverse, plus Johnson’s famous “Single Shaft” construction! Write for new Sea-Horse Handy Chart describing all 9 models for’38 —the most important Handy Chart ever published. Sent free. JOHNSON MOTORS 200 Pershing Road, Waukegan, Illinois Johnson Motors of Canada, Peterboro, Canada FREE! Eee Ser ae OS See ARE] and the Home Modernization Program offers the | | CONTENTS—Continued from page 4 SHORTER FEATURES Stainless Steel Trains And Short-Wave Radio Signaling Mark Railroad Progress - - - 45 Miniature Village Thrills Children - - - 48 Photo Amateur Snaps Bullets Striking Lamp 56 War On Cancer Advances - - - - - - 6 Shadow Amusements - - - - - - - 68 HOW-.-TO-BUILD FEATURES Flower Pot Shell—A Scrap Wood Project - Tt Pocket Electroplating Outfit - - - - - 78 Indoor, Outdoor Playstore - - - - - - 81 Modernizing Outmoded Farm Kitchens - - 82 Swinging Arm Sander - - - - - ~- - 92 FOR THE WORKSHOP FAN Kinks That Simplify Shop Work - - - - 7 Your Cellar Shop Can Be Neat - - - - - "I Pin Improves Tape Measure - - - - - 9 Light Iron Bar Becomes An Efficient Gate Latch - - - - = = - - - - = - 9 New Uses For Rubber Heels - - - - - 91 Time-Saving Handikinks - - - - - - 9% Framed China Dishes - - - - - - - 9% RADIO AND ELECTRICITY Electro-Magnet Lifts Metal Load Weighing |! 83 Tons - - - - - - - - = = - & Builds Giant Television Tube - - - - - 54 Electricity Frisks Mattress - - - - - - 55 Loudspeaker Aids Fire Chief - - - - - 67 Transformer Simplifies Trailer Lighting - - 89 The MM Short-Wave Transmitter - - - - 98 | Electrical Kinks - - - - - - ~- - - 12 AUTOMOTIVE Knee Throttle Eases Driving - - - - -~ 40 Device Records Car’s Speeds - - - - - 54 World’s Largest Trailer Built On Tractor Chassis - - - - - - - - = = = 55 Lincoln Tunnel Equipped With Auto Salvage Trucks - - - - = - = = - - - 6 Auto Kinks - - - - - - - = - - -4 UContinued on page 10] g Accept No Substitutes! Always Insist on the Advertised Brand!

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is the time/ Business is Searching eee ee for YOU, if.... IGHT now, in many lines, there is a search for really good men—managers, leaders— men who can take charge of departments, busi- nesses, branch offices, and get things humming. As always, there are not enough ordinary jobs to go ’round—but rarely before, in the history of American business, has there been so much room at the fop! New jobs are being created by the business pick-up in almost all lines—jobs that pay splendidly and that open the way to lifetime success. Ordinarily, there would be plenty of men to fill these jobs—men in junior positions who had been studying in spare time. But most men have been letting their training slide during these dark years of depression... “What’s the use?”’—You have heard them say. Perhaps there has been some excuse for sticking to any old kind of a job one could get the past few years—but the door is wide open for the man with ambition and ability NOT? And don’t let anyone tell you that “Opzer- tunity Only Knocks Once’—thaz’s one of th most untruthful sayings ever circulated. Op- LASALLE EXTENSION, Dept.4493-R, Chicago Tam in earnest about my success and [ would like to have your special booklet—without any cost or obligation to me—about my opportunities and your success training in the business field I have checked. O Business Management O Higher Accountancy D Traffic Management O Modern Salesmanship O Commercial Law DO Law: Degree of LL. B. O Modern Foremanship O Business English D Effective Speaking O Office Management O Stenotypy O Expert Bookkeeping Oc. P, A._Coaching POSH ION cris Sika iat ae were Address O Industrial Management O Business Correspondence LASALLE EXTENSION: portunities flourish for every American every day of his life. Far more to the point is to be ready—to be prepared—to make yourself interesting to the big-time employer—and LaSalle offers you a short-cut method of qualifying for opportunity jobs in accounting, law, traffic, executive man- agement, and kindred occupations. LaSalle Extension is 30 years old—averages 40,000 enroliments a year—60 American firms each employ 500 or more LaSalle-trained men —surveys show that LaSalle students attain 40%, average salary increase after graduation —10% of all C. P. As in the U. S. A. are LaSalle-alumni. Why not find out what LaSalle has done and is doing for men in your position? Send and get the facts; see what LaSalle can do for you, personally! There’s no cuestion about it—business is picking up—iods are looking for men—the time zas come for you to qualify for prosperity. Mail this coupon today! Ask for one of these booklets—or a similar one on your own field of æ business. They are free! \ When Answering Advertisements Please Mention April Modern Mechanix 9

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IN THESE FAMOUS CHICAGO TRAINING SHOPS YOU CAN (} | COYNE occupies this entire s Modern, fireproof Building. J Ji- ELECTRICITY IN 12 WEEKS AT COYNE Prepare yourself in my wonderful Daylight training shops, for a better job... a job that brings good pay—in the one industry that is constantly going ahead, even through the hardest times. After my Practical shop training in this worid-famous Chicago school you are ready for your start in the electrical field where real opportunities : exist for the trained man. All Practical Training on Real Equipment | You Don’t Need Advanced Edu- Cation or Previous Experience You get triple training at Coyne—through your eyes, your ears, and your hands. And it is all practical down-to-earth training on real, modern electrical machinery and equipment. Real line generators, motors, dynamos, etc.—all right here in big daylight shops for you to work on and gain practical knowledge from actual operation. No dull oks—no correspondence. You don 't even need advanced edu- cation or previous electrical experience to master my easy shop training methods. Amazing Student Scholarship Loan Plan PAY FOR TRAINING AFTER YOU GRADUATE In Small Monthly Payments Lack of ready cash need not stop you from getting Coyne training. If you are ambitious and determined to improve yourself—if you are anxious to get ahead in the great field of electricity — I will let you take your training now...and you can pay for it after rou gradu- ate, in easy monthly payments. And even then you tase a year to complete your payments. Send coupon today for all dee of this remarkable offer. Spare Time Work While Training Employment Help After Graduation I help you to find spare time work to help pay your living eXpenses while training. Then after graduation you are given the service of my employment department any time you need it. DIESEL ° AIR CONDITIONING ELECTRIC REFRIGERATION So that your training will be complete and to increase your earning capacity I will include for a short time at no extra cost training in DIESEL, Electric Refrigeration and Air Conditioning. Send Coupon Today Mail the coupon at once for my big, illustrated FREE BOOK that tells all about Coyne training, the amazing oppor s in the electrical field, and complete details of my spare tice employment service and iy y After Graduation” Plan. H. C. LEWIS, President COYNE ELECTRICAL SCHOOL 500 S. Paulina St. Dept. 48-53 Chicago, Iil. SEND NOW FOR FULL DETAILS! Bae sneaen ec eese Bean anutnseaeuaeunaaunaa H. C. Lewis, Coyne Electrical School, 500 South Paulina St, Dept. 48-53, Chicago, Ul. a Dear Mr. Lewis:—Send me your big Free Book about Coyne Į training, and give me all tails regarding your spare time § taduation” Plan, is employment service and ‘‘Pay After peresress: 10 CONTENTS—Continued from page 8 AVIATION New 50 H. P. Airplane Engine - - - ~- - 41 Army Air Corps Develops Dual- Utility Baloon - =- - - - 47 World’s Biggest Model Plane - - - -'- 49 “Sky Fleas” Popularize Sport Flying = France - - - - - 53 New English Airplane Will Feature Bat-Like Wing - - - - - - - - 54 The Million Dollar Plane That Will Never Fly 61 Plane Features Rapid Climb - - - - - (7 NEW MECHANICAL INVENTIONS Mammoth Process Camera Has 20-Foot Bellows - - - - - - - - -~ - 41 Caterpillar-Type War Tank Attains 50 M. P. H. Speed - - - - - - - - 46 Whirling Cotton Gin Devised - - - - - 46 Engineer Builds Tiny Diesel- - - - - - 47 Liquid-Type Wrist Compass - - - - - 47 “Saw” Has Toothless Blade - - - - - - 49 Museum Technician Builds Planetarium Projector - - - - - - - - - = - 49 Invents Noiseless Coal Chute - - - - - 57 “Pendulum-Type” Streamlined Train Coaches Tested - - - - - - -~ - 67 Tilting Table Aids Veterinarians’ Horse Operations =- - -~ - = - - - -69 DEPARTMENTS Problems =- - ~ - - - ~ - - - += 418 Chips From The Editor’s Workbench - - - 28 Nic Sprank’s Oddities - -- - - - - - 34 Crafts And Hobbies - ~- - - - - - - 71 Photography Section =- - - - - - - - 103 New Ideas for Home and Shop - - - - 154 MISCELLANEOUS Cadets Build Miniature Ships - - - - - 40 Bridge Has Glareless Lights - - - - - 41 Knotboard Shows 144 Types - - - - - 46 Skipper Inspects Ship’s Model - - - - - 55 Scientist Alternates Lights Color In Experiment - - - mob yee 5 Phone Supplements Doorbell - - - - - 57 Fibrous Glass Insulates Shoes Against Heat, Cod - - - - - - - 63 Scrubbing Brushes Used As Surface For Ski Slide - - - - - 63 Carves Novel Tree Figures - - - - - - 67 Accept No Substitutes!’ Akcays Insist on the Advertised Brand!

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wn Details FREE More Than Twenty- Five Thousand sold Commonwealth Are Weilers use in every section of th States, and in practically eign country, They have bee chased for every welding p aud by every type and kind of hess, from the smallest to the est. The United Slates Govern Bethlehem Steel Company, Gu Refining, American Elevator, Swilt and Company, and scores of other nationally-known concerns are on our list of customers. The qualily and are praised in hundreds of letters from en i Get Amazing Details—F R Send today for amazing details about Model 120- FREE with Every Welder Finest Quality DeLUXE ACCESSORIES tion of the price asked for others. Learn how, fo day, you can own this highly efficient, all-purpos MAKING welding machine. Send NOW for full facts. COMMONWEALTH MFG. CORP. 4208 Davis Lane, Dept. G-52 Cincinnati, Ohio Puts This All-Purpose LECTRIC ARC WELDER IN YOUR SHOP TEN DAY TRIAL GUARANTEED TEN MONTHS STOP THROWING TO Pay AWAY PROFITS! DO YOUR OWN WELDING! That’s the modern way And, Yes, you get the sensa- to increase income and customer satisfaction. it takes only 22c a day to do it. tional, professional, ALL-PURPOSE, Commonwealth Are Welder- Model 120-FS, for only 22c a day. Ten whole months to pay out of profits. Now it is EASY for every inventor, laboratory, home workshop owner, garage, repair shop and factory to afford a com- plete welding service for manufacturing, malntenance, experimental ur uir work. Model 120-PS makes and saves money for you gears, brackets, shafts, pump parts, sheet metal, n ne parts tings, bumpers, etc. Ideal for making speclal tools, dies, jigs, fixtures, etc. Works On Both 110 or 220 Volt A. C. Simply plug into a 110 or 220-volt, GO- cycle A.C, line. Economical—costs only a few pennies an hour to operate. Often pays for itself on first or second job—yet you have ten whole months to pay us. Portable—move it anywhere in shop on its heavy-duty, tempered steel Casters, or carry it right to outside jobs in auto, truck, or side r. Anyone can weld Ing, automatically- complete with all Nothi Iding, Sheet Heavy Casting a big, 110-poimd, man- All We welder, costing man; of doing exactly i steel, cast iron, s of them. x instantly handle everything from and light sheet metal to motor blocks and beavy castings. Also fine for soldering and ‘brazing. ses standard welding ‘rods. No experience or special traini necded to operate. Simple. com- plete instructions for doing all kinds of welding jobs included. MAIL COUPON BELOW for complete FREE details mait couren GET 22¢ oi; PLAN with o . . R DETA 5 Dept. G-52, m inet Ot 120-FS : ie all ils 2 at Model tees - S208 Davis Lane, Cincin REE, me actas anout 2 13 220585 E : once. FRI detas : push me at. REE: dte. E Eina S BARE Mess M O Retr E ree > EUEN E L aneno : T eee eee D e er a . gay NAE : a ry © Adaress----777 oe aes ane ane! è Town. ----07777 ee | : | ‘ When Answering Advertisements Please Mention April Modern Mechanix 11

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A frank man to PATENTS- HE world of invention moves on. About a hundred years ago people were saying, “There’s nothing left to invent”—today we know that is one of the funniest things ever said. Just think what has happened in the last hundred years! Autos, radios, airplanes, and thousands of useful, practical devices for home, shop and office have been invented and put on the market. Inventors are con- stantly making the world a better place to live in. Did you see a notice in the paper that an obscure worker, Hans Wach, has invented a simple device to utilize exhaust steam on steam boats. Already, the report states, the steam ship lines have saved more than $15,000 in fuel bills with his invention. Almost in the same breath the Dept. of Commerce announces that it will soon test out a new non- crashable aeroplane, which the average man can learn to fly in a day, which wili travel at 110 miles an hour and sell at the price of a cheap automobile. An unknown Seattle man has invented a robot to go 5,000 feet under the sea and recover millions and millions of dollars worth of gold lying at the Who Are Inventors? You'd be amazed at the men we con- tact in the course of a busy year. Most of them do not consider themselves inventors at all. During their work or Jeisure they get an idea. They work it out on paper. They get in touch with us about Protection. Did you know that a dentist invented the stock ticker, a school teacher the telephone, a farmer the typewriter, an artist the telegraph? Did you know that the crinkly bair pin—sold by millions now—came about because a husband saw his sell have any Can You Answer These Questions? Ask yourself these questions: the Patent Laws protect me? What easy steps can I ta model? to secure financial help? If I do apply for how shall I reach people who can market my invention? Can I protect and NVENTIONS bottom of the ocean since the days of the early Spaniards. Remember this: For every outstanding big inven- tion there are thousands of small, simple things for use in the home, the office, the factory, on the farm, on every sort of travel conveyance. Little articles like you find on the counters of a 10-cent store, hardware store, drug store, toy and novelty shop. Many Little Ideas Have Big Commercial Possibilities A person finds something he’s using doesn’t work right, or it’s clumsy, or costs too much. He gets a happy thought. He improves the old Article. That’s contribution to human progress. That’s the way that many, many men have reached the goal of financial comfort, independence and even wealth. Most of the things millions of us use didn’t come from the brains of engineers and physicists. They came from the mind and maybe the crude home work bench of Mr. Average Man, busily engaged in earning his bread and butter at whatever chance or circumstance has given him to do. The “little” man’s opportunity as an inventor was never greater than it is today. Our Business Is To Help You. Write Us Today For more than forty years, this firm has been helping men with an inventlve tun of mind. We maintain 2 large staff of trained, experienced specialists—Registered Patent Attorneys, Draftsmen, and Searchers to help our clients secure all the protection to which they are entitled. Fees are reasonable, De- ferred payments frequently arranged. Ques- tions promptly answered. Write us frankly with absolute assurance that what you say will be treated with strictest secrecy. But FIRST, send for the FREE BOOKS shown on the op- posite page. They are filled with facts, pic- tures and suggestions, They teil you things How do . without cost. t Should I try to my invention before I it Patented? Is there safe, business-like way a Patent wife twisting the old-fashioned straight hair pin to make it stay in place? Poor men who have no thought of invention now will be financially well-fixed in a few years because of a happy thought that the world could use to advantage. 12 sell an improvement on some invention that has already been patented? These are but a few of the questions which usually confront the average man. You need the answers! YOU CAN HAVE THEM, without cost, trouble, or delay. RUSH COUPON TO WASHINGTON. D.C. TODAY about Patents, Inventions and Selling Inven- tions that we have learned in our long experience, They may save you time, expense, EVEN LATER DISAPPOINTMENT. Simply fill in the coupon. No charge, no obligation. Write us today. Accept No Substitutes! Always Insist on the Advertised Brand!

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and facts there are 115 differ- some mechanical problem. Use 8 p G E S : the coupon or write us a card 6 A 115 Mechanical Move- ments Like These E *] Ẹ E cat mechanical meverenn end Pa BOOKS r letter. > : or lette of Facts and _ Pictures! Besides many other features Book below. Maybe there is with just the idea you need to solve ime nananana : (1) - n È - : VECTOR J. ae om HEN : C ye Vea A A About Selling | W | REGISTERED PATENT ATTORNEYS INVENTIONS MAIN. OFFICE: prp VICTOR BUILDING, h »_D. C. aa tar as we Pnom, the Other Offices; 2610-B, Singer Bldg., New York bef b b- 1445-B, Monadnock Bldg., Chicago liched erore Deen pu 1010-B, Hobart Bldg., San Franclseo lished by any Patent At- 405-B, Garfield Bldg., Los Angeles torney. You are given §14-B, Empire Bldg., Pittsburgh very definite suggestions Send me FREE copies of your books, “Patent Protection’ and on “When and How “When and How to Sell an Invention."’ (Note: Same books sup- to Sell an Inven- plied by any of branch offices listed above.) tion.” It also Name .....cseceeee VHP eenea meena Seana srresassasosasoseessonos comes to you F . Street and No, wo... cece eee eee eee eee eee ee eer rire rer rr er eres CHES OR TOWN 5 pigateediass dvwisibaaais Saeeedaes areces States cceoscceses When Answering Advertisements Please Mention April Modern Mechanix 13

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WK Cash ror SPARE time! MAKE $25 TO $30 PER WEEK AT HOME IN YOUR SPARE TIME THE IDEAL LAWNMOWER SHARPENER c, the Ideal Lawnmower Sharpener makes old, dull. half ne Out inowers cut like new. Simply set the mower in the Ideal and the machine does the rest. Sharpens any Peary to a perfect edge in o 20 minutes, usual charge 51.0: a $1.50. Attach to light socket. Start in your basement or sae? ork in spare time, Attachments furnished for gri many skates, grass a hedge shears, Sickles, seythes, axes, etc. RÉE CATALOG tells complete story. WHAT THESE MEN DID .. You Can Do Remember, No experience a necessary. Most men sharpen_lawnmowers in spare time only. J. B. n Dien writes: '‘Some weeks I earned 840 a week with my Ideal use "as a side linc.” George Seitel writes: ‘I have sharpened over 500 mowers and every customer is well pleased.’ A, M, „arsen writes: ‘I average mowers a day.’’, Roy F. Stier says: a_town of S00 and to-date have Sharpened 200 mowers at $i. 25. Edward A. Mynderse writes: “Have sharpened around season.’ Nick Baltes says: Solase summer 2 sharpened S60 mowers at $1.00 uch. Bueher Battery Co. write: “We sharpened over 600 mowers last year at $1.50 each. FREE BOOK Shows how! Right now before ou forget it, send for a cop Gur TREE BO ae ‘How To Make B58 l h0" per week in’ SPARE TIME.” SEND POST CARD TO THE FATE—ROOT—HEATH CO. 328 Bell Street, Plymouth, Ohio — AGENTS & DEALERS WANTED to Sell or Rent The NEW ies RANGER Scooter for $ For this Marvelous 1 89 Improved RANGER, Cent! and they're selling like hot cakes all over the country. Order your demonstrator while territory still open—- there’s big money in sell- ing to all stores who need quick cheap delivery. EASY TERMS FINANCED So simple, so safe a ehild can run it, YET - strong enough for a Go anywhere—at 30 miles per hour, 120 miles to gallon. hearty man! WRITE QUICK for color folder while special Low price lasts! CYCLE COMPANY Write Us Today Meads“ cs-29 CHICAGO For Free Folder 14 Accept No Substitutes! Always Insist on the Advertised Brand! Earth’s Core A Sponge? The earth’s heavy core as a great metallic sponge filled with hydrogen gas is the latest pic- ture of the mind of science to envision what the center of the earth is like. The Rev. Joseph Lynch, noted seismologist of Fordham University here, advances this idea in a new hypothesis. The speed of transmission and the reflection and bending of earthquake waves, says Father Lynch, are about the only ways by which science can conjecture on the nature of the core of the earth deep below the outer solid, rocky crust. With samples naturally unattainable, scientists must work backward in their deductions. They ask, points out Father Lynch, “what known con- ditions must the state of the earth’s core satisfy?” For one thing the earth has a density averaging about 5.5, or five and a half times as heavy as water per unit volume. But the density of the crust of the earth is only 4.2, so that the core re- quires something—liquid; solid or gas—whose density is close to the value 12. Iron, nickel and other heavy metals have previously been sug- gested to explain this high density, says Father Lynch, But a study of the way earthquake waves travel through the earth shows evidence which demands other properties besides more heaviness. Tidal phenomena require that the rigidity of the core be appreciably less than that of the crust on whose surface man builds his cities that earthquakes occasionally destroy. In addition the core must have the property of absorbing a special type of wave motion called shear waves, for it is observed that while com- pressional waves easily pass through the core, there are few known cases where the shear waves come out, once they are inside. Experiments in his laboratory indicates Father Lynch, show that when the metal element pal- ladium is packed, or occluded, with hydrogen gas to several times its own volume, its properties begin to approach those comparable with what is observed in the earth. Father Lynch disclaims the idea that he be- lieves the center of the earth to be made of pal- ladium (whose value is about $18 an ounce). He merely used the rare metal as a convenient ex- perimental sponge for “holding” the hydrogen. The findings are suggestive, however, of the metallic sponge hypothesis on the nature of the earth’s core. Experiments are now under way to study the effect of the absorbed hydrogen on the elastic properties of the material. When known these properties can be correlated with those ob- served in the earth and additional confirmation or rejection of the hypothesis will then be possible. NOTICE Changes in the make-up and title of this magazine, designed to make your favorite publication better than ever before, will be announced in our next issue. Be sure and reserve your copy now.

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Croft tells you the things you need to know about motors, generators, armatures, Com- mutators, transformers, circuits, switehboards, distribution systems— electrical machinery of every type—wiring for light and power—wirlng of finished buildings—underwriters’ and municipal requirements—il- lumination in its every phase—the most Improved methods of lighting— lamps and lamp effects, etc.—how to do a complete job, from estimating it, to completion. , No money down—easy payments Fill in and mail the coupon attached and we will send you the entire Set of seven volumes for ten days’ Free Examination. We take all the risk—you assume no obligation. If you decide to keep the books, send $1.50 in ten days and the balance at the rate of $2.00 a month. Send the coupon NOW and see the books for yourself. | FREE EXAMINATION COUPON SY McGRAW-HILL BOOK CO., 330 W. 42nd St., New York Send me for ten days’ free examination the Croft Library of Practical Electricity. If satisfactory I l send you $1.50 in 10 f $19.50 is paid, It not id. days and $2.00 monthly until the pr wanted, I will return’ the books prs (To insure prompt shipment write plainly and fill in all | Name coca cs cesce neces ec E eens E een eeesens Home Address City and State Position -.-..--- c [OF Ns PLEASURE or PROFIT Prepare for profitable business or fascinating hobby, at home under guidance of quallfied instructors. No previous experlence necessary, ommon school education sufficient. Many earn while earning. Our practical atudio methods also qualify for well-paying positions upon dyation. Send coy- on below et once for free booklet “‘Opportunities in odern Photography’’, particulars and requirements. =. aa m m amA an a o a n ea e S O A O OA A aG a n N O m m a MERICAN"SCHOOL OF PHOTOGRAPHY seor Michigan Avenue Dept. 2054 Chicago, Ilinois Bend booklct, ‘‘Opportunities in Modern Fhotography’’, full particulars and requiremeni w- 2 -Age- 2 We paid Rev. 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Or that the Dow-Jones stock market averages follow a curve which is very similar to curves based on sunspot numbers? These are only a few of the many remarkable, but unexplained, coincidences between the activities of plant and animal life on earth and the appearance of those gigantic electro-magnetic disturbances on the sun which man calls sunspots. More and more scientists, and others, are prob- ing sunspots and seeking to learn the relation- ship between their appearance and the multi- tudinous activities of earth-bound man. In his newest book, “Sunspots and Their Effects from the Human Point of View,” Dr. Harlan True Stetson, astronomer and research associate of the Massachusetts Institute of Technology, sum- marizes the knowledge which science now has in its possession to analyze for the truth or false- ness of speculation on this intriguing matter. Dr. Stetson goes out on no limb to forecast, in so many words, a definite relationship. Rather he piles up, item by item, an imposing array of facts which offer a true challenge to those who are skeptical of the sunspot’s bearing on ter- restrial activity. Psychologist Uses Radio To Check “Hams’ ” Personalities AN you judge a man’s personality from hear- ing his voice over the radio? The possibility is being tested by a psychologist who is also a “ham” with his own radio transmitter in his study, Dr. E. Lowell Kelly. of Connecticut State College. Fifty other amateur radio fans will take part in the experiment. Each of them will be rated on 36 different personality traits by personal ac- quaintances and also by those who know him only by radio. Comparison of the two ratings will reveal to what extent a man’s personality “gets across” through the medium of the micro- phone. Intelligence, sociability, popularity, initiative, courtesy, cooperativeness, culture, honesty and disposition; these are among the traits to be evaluated on Dr. Kelly’s 36-point scale. 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_ Enjoy a Real Job in Industry Steady Work T As nearly all manufacturing and building starts on the drafting table, the draftsman is one of the first to be hired, last to be laid off. His blueprints, his specifications, give the final word in what the workmen are to do. Good Pay The draftsman has been called the Junior Engineer, which accurately describes his work, position and pay. He combines knowl- edge of principles, mechanism and construc- tion details with ability to draw plans and indicate methods. Usually bis salary is con- siderably above the wages of the mechanic and, of course, less than that of the engineer. EEEE BEES Song heat ; A aS : Chance for Promotion A Job Where You Are Not Old at 40 Helping design new buildings, machines or Athletes, farmers, factory and shop workers—all who rely on construction methods, the- draftsman. knows muscle often are old at 40. Office workers—executives, teachers, what his firm is planning or considering. It professional men, drcftsmen—just approach their prime at 40 may be the superintendent—engineer—even to 50. Training increases your value AT ONCE and continues the prospective buyer with whom he con- to help boost your earning power as you mature. sults. These contacts, plus his experience, place him in an excellent position for promo- Train Now for 40 and the Years Between! tion when next there is a good opening, Even if you are now only 18, 25 or 30, youshould look ahead 2 D rafting F : —hegin training TODAY for the job you want at 50. Training Z Lessons k lee on Te Dra g : helps you to be independent—self-supporting. It helps you to Test Yourself! See how ri

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Editor’s Note: not require special research or involve trade secrets, reply. Address: WHAT IS HORSEPOWER? What is horsepower? Does it mean that an engine of one horsepower can do the work of one horse? It probably means something else but I am not sure.—Herbert Brennan, Pendleton, Ore. Horsepower today has no connection with the amount of work a horse can do. In this country, one horsepower equals 33,000 foot pounds of work per minute, that is, the amount of work necessary to raise 33,000 pounds one foot in one minute. This standard may be applied to any combina- tion of these values as long as the proportion remains the same. In other words, 66,000 pounds raised one foot in two minutes equals one horsepower. Also, 550 pounds raised one foot in one second equals one horsepower. In the eighteenth ‚century, the amount of work which could be done in one minute by an average draught horse was considered one horsepower. The French standard of horsepower is 32,549 ft. Ibs. of work in one minute. WHEEL BASE AND TREAD What is the difference between the wheel base and tread of a car? I notice in advertisements of cars that wheel base is mentioned but I never notice anything said about the tread.—Robert Harrison, Chicago, Ill. Wheel base is the distance in inches between the front and rear axles. This distance is measured from the exact center of each ax! È front wheels, or t: the exact center of ez inches. Although the ir varies, wheel base changes 2. Trea] is the te be tha OHM’S LAW I have heard of Ohm’s Law many times but I don't know what it is. Can you explain it to me?—J. L. Anderson. Miami, Fla. The unit of resistance is the ohm. This is defined as the amount of resistance through which one ampere of current will pass when under one volt pressure. All calculations involving currents make use of this fundamental rela- tionship. Given any two values, the third can be deter- mined by using the formula E= IR, when E is volts; I current in amperes, and R, resistance. 18 Your questions will be answered personally and free of charge by MM experts provided they do Names and addresses of manufacturers of new products de- scribed in this issue can also be obtained free upon request. Problems Editor, Modern Mechanix, 1501 Broadway, New York City. Enclose a self-addressed and stamped envelope for DETERMINING BIAS VOLTAGE What is the formula for determining the bias for a tube used in a Class C amplifier?—R. J. Chavarie, Tulsa, Okla. Divide the plate voltage by the amplification factor of the tube. If cathode bias is used, subtract the voltage drop across the resistor from the plate voltage before attempting to determine the bias. ADJUSTING SPARK COIL What is the correct method of adjusting a spark coil?—= H. H. Parker, Philadelphia, Pa. The simplest method of adjusting a spark coil vibrator is by screwing down the vibrator until a musical “buzz” is heard. If more than one coil is used, try to adjust each vibrator to the same sound. ENGINE LACKS POWER My engine starts easily but I am unable to get much power from it. I use good gasoline and have always taken good care of the engine. What do you think is wrong?— Phillip Miller, New York, N. Y. The engine Also the valves may be leaking. ze ignition for a weak spark. Be sure that the cattery js charged. z2 carburetor for a too-rich mixture. pression. C FINDING CRACKS IN METAL Is there any easy way to locate small cracks in metal, usually not visible to the naked eye? I would like to check my tools to determine if they are as strong as they should be.—Jack Roberts, Memphis, Tenn. Moisten the surface of the tool to be checked with petroleum. Then rub it off with a dry cloth. After the surface is completely dry and clean rub it off again, but this time with some chalk placed on the cloth. If there is a crack in the metal, the petroleum that entered will come out when the chalk is rubbed over it, thereby giving evi- dence of the crack.

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CO., Up To The Minute Bock ON. SHEET METAL WORK— WELDING—PATTERN DRAFTING “Sheet Metal Workers’ Manual” by Broemel ... 5 pages—400 illustrations ... used as text by U. S. Nave í Training and many other schools. Covers Electric and Oxy-acetylene welding . . . Pattern Drafting ... Metal Working machinery and tools... forging—brazing . . . useful tables. Only $2.00 postpaid ... 5 day money-back guarantee, Send for our Free Catalog on Allied Subjects. FREDERICK J. DRAKE & CO. 181 N. Michigan Avenue, Chicago, I. 20 EARN MONEY Make Color-glazed Concrete Products New, perfected low cost method. No molds, power or costly tools, You build your own equipment from Plans we furnish. Experience not necessary to make color-glazed concrete garden pottery, statuary castings E in. home or shop~—to earn money. end 10c TODAY for booklet, colorplate, details of this money making business, No obli- gation. NATIONAL POTTERIES COMPANY Room 8, 13 W. 26th St. Minneapolis, Minn. Convert your car to burn Diesel oi Cheap installation. Different and better, circular No. 5. Save up to 70% fuel costs. Wonderful performance, Proven factory methad. Costs nothing to inrestigate, Write for free HARRINGTON COMPANY 201-204 Manchester Bldg. Portland, Oregon WIND DRIVEN Electric PLANT Build Your Own—We Show You How! Make auto generator light buildings, play radio, run washing machine and other motors. from FREE WIND POWER. Earn money making for others. Dime brings complete building plans and 1938 catalogue listing over 500 Windcharger electrical items. Most complete wind- charger catalog; welders, electric fence, ete., over 100 other generator changes into 6-12-32 and 110 volt plants, LEJAY MFG. CO., 414 Lelay Building, MInneapolls, Minn. How would vou like to save up to 50% on Nationally advertised Radios, such as Strom- berg Carison, Philco, RCA, Zenith, G. E. etc., etc., for home, farm and auto, over 400 models to choose from. Also hundreds of electric appliance items for the home. Write today for the new 1938 giant catalog FREE. § MODELL’S bapt. 55, Cortlandt St., N.Y.€_ 4 MAN IN EACH TOWN To Plate Auto Parts Reflectors, Ricycles, Fixtures, Mirrors, by late method. Simple Dian of manufacturing at home starts you IN GOOD PAYING BUSINESS. Write today for FREE particulars and proofs. GUNMETAL CO., Decatur, MI Ave. P, crease profits, start your own busi- in spare time quickly, Show you very latest methods. particularly interested because latest scientific “How to Ralse Poultry for Profit’? comes to you — SCIENTIFIC POULTRY RAISING Please send me your FREE Book about poultry ralsing, and facts l BIG MONEY: rom ness, or secure a good job in a big Give you facts worth money to yourself or employer. methods mean unusual profils for them. My home- FREE. Mail coupon today, HARRY M. LAMON, Pres., National Poultry Institute, about your Course. | PO U LT RY I show you how to greatly in- Poultry plant. I train you at home Men and women in small towns or suburbs will be strdy course used by thousands, 32-page book, ee ee ee ee ee ee | Dept. 130-D, Adams Center, N Name..—------.------. Address. l City (R.F.D.)---.~---- —— a m ee Accept No Substitutes! Always Insist on the Advertised Brand!

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‘Preserve Your Copies of MOTE, MECHANIK these handsome binders. Made from beautiful red sim- ulated leather embossed in gold, the binders hold six issues each. Magazines are conveniently bound with a snap and are held positively in place; holes need not be punched nor copies marred. MODERN MECHANIX and the year specified are stamped in gold on the back- bone. Volume I and Volume Il to represent the first and last six issues of the year will also be imprinted in gold if de- sired. Each $1.25 plus 15e postage in continental U. S: = ($1.25 plus 75c postage elsewhere) eS ee | MODERN MECHANIX | i Fawcett Bidg.. Greenwich, Conn, l Enclosed ts $... for ..... MODERN MECHANIX binders. | | Imprint year (years) ....... | I imprint year and volume number (years and volume l lo numbers aoia i Name ae l a da eee ee me ; | | ei e S a eee ee nae eee nn sees | | City es yea loue > a, iT ROUS PREVIO | When Answering Advertisements Please Mention April Modern Mechanix “THE BOSS DIDN'T EVEN KNOW MY NAME” “He sar my face was more or less familiar and he remembered seeing me around, but he didn’t even know my name until the I. C. S. wrote him that George Jackson had enrolled for a course of home study and was doing fine work. “Who's George Jackson?’ he asked. Then he looked me up. Told me he was glad I wag ambitious. Said he’d keep his eye on me. “He did too. Gave me my chance when Frank Jordan was sent out on the road. I was promoted over older men who had been with the firm for years. “My spare-time studying helped me to get that job and to keep it after I got it. It certainly was a lucky day for me when I signed that I. C. S. coupon.” How much longer are you going to wait before you take the step that will bring you advancement and more money? It takes only a moment to mark and mail this coupon and send it to the International Correspondence Schools at Seranton. Yet that one step may be the means of changing your entire life. Isn’t it better to get the facts than to wait a year or five years and then wish you had? INTERNATIONAL CORRESPONDENCE SCHO Box 2316-Q, Scranton, Penna. Without obligation, please send full particulars about the sub- ject before which I have marked X: TECHNICAL AND INDUSTRIAL COURSES O Architect O Diesel Engines O Architectural Draftsman O Aviation Eng. O Auto Mechania O Building Estimating O Plumbing O Heating D Contractor and Builder O Air Conditioning and Cooling O Structural Draftsman O Commercial Refrigeration O Structural Engineer O Steam engineer O Electrical Engineer O Steam Electric Engineer UO Flectrio Lighting O Marine Engineer O Welding, Electric and Gas O Civil Engineer Q Highway Engineer O Reading Shop Blueprinta O Bridge Engineer O Telegraph Engineer G Bridge and Building Foreman o fpiephone Work O Radio Z Surveying and Mapping a z. R. Locomotives O Air Brukes R. Section Foreman ‘homistry D Pharmacy CG Coal Mining O Navigation O Cotton Manufacturing D Woolen Manufacturing D Agriculture O Fruit Growing O Poultry Farming = Heat Treatment of Metals O Management of Inventions BUSINESS TRAINING COURSES O Lettering Show Carda O Signs D Stenography and Typing O Civil Service D Mail Carrier Q Railway Mail Clerk O Grade School Subjects O Iligh School Subjects O College Preparatory O First Year College Subjects D Business Management Q Industrial Management O Trafic Management OC. P. Accountancy O Bookkeeping © Secretarial Work O Cost Accountant O Salesmanship O Advertising O Service Station Saleymanship O Illustrating O Spanish O Business Correspondence O Cartooning O French DOMESTIC SCIENCE COURSES D Professional Dressmaking O Millinery and Designing O Foods and Cookery O Home Dressmaking O Tea Room and Cafeteria O Advanced Dressmaking Management, Catering If uou reside in Canada, send this coupon to the International ` Correspondence Schools Canadian, Limited, Montreal, Canada 21

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{| i) | UIA í J BOOKS SENT FREE on approval. Just mail the coupon and we'll send you a ‘set of these remarkable auto books, just off the Whether you are a mechanic or helper, €x- pert or apprentice, auto owner or driver, if you're Interested in knowing all about automobile mechanics, take advantage of this FREE OFFER. GET A BETTER JOB A better job—in the gigantie aulo in- dustry. BIGGER PAY—a chance to go into buzlness for yourself and get a share of the huge profits, are waiting for any man who eren half trles to improre himself. Learn auto engineering with these wonder books a new way—without studying or memorizing. Simply use the JIFFY 1N- DEX to look up the answer to any auto Problem. Built by eleven of America’s greatest automobile engineers, and written in simple language so you can understand Very newest ears, all covered. FREE Privilege of consulting Automobile Engineers of Am ican Technical Society for one year without cost if you mall coupon Immediately : tlon, gold-stamped flex. Books also include valuable articles on ible_bindIng. Service Shop Management. AMERICAN TECHNICAL SOCIETY, Drexel Ave. & Ssth St.. Dept. 44320, Chicago, Ill. I would like to see the new 6-volume edition of your AUTO BOOKS. I will pay the few cents delivery charges only. but if I choose to, I may return them express collect. Ii after 10 days use I prefer to keep them, I will pend vou $2 and pay the balance at the rate of only $8 a month, until $24.80 Is paid. ` Please include free consulting membership as per your offer above Name — Address City. _ Attach lelter stating age, occu Ployer and that of at least one CAN YOU FIX IT? These wonder books tell shimmy in steering—to set TIMING—how to put your finger Instantly on engine trouble and then the quick expert way to FIX it, lewest im- provements fully cove ered. Equal toa complete trade course at less than = a fourth the cost, it. 6 BIG VOLUMES Brand New Edition 2500 pages, 2000 lllus- trations, wiring dia- grams, etc., including Marine Engines. Avia- tion Motors, Diesel e gines, etc. De Luxe ed = Sta! tion and name and address of em- usiness man as reference, LEARN AT HOME Are you adult, alert, ambitious, willing to study? Investigate LAW 1 We guide you step by step— furnish all texts, including14-volume Law Libra- ry. Training prepared by leading law professors and given by members of bar. Degree of LL. B. conferred. Low cost, easy terms. Send NOW forFree,64-page“ Law Training for Leadersxip.” LASALLE EXTENSION, Dept. 4493-L, Chicago COMPLETE ELECTRIC PLANTS Onan A.C. plants furnish same current as city lines, 110 Volt, 60 Cy For farms, camps, con- struction jobs. Operate radios, water systems, all appliances. New models, 350 to 5000 watts, 6, 12, 32 and 110 volt D.C. Models $5750 arid up Also combination A.C -D.C units. Shipped complete, ready to run. Write for details. D W. ONAN & SONS 1669 Royalston Ave Minneapolis Minnesota Amazing New 101 TOOL Makes GARDENING Easy! | s Amazing WONDER Cultivator does ALL work and saves cost of 10 ordinary gardening tools! Entirely new, Take tiring drudgery OUT of § farm; garden and cultivating jobs. No back-straining, chopping or pulling—you PUSH. the Wonder with easy natural movement, Does work easier, quicker, better, Amazingly low priced. Big Profits for Salesmen, Agents! Thousands want Wonder Cultivator~homes, gardens, ff farms, parks, golf courses, nurseries, etc. Big money —easy—takIing orders three to a dozen at a time, Mail postcard for detalls and FREE DEMONSTRA- TOR OFFER. WONDER MFG. CO., Dept. 54 325 W. Huron $t., Chicago, III. NEW! SENSATIONAL E r Fn aks “PUDDLEJUMPER a 3 wheel “Powertrike.”” Runs 5 miles for clutch on electrice type. Instant ac- tion! Varlable and ‘‘Superpower’? controlled by anyone without ex- Perlence! Lights, horns, brakes, PLENTY OF POWER! Charger self-contained In scooter—charge any- where—just plug it up to any light socket! (patented) Unusual range. ULTRA STREAMLINED! “Powertrike’’ has complete finger control and reverse gear! Will run_over 100 miles per charge—built for real up per gal. gas. Clutch, Kick startor, etc. Write for literature and special prices. MIDGET MOTORS CORP., Dept. M-4, Kearney, Nebr. Cards, Stationery, Advertising, labels, paper, circulars, tags, ete, à from factory only, Junior Outfit $9.00. Senior outfits $17 and up. engraving with any of our presses. Print for Others, Big Profits Easy rules sent. Write for free catalog of outfits and ol! details. 3 new models including $59.50 No gas, oll, uP Speeds to 40 m.p.h.! Perfectly windsh lelds, “*Carrypacks. Heavy balloon tires and spring frame give AUTO SMOOTH RIDE! service! Gas models have 34 to 11% h.p, for real SNAP! 123 miles Print YourOwn Save money and time, Sold direct “Do popular raised printing like Pays for itself in a short time. SAALE The Kelsey Co., D-9 Meriden, Conn, PARKS AIR COLLEGE PARKS AIRPORT EAST ST.LOUIS, I Offers you college education majoring In aviation Four courses lead to B, S. degrees in Professional Flight, Aviation Operations. Aviation Mechanics, Aeronautical Engineering. 100 acre airport, 14 buildings, 33 in feculty. 302 enrolled for Fall term. 6,400,000 miles filght training. 1,562 planes. 538 engines repaired and rebuilt in shops. Graduates with all leading aviation companies, Dormitories, dining ball on field. Spring term Mar. 28th, Catalog. Write REGISTRAR, DEPT. MM- 11th YEAR PARKS AIR COLLEGE, EAST ST. touis, ILL, TRIAL LESSON IN More good Jobs now In Drafting. Learn AT HOME ìn apare time (or at our Chicago School). Send post card for FREE TRIAL LESSON and see how easy to learn and get a good job. CHICAGO TECHNICAL COLLEGE D263 Tech. Bidg., 118 E. 26th St., Chicago, Ii. y to college to L Drafting, Engineering Aen ete ioia A Condioning of Radio send fot FREE Blue Book, Want a Career in photography? We gire you personalized training. Commercial, News, Portrait, Advertising, Candid or Motion Picture Pholography. Big money- muking apportunities, Or learn for pleasure. Personal Attendance and Home Study courses. 28th vear. Free booklet. NEW YORK INSTITUTE OF PHOTOGRAPHY p 10 West 33 St, (Dept, 453) New York City 22 Accept No Substitutes! Always Insist on the Advertised Brand!

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Test New Auto Parts With Aeronautical Safety Device DEVICE invented to safeguard the lives of airline passengers now is used in testing Ford V-8 parts for flaws invisible even under a microscope. The device requires only iron dust and elec- tricity to bring into plain sight cracks in the metal so tiny they defy detection by any other method of inspection. The method has proved so successful in “finding accidents before they happen” that the Bureau of Aeronautics urged its use on all vital parts of airplanes and engines. Ford engineers believe they are the first to bring this safety measure into the automobile field. The apparatus is simple to operate. It consists of a powerful coil of new design, which quickly magnetizes the part to be tested. The operator then dusts the part with iron powder. The powder piles up in plain view along the entire length of any flaw in the metal. “A, crack too small to be detected otherwise still is large enough to split the magnetic field,” one of the automotive technicians said. “The field is positive on one side of the flaw and negative on the other. The iron dust therefore, is drawn at once to the flaw and makes it plainly visible.” A feature of the new flaw finder is its adapt- ability to mass production tec’nique. Parts sent through the magnetizer are placed in an oil bath containing iron powder, Any crack is disclosed instantly to the inspectors since the oil makes the line of powder, which collects along the flaw, visible at a glance. Army Orders “Flivverplane” While titles in military forces of the smaller Central and South American countries have been the subject of much humor, Nicaraugua recently went on record as one of the most progressive countries of the world in one respect. A Cub “flivverplane” (40 H.P.) recently purchased and shipped to the Nicarauguan Army at Corinto. Nicaraugua, will be used for primary training of military pilots there. It has long been recognized by experienced instructors that a substantial part of an airplane pilot’s training may be given in low powered eco- nomical airplanes, such as the Cub, with a tre- mendous saving in cost. There are also many benefits to the embryo pilots training in safe, easy to fly planes, leading to greater proficiency and self-confidence. Results of the Nicarauguan ex- periment, therefore, will be carefully noted by aeronautical experts. NOTICE Changes in the make-up and title of this magazine will be announced in our next issue, Reserve your copy now. When Answering Advertisements Please Mention April Modern Mechanix TEPTO Sh INVENTION Find Out Now If Your Invention Is Patentable It Is not necessary to make an expensive model or finished draw- ings. A desoription and sketch is all we need to help you. The Important thing Is to get started NOW, just as quickly and as economically as possible. But FIRST, send for our free Patent and Selling Guldes. you stand NOW Patent Protection. Our Free Books Tell You What Every Inventor Wants to Know They tell you why delay can pree vent you from securing Patent Protection. How to avoid costly mistakes. How to get your Invene tion saleable as quickly as possi- ble. Whom to sell it to. How patent laws protect you. What a Patent costs. What kind of Pat- ents are granted. The importance of secrecy in Patent matters. How a skilled Patent Attorney can se- cure you better Patent Protection. The difference between a good patent and a worthless one. C. A. Snow’s 62 Years of Experience Can Be of Real Value to You We have served inventors In every state In the Union .. In every field of Invention. In fact, we have secured Patents for Inventors In every civilized nation In the world. Ta help In- ventors get started without de- lay, we offer a convenient DE- FERRED PAYMENT PLAN. By this plan, the cost of your patent is spread over several months. Your Patent Application Personally Prepared By a U. S. Registered Patent Attorney Every member of our firm Is a U. S. Registered Patent Attorney. Therefore, your patent applica tion will be carefully prepared IN STRICT CONFIDENGE by a skilled speclallst. A specialist who will secure for you the broad est possible patent protection, he- cause, as a member of our firm, ha has a personal pride In your patent. Send for These FREE = Patent Guides Today Know where in regard te C. A. SNOW & CO. Registered Patent Attorneys Since 1875 3030 Snow Building, Washington, D. C. Gentlemen: Send me your free handbooks for inventors by return mail, No obligation on my part. “NAME . ADDRESS CITY anand 23

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| TOA PRACTICAL UNDERSTANDING OF ELECTRICITY @ AUDELS HANDY BOOK OF ELECTRICITY $ HANDY For Engineers, Electricians, Students and all inter- SIZE ested in Electricity. A quick, simplified, ready reference, giving completeinstruction and practical information. Easy to understand. A reliable au- thority and a handy helper that answers your questions. @ INSIDE TRADE INFORMATION ON The Rules and Laws of Electrice ity--Maintenance of Machinery A.C, and D. C. Motors--Arma- ture Winding and Repair--Wir- ing Diagrams «House Lighting + Power Wiring--Cable Splicing» Meters--Batteries~Transformers øs Elevators « Electric Cranes ~ Railways~-Bells--Sign Flashers- Telephone--Ignition-Radio Prin- ciples--Refrigeration Air Con- ditioning-OilBurners--Air Com- pressors~Welding, and many Modern Applications explained 60 you can understand, Togetthis assistance for yourself, simply fillin and m Siti HEO. AUDEL & CO., 49 West 23rd Street, New York „Please serd me ‘‘Audels Handy Book of Practical Elec- ‘icity’? for free examination. If satisfactory, 1 will send ou g1in 7 days, thea $1 monthly antil $4 is paid. Otherwise will return it, 1340 PAGES A FOR Occupation. $ For several years, Diesel engines have been replacing steam and gasoline engines in power plants, motor trucks and busses, locomotives, ships, tractors, dredges, pumps, 1 etc. And now the first Diesel-powered passenger car is om 5 the market. Our home-study course offers you a real op- portunity to prepare for a worth-while position in thig new field, Write TODAY for full information. No obligation. “American School, Dpt. D-428, Drexel at 58th, Chicago BIG MONEY BUILDING MEAD’S NEW Portable OUTBOARD > BOAT! horsepower, fected alumin guarantees succi economically, GLIDERS, 15 Get Into AVIATION Train At LINCOLN Takes Any outboard essfu. Rush d S. Market, Dep Now Is the time to get Into aviation! Airplane factories are flooded with orders! Atrlines continue to expand! Airline Pilots earn up to $6,000 a yeat— mechanics up to $2,400! Come to LINCOLN now and train for one of the many good pay jobs open to Lincoln- trained men. Lincoln Gorernment Approved Flight Training prepares you for any Pilot's License, Lincoln Government Approved À Mechanic's Training prepares you for your Mechanic's License, 4 Modern Training Planes, 12 Shops and Laboratories. Now in 28th year, 18th year teaching aviation, Lincoln Pilots and Mechanles in demand. We assist graduates in locating positions. WRITE now for complete information, State your age, LINCOLN AIRPLANE & FLYING SCHOOL, 402- H Alrcraft Bldg., Lincoln, Nebr. 24 D8) witiess Pocket » wreLess LOCReET A Bch WORLD'S SMALLEST REAL PERFORMING Amazing m et radio weighs only 3 Sas. complete. Receives R A D l (9) stations with clear beautiful tone. No static or interference. Nothing to ad- just or wear out, Should last for years. ENTIRE- LY NEW DESIGN! Not to be confused with cheap so-called Radios.” Music and programs COME DIRECTLY FROM GR RADIO. Has patented_new ‘‘Speakophone’’ which gives more volume and stations. NOT A TOY. Tunes broadcast band, police and alrplane calls, The newest radio sensation of the year. Absolutely complete with instructions for use in hotels, autos, boats, bed, ete. TAKES ONLY A SECOND TO CONNECT—no messy hook-ups to any current and no extra wires. SATISFIED OWNERS REPORT wonderful service in ALL PARTS OF THE WORLD! THESE ARE FACTS. Beautiful two color cabinets in six colors. SEND NO MONEY Pay postman only $2.99 t or send $2.99 (Check, will be sent postpaid. GUARANTEED. Can most unusual value, ORDER NOW! TINYTONE RADIO CORP. DEPT, M-4 “Pocket ILL OF lus postage on arrival . O., Cash) and yourg be used by anyone. KEARNEY, NEBR. HAVE YOU SOME SPARE ROOM a basement or garage where you ean do light work? We can offer you a profitable proposition, casting 5 & 10¢ novelties, ashtrays, toy autos, etc. as Manufacturer for firm of many years standing. No experience necessary as we furnish full instructions with moulds. If interested in devoting spare or full time to profitable work write AT ONCE stating age and space avallable as we are how closing arrangements for 1938 supply of our goods. METAL CAST PRODUCTS CO. 1696 Boston Road, New York, N. Y. Dent. 2, Learn WATCH REPAIRING AT HOME You can learn by our modern and orlginal system of Instruction every. Part of the Watch repairing Trade at home. You can earn money while learning and prepare yourself for a well paylng position or start In business after completing our course of Instruction, Good watch repairers are in demand and Generally earn very good salaries. For pare tlculars apply to the WISCONSIN SCHOOL OF WATCH REPAIRING 524 E. Mason Şt., Dept. Ç. Milwaukee. Wis. SAVE ONE-HALF—10c A DAY Nationally known makes, Recent standard models recon- ned, refinished. Fully quaranteed! Look and operate e newl ALSO PORTABLES, FREE SHORTHAND AND im TYPING COURSE. Easy terms or as low as $10 cash. ee FREE TRIAL! MONEY BACK GUARANTEE. Send for * illustrated circular and details TODAY. Special Prices on Duplicators, Addressographs, Adders, Multigraphs. PRUITT CO., 788 PRUITT BLDG., CHICAGO Write for free booklet describing *107 Plans for | Operating a Successful Business of Your Own”. @ tuma Ò Make from $20 to $100 a week starting in spare K a time at home. No peddling or house-to-house selling. $ Booklet sent free, and without obligation. Write for your copy today. t ELITE PUBLISHING CO. Dept. G 214 Grand St. New York, N. Y. t the best for your motor scooter? equip it with our DISC WHEELS and on Tires, Your choice of famous 2 (GOODRICH—G00D YEAR—FIRESTONE) S SS At lowest prices. We provide Scooter Kits at big ff X j Savings. Build Now! We also carry larger Tires, ¥ QF Wheels, Motors, etc. Write for prices. i BILD-UR-OWN DEVICES, 5237 Lake St., Dept. B-4, Chicago, Ill. § EARN GOOD MONEY Be our representative in your locality No experience Every business prospect. Advertising embroid- ered on garments great sales featare. Increase your income every Week. e supply everythin Deede onae tones, including PREE OUTEIT: Write immediately. BEN DOVE GARMENT CO., 801 S. Fourth St., Dept» 847, Kankakee. lll, for Dove Work Garments. necessary. Pleasant, simple work. Accept No Substitutes! Always Insist on the Advertised Brand!

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THIS NEW P-A @ Such beautiful tone, and so easy to play! Just toucha key and blow normally; you can’t miss. Nothing to com- pare with these new P-A Saxes, Clarinets, Trumpets, and other P-A instruments. Fully guaranteed; your suc- cess assured. See your music dealer or write direct for beautiful free book. No obligation, Easy terms. Greatest fun, easiest with P-A, Write today sure, 1284 PAN-AMERICAN 430 P-ABldg., Elkhart, Indiana BE SUCCESSFUL Read Invention & Finanee—it’s your chance to make money. Two year subscription $1.00 entered upon promise to pay on receipt of first copy, Place your order by cutting out and mailing this advertisement. INVENTION & FINANCE MAGAZINE 80-H WALL ST., NEW YORK,N. Y. ANY BOOK IN PRINT! your door. We pay postage. Standard authors, new books, popular editions. fiction, refer venes Medical. mechanical, children’s books, ete. —all at guaranteed savings. Send card now, for Clarkson’s 1938 Catalog, FREE x Write for our great illustrated book Catalog. A short course in literature, The buying guide of 300,000 book lovers. The selection_of_a mètro- politan book stere brought to your home, FREE if you write NOW—TODAY! CLARKSON PUBLISHING COMPANY Dept, MB, 1253 So, Wabash Ave., Chicago, HI. Delivered at APPRENTICES BIG PAY GOOD FUTURE If you are interested in working yourself into a highly pald position in Aviation under our Apprene tice-Plan—Write, immediately, enclosing stamp— MECHANIX UNIVERSAL AVIATION SERVICE CO, Strathmoor Station Dept. A Detroit, Mich. oe ay oe d iy SEND $ GET 2 DIFFERENT N ONLY BUNGALOW ir ees BLUEPRINT i $1 ea.) PLANS (22” x 17° 3 Build a beautiful inexpensive summer home from these plans, your family—gain vigor for winter tasks, RENT ie Reason when not living in it yourself. G-pese Easy building directions with all dimensions, Mr 1 satisfied. Charterock Corp., Dept, R, 79 Madisen Ave. LIMITED GIFT OFFER—5-fold carpenter's rude cae" oG each order. Send for your Free copy cf ‘‘List cf Dp —of Bargains in Military, Outdoor and Sport Goods, Clothes, Shocs, Boots, Blankets, Tents, Firearms, Boy Scout Sup- plies, erc. Send 10¢ for copy to be redeemed on first orders fh JEST. 1868 Formerly Army & Navy Supply Co.’ 4813 Lester Se, Richmond, Va.© When Answering Advertisements Please Mention April Modern Mechanix Jobs Now. DRAFTING Is VOUR Opportunity You'll be for emazed at the speed with which you can. jearn in your spare time. Let Engineer Dobe Train You at Home Engineer Dobe can prepare you just as he has trained thousands of successful students, aged 16 to 18 to past 50. His practical “Work-Job” method requires no previous experience. High school education not needed, He offers you a real opportunity to get a complete training in drafting right in your home in a surprisingly few months. Enginee! r Dobe teaches his students until thoroughly trained and until holding a good paying job. The draftsman has rich opportunities for advancement and better pay in scores of fields. In Machinery, Building, Aviation, Electricity, Transportation, Automotives—drafts- men must be used, Many trained draftsmen will be needed on better jobs at better pay and shorter hours. Open Mail the coupon today for FREE illustrated book ‘Successful Drafts- manship” and full detaiis of Engi- neer Dobe’s remarkable offer that includes all necessary tools and equipment. Learn just how you can be trained successfully at home in your spare time. Time is money. Now is the time to prepare, Don’t wait another day. Send the ccupon below NOW for Engineer Dobe’s FREE Book, SEND FOR FREE BOOK ENGINEER DOBE, Div. 4734, Libertyville, Ill. Send me your free book “Successful Draftsman- ship.” Please explain how you assist your graduates to good positions as draftsmen. THESE TOOLS. and other equipment“ FURNISHED When You Start Name Address TODD erea S x State . ... TUULT] N on

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© Make big money out of clubs, country estates, hotels, homes—every place which uses furniture, with our new electrically operated DETERGER, which washes upholstered furniture right in your customer’s home, with a new soap- less soap which it whips into DRY suds. We have helped hundreds of men get into business for themselves with our automatic equipment used by the U. S. Government and many of the world’s largest hotels. NO SHOP — NO STORE — NO RENT You save all of this money for you do the work, right in your customer's home, Burrett says “Made $28 in 8 hours.” Corson made $279.50 his first month, We want an honest, ambilious man in every loculity for the same kind of opening and if you are that man we will help you get started in this NEW Business. Only a limited amount of money is needed for the first payment— the balance you send on easy terms, The DETERGER is ready to run when you reesive it and If you follow our instructions you should be able to make money the first day. = BOOK, “Your Own Business” J Write tol:y for this hu Sent FREE! building book, i a brand new opportunity, Let us t it is to get started In a year around you are your own boss and can SLOP woi just a job, Write today—NOwW,. VON SCHRADER MFG. CO. 544 PI, Racine, Wisconsin Mator Speed Reducer Ratio 144 to 1; Ball per white metal housing up to 2 Equipped with Clutch for overload nally sold for $2 long, 6” wide, 5 Close out_price.............- SEND FOR FREE CATALOGUE of SPRAY EQUIPMENT. 860 W. Washington Blvd., ventesuor m. NATIONAL ELECTRIC TOOL CO., THE ATLAS HAS EVERYTHING I WANT Free NEW CATALOG All who see the Atlas pre- cision lathes and other shop equipment are amazed at the power, versatility and extra features of these modern ma- chine tools, See for yourself before you buy, Send for new 1939 Catalog today. ATLAS PRESS Co. 452 N. Pitcher Street Kalamazoo, Mich. 26 WORLD'S aoa RADIOS Just a bandful—Wt, only 2lbs,—Size 312x5"—4 tube performance! Midget BUILTIN LOUDSPEAKER and AERIAL—Re es no ground—Hi-efficiency circuit and quality parts s Broadcast, short wave and forelgn bands le to operate— dureble—trouble free, Ideal dio for Office, Aplis., Bedrooms, College, Campe, Trailers, Tourlats, ete, Battery model han h batteries inelde case for use on farme, boats, autos, ete. Electric model uses 0 A,C.D.C. Either model kit of parts for $6.49—Wired and checked 50c exire = 36.99 > ON ready to 1 Penutitut breakproof cabinets, State Color. SEND ON LY $1 and pay postman balance on avery, pat- teries for battery model $1 oe .) Free catalogue listing 100 other radios at factory price. Order a t Guaranteed. TINYTONE RADIO CO. KEARNEY, NEBRASKA = (SAVE Ti T OLD TIRE Amazing new plastinoid “putty” —S0-LO —fills cracks, holes in old tires, shoes, ONLY boots — anything of rubber, leather or cloth. Spreads on like butter. Dries tough overnight. Water- ~ _ proof, flexible, non-skid. Won’t 3 come on E teed! 25c package repairs) shows ) many uses. Get SO-LO at So-Lo any 10c or hardware store. Good Pay—and a Job with a Future Trained Railway and Bus Traffic Inspectors are in constant demand. Our graduates are pleced in po-itivns at up to $195 Der month, pius expenses to start, or we refund tuition. Rapid advancement for ambitious men—19 to 60, who complete our ea home-stay course. Write for FREE Book'et with FACTS. STANDARD BUSINESS È ORIGINAL CARTOONS at home that you a> RAYE BURNS SCHOOL, Dept 3, Box 2194, Cleveland, Ohio NOW—yon can buy WIHl’s fresh, genuine Eclipse cellent duality SIL at only Gie per 37 ft. coil, TRAINING INSTITUTE, Dh. 6104, Buffalo, N. Y. E = COPY - LEARN TO ORIGINATE! RAYE BURNS will teach you HOW to Frou an 98 8 SELL! Course has 26 lessons and 600 illustrations, Send name and address for free details. Only... Earn Money, Too ! SPLIT GUT tennis strings direct-from-factory for as little as $2, PER SET postpaid. Also—exe postpaid. Rush your order now! _ Satisfaction GUARANTEE New 1933 CATALOG of Tennis es. Vise: gauipment now ready. Get Boe š L FREE copy. Send today. . E. WILLS CO., Dept. ad 2354, 1047 W. 47th st; CHICAGO, U. S. A. HOME WORKSHOP FANS Get full advantage from your shop by building that project you have long had in mind. No doubt you'll find it explained fully in the 1938 How-To-Build-It book which contains plans for making midget racers, auto trailers, furniture, radios, games and toys. Send your 50c now for this big 148-page book—-contains 500 pictures and plans all in rotogravure, MODERN MECHANIX PUBLISHING CO. Fawcett Bldg. Greenwich, Conn. Accept No Substitutes! Always Insist on the Advertised Brand!

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a SOPRANI Simplifies @ Lighter, easier to play, lese bellows- ing, plus more beau- tiful tone and vọl- ume, — that’s how Soprani’s exclusive Ampliphonic fea- ture has simplified this accordion. As- sures rapid prog- ress. Home trial. Easy terms. Seeyour music dealer or send for beautiful free book. Write today. | SOPRANI, INC. °° tetesa maene VENETIAN BLINDS Make your own at low wholesale cost. It’s easy under our unique plan. All materials supplied. Send 20c for circular and samples of Ladder Tape, Cord, Rails, Slats, 15 color samples of tape and chart listing most decorative and attractive color combinations. VENETIAN BLIND MFG. & SUPPLY CO. 1760 Lunt Ave., Chicago, Ill. AMPLIPHONIC œ ) Playing Nunzio, NewYork, N with his Soprani s Minnows, Eels, Mink, Musk- rats, ete., in forge numbers with our Folding Galvanized © STEEL-WIRE TRAPS. They catch them like a fly-trap catches files, Write for our FREE TRAP OFTER, bargain catalog anf other specialtles. SURE LURE, makes 'em bite day or nighi. New principle used, it coaxes fish. Put up in tubes 5_inches, Price 30¢, 4 tubes for $1. Walton Supply Co., 3501 A-Juniata St., St. Louis, Me. The Plastex Industry needs manufacturers on small scale and for big production of Art Goods, Novelties, Souvenirs, etc., in Plastex and Marble Imitation. Experience unnecessary. Equipment and simple instructions furnished for speed production. Small invest- ment brings big returns. Nation-wide demand for these low priced goods. Ambitious men have chance for real prosperity. Our free book will interest and benefit you. Big wholesale season now starting, PLASTEX INDUSTRIES, Dept. 3, 1085 Washington Ave., New York, N. Y. easily, Absolutely 33c a day. Lundreds direct at low factory price A trial—satisfaction guarar dy for your free colorful catuloz. PIONEER MFG. CO. Dept. H-48 West Allis, Wis. YOU MAKE ro 100% —on Fast-Selllng Carded Product! Build 2 Retail Store Route with BROMO-PHOS; remedy for headaches, sour Have your own effervescent stomach, heartburn, ete. permanent REPEAT ORDER BUSINESS in your territory, NO-RISK STARTING OFFER! Write BROMO-PHOS, 741 Wal- ton st., Dept, 196, St. Louis, Mo, NOT WANTED MEN CONTENT WITH THEIR PRESENT INCOMES IF you're satisfied with what you're making — If you're content to just hold onto your present job—If you see no advantage in modernizing your training — Then — This coupon doesn't in- terest youl e BUT — If you'd like to follow the path to more money, already blazed by thou- sands of ambitious men, then this coupon may be the turning point in your earning careerl INTERNATIONAL CORRESPONDENCE SCHOOLS Box 2317-0, Scranton, Penna. Without obligation, please send full particulars about the sub- ject before which I have marked X: TECHNICAL AND INDUSTRIAL COURSES U Architect D Diesel Engines O Architectural Draftsman O Aviation Eng, O Auto Mechanio £ Building Estimating O Plumbing J Heating J Contractor and Builder O Air Conditioning and Cooling D Structural Draftsman O Commercial Refrigeration J Structural Engineer Steam Engineer O Electrical Engineer O Steam Electric Engincer O Electric Lighting DO Marine Engineer D Welding, Electric and Gas D CivilEngineer C Highway Engineer O Reading Shop Blueprints C Bridge Engineer O Telegraph Engineer C Bridge and Building Foreman D Telepho: V G Radio Surveying and Mapping 2 2. R. Locomotives O Air Brakes t. R. Section Foreman R. R. Signalmen C Chemistry O Pharmacy O Coal Mining C Navigation O Cotton Manufacturing O Woolen Manufacturing Treatiwens of Metala O Agriculture O Fruit Growing gement of Inveations O Poultry Farming BUSINESS TRAINING COURSES J Business Management O Lettering Show Cards J Industrial Management O Stenography and Typing J Trafic Management O Civil Service J Mail Carrier OC. P. Accountancy D Railway Mail Clerk O Bookkeeping O Grade School Subjects O Secretarial Work D Tigh School Subjects O Cost Accountant O College Preparatory O Salesmanship O Advertising D First Year College Subjects O Service Station Salesmanship O Iustrating O Spanish O Business Correspondence O Cartooning O French D Signa DOMESTIG SCIENCE COURSES O Professional Dressmaking D Millinery O Foods and Cookery O Tea Room and Cafeteria Management, Catering and Designing O Home Dressmaking O Advanced Dressmaking Name... Address. City... Present POSiLtON.......ecvcccceveceercessnneeeceeete nance ec eeee cnet tee eeenbat ete es wniesienia If you reside in Canada, send this coupon to the International Correspondence Schools Canadian, Limited, Montreal, Canada When Answering Advertisements Please Mention April Modern Mechanix 27

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Built entirely from salvaged parts of old automobiles by 78-year-old M. O. Stetler, of Kingfisher, Okla., this garden tractor features six forward speeds and a one-wheel brake. AWARDED first prize of $5 in this month's Workbench contest, a letter received from Bob Stetler, of Kingfisher, Okla., will undoubtedly interest many of our rural readers. The letter says: Dear Editor: Enclosed is a photo of a home-built yarden tractor made by 78-year-old M. O. Stetler. The parts were all taken from discarded autos and trucks, the engine, frame and transmission being sal- vaged from a 1928 auto. The front axle was taken from a popular car, but was shortened and inverted to give greater clearance. The rear axle is from an old truck. The engine incorporates a centrifugal-type governor, driven by a fan belt and controlled by a choke assembly running through the steering column. Braking is ac- complished by means of a lever and shoe attached to the right rear wheel, Bob Stetler We don't know w? Stetler, builder of don’t blame him for being proud ci craftsmanship. k arenes tkk Midget racer fans will be interested in a letter received from Charles and Francis Dusch, of Ashland, Pa., which was awarded a prize of $3. The letter reads: Dear Editor: We are sending you two pictures of our midget racer. It was built from plans that appeared in MM quite some time ago. The car weighs 136 pounds and has a four-foot wheel base. It attains a speed of about ten miles per hour, powered with a 34-horsepower washing machine engine. 8 to Due to the size of the car, we were forced to change the position of the engine, which is connected to the rear wheels by a combination belt and chain arrange- ment, as shown in the photos. We will gladly answer questions from MM readers if they enclose a stamped return envelope with their letters. Charles and Francis Dusch, Here is a chance for you midget racer “bugs” to correspond with two brothers who undoubtedly are good craftsmen. kkt A letter from Howard Allen, of Hammond, N. Y. describing his home-built outboard motor boat was also awarded a $3 prize. He says: Dear Editor: I am enclosing a photo of “Buzzer”, built from plans in the MM book—"How To Build 29 Boats’. I built the boat a little heavier than called for in the book, but it goes 27 m.p.h. with a 22 horsepower outboard motor. The boat handles very nicely and I have been out during some of the strong winds that sweep the St. Lawrence River, shipping very little water. Several people have admired the boat and said they were going to send for the plans. Please print more boat plans In the future. Howard Allen. Charles and Francis Dusch proudly pose with the midget racer they constructed from MM plans, The close-up shows details of the tiny car which is powered with a 3⁄4 -horsepower engine. Modern Mechanix

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Boat fans will readily admit that Allen’s “Buzzer” has trim lines and the strong winds and rough water evidently proved its sea-worthiness. How about it, fans? Why not get a copy of the MM boat book (price 50c) and build a “Buzzer,” too. Make summer time boating time. aK Model plane enthusiasts are usually prolific builders of solid and flying models, but how many can equal Marshall Anderson, of North Warren, Pa., who, in his letter which was awarded a $3 prize, states that he has built 35 models? He writes: Dear Editor: I am sending you a photo show- ing a few of the 35 airplane models I have con- structed. I would like to see plans for a compressed air model in MM. I am 16 years of age and would like to hear from fellows who are interested in model plane build- ing. Please men- : tion this if you An unusual overhead view o . “Buzzer,” built by Howard Allen. prin ni cers! Good work. Marshall. Buz models is quite an achievement. that other MM model plane tens will re giai z: correspond with you. Marshall Anderson, a prolific MM model plane builder, is shown here with a few. of the 35 flying models he constructed. April, 1938 This splendid action “shot” was sent in by Tom Griberg. Ie shows the MM “Sunray” sailboat he built at a cost of $84.01. Tom Griberg, of Moline, Ill, sent in a letter which was awarded a $3 prize. The letter reads: Dear Editor: Most of the pictures you print of sailboats built by reacers show the boats either moored or sailing G e-ciosing a real action photo of “Sunray”, Vie have found that even with a 170- pounce man sitting on the low side and the water run- ning along the top of the cockpit coaming, the boat is still stable. My “Sunray” was built in five weeks of spare time at a total cost, including sails made from airplane fabric, of $84.01. For the second season of sailing, I replaced the centerboard with a metal fin. Tom Griberg. ‘a Ve We try to get action photos of all boats built by MM readers, Griberg, but most of the photos submitted show the boats moored, as you say. Remember this point when sending in photos of your boats, readers. ek An interesting letter received from Charles Fottler, of Dorchester, Mass., was also awarded a $3 prize. His letter reads: [Continued on page 31]

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: 7 irc Welding | Revolutionizes modern Industry | U S Manufacturers desire men to learn Elece tric Are Welding and get practical experience under actual production conditions in the laboratories of the School of Engineering. Moderate training Fee. Accepted applicants will be fully trained until ready to pass rigid test and assisted in securing employment. Arc Welding presents one of the outstanding op- portunities for steady. income and future success, Welding is growing rapidly, replacing large and intricate castings, rivets, nuts, bolts, screws. It is comm nly used in assembling . . Engineering eranes, s, bridges, structural steel work, etc. No limit to the application of welding to indus- try, increasing durability and reducing manufacturing costs. There is a decided shortage of properly_trained Welding Operators, Technicians and Welding Engineers. Why be content with ordinary work, hit and miss jobs and LOW pay when in a short time you can become a trained Specialist in Welding? we MIL WAU K E Ee ACHAL of ENGINEERING 9 Sndtitute of Electrotechnics MM-438 Broadway and E, State, Milwaukee, Wis. oeooe Without obligation _send. Free Booklet ‘The Industry and Its Outstanding Opportunities.” Also tell me how to become a Welding Operator (3 mo.).--. Gas Welder (6 wks.).------ Welding Technician (6 mo. Welding Engineer (1 yr.).--= Electrical Engineer B. S. Degree (4 yrs.)_ Student Loan Plan_~. Refrigeration and Air Condi- tioning Technician (8 mo.) Air Cond. Engr, (1 yr.)---- Radio, Television (6 mo,)_-.--- Commercial Radio Engineer (1 yr.) Earn Part Expense Plan__----- Name MM-438 move. DRAW-O-MATIC *"scano ATTACHED, SLIDING, SELF-ALIGNING, PARALLEL-BAR With Set of A SELF-CONTAINED UNIT BUILT Triangles TO A STANDARD OF QUALITY. Thousands in use by Draftsmen, Stu- dents, Architects, Artists, Engi- neers, Designers and Executives. Herd composition board rtays flat Bar elidon uc- n À WII Last a nates thur ifeti Agonis wanted ï Breme AGGURACY A ” WITH AC bs 12/16" 00, 197120” $4.00, 20x25” $5.00 plus postage. Aco 15 seen ooo y Edas and triangles ere dæired. FREE CIRCULAR. ROLLIN PRODUCTS CO. Dept MX8, 212 W. Hubbard SL, Chicago, IEinsis ron jo-l2 WEEKS FOR SHOP TRAINING EASY PAYMENT PLAN Get Details of My Amazing Offer! Prepare for, jobs in the many p able branches of Radio by twelve weeks of practical Shop work in the great Coyne Radio Shops, on real actual equipment. You don’t need advanced education or experience. Free Employment Service for life, Many earn while learning. Mail coupon today for free book which tells you how hundreds have becomc successful Radio men after getting a training and all details of my ‘‘Pay-Tuition-After= Graduation’’ Plan. H. C. LEWIS, Pres., COYNE RADIO SCHOOL | 500 S. Paulina Street, Dept.48-1H, Chicago, Illinois Send Free Radio Book and facts. Tell how 1I can pay for my gourse on easy payment plan after getting my 12 weeks’ raining. NAME ADDRESS CITY. AGE — You can do almost anything with the WHIZ ELEC. TRIC POWER TOOL. Sharpen knives, selaaors, toole; grind axes, dies, molde; remove paint, rust from autosfenders, woodwork, and metela; smooth finish off machinery castinga: w metala, wood: drill holea in steel, woud; h glass: polish metsis; and 1001 other jobs—In the heme workshop or face tory, Ready to work the Inatant vou p ug It into any light socket—110 volt, AC or DC powerful mator, 1/4 inch chuck capacity, ball beating thrust, STAND- ARD M“DEL with Normal Speed (uses 50 different accessories) only $6.95. FREE Accessory outfit (Value $2) includes set of drills, mounted 11” grine der, sanding discs, cutting wheels mounted brush, poliehing wheel ete, FREE with each outfit ordered NOW. We EY postens. on all shipmentes will send C.O.D. if desired. 10 DAY TRIAL—-MONEY BACK GUARANTEE. SPECIAL “2-SPEED” MODEL, combines Normal Speed and High Speed In one éutht (uses 200 different accessories) only $8.95 comple’, including set of acces- sorles FREE, PARAMOUNT PROD. CO., Depl. 4-8, 46 t 48th St., Now York Learn Public Speaking Athome—in spare time. Many overcome **stage-fright,’* gain self-confidence, and increase thelr earning power, through abllit: to sway others by effective speech, Write for free booklet, How to ork Wondera With Words and requirements. NORTH AMERICAN INSTITUTE, Dept. 2054 3601 Michigan Avenue Chicago, Minois E ee = a — do~it—with—squabs Marketed when only 25 days old. Write a post-card, get FREE EYE-OPENING Picture Book. Why breed for ordinary markets are wide open for all the SQUABS you can ship, every day in the year? Go after this desirable, profitable trade now. Write today to trade when these great luxury national RICE FARM, 602H St., Melrose, Mass. Send for FREE BAIT BOOK This practical handbook, for fishermen, is a fascinating, reliable guide to better fishing! It tells how and why Creek Chub True-to-Nature Lures and Flies Catch More and Bigger Fish! Beautifully luse trated! Sent FREE upon request! CREEK CHUB BAIT COMPANY 434Randolph St. Garrett, ind. WANTED: AMATEUR Newsreel Photographers NO EXPERIENCE NECESSARY—WE SUPPLY ALL EQUIPMENT, tR derate cost. We want Representatives, Full or Part time, in af the country. Fascinating work, Good pay, Send and Address with letter of Application, Enclose ply ng full details. ASSOCIATED NEWS REELS i431 Broadway, New York, N. Y. PATENTS Personal service Strictest con- fidence on all your patent problems. Send PERSONAL SERVICE me a model or draw- description of your invention, and $5.00. xê a search and report promptly as to its patent- ability and send you a copy of my 72-page booklet. Or, if vou prefer to read my booklet first, write today for FREE copy. Registered Patent Attorney. L. F. Randolph, 341 Victor Building, Washington, D. C. HOME WORKSHOP FANS Get full advantage from your shop by building that project you have long had in mind. No doubt you'll find it explained fully in the 1938 How-To-Build-It book which contains plans for making midget racers, auto trailers, furniture, radios, games and toys. Send your 50c now for this big 148-page book—contains 500 pictures and plans all in rotogravure. MODERN MECHANIX PUBLISHING CO. Fawcett Bldg. Greenwich, Conn. 30 Accept No Substitutes! Always Insist on the Advertised Brand!

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Editor’s Workbench Chips [Continued from page 29] Built by Charles Fottler, this practical power-driven saw is capable of sawing lumber up to four inches in thickness. It is pivoted on a bench so it can be operated at many angles. Dear Editor: I am sending you a photo of a sawing machine that I built last winter. It is powered by a 144-horsepower gasoline engine and cuts lumber up to four inches in thickness. The saw is pivoted to a bench so that it can be set to cut lumber of any length at various angles. The engine, of course, is stationary. One gallon of gaso- line runs it for eight hours. : Charles Fottler Practical projects always interest MM readers and we wouldn’t be surprised if Mr, Fottler re- ceives many letters asking for full details of his home-built power saw. DET Now is the time of the year when home crafts- men should check over their workshop. making a list of all tools and other equipment suchas to ascertain just what items are needed in order to bring the “shop” up to maximum operating efficiency. For mechanically minded readers, no project presented in MM is too difficult to tackle. whether it be an off-shore sailing cruiser. a midget racer, or a simple model plane, provided the proper tools are at hand. It is not always a question of how many tools you have, but how good are the tools. Build up your workshop, tool by tool, but make sure you purchase such equipment from nationally advertised manufac- turers who have reputations for producing quality products and who will treat you fairly. A list of addresses of manufacturers of items mentioned in MODERN MECHANIX will be sent to any reader upon receipt of a stamped, return envelope. ‘was damage or destroyed ? y Smokes! can’t Hol l Every polic states thot a complete list must be supplied. QUSEHBLD F R EE Be Frad : KEEP THIS BOOK IWA SAFE PLACE 2! AMERICAN INSURANCE CO. | 15 Washington St. (Dept. 21/1) Newark, N. J. Gentlemen: Please send me a copy of your free “HOUSEHOLD INVENTORY” booklet. It will help me list, room by room, the things covered by my fire insurance, I want to be ready in ease a fire occurs, I under- stand that this book will cost me noth- ing and will not obligate me in any way. Name Address. Place _________-__-State. [PEs enseeseesseeessessee When Answering Advertisements Please Mention April Modern Mechani# 31

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High School Many Finish in 2 ==, Go as rapidly as your time and abilities permit. = Equivalent to resident school work—prepares for T entrance to college. Standard H. S. texts supplied. = Diploma awarded. Credit for H. S, subjects already f ©) completed. Single subjects if desired. Bulletin on request. ` Specialized training is absolutely essential to Success today. Over 150 noted Educators, Engineers and Business Men helped prepare our spe- cial instruction material, used by g p resident schools and colleges, of WN Navy and Province of Mani- toba, Can. Train at home for best-paying lines as listed below. No interference wi present earn- ings while preparing for better J American School, Chicago American School, Depts H- 428, Drexel at 58th, Chicago Tell me how to train for success in line checked. s | igh School Course i in 2 Year: Air Conditioning Electrical Refrigeration Architecture. and Building Highway Engineering Automotive Engineering Liberal Arts (College) Aviation Mechanical Engineering Business Management Private Secretary Civil Engineering Professional Accounting Complete Law incl. C. P. A, Coaching Diesel Engineering Radio and Drafti! nd Design Salesmanship Electrical Engineering Steam Engineering Name.... Start a POTATO CHIP BUSINESS IN YOUR KITCHEN and MAKE MONEY! UY potatoes for 2¢ a Ib. sational new ‘‘Greasel Chips and sell for Ideal business for men or women spare or full time. | JL investment buys complete equipment. No expe- rlence needed. I show you how to get. to sell all you make; tell you how to emake profit first day. information, pictures, prices and terms sent free. Send a postal card for Free Facts on big ‘‘Home Business’? aaa G. H. HARDT, Dept. D-244, 325 West Huron $ Chicago, IN. IE WWRITER Ye Price Easy Terms oe 10c a Day Save Mig'a~i Origl. Price on ell standar up-to-date office models. SEND NO MONEY Benmtional saving on all lato models m come pletely refinished like new. FULLY GUAR. Feather ED. Big Free Catalog ehowaall makes in Weight. Aull colors. Send post-card for lowest prices Mode bec PORTABLE BARGAINS = AT The biggest bargain we know of] Nothing like it anywhere! ONE Card contains 30 high quality, easy seine tams Heva Lat Aspirin, Razor Blades, Perfume, ete., ete. Costs only SL ou make almost 100% profit! You can’t miss on this POST PAID — it's red hot! Yet it’s only ONE of our many SMASH-HIT items, We have 220 others. 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This scooter is not a toy but a m™—"vehicle that has proven itself to be a practical, healthful and economical method of transportation. This scooter is also easily adaptable to a light, quick delivery rig. POMEROY MFG. CO., La Crosse, Wisconsin, U. S. A. FREE RADIO PROFITS ENE! ROA Victor. FB tiie, GB Peete perso" mers BUY WHOLESALE—SELL RETAIL p= seeps S j i = radios for bie prolis. AGT AT ONCE! WAIE CSO FSi Eo RADIO DISTRIBUTING COMPANY SALES PLAN 106R NORTH HALSTED STREET CHICAGO, ILLINOIS SENT TO SERVICEMEN py US! am. SHOW wee SIGNS ; CARDS N POTERNE IETTENNÉ" N Write Dept. REGINA SCHOOL OF ‘LETTERING W. Washington » Chicago, STOP Backtracking = Haven’t you often driven the wrong road and had to backtrack many miles? The Huil Stream- line Auto Compass always shows your direc- tion of travel, prevents backtracking, saves money and time for only $2.95 at your dealer. Two-piece model $1.95. Write for circular. HULL MFG. ÇO., P. O. 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Send for FREE bookle PANDICULATOR CO. 416 NewmansternBidg., Cleveland, O. 32 Accept No Substitutes! Always Insist on the Advertised Brand!

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Free Catalog Just Off the Press Fully illustrated, showing special footwear and clothing for fisherman and camper, also special fishing tackle. L. L. Bean, Inc., 174 Main Street, Freeport, i | { | | | Maine in Mado-fo-Order Sults Show friends Made-to-Order Clothes ‘Styled == for the Stars’’ at big savings. New Fashions, Fabrics, In- spired by Hollyswood’s fashion plates, Buddy ot] . Take orders spare time. arn big prod your own osutt s Free as bonus, Our clothes guaranteed to and satisfy. Big outfit 100 large samples Free. Write today. JIM FOSTER, INC., Dept. G-4 2253 So, Spaulding Ave. Chicago, Illinois LECTRICA ° ENGINEERING * ONE YEAR condensed course prepares for technical work in the electrical field. Thorough training in principles, with practical applications in loboretory and shop. High placement record. Modern buildings, dormitory, dining hall. Campus. 46th year, Catalog on request, ELECTRICAL SCHOOL W BLISS “amuse Rogers, Cesar dy Radat Washington, D., C, [MIDGET RACING de ion, öö C. 0. D. RAY F., KUNS, Dept. A-16, Madisonville, Cincinnati, Ohio. Brand new way to refinish cars quickly. Restoren, a color like new, Selling lke wild OVER 20,000, 00 PROSPECTS Keeps car Hooking like new paint job. zoc sample refinishes 2 cars. Give car colors. Profits Guaranteed To Aaents AMAZING 3-way plan makes this best moneyinaker in years. Write before best AUTO. Wi gon KÖTE C Dept. AYT DN o. OTRE Bie. Chicago, Ul. ENTARGEMENTS Ta Photography your hobby? Do you want a profitable eas business at hume? Make OTO ENLARGEMENTS [or yourself end otbers. Your cost Sc each and lege, The Ideal I’hoto Enlarger is AUTOMAT- No experience required. Also ANY "COPIES any picture. $5.94 COM- PLETE. Interesting circular FREE > IDEAL-¥ 122 Encl 25th Street, REW YORK CITY SIZE THERE'S MONEY A) IN YOUR CAMERA! Others make good in- comes selling pictures to ublications. FREE BOOK- ET describes home-study course. (which may be paid for In easy install- ments) and tells how YOU can do it, toot . 334, 10 W, 33 St., N. Y. C. “GOVERNMENT START $1260 to $2100 a Year MANY 1938 APPOINTMENTS EXPECTED Rallway Postal Clerks Railway Postal Clerks get $1,900 the first year regular, being paid on the first and fifteenth of each month. ($79.17 each pay day.) Their pay is automatically increased yearly to $2,450. Advance may be had to Chief Clerk at $2,700 a year. ($112.50 each pay day. ) 3 r usually work 3 days ani ý à woportion, During this o though they were working. They travel & iness. When they grow old, they are retired City Mall Carriers, Post Office Clerks Clerks and Carriers now get $1,700 the first year on regular and automatically increase $100 a year to $2,100 and $2,300. Customs Inspector Salary $2,100 to start. Men 23 to 45. Work connected with examining baggage and merchandise entering the country from foreign parts covering boats, trains, roads, automobiles, etc. Many Other Positions Many other positions are obtainable. Those wishing these positions should qualify at once. Get Free List of Positions Fill out the following coupon. Tear it off and mail it today—now, at once. : . n 7 This investment may result in your getting a big-paid government Job. Le eee ee ee ee ET FRANKLIN INSTITUTE, Dept, N262, Rochester, N. Y. Rush to me, entirely free of charge (1) o full description of U. S. Government Jobs; (2) Free cony of illustrated 32-page book, “How lo Get a Government Job’’; (3) List of U. 4. Government Jobs; (2) Tell me what to do to qualify for a U. S. Government Job, ‘CUSTOMS INSPECTOR Name serere Deedee ene e anne ere t erence er eernaeeree ee Address Use This Coupon Before You Mislay It. Write or Print Plainly. When Answering Advertisements Please Mention April Modern Mechanix 33

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“Merrimac” Had Tallow Protection NIC SPRANK OFFERS $5.00 FOR BEST ODDITY ALLOW PROTECTED MERRIMAC” -TO DEFLECT CANNON BALLS, THE SLANTING SIDES OF THE CONFEDERATE WITH TALLOW. NINE YEARS AGO THIS MODEL 2, Gott, Brooklyn, lowe. oo gg LOCOMOTIVE HIT A 120-MILE PER- es “ HOUR SPEED, IT WAS DESIGNED TO HAUL A FREIGHT TRAIN FROM NEW YORK TOSAN FRANCISCO IN 24 HOURS- ÆA. Page Jz, Rockford, Il. oes Zz La og GREASED LIGHTNING LELES ` [PILOTS]. LICENSE ; /-MERE Bors LICENSE FOR MODEL PLANES !- IN MASSACHUSETTS AND CONNECTICUT PERSONS Geers |i NOX E WHOFLY MODEL PLANES a i Cee la, SY WY. POWERED BY GASOLINE "A YEAR Y OFA ENGINES MUST FIRST OBTAIN THE ASPIRIN COMSUMED. YEARLY A PILOT:S LICENSE FOR REAL THE UNITED STATES, IF PLACED END TO END, PLANES.— WOULD STRETCH 29,553 MILES,OR MORE THAN David Score Mintirpelass ENOUGH TO ENCIRCLE THE EARTH-V/Prientvall Chester. Five dollars will be paid for the oddity selected by Nic Sprank as the best of the month. One dollar will be paid for-all others used on this page. Send your oddity to Nic Sprank, Editorial Office, Modern Mechanix, 1501 Broadway, New York, N; Y. Source or proof of each oddity must be given. Send all oddities separately, not with other manuscripts or letters. 34

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Volume XIX No. 6 APRIL 1938 Robert W. Gordon ETWEEN the well-meaning idealist who would have us disarm completely in a world that is arming to the teeth, and the alarmist who sees our cities wiped out in a day, there seems to be a wide divergence of opinion as to just what our defensive needs really are. Before the question can be in- telligently. decided, before the taxpayer can be sure he is getting adequate war insur- ance at the minimum premium, it is neces- sary to define what we mean by “defense.” There are several ways in which the United ` States might be drawn into war.. For in- -stance, there is Alaska, a vast sprawling treasure house, rich in gold, silver, copper, coal, oil, lumber, fish, seals and reindeer. At this writing, Japan is already raiding our salmon fisheries. If she gets away with this, might she not be encouraged to appropriate the oil fields, which she desperately needs? 35

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Certainly we would defend Alaska. Then there is the Panama Canal which, in addition to its enormous commercial advantages, saves us the expense of main- taining two fleets. We would fight to pre- vent the canal from being destroyed or falling into foreign hands. And the Hawaiian Islands! We would never permit a foreign power to seize them _ and thus establish an important base off our Pacific Coast. Getting out of the realm of fact, into that of political speculation, would we en- force the Monroe Doctrine in case of an aggressive move by a foreign power in either Central or South America? Would we feel obligated to defend the Philippines, shortly to attain their inde- pendence? Would we defend our trade and citizens in foreign countries or traveling on the high seas? Would we again attempt the role of defenders of democracy throughout the world, as we did in 1917? The continental limits of the United States are not in much danger of being in- vaded—as long as we have our fleet, now the second largest in the world. The time may come when an invasion by air is possible, but we need not worry about that now. Planes can now fly the Atlantic in one jump, but none can make the round trip, carrying a worthwhile load of bombs one way. Any troops that could be flown ‘across could be handled by the local police. Invasion of the United States, it is gen- erally conceded, would have to come by sea. And no such invasion would ever be at- tempted as long as our fleet was in existence, unless it should be caught in the wrong ocean and held there by destruction of the Panama Canal. The Canal, for this reason, needs to be made impregnable. Its present defenses consist of a mobile brigade to repel landing parties, our air force, anti-aircraft artillery, and coast defense guns, which are adequate to protect it from a raid (unless it should be a surprise raid made before a declaration of war). Its major defense is the Navy itself, which alone can prevent a major operation against it, Since such an attack would have ‘effectively. blc plocke by the simple expedient „of blowing u ‘Up ing through it - done before ugh agua, would be an ex- caflent defensive investment, far less Realizing the value of aircraft as fighting and scouting auxiliaries, the U. S. Navy has added another carrier, the S. S. Yorktown (be- low), to its fleet. Circle —Taking off from the flight deck of the U. S.-S. Lexington. one

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= _ fire—there is no reason to suppose _ they cannot stand up as well agains versy is in the same category. capital ship has ever been sunk by ~ “blisters” _ "Waterline - to ex ee plenish its ammunition supply. Such bases must be strongly defended by anti-air- craft and coast defense guns, and a land force strong enough to repel surprise raids aimed at their destruction. We have four such bases at New York, Norfolk, Puget Sound and Pearl Harbor. We have an undefended base at Guantanamo Bay, Cuba, which should be fortified, for it is vital to the defenses of Panama. Since the Key West —Havana route is the line of supply for Guantanamo, Key West should also be strongly fortified. We also need another base on the west coast. Complete docking facili- ties are all that is necessary to make San ‘Diego. such a base. It has been frequently asserted that a navy is obsolete, since an airplane bomb can sink any ship. This has yet to be proved, for no first line, battleship has ever been sunk by an aerial bomb. In the Battle of Jutland, 50 capital ships hurled big caliber shells at each other for hours, yet only one battleship - was sunk (there were 24 other ships sunk, but all were cruisers or lighter craft). 14-inch shell and a one-ton bomb are about equal in destructive effect, the shell having — _a greater armor-piercing quality. Long- range shell fire falls almost vertically, and decks are armored to withstand such bombs. A well-placed bomb can, of course, sink any other type of ship. — The “submarine battleship contro- Nae -a submarine. - (false Ê Battleships have es) below the—, ode torpedoes _. F- S = Although it is claimed that submarines have never s a capital ship, their ability to observe enemy ports and coasts unseen while operating against merchant marine vessels has resulted in the building of more underseas craft by foreign nations, as well as by the United States. One of Uncle Sam’s sub- marines, the P-1, is shown below. Circle— ` Obsolete World War equipment is still used by the U. S. Army Signal Corps for training purposes due to lack of modernized apparatus. before they can do serious damage, the hulls are minutely subdivided as well to localize the damage of any penetration. Besides, battleships never operate without their protecting screen of destroyers, which, with their hydrophones, depth bombs, and great speed, are more than a match for any submarine. So the Navy needs battleships because they are the only type of ship that. can fight other battleships. It needs cruisers —fast long range ships—to fight off lighter craft, and to scout and locate the various components of the hostile fleet. The Navy also needs destroyers as pro- tection against submarines, to make fast torpedo attacks against the hostile line (too many torpedoes, just as too many shells or bombs will sink even a battle- ship), and to lay smoke screens in front of the big ships to prevent accurate, aimed fire from the enemy’s surface craft. | Because of such smoke screens, as well as because of the extreme range of big guns, battleships must have airplanes for

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spotting their own shell fire. To protect the spotting planes, fighting airplanes are needed, and for this reason we must have enough air- plane carriers to transport these planes, which can also be used for bombing and scouting operations in co-operation with the fleet. ‘Although submarines aren’t much good in fleet operations, they are needed for ob- serving enemy ports and coasts unseen, for helping to locate the enemy fleet, and for operating against lone ships of inadequately protected convoys. Various types of auxiliary ships, such as airplane, destroyer and submarine tenders are needed. Such ships operate with the fleet and are capable of performing almost any repair, no matter how great, for the craft they are designed to service. such as oilers, ammunition ships, store ships, ocean tugs, hospital ships, mine-layers and mine-sweepers are also needed. Our Navy is said to be particularly deficient in these auxiliaries at present. Any one or several of these types of ships Other ships, . = Used for reconnaissance by officers, armored cars like the one x equipment, | is peeded to fully modernize the Regular Ar could be dispensed with, if other naval powers dispensed with theirs, but to be deficient in any one type would invite defeat in case of war. There is no such thing in warfare as second prize. “You either win or lose. Our Navy should be strong enough to win within its own operating range. This operating range is the distance from the base in which it can operate as a complete unit, and is limited to the range of destroyers, which is . 2,500 miles. Though the Navy is the first line of defense, we cannot afford to depend upon it alone. Should it be defeated, should it be afloat in the wrong ocean through the blocking of the Canal, or should we be attacked simulta- neously by a European and Asiatic power, we would have to count on our other arms. The Air Corps would be the first to. see action. Highly mobile, our entire fighting force could be assembled at one point within 24 hours. In an action near our shores the long range bombers (of which we now have the best in the world) could patrol the seas, either alone or in conjunction with the Navy. Having discovered an approaching force they would attack with bombs, but it is doubtful if the Air Corps alone could prevent a land- her on our own shores or in adjacent Canada or ‘Mexico. | A landing force would then have to be expelled by adequate forces ` representing all service arms.” shown at left are helping to modernize our army. However, great numbers of these cars, as well as other mechanical iceaft and naval operations, diis battery ‘al p uns (lower left) would play lawaii in event of war. Below : E idir with a new type i is

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Much more likely than this sort of a war, though, is an invasion of Alaska or the Philippines. There is little question that we would fight in either event, yet we are now inadequately prepared to resist such an in- vasion. Our Naval base at Hawaii is 5,000 miles from Manila and about 2,000 miles from southern Alaska. If we plan to hold Alaska, we need a naval operating base at Dutch Harbor, and an Air Corps base farther inland, with the necessary coast and anti-aircraft defenses, plus enough ground troops to resist any landing attempts near these bases. We do not need a large army, but the one we have should be highly trained, and equipped with the best weapons available. While our Springfield rifle is the best military rifle in the world, the fire power of the infantry could be increased five times, by equipping them with semi-automatic rifles. We now have only 3,000 such rifles. We should have at least 50,000. Until recently our Army had only six modern tanks—not nearly enough for train- ing purposes. This amazing deficiency has been remedied, but we still need more, Two _ hundred would be a conservative“ mini- mum in view of world affairs. We have four thousand °75’s left over rom. the World War. An excellent weapon in its day, we have since developed a field piece that weighs the same, yet fires twice as far; and it can be towed at fifty miles an hour behind trucks. The old dione aT gun is. damaged if towed faste i miles ani prov, ds Designed to upport for ie 73 mm. howitze ec tegag 7 ean tol „the: iÀ modern guns and this is rapidly being done. ` Anti-aircraft artillery, surely a defensive weapon, has been wonderfully improved since the World War. We need to equip our anti-aircraft Regular and National Guard regiments with the latest in these types of defensive weapons. In short, all of our Regular Army and National Guard units should be supplied with enough of the latest equipment to enable them to take the field at once, as a modern force. There will be time enough to equip a large wartime army while we are training the men, but our permanent force should be- the best trained and best equipped force of its size in the world. Only if it is so can we afford to keep it small, There should be enough ammunition of all calibers in reserve, to last our regular forces for 30 days. [Continued on. page 118]

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Electro-Magnet Lifts Metal Load Weighing 83 Tons Possessing powerful attraction, the electro-magnet shown here successfully holds metal forgings weighing up to 83 tons. The magnet is installed in a German industrial plant Knee Throttle Eases Driving ELIEVING the strain on the right foot and leg when driving long distances, a newly developed knee-operated automobile throttle actuates the regular foot accelerator, permitting the foot to rest comfortaLly on ‘the floor. The knee-accelerator is attached to the steering post and is controlled by push- ing the side of the knee against it. The gaso- line feed is cut off when the knee pressure is relaxed, switching control to the regular foot accelerator. , The knee accelerator is easy to install on any automobile and is of simple, but sturdy, construction. When not in use, the felt- padded knee pedal can be swung downward along the steering post so as to be out of the way when entering or leaving the auto. & Easily installed on any auto, this knee-operated accelera- tor relieves strain of holding foot on usual gas pedal. 40 NSTALLED in an industrial plant in Essen, Germany, a huge electro-magnet is said to lift loads of metal forgings and castings weighing more than 83 tons. The magnet is a circular type with a diameter of more than five feet. The powerful magnet is at- tached to an overhead conveyor by means of chains and hooks and is used to transport the heavy forgings from one part of the plant to another without interfering with workers operating machines on the floor below. Cadets Build Miniature Ships 2 ay Building ship models is part of the training which cadets must complete before they can become British Naval officers. OYS attending the Nautical College in Reading, England, in preparation for careers as officers in the British Merchant Marine Service or Royal Naval Reserve, are required to construct scale models of full- rigged sailing ships as part of their training. The models must be complete in every detail. Carbon Socket Saves Lamp ESIGNED specially for use in the chem- ical industry, where the proximity with corrosive substances causes a metal-capped electric light bulb to deteriorate long before the filament has been burned out, lamp sockets of synthetic carbon have ‘recently been developed. The carbon is not readily attacked by chemical reagents, insuring longer life for the lamps. Modern Mechanix

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Mammoth Process Camera Has 20-Foot Bellows ESIGNED for color separa- tion work, a process camera recently installed in a Cleveland, Ohio, manufacturing plant is be- lieved to be the largest of its type in the world. The huge camera has a bellows measuring five feet, ten inches by five feet, six inches, which can be drawn out to occupy a space twenty feet long. Costing $25,000 to build, the mammoth camera is mounted on a slide track together with a focusing easel. Two men are re- quired to operate the camera and powerful arc lamps are used to provide illumination. Mounted on a slide track which enables its bellows to be drawn out to a length of 20 feet, this process camera is said to be the largest in the world. It cost about $25,000 to build. Bridge Has Glareless Lights HE newly erected toll bridge that crosses the Delaware River between Phillips- burg and Easton, Pa., is equipped with special vapor lamps, which are set so as to eliminate shadows and glare in an effort to make night driving as safe as day driving for motorists using the structure. The lighting system has earned for the bridge the honor of being called the best illuminated bridge in the United States. The toll bridge, which accom- modates four lane traffic, was constructed at a cost said to exceed $2,500,000. Thousands of dollars were spent for the special lamps. Capable of developing 50 horsepower at 2,550 R.P.M., this engine weighs 156 pounds and is only 27}; inches wide. EIGHING only 156 pounds, a new light plane engine developed by a Los Angeles, Calif., manufacturer produces 50 horsepower at 2,550 R. P, M. The motor is a four-cylinder horizontal opposed type and features a large fin area to provide efficient cooling qualities. Known as the M-50, the compact engine was designed specially to power the various types of “flivverplanes” which have become popular throughout the country. The overall width of the powerful k 5 A 5 os Night scene on the new Delaware River toll bridge at Easton, little engine 1S only 2125 inches. Pa., showing the glareless and shadowless vapor lamps used. April, 1938 41

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ENTER WATER SAND AND 2 TE WATER PUMP OFF NTER WATER ND GRAVEL Deep-well digging ranks as one of the : most marvelous of 20th century en- gineering feats. ANDY CLAY ND GRAVEL ul Sweitzer, who is : one of the world’s foremost authorities rn scientific deep-well digging. x MUD WALL WATER BEARING SAND Cross-section drawing showing con- struction of a deep-well reamer. Its operation is fully described in text. OU probably have been thrille of the big game hunters of th the experiences of horror and the escape of adventurers penet depths of unknown forest j Roughly a third of the people of States use underground water. 'I Daily these uses are growing a methods of searching out this wat Para Ho into the earth for a distance of 400 feet. Sixty inches in diameter means No wonder Mr. Sweitzer (wearing hat) and his as- Ss i sistant are smiling—the water pouring from the = five good feet of earth. In this circular space pipe during a test indicated that the new well in the background would yield two million gallons daily. 42 Modern Mechanix

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sag x a deep-well being “flushed” by forcing water into its depths by means of a hydraulic reamer fitted with jets. Right—~A huge slab of clay that became wedged between the cutting blades of the reamer. April, 1938 Treasure Hunting by John L. Coontz four men could stand) with comfort. But more than this. Imagine, at the bottom of this black shaft a great/mass of earth mowed - out, a huge pit created, and created neither by hand or steel shovel. Imagine the filling up of this pit or hole again with gravel and stone from the earth, packed symmetrically ‘and in accordance with certain engineering specifications. “Modern deep-well digging accomplishes this—and more,” says Paul Sweitzer, one of the world’s foremost) scientific deep-well diggers. Mr. Sweitzer has dug wells for the -Federal government in Washington, giving to 4 ‘ the great St. Elizabeth’s Hospital in that „ city, millions of gallons daily of the purest water in the world; for the cities of Sa- ` vannah, Georgia, Houston, Texas, Annapolis, “Maryland, Jamaica, Long Island, St.

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Petersburg, Florida, and a host of others. “The first step in deep-well digging today,” said Mr. Sweitzer in a recent interview with the writer, “consists in obtaining from the United States Geological Survey a ‘log’ of the under-surface area surrounding the locality where the well is desired. With this ‘log’ in hand drilling operations commence. “The first hole sunk,” he continued, “is the ‘pilot hole.’ This hole is from two to eighteen inches in diameter and is designed to secure samples of water-bearing strata in the area. If water is found in sufficient quantity, real operations begin. The ‘pilot’ is drilled with a specially designed bit, one that my company has developed, capable of cutting through all underground material, such as rock, clay, sandstone.” Now that we have got a clear idea of how a deep-well is started let us take one of Mr, Sweitzer’s latest accomplishments—that of the deep-well at St. Elizabeth’s Hospital in Washington. This well was dug low down along the Anacostia River flats behind the high ground on which the hospital perches. Propper rigging, like an oil derrick, is on the ground, sitting directly over the spot where the well is going down. The ‘pilot hole’ has already been sunk and tests show that water is to be had in sufficient quantity to warrant larger drilling operations. “The first thing done after the ‘pilot hole,’ has been sunk,” says Mr. Sweitzer, “is the reaming and casing of it. The size ranges all the way from 24 inches in diameter to 60 inches in diameter, according to the forma- tion encountered. If sand is the formation the hole is made larger than otherwise. “Reaming is accomplished with an instru- ment called a ‘reamer.’ This is a huge boring instrument composed of a heavy reaming shank and various cutting blades arranged 44 Le f t—Preparing the outer casing of a well. When in an upright Position’ over the well hole, these’ huge pipes pee will be welded together electrically so that they, will: form one continu- ous cylinder reaching to the well bottom. Be- low-——Cores of various kinds of formations en- countered. during “the digging of a deep-well: ' The ‘numerals indicate depths at which forma- “tions were located. — It is in series of 4 to 8 blades, vertically. usually in two sections and the diameter of the blades is equal to that of the hole to be reamed. “In operation this reamer loosens the earth, breaks it up and washes it out of the well, This last act is accomplished by a stream of water which flows down the center of the reamer shaft from the top to the bottom of the shank. Reaming out the hole and washing out the refuse are thus accomplished in one operation. “Following the reaming of the well, it is eased off, This job consists of sinking huge sections of tubular steel, superimposed on each other and electrically welded together, end to end, down into the well. They are carried down by their own weight, spring steel guides along their sides keeping them centered in the well.” The well having been reamed and cased off the most delicate of all the operations in deep-well digging, and the most amazing of all engineering feats in deep-well construc- tion, is proceeded with. This is the operation [Continued on page 126]

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Flashing over the rails between New York, N. Y., and Philadelphia, Pa., this new streamlined train is the last word in pas- senger service and comfort. Except for wheels, axles, and truck assemblies, the entire train is constructed of stainless steel. TTAINING new heights in modern trans- Marking another step in railroad moderni- Š portation science and artistic skill, a new zation, the Pennsylvania Railroad has stainless steel, streamlined train has been equipped some of its locomotives and ca- placed in service by the Reading Railway booses with short-wave radio transmitters System, covering its route between New York, N. Y., and Philadelphia, Pa. The complete train consists of five cars and a locomotive representing an investment of about half a million dollars. The passenger cars are said to be the last word in design, comfort, and beauty of interior decorations. The stainless steel construction gives each car a weight of only 97,000 pounds as compared with a weight of 170,600 pounds for conventional type passenger coaches. Each coach is equipped with 56 reclining seats, while the dining car is equipped to seat and feed 24 persons at a single sitting. Freight trains go modern, too. Shown above is a scene in a locomotive cab as a crew member talks over a short-wave radio system to fellow workers in a caboose at the end of a long freight train. Left-—Rigid aerial mounted atop caboose roof. and receivers, providing a scientific method of replacing the old hand signals and lanterns formerly used for crew communication be- tween the front and rear ends of long freight trains. Rigid-type aerials are mounted on the roofs of the cabooses and locomotive cabs. 45

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Caterpillar-Type War Tank Attains 50 M.P.H. Speed AS Weighing seven tons, this new type war tank not only climbs embankments with ease, but travels over level ground at a speed exceeding 50 m.p.h. Note how belt teeth engage wheels. Knotboard Shows 144 Types EQUIRING about one year of spare time effort to complete, a huge instructive knotboard developed by James W. Mackay, of Flint, Mich., features 144 knots, bends, hitches and splices. Mackay is a former U.S. Coast Guard boatswains mate and con- structed the board at the request of a local American Legion Post, which presented the board to a Boy Scout troop. The knotboard is six feet high and eight feet long and the knot collection is said to be the most complete of its kind. Many of the knots featured are of types no longer used by seamen and required quite some research before they could be authentically duplicated for mounting on the board. Featuring 144 knots, bends, splices, etc., this huge knot- board was developed by James W. Mackay, former U.S. Coast Guard sailor, and presented to Scouts for instructive purposes. 46 N A TEST demonstration before United States Army observers, a new seven-ton war tank designed and built by J. Walter Christie, veteran automotive engineer, at- tained a speed of 50.14 m.p.h. over a measured course on the airport at Westfield, N. J. After the speed test, the tank was taken to another field where it demonstrated its ability to climb up and down 15-foot embankments. The tank, a number of which have been contracted for by the British Army, accord- ing to reports, is equipped with four large and two small wheels on each side which engage a caterpillar-type belt to provide locomotion. The tank’s armament consists of a small cannon and several machine guns. Whirling Cotton Gin Devised Employing centrifugal force, this cotton gin removes seeds from cotton without altering the original fiber length. NEWLY developed cotton gin whirls the cotton in a rapidly revolving drum to free it of seeds and impurities by centrifugal force instead of tearing the cotton to pieces with mechanical claws, as has been the usual ginning practice in the past. The machine, devised by Frank H. Watson, a planter in Jonesboro, Ark., also has the advantage of not altering the original fiber length as ordi- nary ginning methods do. + A list of addresses of manufacturers of items mentioned in MODERN MECHANIX will be sent to any reader upon receipt of a stamped, return - envelope. : Modern Mechanix

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Army AirCorps Develops Dual-Purpose Balloon FFICIALLY designated as the C-6, a new type of observation balloon has been developed by the U. S. Army Air Corps. The balloon is a dual-utility type and can be used as a “captive,” being connected to a winch on the ground by means of a long cable, or as a “free” motorized balloon by replacing the usual observation basket with a small fuselage gondola, which is equipped with a 90-horsepower engine and propeller. The fuselage is fitted with a three-wheeled land- ing gear to facilitate landings. Engineer Builds Tiny Diesel W. H. Greenfield, a marine engineer, proudly displays the tiny Diesel engine he constructed. Motor develops 1/-horsepower. TANDING less than two feet high and weighing about 40 pounds, a tiny Diesel engine constructed by W. H. Greenfield, a marine engineer, is said to develop one-half horsepower at 3,000 revolutions per minute. The motor is believed to be the smallest working Diesel ever built, having a bore of one and one-tenth inches and a two-inch stroke. The novel motor also features a built-in supercharger. April, 1938 The U. S. Army Air Corps’ new C-6 observation balloon can be used as a captive type, connected to ground winches by cables (lower), or as a free type (top) by exchanging regular observers’ basket for a smali gondola fitted with an engine. Liquid-Type Wrist Compass A COMPACT liquid-filled wrist compass devised by a Swedish engineer is said to be more accurate than the ordinary air compasses generally used by campers and outdoor men, the liquid serving to effectively mini- mize the oscilla- tions of the magnetic needle. The glass used in the compass is shatter-proof and the case is leak-proof, eliminating the necessity of re- filling. Photos at right show the compass close up and in use on the wrist of a hiker. 47

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The tiny village’s airport (left) and country club croquet lawn (right). ESCRIBED as a veritable children’s paradise, a miniature village constructed by G. S. Grey, of Beaconsfield, England, is complete in every respect, having its own airport, wharves, model liners, tugs, barges, _ trains, ete, as well as a country club with tennis courts, a golf course and croquet lawns. Known as Bekonscot, the novel vil- lage is designed on a scale of one inch to a foot and covers 1,100 square yards. The houses and shops in the diminutive village are constructed of actual building materials—tiny bricks, tiles, plaster, timber, etc., and the roads are made of asphalt, cob- blestones and wood blocks. The village’s electric railway system has a main terminus and five stations, while the “steamship” lines have individual docks. Life-like wooden 42 The miniature village of Bekon- scot features a waterfront, com- plete with quays, cranes and model ships, which are the delight of youthful visitors (above). The railway system (right) is an- other attraction. SS ie AA IAUN TTS figures of men and women comprise the population of the novel village.

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Museum Technician Builds Planetarium Projector OSTING $12,000 for materials, a plane- tarium projector constructed by Frank D. Korkosz, a technician at the Springfield, Ohio, Museum of Natural History, is said to perform as efficiently as similar projectors imported at a cost of $100,000. Korkosz, son of a Polish immigrant coal miner, has at- tracted nation-wide attention with his home- built projector equipment. The projector is comprised of numerous electrically operated lanterns, each of which throws a picture of a portion of the sky onto an overhead dome. The pictures, all match- ing together, without overlapping, produce a panoramic replica of brilliant stars. “Saw” Has Toothless Blade Featuring a diamond-impregnated blade, this machine is capable of cutting tile, stone, glass, etc., yet the operator's fingers can be placed directly against blade without injury. e NEW machine “saw” developed by a California manufacturer can be used to cut tile, glass, stone, non-laminated plastics, porcelains and vitrified products, yet it’s cutting blade has no projecting teeth and cannot break or fly to pieces. Despite the machine’s unusual cutting ability, the opera- tor’s finger can be placed directly against the cutting edge without injury. The “secret” of the new cutting machine is a circular diamond-impregnated metal blade. The unexcelled cutting quality of the diamonds enables the blade to cut the most brittle materials with unusual cleanness. Even delicate porcelains can be cut without marring the glaze, it is claimed. If you are interested in any of the items mentioned in this issue, send a stamped, return envelope for the address of the manufacturer. Frank D. Korkosz, a museum technician, demonstrates the planetarium projector he constructed at a cost of $12,000. The apparatus projects pictures of stars onto a dome “sky.” World's Biggest Model Plane LAIMED to be the largest model airplane in the world, a scale model of the flying boat Canopus was recently placed on display in a London, England, department store. The model has a wingspan of 15 feet and weighs about 23 pounds. The unusually large model plane is equipped with four miniature gasoline en- gines and after it has served its purpose as a display object, it is planned to test its flying qualities. The prototype Canopus flying boat is one of the huge trans-oceanic air liners now being operated by Imperial Airways between England and America. Equipped with four miniature gasoline engines, this replica of the Imperial Airways’ flying boat Canopus is claimed to be the largest airplane model in the world. Wingspan is 15 feet. 49

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The installation of self-clean- ing oil filters, such as the type shown below, enables fleet owners to save hundreds of dollars annually in reduced oil bills alone, to say nothing of the savings in engine wear and tear. Some filters feature renewable clarifier cartridges which keep the oil so clean that many operators instruct their drivers to change oil only every 5.000 to 8,000 miles. OW would you like to cut the cost of operating your car from 25 to 50 per cent? Or do you think that is an idle dream? Believe it or not, this pleasant reverie can come true, if you will merely put your mo- toring on a business-like basis. It is a matter of adopting the sort of management that is helping large companies save sizeable sums in the operation of their traveling employees’ cars, trucks, buses ete. Follow the fleet owner, if you want to enjoy more miles to the dollar. His rules are fairly simple, yet they produce results that seem incredible. The fleet owner does not think there is anything exceptional about the lowered cost of operating his cars. He ex- pects it. The savings are yours, too, if you will handle the subject as you would pour own business. By rotating tires (switching from one side of the car to the other, and shifting the rears to the front in a counter-clockwise direction) it is possible to double their life. One firm 50 Have ycur car tested regularly with modern equip- ment (above) if you want to keep repair bills down and efficiency up at economical operating levels. found that by insisting that their men rotate tires every 6,000 miles, working in the spare, mileage jumped from the usual 15,000 to 30,000 or more. Tests showed that, although in some cases it was better to switch tires in the way I suggest, it was the mere changing of the tires that produced the real savings. A tire that stays in one position too long may be punished for any irregularity of the brakes or misalignment of the wheel on which it is mounted. Since bringing all of its cars under one management the motor vehicle department of an eastern state has raised gas mileage four miles per gallon in individual cases. Tests show that most carburetors are adjusted too rich, providing extra acceleration which drivers do not actually need. Operators are being educated to realize that in emergencies better acceleration can be obtained by drop- ping into the modern fast second gear. In many cases it is found that the automatic choke is not properly adjusted, or that it isn’t Modern Mechanix

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Applying the suggestions made in this article may reduce your auto operat- ing costs as much as 50%. Bus line operators regu- larly check their vehicles for wheel misalignment (right) because they know it causes premature tire wear and faulty braking. by precence CG. . Russell THE FL working properly. Drivers also. are ‘cautioned against allowing the engine to idle for warming up purposes where an automatice choke is used. Under such conditions an engine merely loads up, not only wasting gas but diluting the engine oil as well. Since 1928 the operating cost per mile for several hundred cars op- erated by an insurance company has dropped from 8.6 cents per mile to 3.4. This has. been accomplished despite the fact that the company uses a large percentage of cars which do not provide high gas mileage. The management was unable to lower the cost materially until it discovered that there is a very definite period beyond which it is more economical to trade in for a new car. This point is found to be just before the owner is faced with the necessity of having major re- pairs performed on the car and can Unbalanced wheels may easily cause rapid fire-tread wear and front wheel shimmy,” so thrifty drivers check them regularly. April, 1938 5i

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be recognized by a marked drop in the car’s operating efficiency. Three years ago the management officials of a well known firm were criticized for trading in so frequently. The officials began to wonder if it wouldn’t be better to make major repairs, hoping that the cars would take a new lease on life and be as good as new. The cost per mile immediately started to climb. To check this rise it was necessary to trade in all the cars. Fleet operators are saving dollars in a va- riety of new ways. If cars come through regularly equipped with four-ply tires they pay a small difference and specify that six- ply tires be installed at the factory. They are equipping engines with clarifiers, not merely oil filters. These clarifiers keep the oil clean and free of acids. Oil changes, ac- cording to one company’s instructions to employees, are to be made every 8,000 miles in summer, every 5,000 miles in winter. It is believed that the oil could be used with safety over even longer periods. Some of the savings in oil are offset by the cost of replac- Proper maintenance not only lowers operating costs, but enables bus line operators to keep their equipment at the, _ degree of efficiency required in order to maintain schedules. Inspectors (right) supervise all servicing to assure better work and lessen the chances of an oversight. Above-—-Check- ing an oil clarifier after a 5,000 mile run without chang- ing the oil. These devices can be installed on any car and pay for themselves quickly in savings on lubrication bills. 52 ing the clarifier cartridges, but it is found that filtration and clarification of the oil more than pay for themselves in terms of savings in engine wear and tear. Inspection plays an important role in fleet operation. One company requires that the service stations which benefit by its business must make confidential reports on the cars to the home office. This must be done once a month. The report tells the fleet manager such details as the inflation pressure and condition of each tire. All of the usual things considered in a normal check-up are re- ported, but in addition the service station must advise if the clutch pedal clearance was found to be correct, and whether the quality of oil in the crankcase was up to standard. It is apparent to anyone who studies the marked savings in the operation of fleets that the average car owner pays dearly for the _ privilege of being his own boss. ‘One reason so many owners pay so much [Contnuee on page eee Modern Mechanix

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EVERAL years ago a Parisian inventor. Henri Mignet, excited the amateur avia- tion world by designing and building a tiny plane which was unusually novel in appear- ance and radical in the method by which it was controlled. The Pou du Ciel or “Sky Flea,” as the plane was known, required little skill to build and, since Mignet flew his first “brainchild,” more than 1,000 have been con- structed by French amateurs. Another reason for the popularity of the “Sky Flea” is that, equipped with a ten to seventeen horsepower engine and featuring a fuselage consisting of a spruce framework eovered with plywood, the plane costs less than $500 to build. The wings are very easy to construct, being made of metal ribs, wood spars and fabric. Simple tools such as saws, hammers, pliers and hand-drills are all the tools required to build the entire plane. The “Sky Flea” replaces the aileron and April, 1938 Above — Henri Mignet, designer- builder of the first “Sky Flea,” pre- pares for a trial flight in France. Note the novel wing arrangement. Only a few simple hand tools are needed to build a “Sky Fiea” (center). The light-weight wings feature metal ribs and wooden spars and can be assembled in fast time (above). elevator controls found on conventional air- craft with a large main wing, which is pivoted on a tubular metal support in front of the pilot’s cockpit in such a manner that the leading edge of the wing can be moved up or down and tilted laterally to control the climb and descent or banking of the plane, respec- tively. A fixed wing is mounted close to and slightly below the main wing. Mignet published a book telling how to con- struct a “Sky Flea.” It enjoyed a large sale in France as well as in many other European countries although the flying of “Fleas” has been banned by England. 53

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New English Airplane Will Feature Bat-Like Wing Resembling a bat in appearance, this model was constructed by P. N. Willoughby to demonstrate his design for a new plane now being built in England. Note twin motor arrangement. Device Records Car's Speed SIMPLIFIED speed register for auto- mobiles, which is said to provide an ac- curate record of a car’s speed for each quarter mile of travel, has been invented by Matt Niemi, of San Francisco, Calif. The device features a paper roll on which barometer-like markings are perforated while the auto is in motion. The paper roll is replaceable. This automobile speed register device features a paper roll on which a car’s speed is recorded by scale perforations. 54 NEW type aircraft of novel design, featuring a wing ar- rangement that makes it look like a bat in flight, is under construc- tion in Oxfordshire, England. P. N. Willoughby, designer of the plane, has constructed a model of the plane for demonstration pur- poses. The model indicates that the full-size plane will be a high- wing monoplane with accommo- dations for a pilot and passenger in a nacelle-type fuselage. Two American engines of 125-horse- power each will be used to power the finished aircraft, Builds Giant Television Tube Allen B. DuMont examines the giant cathode-ray television tube he has developed. Tube has a diameter of 1312 inches. ESCRIBED as the “Big Bertha” of cath- ode ray tubes, a new television tube de- veloped by Allen B. DuMont, of Montclair, N. J., has a diameter of 13% inches. The largest tubes heretofore available for oscillo- graph work have been of a 9-inch diameter. The new television tube is distinguished by its rounded sides, which provide the neces- sary added strength to withstand the atmos- pheric pressure on the highly evacuated glass bulb of the tube. Modern Mechanix

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World's Largest Trailer Built On Tractor Chassis HEN executives of a large midwest electrical appliance company travel, they use what is believed to be the largest trailer of its type in the world. Called “The Flagship,” it is probably the most completely equipped trailer in existence. It is equipped with special Pull- man berths, air conditioned by a one-ton air conditioner, heated by a hot-water system, lighted by a 2,000-watt plant, and has two radios. : A special feature is the cockpit or observation deck which seats four persons and is used as sleep- ing quarters at night by the “crew.” This trailer has a perma- nent personnel including a cook and chauf- feur. The galley is modern in every detail, having mechanical refrigeration, a gas stove, hot and cold running water, and all the es- ` sentials for serving twelve persons. Electricity Frisks Mattress Hidden metal objects in a mattress can be found quickly and easily with this device. Once a day every mattress in ithe Penitentiary is subjected to its scrutinizing inspection. F PRISONERS in the Joliet and Stateville, Ill., penitentiaries should hide pistols, knives or saws in their mattresses, this machine will detect them. It is wheeled around the prison, and every mattress is sub- jected to its scrutiny once a day. April, 1938 Note the special observation tower in which four persons can ride. It serves as sleeping quarters during the night for the crew. The trailer itself measures twenty-eight feet, while the trailer and tractor together are thirty-six feet long. Skipper Inspects Ship’s Model When the Pennsylvania was in Havana, Cuba, harbor, this . 5-foot model was brought aboard by a Western Union messen- ger, Armando Martinez Petit, who offered to sell it for $150. APTAIN HAROLD L. WINSLOW, skip- per of the Panama Pacific Liner Penn- sylvania, is shown on the deck of his ship as it reached New York with a five foot model of the liner. 55

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Photo Amateur Snaps BULLET striking LAMP Francis Behn Riggs, Jr., Har- vard University freshman and an amateur photogra- pher, examines the ordinary film-pack camera with which he successfully took pictures of a bullet striking a lamp. The pictures were taken in a dark room, using special light-flash apparatus con- structed from discarded auto and radio parts. The only purchased item was a special electrical tube costing $12. _ its bullet struck a wire, connected to the flash apparatus, before hitting the bulb. The bullet, striking the wire and breaking it, tripped the electric flash, providing the one- millionth of a second illumination needed to enable the camera to photograph the bullet in action. A box of sand was used as a back- stop to receive the fired bullet, which traveled at a speed of about eight hundred feet per second although Riggs’ unusual photos make it appear as though it were standing still. The sketch below shows how Riggs arranged his camera, revolver, light source, and other apparatus in order to take the photographs. The exact point at which to place each object was determined by experimen- tation. Above— The bulb shatters as the bul- let passes completely through it. SING an ordinary film- pack camera equipped with an F. 4.5 lens and devising a special flash ar- rangement so that no rapid shutter action was neces- sary, Francis Behn Riggs, Jr., a 19-year-old amateur photographer attending Harvard University, has succeeded in taking pictures P,"P*pPhote above, of a bullet striking an ere, See electric light bulb. The light bulb. In the electrical apparatus used to Pete st the right produce the split-second the whizzing bullet flash was built by Riggs it dacerat ite EOE. from old automobile parts, . discarded radio sets and other household junk. The only item actually purchased was a special electrical tube, costing about twelve dollars. To produce a bright flash of short enough duration so that the pictures of the -We bullet would not be blurred, the young OF | TRAJECTORY OF BULLET 1-2" college student rigged up a .44 calibre re- ! 79 FT PER SECOND volver within a box in such a manner that Saw 3 BOX CONTAINING LIGHT KODAK FILM PACI SOURCE AND TRIPPING : Peds 5 APPARATUS ; : 2 56 Modern Mechanix

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Scientist Alternates Light’s Color In Experiment XPERIMENTS being conducted in Chi- cago, Ill, by Dr. O. P. Cleaver, who is affliated with a well known electrical products manufacturer, indicate the possi- bility that commercial apparatus may soon be produced which, by the mere flicking of a switch, will enable the color of lights in the home to be changed at will. Dr. Cleaver’s ex- periments involve the use of long tubes con- taining illuminated Argon gas which, by special electrical treatment, he has succeeded in alternately changing the color of from red to blue. Phone Supplements Doorbell Lt: Changing the color of lights in the home by flicking a switch is a future possibility as the result of Dr. O. P. Cleaver’s electrical experiments with tubes filled with Argon gas. Invents Noiseless Coal Chute IRED of the clatter made by coal sliding down a tin chute to basement bins, R. E. Wall, of Winston-Salem, N. C., has invented a slide-type coal unloader which, it is claimed, unloads coal 50 times faster than any other method and—absolutely silently. The new unloader consists of a chute constructed of special composition material. A compact kitchen telephone connected to a loudspeaker- microphone unit mounted on the outside doorjamb enables a housewife to identify callers before admission to the home. s HE doorbell is ringing, answer the tele- phone” may sound like a radio come- dian’s dialogue, but a newly developed house device calls for such advice. The device consists of a special telephone mounted on a wall within a home and a combination loud- speaker-microphone which is mounted in the outside doorjamb, When the doorbell rings, the person within the home speaks into the telephone, asking the caller’s identity. The caller, hearing the inquiry through the doorjamb unit, answers directly into the unit, establishing identity. Two way conversation can be maintained as z Constructed of special composition material, this new chute is long as desired. said to eliminate the noise caused by coal sliding to bins. April, 1938 57

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A high board fence can be used effectively when teaching a dog to “heel”. By pressing inwardly with his leg, as shown above, the trainer blocks dog’s passage, forcing him to retreat until it becomes habit to walk at his master’s heels. OUR dog may not be cut out for the movies but he can become an obedient, well-mannered pet if you adopt the training methods suggested by Hollywood’s ace canine instructor. His name is Carl Spitz and he has spent more than twenty years in preparing dogs for police and Red Cross work, “Seeing Eye” duty, the stage and motion pictures. The effectiveness of his methods may best be shown by the success his dogs have achieved in numerous motion pictures. At the film studios, Spitz is an institution and whenever a script calls for a dog, one of his pupils generally gets the assignment. 58 Breaking a dog to a leash is the starting point in the ani- mal’s education (sketch). Shown in the circle below is Jane Withers, popular juve- nile movie star, with “Buck”, famous canine screen actor. They have appeared in more than fifty-five motion pictures. The stars of his troupe, Buck, a St. Bernard, and Prince, a Great Dane, move from one set to the next in the manner of busy human stars. They are products of the film training school operated by Spitz and his co-worker, Fritz Bache. It is one of the most complete layouts in America and the kennels are modern, to say the least. They are even equipped with radios to provide music, which, Spitz says, they enjoy. But one radio also serves a more practical purpose. It is con- nected up to a microphone at the trainer’s bedside, and when a dog starts barking during the night he can be silenced by a blast Modern Mechanix

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Your by Marty Soden Daily lessons will make your dog an obedient pet. A canine “pupil” can be taught to sit down on all fours by grasping his two front paws with right hand and stretching him out with the other, as shown above. Exerting a small downward pressure on a dog’s hind quarters while holding leash, as shown below, teaches the animal to sit. The lessons must be repeated daily until the dog asso- ciates the actions with your orders. Above—"Buck”, fa- mous’ St. Bernard __ dog of the movies, “engaged in practice drill at a Hollywood canine: school under on a whistle or a sharp rebuke from the reclined -trainer. Spitz believes a dog’s education should parallel a human’s and consequently his pupils are separated into three divisions— grammar, high school and college. A film contract usually awaits the college “graduate.” Once in a blue moon a student completes his academic work with flying April, 1938 ae, 59

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colors and gives his owner income tax wor- ries due to the “star’s” salary. The preliminaries in a dog’s education are most important, Spitz says. The ABC’s must be learned and learned well if a dog is to be properly behaved. Breaking a dog to a leash is the starting point in his education. There is a lot more to this than the average owner imagines. In fact, it is the foundation on which. the whole of canine training rests. Just because a dog does not object to a leash is no sign he has been properly broken to it. There shouldn't be a constant straining and pulling on the dog’s part, nor should the owner be required to jerk sharply on the strap every time he wants the dog to halt. If properly leash- broken, the dog walks without the slightest consciousness of its presence. With his at- tention centered upon his master, he is responsive to his slightest movements. ` The dog does not give orders—he obeys them. When a dog is being taught simple commands he should be kept on a leash. It aids him in keeping his mind on the work at hand and checks his tendency to investi- gate all outside distractions. Training a dog to sit down can be effected by holding the leash short in the right hand and placing the left hand, in the shape of a tongue, just above the hind quarters. Then, by exerting a small amount of pressure in a downward movement, the trainer gives the command “Sit’—not “Sit Down.” Naturally, the dog will try to squirm away but he will be unable to do so because of the pressure of your hand on the small of his back. Like- 60 “Buck” studies his lessons. wise, if he tries to lie down all you have to do is pull upon the leash. This lesson should be repeated over and over for several days until it becomes second nature to the dog and always the same command should be given. Spitz believes all commands should be as simple as possible in order not to confuse the animal during the training period. It is an easy matter to get the canine pupil to sit down on all fours by holding the leash in the right hand and grasping the dog’s two front paws with the other, stretching him out until his body is on the ground. Here th command is “Down.” i To get the dog to remain in this position may require a little extra patience on the teacher’s part the first three or four times. When starting out, he should drop the leash gently and back away from the dog a few steps. While doing this he should have the- dog’s full attention and impress upon him the fact that he is to remain‘in the position placed. If he gets up, the routine should be repeated. By widening the gap between the dog and trainer by de- grees, the idea will be drilled into the dog. With the aid of a clothes line, a dog can be taught to come when called. With one end of the rope affixed to his collar and the trainer holding [Continued on page 124] Connected to a loud- speaker in his kennels, a bedside microphone en- ables Carl Spitz, trainer of Hollywood canine stars, to whistle or voice commands that serve to quiet any “pupils” that start to bark during the night or early morning. Modern Mechanix

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A Million Dollar PLANE That Will The “mockup” air liner was built only to enable engineers to check their design, plan the cabin ar- rangements, location of berths, etc. The photo at right shows a dummy ladies’ room in the huge model. The new. four-engined Boeing will be 74 feet long, with a 107-foot wingspan. and will carry 33 passengers at a speed of about 240 m.p.h. For night travel, the air giant will feature 16 large berths, like those shown in the “mockup? (above). To help the engineers decide on the arrangement of the plane’s instruments and controls, a dummy panel layout was set up in the “mockup”, as shown in photograph at right. April, 1938 Representing an engineering cost of one million dollars, this “mockup” of a new Boeing air liner is constructed of wood and fabric and will neyer leave the ground, being just a full-scale model.

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Naval Academy Receives Famous Model Collection HE United States Military Academy at Annapolis soon will placẹ on exhibition this famous collection of sailing ves- sels. Assembled by Col. Henry H. Rogers, the collection is valued at $300,000. Fred Avery, model maker who has charge of setting up and displaying the collection, is shown at work on a model of an American Merchantman of the type sailing the seven seas in the year 1875. The workmanship shown by these models can serve as an inspiration to all model builders. The vessels in the fore- ground show clearly the perfec- tion of the craftsman’s work. New Star Has Record Size Dr. Otto Struve is shown at the telescope at Yerkes Observa- tory at Williams Bay, Wis. Dr. Struve discovered the new binary star, a part of which is 2,000 million miles in diameter. NEW star, 3,000 times as large as the sun has been discovered by Dr. Otto Struve, shown here at the telescope in the Yerkes Observatory at Williams Bay, Wis. The star is the largest ever reported and has been named “Epsilon Aurigae.” 62 The photograph above shows Fred Avery, model maker, work- ing on a model of an early American Merchantman. It is part of a collection to be placed on exhibition at Annapolis. Device Checks Color Change NEW machine has been developed that measures the change in colors in an or- ganic compound whose colors change with the acidity. Formerly such changes had to be measured by sight and described as well as the chemist could remember. A demonstration of this device was made at the convention of the American Association for the Advancement of Science, held in In- dianapolis, Ind. Professor J. Allen (left), of Purdue University, watches as G. H. Vane- man demonstrates the machine. Allen of Purdue University watches as G. H. Vaneman demonstrates the machine that measures the colors in an organic compound whose colors change with its acidity. Professor J. Modern Mechanix

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Fibrous Glass Insulates Shoes Against Heat, Cold HOES are now to be insulated against heat and cold just the same as houses, stoves, refriger- ators, and trains—with glass in fibrous form, the manufacture of which was explained in an article that appeared in the February is- sue of Moprrn MECHANTIX. Months of testing shoes insu- lated by spreading fibrous glass between the insole and outsole and worn by patrolmen of the Inserted between the soles of shoes, as shown above, fibrous glass effectively insulates the feet against heat and cold. Lef ft—Checking the temperature within an insulated shoe with a thermocouple device. Columbus, Ohio, police department on sizzling sum- mer pavements and in snow and slush during winter months, has convinced a shoe manufacturer that he has hit upon a revolutionary construction feature, and so glass-insulated shoes will be introduced na- tionally during 1938. Tests with a thermocouple device indicated a temperature variance of 20 degrees between glass-insulated shoes and the ordinary kind. Scrubbing Brushes Used As Surface For Ski Slide NDOOR ski training slides have been con- structed of waxed wood, straw, and va- rious other materials, but a slide recently developed in Germany is believed to be the most novel of all inasmuch as it features 4,500 upturned scrubbing brushes (right), the hard bristles serving effectively as a surface for the slide. The resiliency of the bristles enables the skiers to “crab” back up the slide, as shown in the photograph below. April, 1938 : 63

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Model Of “Super” Railway Car Travels 70 M.P.H. Banked curves (above), inclined car wheels and tracks are fea- tutes of a new tailway designed by a college professor in Swit- zetland. This model, used to demonstrate the practicability of the design, attained a 70 m. p. h. speed over a 900-foot track. Cartridge Starts Up Engine APABLE of starting any gasoline engine up to 600 horsepower in size, a new type “cartridge” starter has been devised by a well kriown manufacturer. The starter features a series of long tubes connected to a cylindrical chamber, which opens up to receive a special cartridge much in the manner of a gun breech. Detonation of the cartridge creates a powerful air blast in the tubes, serving to turn over the crankshaft. Loaded like a shotgun, a new gasoline engine starter features a cartridge which is detonated to turn over the crankshaft. 64 SCALE model of a new type “super” railway car, which attained a speed of 70 m.p.h. over a specially con- structed 900-foot track, has been con- structed by Professor Kurt Wiesinger, technical lecturer at Zurich University in Switzerland. This corresponds to an esti- mated speed of about 230 m.p.h. for a full size car of like design. The scale-model car is four feet in length and is powered by a small gasoline engine. A full size railway car built to Professor Wiesinger’s design would weigh only about Close-up showing car’s inclined wheels and tilted tracks. one-fifth that of a present day car, according to the inventor. In order to prevent derail- ment, the wheels of the car and the tracks over which it would travel would be inclined inwards at an angle of about 30 degrees, as shown on the model railway car in the pho- tograph above. Novel Ice Bag For Face A NOVEL ice bag that looks like a pair of over-grown eyeglasses and which may turn into the latest method for treating facial troubles adjacent to the eyes, ranging from sinus infections to the well-known “shiner,” has been patented by a Washington inventor. The bag consists of two miniature “balloon tires” connected by a bridge which rests across the wearer’s nose. A list of addresses of manufacturers of items mentioned in MODERN MECHANIX will be sent to any reader upon receipt of a stamped, return envelope. Modern Mechanix

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One of the “weapons” used by scientists in their | war on cancer is radon, ` a gas derived from radium, It is created in the odd-looking appara- tus shown in top photo. Right—Powerful X-ray apparatus enables doctors to treat deeply rooted cancerous growths. ANKING second only to heart disease in its mortality rate, cancer has long balked the efforts of the medical profession to discover a positive cure. Nevertheless, the war on cancer continues unabated in hundreds of laboratories and hospitals throughout the world. ; 3 > The lead case with Surgical removal of cancerous growths, round slots, shown at : "i s right, carries gold either by X-rays or radium treatments, e eA ik has been used for many years. However, radon. The slots are , A numbered to indicate there have been notable advances made in the strength of the : S capsules they con- this form of treatment recently, the most ER The neile iR outstanding being the development of pow- used for planting the x “Ws “seed”? in cancerous erful X-ray apparatus. using one million growths. Above—A : technicians hand volts, enabling the rays to reach deeply ted aana rooted cancer-ridden parts of the body. nosed forceps, which grasp a hair-thin gold 7 tube filled with radon, April, 1938

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Model Railroad Hobby Grows Into Paying Business L. G. Jenkins stops his engine before a miniature water tower for refilling tanks. The locomotive was built in 1907 for the Jamestown Exhibition, and is capable of a 40 m.p.h. speed. Acetylene Becomes Car Fuel WO ingenious mechanics, brothers An- thony and Michael Fonzo, recently astounded Rome with what is said to be the first automobile to run on acetylene gas. This fuel is claimed to be superior to other motor fuels and it is said that very little residue is left after it is burned. The engine of what is said to be the first automobile to run on acetylene. This new fuel is claimed to be superior to other motor fuels. Very little residue is left after acetylene is burned. 66 HE Jenkins Railway System has grown from a hobby to a paying business, having taken in $5,000 during the past four years. Built by Baldwin in 1907 for the Jamestown Exhibition, the train was found in a shed in Greensboro, N. C., by L. G. Jenkins of Star, N. C., who promptly purchased it and set it up on a quarter-mile 15-gauge track which encircles his yard. i The business end of the railway has grown gradually. Mostly the railway is fun for Mr. Jenkins, who acquired it because he never outgrew his fondness for toy trains, and for the conductor and assistant conductor, Junior and Billy Jenkins, aged 12 and 6. Popularity of the small train has increased patronage so much, and vacationists on the highways alongside the train are stopping, looking and riding in such numbers, that the system is now moving to a larger lot. Giant Tire Aids Road Making = This giant tire is one of many which were designed and con- structed to replace metal wheels on road building equipment. Note depth of tread, indicating ability to “bite” into ground. NE of the giant tires of the type which is displacing metal wheels on road building equipment, with its more than four- foot diameter, affords a hiding place for five- year-old Ellis Ebersole, shown sitting in the hub space. Modern Mechanix

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“Pendulum-Type” Streamlined Coaches Tested RAVELING without a jounce over a ten-mile stretch of spur-line trackage near Inglewood, Calif., their light bodies swinging on special sup- ports, two new ‘‘pendulum-type”’ streamlined railway coaches recently completed test runs to determine their practicability. The two coaches are mounted on three rail-trucks, so as to form one essential unit. The center of gravity of each coach has been low- ered, and the special truck-mounting supports enables them to be banked on turns. The coaches measure 149 feet overall and weigh less than 60,000 pounds as compared to the 88,000-pound weight of streamlined coaches now in use. Loudspeaker Aids Fire Chiet Speaking into a hand microphone connected to a powerful 100-watt amplifier, Chicago’s fire marshall is able to effici- ` ently direct his men’s activities despite noisy confusion. SPECIALLY designed 100-watt loud- speaker mounted on a swivel atop the cab of a light-generating truck enables the voice of Chicago’s fire marshall to be heard for several blocks above the din and clatter that is present at all big fires. The power amplifying equipment is housed within the truck and is independent of the truck’s power supply system. A hand microphone is con- nected to the loudspeaker by a long cable. April, 1938 Featuring pendulum-type supports, these two new streamlined railway coaches are mounted on only three trucks. The special mounting enables the coaches to bank when rounding curves. Plane Features Rapid Climb Poro by a twin-row radial engine of 1,200 horsepower, a new Seversky low- wing monoplane features a climbing speed of 4,000 feet per minute and a straightaway top speed of 340 m.p.h. The plane, known as the “Executive,” is a commercial adaptation of the speed plane in which Frank Fuller, wealthy sportsman pilot, won the 1937 Bendix Trophy Race at the National Air Races in Cleveland, Ohio. The fuselage of the Executive plane is of monocoque, all- metal construction with an overall length of 14 feet and has a small two-seated cabin. Carves Novel Tree Figures RAVELERS passing through Woolmer Green in Herts, England, are attracted to the shop of Harry MacDonald, a young carpenter, by a display of all kinds of gro- tesque figures which he has carved out of tree trunks. The carved figures range from a few inches to several feet in size, the main attractions being figures of goats and human beings in various attitudes. Harry MacDonald, a_carpenter in Herts. England, attracts yisitors to his shop with figures he.carved from tree trunks.

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Many novel shadow pictures can be created: through use of paper cut-outs. Shown at “eft is a set of cut-outs which, when- held between a light and wall, produce - “the “Dentist and Patient? (above). | Interlocking the thumbs while holding palms open. as above, produces the simple shadow picture—''The Butterfly.” HILDREN and grown-ups alike are in- trigued by shadow pictures. Many house parties have been salvaged from the depths of boredom by the arrival of a guest who knew how to flick his fingers before a table lamp in such a manner as to cast mirth-pro- voking silhouettes upon the living room wall. Shown on this page are a few simple shadow pictures you can duplicate with a little prac- tice. While a great many shadow pictures can be created through use of the hands alone, you will find that pipe cleaners, bent wire and other easily obtained “props” help to produce many startling and novel effects. Another simple shadow picture is “The Camel,” shown above. Somewhat more. difficult to produce is the “Cigarette-Smoking Irishman,” shown at lower right. 68

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Tilting Table Aids Veterinarians’ Horse Operations ESIGNED specially to facili- tate minor surgical opera- tions and tooth extractions on horses, a huge “operating table” devised by veterinarians features a top that can be tilted at various angles so that the surgeons can have unrestricted access to the operating field. The horse’s body is held rigidly in place atop the table by means of padded straps. Prior to the operation, the horse is stood next to the table top, which is placed in a vertical posi- tion. A small dose of a general anesthetic is then administered while the padded table straps are placed gently around the animal’s body. As the amount of anesthetic is in- creased, the horse sags, its body being sup- ported entirely by the belly straps. Straps are then fastened around the horse’s legs Pe ary i The photos above show how a horse is placed on the operating table by setting top in a vertical position while belly straps are adjusted, after which the top is tilted to any desired angle. Left—Ciamps hold the anesthetized horse’s jaws open for the operation while its head is held rigid by harness, and head after which the table top is tilted to the desired operating position. Lincoln Tunnel Equipped With Auto Salvage Trucks EATURING a capacity for traffic greater than that of the famous Holland Tunnel, the new Lincoln Tunnel, which also connects the states of New Jersey and New York, is equipped with the latest type of auto salvage trucks to meet any emergencies arising from autos crashing, stalling, or bursting in flame while en route through the tunnel. The salvage trucks can be steered from either end, eliminating the necessity of turn- ing around while in the tunnel. Each truck is equipped with fire hose, water buckets, chemical extinguishers and small cranes. A list of addresses of manufacturers of items mentioned in MODERN MECHANIX will be sent Standing at entrance of the new Lincoln Tunnel, which connects to any reader upon receipt of a stamped, return envelope. New York and New Jersey, passing under Hudson River, this well-equipped salvage truck is ready to aid distressed motorists. 69

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(ee ee 3 SEYLON “Type collect- ing” gives new. opportunity to have a filled al- bum at low cost. by Montgomery Mulford HE 1938 postage stamp catalog lists 2,018 more stamps than the edition of the previous year. The ’ average number of new postage stamps appearing an- nually seems gradually to be mounting, thus creating a problem for-the general collector. The solution is not always in specializing in any one country, or a group. There is still a host of general collectors who, it is admitted, are still the backbone of the hobby. Collectors still desire to save the postal papers of all the world, and yet they are faced with a veritable deluge of issues. The Spanish civil war alone has resulted in as many as a hundred and fity new stamps! When a collector is enthusiastic about all the stamps of the world, he should never attempt to turn from them and force himself to collect some special field. He should always collect what he desires; otherwise interest will wane. And so he may continue to collect stamps of the world, mounting every type, and yet not be forced to collect every stamp-value! The answer, to be outlined, is in the “Type Collection.” This sort of collecting is one in which the collector saves every type, and not every issue. For instance: an issue from some country may appear, all the values bearing the same design. Canada, in 1937 issued postage stamps, three in number, portraying George VI. All three of the values—one, two, three cents—show the same likeness. The “type collector,” therefore, is not faced with the necessity of collecting all three; merely one of these stamps. He has one stamp to show the type of that issue, without all the values. : If an issue appears, again, showing two types—two different designs that is to say—although more than two stamps appear in the series, he need collect only two stamps of the issue. For example, Russia in [Continued on page 132] 70

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A Scrap Wood Project Avore— tae sim Goce semen by Dale Van Horn Right—Side strips HIS project requires a piece of white pine 11 inches long, 8 inches wide and 13-inch thick. Scribe two circles, 5% and 434 inches in diameter, as near one edge as possible and saw them out. From the waste, rip the 13 pieces 3/64ths of an inch thick and 5 inches long. If you have one of the new, larger band saws and a rather wide blade you will find f that ripping the strips with it will be better than using the bench saw because of less waste and a smoother cut. Turn the bottom to the dimensions shown, making the lower groove with a sharpened file tang. Sand smooth and | then rub with fine steel wool. Cut the | top ring in the same manner, shaping the edge first, then cutting half way through f from one side and later completing the [Continued on page 120] Right—Constructional details of the flower pot shell. The strips are inserted i aiy one at a time and spaced as À F 5 Spare STRIPS evenly as possible. ae > 5" LONG, ; 3 3-64 IN. THICK GROOVE l-4" DEEP WITH FILE TANG ‘WOODWORKING . RADIO . | METALCRAFT . PHOTOGRAPHY _SPORTSMEN'S CAMPFIRE . HOME AND SHOP PROJECTS . HANDIKINKS

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with a Designed for the ama- teur scientist, this easily- built instrument records earth tremors occurring in all parts of world. | | by Don Murphy VERY few minutes, an earthquake vibrates through old Earth’s rocky crust. On an average, more than 9,000 of these shocks occur every year—some of them sending buildings crashing to the ground and leaving ruined cities in their wake, others going unnoticed except by a few scientists who specialize in this subject. “Fishing” for these tremors with a home- made instrument, built from odds and ends at little or no cost, is a sport with thrills all its own. Using an instrument similar to _ that described below, Martin G. Murray, its designer, bagged com- plete records of the disastrous March, 1933, earthquake that devas- tated a whole section of southern California. So good were his ’grams that seismologists of na- tionally known observa- tories were glad to exchange records with In the picture above, Martin G. Murray is seen examing a seismogram made on his earthquake recorder. A close-up of seismo- graph appears at left. Note that it in- corporates such special refinements as a rubber tired drum carriage and vanes submerged in oil to dampen vibrations.

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Electric magnets attached to the recording arms of the seismograph are automatically raised each hour to provide a time check on the record itself. A sweep second electric clock, with face removed, is provided with electric contacts that close magnetic circuit. home-made Seismograph him from their big, complicated machines costing hun- dreds of dollars. te FA ORLE ano A seismograph is nothing but a large pendulum with i =- -TAP FOR 1/4" BOLT a pointer which scratches a fine line on a revolving drum. N N A Strangely, when a quake comes, it moves the drum itself SHOWN IN E —not the pendulum, which swings freely and whose Pa pease inertia keeps it at rest, while the ground and everything a K attached rigidly to it quivers and shakes. The vibration E oier oF of the earth is greatly magnified by a long arm attached ee to the pendulum bob, so that the record may be more USED IN ; easily studied. Simply by changing the length of the PLACE OF | . [23 ” L IRON ANI 4 pendulum, the machine may be “tuned” to far-away | quakes much as a piano is set to a tuning fork. EA Me . To build a simple, yet effective, seismograph, first cut a triangular piece of scrap plate 3 or Y2-inch thick and E 18 to 20 inches on the side, as shown in Fig. 1. Your 42" i local blacksmith will help you out on this for a small i T charge. Drill a 42-inch hole through the plate near each A ee corner and weld a 42-inch piece of 2-inch angle iron, vertically, in the center of it. Near the top of the angle iron, drill a %4-inch hole through each face and fasten a % by 14-inch bolt. .\ BASE CENTER © PUNCH Y Va FIG.3 LEAD WEIGHTS. MOTEN R PHONOGRAPH NEEDLE 3/8" DIAM. WOODEN DOWEL FIG. 2- SUSPENSION ARMS-—2 REQUIRED 2" PIPE Sa 8" BOLT OR WELD TO 4 BASE PLATE ai: COPPER TUBING : FORMS CORE FOR A: | SUSPENSION ARM | CORE FOR g Bia tare: NOE ae % RECORDING : SHAFT HOLE ' Details at left show the WELD = pier suggested by the designer as well as a simpler pipe column which may be substi- tuted. Fig. 3 shows the method used in casting CUT FROM lead pendulum weights. raat Small tin cans serve as molds for molten metal. FIG! DETAILS OF THE PRIREOR 73 1/2" BOLT PIER & BASE PLATE SALMON TIN OR SMALL CAN

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` | SLIDING DRIVE SHAFT —>— 3/8" BRASS ROD 12-16 THREADS PER INCH ___ DRIVING FIT A> INTO TUBE A FIG.4 DETAIL OF DRIVING ROD AND DRUM SPINDLE Detail below shows how a large nut may be converted into a universal joint for connecting the drive rod to clock mechanism. Approximately 7 inches above the base, make three or four center punch marks, one above another, on each face of the angle iron. This frame comprises the pier or support for the magnifying arms. It is now ready to be bolted to some firm, stationary founda- tion such as the garage floor. Care should be taken in placing the base (see Fig. 6), so that the faces of the angle iron will be in a true east-west, north-south position, so that you may determine the direction of a disturbance registered by the instrument. By using double nuts on the foundation, you are able to level the base and so keep the recording arms, to be mounted later, parallel to each other. These magnifying arms should be made of some light metal beam, thirty inches long. Strips from an old Venetian blind or other light wood may be used instead, provided cross members and wire braces are attached to stiffen them. Fashion two wooden shafts, as indicated 74 WASHER SOLDERED The seismograph is prepared by smoking a sheet of wrap- ping paper, attached to the drum, with a kerosene lamp. Finished seismograph is pro- tected by dipping it in a so- lution of shellac and alcohol. The operation of the sliding spindle on which the record- ing drum revolves is clearly shown in the plans above. BRASS NUT OR WASHER WIRE INTO END OF TUBE DETAIL AT “A” = UNIVERSAL JOINT BRASS WASHER 3/8" DIAM. HOLE SQUARED TO SLIDING FIT i a e y 1/8" SQ. DRIVE % i N SHAFT ABOUT 12" LONG 3/8" BRASS TUBING & SS = SIRS HOUR SHAFT OF CLOCK

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eee A aW CORRECT SETTING FOR PIER f REGULATE PERIOD OF in Fig. 2, about 3%-inch in diameter and Sach Anon wat colts from 4 to 8 inches in length. Into one $ G end of each, insert an old phonograph needle, : i a E pointed end out. The other end of each ; y : shaft is later fitted with the lead weights. Referring to Fig. 3, make two lead weights, exactly alike in heaviness, by eee pouring lead into two small tin cans. Li À WEIGHT The weight of each should be between 5 and 10: pounds. Before pouring the lead, fasten in place two lengths of cop- per tubing such as used for automobile oil lines. One tube should run down the center of the tin can; the other should be run diagonally through the can, forming an angle of 45 degrees with the center tube. After the lead has cooled, errena SCREW EYE IN WooD PLUG E- WEDGE ARM iNTO TUBE OR DIRECT INTO WEIGHT DETAIL AT WEIGHT Fig. 5, below, shows as- sembly of the recording needles. Magnets for rais- ing needles hourly are op- tional and may be installed to end of magnifying arms by wiring them as shown. SUSPENSION WIRES REST POINTIN CENTER PUNCH INDENTATION CROSS-PIECE OF WOOD BRACE WIRES Yi A Bs “NUT ABOVE ——— AND BELOW TO ADJUST seh BASE LEVEL 4 RECORDING OR 1/2" BOLTS A a MAGNIFYING ARM. IMBEDDED - > 30" LONG = INCONCRETE CARDBOARD DRUM 20" X 6" OR 8" DIAM. z _—_ CLOCK DRIVE BLOCK UP TO SHAFT LEVEL SEE FIG.4 FOR LIGHT METAL SHAFT DETAIL SHAFT SUPPORT The completed seismograph is depicted above in per- spective. A careful study of the details will insure the builder of an instrument of precision accuracy. remove the tubing and insert in the resulting holes the %-inch rods, leaving the needled RECORDING end protruding about 4 inches. Into the SHEET diagonal hole is fitted one end of the PLANK BASE [Continued on page 130] FIG.6 PRINCIPAL ASSEMBLY 75

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KINKS SIMPLIFY SHOP WORK Steel Tubing Handle Extensions Increase Use Of Pliers HEN pliers are used for removing red hot pieces of metal from a forge, the heat at times becomes too great for comfort. When this is the case, two pieces of steel tubing slipped over the handles will make it possible to reach the object without the hands being burned. Before the tubing is fastened in place, straighten out the handles so that the tubing will not touch and thus prevent the jaws from closing. As the pliers can be adjusted to two opening sizes, they will pick up thin or thick pieces. In use, too much pressure should not be applied to the handles as they might show a tendency to bend.—H. Paisley. Inner Tube Prevents Hammer Marks PIECE of old inner tubing fastened over the top of the hammer as shown in the drawing will prevent unsightly dents or marks when the hammer is used in a small space. After the holes are cut in the rubber the hammer handle is passed through one end. The hammer face then is passed through the other hole. The strip should be of such size that it fits tightly over the hammer. When the claws are to be used for drawing nails the rubber strip can be removed. Steel Wool Becomes Good Filter HEN straining some types of liquids and the correct filter is not available, a piece of steel wool in a funnel becomes a good substitute. Use plenty of wool but do not pack it too tightly. If the liquid does not pass through rapidly enough, loosen the wool slightly. This material is not suitable for acid or alkaline solutions, as the metal would be affected. Various grades of steel wool can be tried according to the material to be filtered. —H. Paisley. STEEL WOOL 7 pe CAP J DRILLED Air Nozzle From Valve Cap MALL air nozzles can be made easily from a valve stem and cap. The stem first is cut from the inner tube and the valve core removed. A hole then is drilled through the valve cap. The rubber hose from the compressor next is fastened securely to the end of the stem. The valve cap is screwed into place and the device is ready for use. The amount of air flowing from the nozzle can be regulated according to the size of the opening. Several sizes can be drilled and used when necessary.—H. Paisley. Modern Mechanix

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NEAT shop usually is also an efficient shop, in that tools and supplies can be found quickly when they are needed. The man who throws chisels, screwdrivers, pliers and brushes indiscriminately into an old fruit box certainly is not a good workman. The above illustration shows a very simple but highly con- venient arrangement of tools. Everything is in open sight and is accessible for instant use. The backboard consists merely of three four-foot lengths of shelving cleated together on the back and hung from the wall of the cellar by means of a couple of large expansion bolts driven into the cement. The tools themselves are placed over finishing nails driven partly into the board. A four-inch wide shelf of April, 1938 £ are Glass jars with screw caps make ideal containers for screws, nuts, washers, soldering lugs, etc. They do not need labels, as their contents are clearly visible. soft pine, bracketed to the lower edge of the backboard, holds small tools such as screw- drivers, pliers, center punches, nail sets, files and wood chisels. The fine edges of the latter rest in slots cut in a bottom board, and are thus protected against - injury. The bottom board is also useful for holding small flat objects such as rolls of tape, cans of soldering flux, etc. This bottom board should clear the top of the workbench by about six inches. If the house uses a coal burn- ing furnace and dust is a prob- lem, it is a good idea to fit the tool rack with a curtain made of heavy cloth. This can be pinned aside when the shop is in use. Some men prefer hinged covers which swing open. These are useful for holding light, flat tools. 77

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Pocket Electro The ends of the glass tubes used in making electrodes are flared over a bunsen burner flame (below). ERE is a complete electroplating outfit —hatteries, chemical solutions, applica- tors and polish—which is contained in a case no larger than your hand, and small enough to easily fit in your pocket. An even smaller outfit, for the vest pocket, can be made by using tiny “penlite? size batteries, and by substituting glass vials for the 1-ounce plat- ‘ing solution bottles chosen for this model. Despite its miniature size, this is a thor- oughly practical outfit and with it you can electroplate:a thin or a heavy deposit of gold or silver'on any small article. It is particu- larly suited to the plating or refinishing of A as doth, for burnishing the pled silver’ or gold, is made by rubbing a strip of. flannel with jewelers’ rouge (below) - PIECES. OF: GOLD. OR” SILVER METAL JAS ANODE: —— : Right — Complete A home-built - unit that turns out permanent, low-cost jobs. = ee = Plating articles of jeweley with the compact electroplating outfit, shown above, is an easy and simple process, but be clean and free of grease, otherwise the job will appear streaked. the objects must small pieces of jewelry, on which it does first- class work in a remarkably short time. As for larger work, it will handle the replating of silverware, and you can gold plate the handles of knives and forks and similar ar- ticles if you wish. Automobile head-lamp reflectors can be resilvered when the finish becomes dull, and other automotive parts can be gilded, if you wish, at a cost of only a few cents. The work done by the outfit is as durable and permanent as that done by professional, large-scale plating methods. First construct the case, using pressed wood and following the dimensions shown in the accompanying drawings. Although for purposes of illustration the case is made of = CARBON FROM FLASHLIGHT 5 - BATTERY WITH CONNECTOR a “SOLDERED TO TOP “ELECTRODE FOR GOLD AND WIE Tm IVER SOLUTIONS BOTTLE CAP DO “GLASS TUBE A o GLASS ROD. WITH” aL PIECE OF FLANNEL CEMENTED TO END construction. de- tails of the carry- ing case, the bottle- ‘cap electrodes and the applicators. | APPLICATOR: FOR MERCURY SOLUTION COTTON=FILLED WAD OF “FLANNEL:

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Plating 0 by Kenneth Murray 1's voLts PARALLEL CIRCUIT ip V. Š WIRING DIAGRAMS Ra tae The compact carrying case (above) holds everything’ you need for electroplating with gold or silver. On opening the lid of the case (left); the ‘plating solutions and current source are readily ‘available. Left, above—Wiring diagram “showi how change of circuit can be made to in-) crease voltage delivered by the batteries. ~ lower compartment, is just large enough for small flash- light cells. The method of making contact is shown in a photograph on page 80; two pressed wood in the natural finish, you can strips of thin spring brass, each 1% by 4 also build it in ebony black, which presents inches, are given a slightly convex bend so as a very fine appearance. Small brads, cut %- to make good contact with the positive and inch long, are used for riveting the hardware negative poles of the batteries. Small tabs hinges and lock in place. Four brass up- left on the ends are rolled around a piece of holstery tacks may-be attached to the bottom wire to receive the tinned leads which con- ‘to serve as rests, if desired. nect with the electrode and the spring clip You will notice that the battery space, or with which the work is held. This circuit will deliver about 14% volts to USE BRADS Aes eS OR SE EVABT E” WITTE the electrode, which is usually sufficient. BOBS RES, 5 CELLULOSE CEMENT, According to the amount of resistance in the electrode, as will be mentioned later, it may be desirable to use a series-parallel circuit, delivering about 3 volts, in order to speed up the deposition of plating metal. The . method of wiring the batteries for a series- parallel circuit is shown in one of the ac- companying drawings: In order to make the combined electrodes : le and plating solution container units, get three use 44! pressed wooo) KS 1-ounce wide-mouth glass bottles from your 79 DETAIL OF CA

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Loading an electrode by dropping small snippings of the gold or silver anode metal into it (above). The electrode then fits into the bottle cap, shown on table, so that the piece of carbon makes ‘contact. Below— Placing 11/4x4-inch strips of ‘spring brass in the battery. compartment of — the case where they serve efficiently as contacts. . druggist. Those illustrated are of green glass, about 11⁄4 inches in diameter and 21⁄4 inches high, including the black bakelite cap. Each bottle is to be half filled with the re- _ spective working solution and labeled. The labels can be protected and neatly finished by covering them with strips of celluloid ce- mented around the bottles. The bottle containing the mercury solution is fitted with a narrow glass rod, or tube, which is cemented into a hole drilled part way through the center of the cap. Wrap a - strip of flannel around the free end, using a little cellulose cement to hold it, so that it can be used as a swab. The electrodes for the other two bottles, 80 Riveting the hinges to the case with small brads. containing gold and silver plating solutions, will require two 13%4-inch lengths of glass tubing of about 34-inch diameter. Heat one end of each in the fame of a bunsen burner and widen or flare it outward with the tang of a file, as illustrated on page 78. Cement a part of a cork inside each bakelite cap and drill a hole in the cork to take the other end of the glass tube. Passing the drill through the center of the hole in the cork, make a hole in the bakelite cap to receive a piece of clean round carbon taken from a small flashlight battery. Ce- ment it into the bottle cap so that only the brass cap on the end of the carbon projects. To this solder a connector for the wire to the positive side of the battery circuit. Returning to the glass tubing which you have prepared, pass the ends of a short strip of flannel into the flared end, and with a bit of cotton in the fold. The object is to make a wide swab with which the electroplating solution may be “painted” over the metal surface that is to be plated. Stuff a little more cotton into the tube, from the other end, and on top of the cotton drop a few pieces or snippings of gold or silver, as the case may be. [Continued on page 120]

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MUSLIN ae GLUED TO ROOF 21"—WINDOW \ \ anf 3 Oe ROOF LIFTS OFF & FOLDS BACK “WALLBOARD™ ROOF AND SIDE WALLS FOLD IN HIS play store has the double advantage of being very inexpensive to build, and when completed can be folded flat and stored in a small closet. It.can be constructed from two panels of light wallboard, one of them 4 by 8 and the other 4 by 4 feet. Odd pieces of lumber will do for sills, eaves, etc. The shutters are simply scrap wallboard cut from the front window. Three pairs of hinges are riveted to the wallboard on the inside for the folding side walls. The roof is hinged with muslin glued along the ridge after the roof is in place, cleats having been fastened to the under side along the line of the eaves. A counter is made as shown in the sectional drawing, to be set over the front window sill. Folding shelves are built as shown, and can also be stored in small space. BRACE \ bay ASSEMBLY DETAIL Constructed of light wallboard and odd pieces of lumber, this play store is easily buile and will give the young- sters a convenient and pleasant place in which to play. When not in use, the entire structure can be folded flat and stored. Because of its light weight it can be moved easily. Bright colored paint adds to its appearance. if E DOWEL JL T ORREL Li JJ WASHER Sec oes YZ š — COUNTER LIFTS Sees OFF WINDOW SILL ; sr. SCREW—_>"SQ 81

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QNIZING wE FARM KITCHENS Seer, Sy LINOLEUM

Uha,

LINOLE!

i HARDWOOD E coo ) uote MOLDING N INSTALLED AFTER SINK Kar WALL 13 PLACED CLEATS LOCKERS

w : : de CABINET TOP VIE CABINE

r=- oreo at i i i DRAWER! į BREAD | |DRAWER ||| SINK 1 í BOARD j ! ma l j lei —>] 1 pce ei =

BASE PLAN OF CABINET ee

DETAILED SECTION THRU SIDE & SINK.

It is not necessary to change the location of the plumbing, water heater, windows or any other features, because the new cup- boatd and sink are designed to fit the space occupied by the old ones. Linoleum in a solid color will give a striking effect. Lighting arrangements can vary with individual requirements.

FRONT VIEW SIDE VIEW HE possibilities in improving the appearance and convenience of old, out- moded kitchens are so great that one will not begrudge the time and cost of materials in making the change. A typical example is illustrated in these photographs. This case is interesting because originally it was a lean-to built on to the house in the manner of an enclosed porch. It is not necessary to change the location of the plumbing, water heater, windows or any other feature because the new cupboard

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and sink were designed to fit into the space occupied by the old ones. Dimensions given in the drawing are general and can be adapted to the indi- vidual case. Construction throughout is of pine and since it is to be painted, the most expensive grade is not required. Construction of the cabinet follows stan- dard practice, with the usual drawers, rails, cleats, door stops, sink compartment, etc. In this job the sink bottom rests on boards instead of being suspended by the rim, permitting installation after the cabinet top is put on permanently. Cabinet doors are simply four mitred and rabbeted frame-members as- sembled upon a plywood panel, and secured with casein glue and cor- rugated fasteners. Drawers and bread-board are provided, the former fitted with drawer pulls, the latter having a strip across the front. The top is covered with tile-pat- tern linoleum bound with aluminum or, if you care to go to the extra ex- pense, chromium-plated angle-strip. a BINDING STRIP LINOLEUM EZ" DRAWER Above—À typical example of outmoded kitchen cabinet and sink in many farm homes. Below is shown the same kitchen after a little work and small amount of material have changed the old style into a kitchen as modern as those in many new homes. While actual placement of original features has not changed, the kitchen as a whole has taken on an entirely new appearance and gives added convenience to the housewife. kq PLYWOOD PANEL CORRUGATED FASTENERS CABINET FLOOR 1-4" PLYWOOD PANEL BASE RABBETED b4” Details of the cabinet construction. Cabinet doors are mitered and secured with casein glue and corrugated fasteners. Although adding to the cost, chromium angle strips will improve the ap- pearance of completed project. Careful drawer con- struction will prevent sticking and frayed nerves.

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CHAINS SECTION OF INNER TUBE TIE MOUTH OF BAG TIGHTLY When tire chains are carried in the car, they often cause con- siderable noise when the car is driven over uneven road sur- faces. This noise can be eliminated by carrying the chains in a bag made from an old inner tube.—H. V. Tracy. CUP GREASE INSPECTION OIL DRIPPINGS > Occasionally broken bolts or small pieces of metal fall into the flywheel housing and are difficult to get cut. They can be re- moved by opening the inspection plate and placing a large lump of cup grease on the flywheel gear. By turning the flywheel Rains Arye slowly the pieces of metal will stick to the grease as it passes EDGE OF STOVE BOARD around the housing. AND SEALED WITH PLASTIC WOOD AROUND EOGE ANOMAKING SAME OIL TIGHT An old stove board makes an ideal drip board for use under a carina garage. When a quantity of oil has dripped on it, it is a simple matter to wipe it off with a dry rag. If desired, old newspapers can be spread on the board and when they have soaked up all the oil possible, they can be disposed of by burning. Strips of quarter round should be fastened to the edges of the board.—Bob Poulson. ieee iz ~ — [THINK WELL MAKE z THE NEXT WATERING TROUGH, CASS? j 4 NN TS af YEP ~1F THE COAL HOLDS N WE M BUILT A STEAMER WITH A ROTA! ENGINE — BUT THE STEAM WOULON T STAY IN THE BOILER UNTIL CALLED FOR EVERY TIME IT AMBLED DOWN MAIN STREET THE NATIVES WERE TREATED TO ATHREE DAY RAIN AND FOG?

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HOSE TO FIT TIGHTLY | HOSE ABOUT OVER THREADED END © 5" OR 6” RUBBER OF PLUG STOPPER S PRESSED TIGHTLY IN ONE END OF HOSE 5 CENT PACKAGE OF SEWING NEEDLES PLACED IN HOSE WITH POINTS TOWARD PLUG HOLD VERTICALLY AND SHAKE i A short piece of hose, a cork and a few needles make a handy 2 and efficient spark plug cleaner. The hose should have a diameter slightly smaller than the spark plug so that it will fit tightly. After the spark plug is in place, put in the needles and cork up to the other end. 2X4 ABOUT 12 INCHES LONG A 2 by 4 fastened to the rear wheels of a car as shown in the drawing will greatly speed the process of freeing a car when it is in a sand or mud hole. When starting be sure to do it slowly so that the wood will not strike the fender—A. H. Chronicles” Y= ROUND AND I DON'T BELIEVE, IVE GAINED AN INC! 3 . 4 2 M Zla Thiet years aco CAYTSHUEY OF SOUTH BEND WAS ATTACKED IN HIS OWN GARAGE SYA LITTLE ANIMATED TEAWETTLE CALLED A "MOBILE STAN- HOPE” IT HAD BEEN LEFT STANDING WITH A FULL HEAD OF STEAM WHEN AN INQUISITIVE STRANGER OPENED THE THROTTLE. pisivley~ SPACE FOR PENCIL MARKS The drawing shows a home-made measuring stick for measuring the toe-in of an automobile. Two wooden curtain rollers are spliced together. One end is cut square. A piece of wood is shaped as shown in the drawing, for the other end, from which the spring is removed. The small piece should be free to move in or out of the long strip, and can be marked when toe-in is checked.—A. C. Hill.

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by Julian D. Corrington, Ph D A binocular microscop k lar Mce, Bi sheriff's / Mie Under the oe i ant record. = prenter is for bullet old Sir} Ma BE ; PG Z bowing an 3 when an € note and the s made to le disguised PADRE At tight 1 was atte innocent mpted- UPPOSING you had done a successful job of kidnaping—successful, that is, up to the point where you were about to sit down and write the note demanding ransom. How would you go about this ticklish part of the procedure? Would you write it out long- hand, print it by hand, or use a typewriter? If you were very, very stupid, as so many criminals are, you might not even give a thought to this part of the business, or might 86 The microscope shows glaring differences while naked eye sees duplicates. conclude that the police could not possibly be smart enough to trace your handwriting; in either case you would be likely to write or print as best your limited education per- mitted. If you were a trifle less stupid but still far from wise, you might decide that handwriting is a give-away but that anonymity resides in the typewriter, and hence you would use such a machine should you have access to one. The really intelli- gent malefactor knows that, as a matter of fact, it actually doesn’t make any difference— the scientific detective can easily trace any of the three forms of communication. Documents comprise one of the major di- visions in modern crime detection—a subject introduced in the preceding installment (in the March, 1938 issue) by detailing the fingerprint system of personal identification. There are still other chapters in criminology that are fascinating, but scarcely any more interesting than that having to do with trac- ing and identifying all forms of written or printed material, and entering nearly every type of crime from homicide and kidnaping through embezzlement and forgery to black- mail and poison-pen letters. We all get a big kick out of newspaper accounts telling how Modern Mechanix

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f LUIMTILy bbuUle ‘Tea, The 26 are being wat ray from the jOO0 in fives su hear from what to do. EVIDENCE ana us for the Pol Smith type = As f the suspec, of Chk bs 21 chi COD: teq, = Suspe The series pa. Seria; been filed se. Ted o G-men traced a ransom note or ran down a notorious band of counterfeiters. Just how are these marvels of scientific sleuthing ac- complished, and can we perform some experiments with our own microscopes that will simulate real cases and teach the | methods? Many channels of communication are open today, but handwriting is still one of the chief resorts of the criminal and its study forms a necessary part of training in criminology. It would be out of place here to describe indi- vidual traits of penmanship, but aside from constant differences in the shaping of separate ‘letters, there are charatteristic methods of spacing, punctuation, sentence formation, choice of words and the like that are as diag- nostic as the Bertillon system of physical measurements. Most of these points are discernible with the unaided eye, but low-power magnifica- tion—as with a reading glass, fingerprint reader, hand lens or binocular microscope— brings out the differences much more force- fully. Such aids to vision are constantly in use in examining documents and those who wish to study applications of the microscope April, 1938 mila: © Writ tt no zities in thet on on th he lett 2 is ap © Written letter tta”? srne a pochin Empia ote sam, mples, Below—-An enlargement of the work of a machine having clear individual characteristics. Note top of letter ‘a.”” The line is unusually heavy. Also, the dot on the “i” runs into body of letter. Bottom—Same sample, greatér enlargement. on a machine of oproximately tne id in the suspec s time for all g the aid of their 1 0n a machi ipproximatel e time for the aid of?

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changes. amounts. Pay TO THE At the right is a chart of pen Dotted lines indicate additions made to raise various Note the very slight addition necessary for raising two thousand to five thousand. Chart of Pen Changes (Before and After Changes wre made) soo ete Fo < 1 Q2 Leelee. ae

t

ORDER OF Above—The top signa- ture is an enlargement of an original, while the lower one is an enlarge-

ment of the same signa- ture when an attempt was made to reproduce it by another person. Note the differences in letters “n” and “o.” Right-—Ex- ample of a raised check. low — A mechanical check writer is protection against check raising.

WSUED BY

to criminology should provide themselves with some form of simple magnifier in addition to a compound mi- croscope. The low-power or projection eye-piece in an ordinary compound microscope is also to be recommended. A favorite method of enlarging handwrit- ing as well as other forms of documentary evidence is by projection. The old-fashioned “magic lantern” and its modern improvement, the projection machine or lantern, are both actually microscopes in that they employ lenses to produce a magnified image. They differ from ordinary microscopes in that they throw their images upon a screen or wall in- stead of upon the retina of the eye. Two-choices of projection method are open. In one the original document—for example, a letter written on ordinary paper in ink— is placed in an instrument known as an opaque projector. Brilliant illumination from a 500-watt lamp plays upon the sheet, held flat on the bottom tray of the machine; the reflection is picked up by a mirror and sent through a lens which focuses it upon the distant screen, greatly enlarged. This is the system. of reflected light. In the second method, a photograph is taken of the original and a positive print made on glass as a transparency, the image then being produced by transmitted light as with any form of 88 THE TODD COMPANY, INC. ROCHESTER, N. Y. aesa lantern slide, and thrown thence to the screen. Small details stand out. conspicu- ously, and compari- sons are readily made. Such exhibits are frequently brought into court as evidence. As an experiment, write out a paragraph of material of any nature and ask a dozen of your friends or associates to copy it in their own hand- writing, placing their names on the backs of the cards. After studying these samples carefully with a reading glass until you have made out the chief individual characteristics, have some one of the group, identity unknown to you, write another card, a short sen- tence this time, and see whether or not you can pick out the author by a com- parison of the features. Practice and study of this sort places one on the road to becoming a handwriting expert, and is an amusing game. , As shown by accompanying illustra- tions, attempts to disguise one’s proper handwriting are not successful, since many inherent traits will crop out in spite of all that one can do. Even greater interest results, how- ever, when one person attempts to imitate another’s handwriting. More often than not, this effort is limited to [Continued on page 122] Gey A

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Transformer Simpliliss Trailer Lighting DISCONNECT 6 V. LEADS FROM BATTERY. RGE VIE "Or Sera TRANSFORMER BAYONET PLUG NN ANY house trailers are wired for lights operating on a six-volt system, utilizing the bayonet base bulbs similar to those in car headlights. These become useless in camps where 110-volt current is supplied, but on the other hand the six-volt bulbs with standard screw base are costly as well as difficult to obtain, The lighting system illustrated in the ac- companying sketches is practical and allows one set of bulbs to be used—the bayonet-base type, eliminating troublesome and dangerous extensions. Another point generally over- looked: the heat dissipated by the low- voltage bulbs is negligible—no inconsiderable factor in small trailers on hot nights! A transformer plug-in system is utilized to drop the 110-125 volts, A.C. to 6-8 volts. The prospective user has the choice of several units, but the best, perhaps, is one of the small transformers, used to run toy trains, motors, etc. Practically all of these have a six-volt tap, and the amperage delivered to the secondary is high enough to LEE GO ET E E 5S Trailers fitted with battery- operated six-volt bulbs can use the same lighting system when parked in camps where 110- volt A.C. is provided by rig- ging up a transformer plug-in as shown in sketches at left. operate several lights without overloading. A ventilated box to house the transformer is strongly recommended. It may be con- structed either of metal, pressed wood, or similar material, with leads well insulated. It can be mounted conveniently in some upper corner of the trailer—close to an . available bayonet socket for the plug-in. The illustrations show the method em- ployed. The output of 6-8 volts is wired | into a plug adapted to the type of light socket one uses, same type as the light base. If a double- contact bulb of one filament is used, the six- volt leads must be connected to these two contacts. If a single contact bulb is to be used, one wire of the plug goes to said contact, while the other is grounded to the metal sleeve of the socket. The writer used the filament type of trans- former designed for low-powered radio’ transmitters. A discarded radio receiver transformer—if it came from a set with a large number of 6.3 volt tubes—might also be used. Extreme care must be exercised. not to contact the high voltage leads of this type of transformer, and it must also be in- sulated from accidental short circuits. In any case when using transformers, the - “On-Off” switch must be placed in the. primary circuit; i. e., where it joins the high line, otherwise the transformers will remain “On” continuously. 89 That is, the plug must be of the...

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Light Iron Bar Becomes An Efficient Gate Latch SIMPLE and effective gate latch can be made by bending a length of -inch bar iron to the form shown. Use a blow torch to heat the portion to be bent.—A. H. Pin Improves Tape Measure REMOVE RING AND æ SLIP SAFETY PIN ON “A “-BARS,RODS ETC. { Spee STAKE OR POST FABRIC fox HE ordinary tape measure can be im- proved by fastening a safety pin to the loop at the end of the tape. When it is neces- sary to measure a long piece of wood, many 90 times it is difficult to hold one end in place while the other is being moved. By driving a small pin in the end of the lumber, the safety pin can be slipped over it and will thus hold the tape in place——A. Tempe. Cleats Made From Old Tire OR fastening small ropes or cords from porch flaps, awnings, roll shades, Venetian blinds, ete, the | tieless cleats | shown in the drawing will be found most convenient. Two strips cut from an old tire and fastened as shown will hold light rope or cord just as securely as the more conventional wood or metal cleats——A. H. STRIPS CUT CROSSWISE FROM OLD AUTO CASING | a > ae TWO a STRIPS ~ ye NAIL Water Stops Roofing Tears AR paper roofing many times will tear as it is unrolled be- cause of the ends sticking together. This condition can be elimi- nated by pour- ROLL OF I ing boiling water ss peg p ENE | on each end of the deact ‘roll before it is unrolled.—A. T. Sulphur Holds Loose Screws HE screws holding hinges often be- = suipuur Z come loose after IN HOLE>¢® a few months of p 6 use. This an- (@ TER noying condition `~ THEN HEAT SCREW Tn be a 1 : m i 2: AND DRIVE IN nated by placing a small quantity of sulphur in the hole before the screw is in place. The screws should be heated until it will melt the sulphur, and then screwed into place. When it has cooled, the sulphur will harden and hold screw securely in place.—Waychoff. LOOSE SCREW PLACE PINCH i eee OF POWDERED | Modern Mechanix

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BUMPER FOR Use a sharp knife to cut the rubber heels. When making faucet washers, trim off the embossing as shown above. power jig saw will speed the cutting operation and produce neater work when cutting the heels to intricate shapes, although its use is not essential if careful work is done. HE next time the door of your car rattles, hunt up an old pair of shoes and cut off a piece of rubber heel. Long-wearing and tough, it has just enough “spring” to silence noises of this kind. A larger piece, cut into the shape of a wedge, makes an excellent and practical door stop in the home or workshop. Unusual ways in which rubber heels can be utilized are shown in the illustrations. Purchased new at the department store, they cost only 10 cents a pair. Be sure to select the largest size available. The material, while not composed of pure rubber, is often a good and inexpensive substitute for small blocks of fibre in radio and many other types of construction work. It cuts easily with a sharp knife, especially if wet, and more accurate cutting can be done with a hand or power scroll saw. In order to cement it to [Continued on page 128] April, 1938 Faucet tap “bumpers,” camera tripod GLUE “anti-skids”’ glue pot corks are ` BOTTLE but a few of the many novel uses for CORK old rubber heels usually thrown away. FOR CAMERA TRIPOD TO SAVE MARRING FURNITURE A block of rubber inserted under a claw hammer makes ıt ım- possible to mar the surface of woodwork when pulling nails. Block may be permanently attached to hammer with counter- sunk machine bolt. Below—An effective paring-knife guard.

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REGULAR SLIDING END BLOCK ADJUST AND SET CLAMP COLLAR TO OBTAIN THE FREE WORKING HEIGHT INDICATED HERE SUPPORT COLUMN SEE DETAIL OF BASE FIG. SIDE ELEVATION (BRACKET CLOSED) ERE is a home-made, motor-driven tool ` which will appeal to every cabinet maker and home-workshop enthusiast. It solves the problem of machine-sanding large sur- faces. It is powered witha 1⁄4 h. p. or 4h. p. motor and will turn out excellent sanding jobs on big table-tops, dresser-tops, large panels, wide boards, ete. It eliminates the laborious task of hand sanding, which is prob- ably the most unpleasant part of woodwork- ing. i 92 ARM by Dick Cole The construction and operation of the sander are visualized in Figs. 1, 2 and 3. It will be seen that the sanding disk is mounted directly to the end of the motor shaft. The motor itself is mounted verti- cally at the end of a parallelogram type extension braeket, which, in turn, is free to swing on the tubular supporting column. Thus the sanding disk is always parallel to the surface to be sanded and can be moved over a wide area. An objection to a disk-type sander— that it leaves circular scratches on the job—is overcome by using a bevel-face disk to finish off the work. The disk is moved with the grain of the wood and produces a first-class job. The swinging arm sander is intended to be mounted directly to a drill-press column. When not in use, it can be swung to the side, and will not impede any of the usual drill-press operations. If one does not have a suitable drill- press, then a column must be made as shown in the drawings. This consists of a 48” length of 234” iron pipe, dressed down to 2%” outside diameter, and tightly screwed into a 244” floor flange. This is mounted on a 16” wooden disk, which, in turn, is secured to the floor with lag-screws. The base is actually built up of two 34”x16” disks glued together with grain opposed. Hardwood is recom- mended for the base, but ordinary pine will serve. We now come to the construction of the ex- tension bracket itself. If the prospective builder will check each individual part against the plans and the photographs, he will glean a complete understanding of the construction of the assembly. Now let us start building the bracket from the eolumn end outward. First we have the sliding end-block. It will be seen that this is built up of select maple into a composite unit (Fig. 3). It is well to Modern Mechanix

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Easily constructed tool solves problem of sanding large areas with little effort. bore the holes on a lathe for accuracy. If desired, these holes can be bushed with a brass ring, but the bushings will serve very little purpose. The maple alone is amply strong and, when polished and greased, makes an excellent bearing surface. In any parallelogram type extension bracket one end of the arms at each end of the bracket must be free to have ver- tical movement. On this bracket the end arms are attached to a cross-shaft with rollers which travel in a channel made of 3” x134”x134” angle iron. The formation of these channels is clearly shown in the detail of the sliding ENTIRE ARM FREE Ti o SWING LATERALLY ABOUT SUPPORT COLUMN AXIS NOTE TRAVEL oF ROLLERS IN CHANNEL MAXIMUM EXTEN WEIGHT OF MOTOR BAI LANCE! ON SOFT COMPRESSION SPRING 14" VERTICAL MOVEMENT on. connexon vg TAINED BY PARALLELOGRAG” — Fon SANES - ARRANGEMENT OF SHACKLES `a a Right—-Drawing of the sander completely assembled. Note that when the bevel-faced disc is used, the mounting is tilted to correct angle for flat contact with work. Below-— The completed sander mounted on a drill press column. BOLT BASE TO FLOOR FIG. 2 - SIDE ELEVATION BRACKET EXTENDED DETAIL OF BEVEL-FACE Disc HOOK- UP end-block. The elevation of the bracket on the column is set with the simple clamp collar shown in Fig. 3. The middle arms of the bracket are of select maple. Fig. 3 shows the special arm used at the column end of the bracket. It will be seen that a ṣẹ” rod, with a roller on each end, passes through the arm. The rod “April, 1938 i

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NOTE DIRECTION OF GRAIN GLUE AND 3" SCREW IN PLACE TO END BLOCK MAKE 2 SLIDE BLOCKS THUS OF HARD MAPLE 354'0.d. he gi" 4 LUGS WELDED ON SPLIT AFTER WELDING “rt lig SHELBY TUBE NOTCH 174" DEEP FOR SLIDE BLOCKS INNER END-BLOCK MAKE | CLAMP COLLAR THUS + USE SELECT MAPLE THROUGHOUT * SLIDE BLOCK: INNER END- BLOCK CLAMP COLLAR SPECIAL END ARM OUTER ARMS IG" X 3/4" CRS, OR DURALUMINUM H BAR DRILL 1/4" DIAM. 8 PIECES NEEDED. j SUPPORT COLUMN | 5 2 v2" IRON PIPE (TURN Down To 2%4"0.D). 1/4" DIAM. 4 THREAD 28 22 FLOOR FLANGE 12 BOLTS THUS REQ'D. FOR ARMS CLIPS AND SHACKLES 3/16" X 3/4" STOCK 3/8" LAG SCREWS > BASE- 16" DIAM. BY m 51g WOODEN DISCS GLUED TOGETHER - GRAINS OPPOSED. Fic.3 THE COMPLETE ASSEMBLY is a press fit in the wood, and the rollers turn on the rod. This is mentioned because at all other points in the bracket construction, the cross-rods turn freely in the wood. Similar rollers are used at the outer end of bracket, so four rollers are required, all of them 7%” diameter and not more than 3” wide. The other three middle arms differ but slightly. The pattern can readily be cut out on a scroll saw. Care must be taken in boring the holes. If these are inaccurately spaced, or not exactly parallel, it will cause binding in the operation of the bracket. A reasonably accurate jig can be made of hard maple, which will serve in boring the metal arms as well as the maple arms. 94 ` SLOT È x 28 i CUTFROM 3/32" CHANNEL IRON = WIDE AT HUB 7/8" DIAM, ROLLERS TIGHT ON SPECIAL END |\ ARM THUS AT TOP gu } A 3] ay x ok © H 2 Gi 1 be 1/8" STEEL PLATE OUTER END-BLOCK joe MIDDLE ARMS f| SIMILAR AT SPRING BOTH ENDS ALL HOLES 5/16" DIAM. be— 3" —> DETAIL OF INNER ARMS ( END ARM, 3 MIDDLE ARMS) 716" CAP SCREW F 173" DIAM, ROD ~ BRACKET AND HANDLE TO SUIT FOR HINGES “ ag 3" ELECTRIC ee MOTOR MOTOR BASE: exact STANDARD DESIGN TO SUIT MOTOR GRINDING ARBOR ROLLER CHANNEL SPIDER PERMITS 71/2? FLEXIBILITY TO SANDER HEAD AND DISCS „ea HEAD SOFT: SPRING SHACKLE Above is shown the construc- tion details of the arm support- ing the motor and disc sander. By careful study of each part before work is started, the final assembly job will be simplified. DETAIL OF OUTER END BRACKET BLOCK Eight outer arms are required. If 7;’x34” dural bar is readily available, its use is recommended. Otherwise use cold rolled steel. It is well to refer at this point to the outer end roller shaft. Fig. 3 presents the plan cross-section of the bracket block, outer end. Again Modern Mechanix

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#e"x134’x134” angle iron serves as a chan- nel for the rollers. The outer block is really a composite of three blocks held together with shackles and hinges, so that the motor has a limited vertical and tilting movement. By checking each individual part against the complete assembly, the construction will be obvious. Novelty and practicability are incorporated into the sanding disk assembly shown in Fig. 3. The attachment to the motor shaft is made with a standard arbor. The spring brass “spider” is held between the flanges of the arbor and the ends of the “legs” are bolted to ea ne me 5u è DRILL FOR 3/16% u STOVE BOLTS. 1a # A 3 ALLOW To aeREwsS SLIGHTLY P TO ENTE ne SLOTSIN aI BAND 5 ©. COUNTERSIN HOLES FOR NY CENT! OR N our EaR OR LAYING urs fi 1/2" Bry EQUALI SPACED SANDER HE, Woop YON 2-14" DIA, , @oLT to eh DETAIL oF f ER) 578" #6 SCREWS NDER Disc A REGU, DIAM, STANDARD SA FASTEN THUS To LAR DISC UNIT HARD Woop #OGARNET Paper B ~ EVEL FACE Discs MADE THUS the sander head. The sanding disks proper are made of 4” plyboard with a 1” metal band around the circumference. Twenty -two gauge brass or monel metal is recommended for the bands, but galvanized iron can be used. The sanding disks attach to the head disk with bayonet type fasteners. Obviously, April, 1938 AREA COVERED BY EXTENSION MOVEMENT ALONE PLAN VIEW-PARTIALLY EXTENDED y Above is shown the sander in operation. At left is a plan BRACKET CAN BE view of the arm partially ex- SWUNG THROUGH tended, Below are construc- AN UNLIMITED ARC tion details of the sander disc. e the bevel-face disk is merely a modifi- cation of the regular disks. It is well to make about three regular disks and fit them with a variety of sand-paper. Any motor capable of withstanding nominal end thrust can be used with this tool. A 43 h. p., 3400 r. p. m. motor is especially recommended for this tool, but a 1⁄4 h. p. or 4% h. p., 1750 r. p. m. motor will serve satisfactorily. The small cost involved in building this useful tool should commend it to every home workshop fan. It will save hours of time and plenty of “elbow grease” when large surfaces must be smoothed. Those who have had to sand down a table top, particularly a large one, know that considerable effort was necessary before the desired result was obtained. With this tool, all the work is done by the motor, the operator merely moving it over the area to be smoothed. If a coat of enamel is applied to the tool, the finished job will not only be useful, but will present an attractive appearance. As shown in the photograph, the sander can be attached to a drill press column without disturbing the drill. This is particularly helpful when extra space is not available in the workshop. When the sander is not in use, it will take up very little room. 95

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Time-Saving Handikinks Bend Improves Paring Knife SMALL loop bent in the end of a paring knife will increase greatly its value when preparing fruit and vegetables. Before Q) . oft AN Me the bend is made, the end of the blade should Bee On eae be heated to a dull red. A metal rod or heavy bolt should be used as a form around which the bend can be made. If the edge has be- come dulled because of the heat it can be sharpened with the aid of a small file. If the heat has removed the temper, heat it again and plunge it into cold water. In use, the small loop will be very helpful. ORDINARY PARING KNIFE POTATO EYES ETC EASILY SCOOPED OUT Scratches Aid Circular Cutting DIAGONAL C a NE of the most difficult problems for the home mechanic is that of cutting circles in glass. The correct procedure is as follows: Scratch the circle + CIRCULAR SCRATCH CUTTING ROUND GLASS in the glass with a glass cutter or the sharp end of a file. Then make several diagonal cuts from the edge of the glass almost to the circular scratch. Be sure that the diagonal marks do not touch the circle, or when the glass is broken the break will continue through the circular section. Tap the edge with a metal object and one section at a time will break off. Celluloid Cement Repairs Screens ELLULOID cement will be found very useful for patching up holes in screens used for doors and windows. Holes up to one-half inch in diameter can be filled in easily with one coat. Larger holes should be criss-crossed first as shown in the drawing, and then filled in. When dry the film is translucent, strong and withstands weather. It also has the advantage of cover- ing the sharp edges of the screen so that clothing will not be torn or hands scratched. Be sure to give the ce- ment time to dry before applying a second coat. Several coats will build up considerable thickness. AROUND HOLES IN SCREENS REPAIRED WITH CELLULOID CEMENT SMALL HOLES COVERED IN ONE COAT Naha suum | Fire Removes Broken Handles HANDLE HEN the handle of an axe, shovel, hoe or other implement breaks off, many times it is diffi- .cult to remove the wood without burning and the resultant danger of drawing the temper from the metal. This danger can be removed by burying the blade, or at least the tempered portion in the ground up to the part containing the wood. With the blade surrounded by cool earth, the heat is BURY AXE : TEMPER IS NOT DRAWN C THIS WAY conducted away, thus preventing the metal from „BURIED IN SOIL ; ; softening and losing its temper. 96 Modern Mechanix

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| | i | Providing decorative charm that will brighten any bare strip of wall (top), framed china pictures are easily made. The wood stock is turned on a lathe, the rings being cut (right) so that they are one-quarter-inch thicker than the height of the dishes they will frame. This insures the frames lying flat against the wali when completed. HE simplicity and charm of framed china dishes, which are imprinted with pictures, make them an ideal one-evening project for the craftsman. Their decorative beauty will brighten any strip of bare wall. The size of the ring frames is governed by ‘the diameter of the dishes used. Use any wood stock and turn it on a lathe, making sure that the finished rings will be at least one-quarter inch thicker than the height of the dishes so as to permit the frame to lie flat against the wall after the dishes are in- serted. After cutting the back recess to fit the dishes, the edges and front faces of the rings are fluted, sanded and finished. The ring centers are removed easily with a small skew chisel held on edge and the resultant rough inside ring edges are then sanded as smooth as possible. April, 1938 The plate is held in ring with smali brads (above). Picture hangers hold frame to (below). wall After cutting the back recess in each ting to fit the dish, the edge and the front face of each ring are fluted (right) and then sanded smooth for finishing. The sketch below shows how the dish is held within the ring frame by brads. The sketch also gives the dimensions of the ring edge and recess. The diameter of the ring is necessarily depend- ent on the diameter of the dishes used. ~ 97

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A side view of the completed trans- mitter. The two bottom shelves hold the power supplies. The driver and modulator are on the third shelf. The next two shelves hold the radio fre- quency section. The antenna tun- ing unit is at the top. Above. is a front view of the transmitter. All dials are insulated from the condenser shafts by flexible couplings and short insulator rods. LMOST every amateur at some time finds himself with a desire to go on phone. Those who constructed the transmitter de- scribed in the February and March issues will find this modulator and speech amplifier ideally suited to the rig. The tube line up shown will permit the modulator to “loaf along” and still give 100 per cent, or the more correct 95 per cent, modulation. With no need for working the equipment up to its limit, the quality will be excellent, with a minimum of troubles to clear up. Two power supplies were used; one for the speech amplifier and driver, and one for the modulator. The small supply should deliver 400 volts to the drivers, with approximately 275 volts for the speech amplifier. This can be obtained either by tapping off the bleeder, or by a dropping resistor. : The modulator was laid out to give plenty of room between parts. The filament trans- Modern Mechanix

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PARTS REQUIRED R1 50,000 ohms (IRC BY-2) R2 4 megohms (IRC BT-2) R3 1,000 ohms (IRC BT-2) R4 2 megohms (IRC 8-2) RS 500,000 ohms (IRC BT-2) RG 500,000 ohms ton control (IRC 11-133) R7 500,000 ohms volume control (IRC 11-133) RS 1,000 ohms (IRC BT-2) R9 100,000 ohms (IRC BT-2) R10 150 ohms (IRC 8T-2) R11 60 ohms center tap (IRC M-832) R12 40,000 ohms (IRC EPA) R13 100,060 ohms (IRC HOA) ci .5 mf. (receiving type) C2 25 mf. 50-volt working (Aerovox) C3 .1 mf. receiving type C4 .02 mf. (Aerovox receiving type) CS .005 mf. (Solar receiving type) C6 .1 mf. receiving type Cc? 25 mf. 50-volt working (Aerovox) c8 25 mf. S0-volt working (Aerovox) C9 2 mf. 1,000-volt working Cornell-Dubilier TJ-10020) C10 2 mf. £,000-volt working (Cornell-Dubilier TJ-10020) C11 2 mf. 2,000-voit working C12 2 mf. 2,000-volt working T1 Driver input transformer (Kenyon T-52) T2 Driver transformer (Kenyon T-263) 3 Class “B” output transformer (Kenyon T-465) T4 425-0-425-volt, 6.3 volt, 6.3 volt, S-volt secondaries (Kenyon 1-244) TS 1460-0-1460-volt (Kenyon T-666) $ ri i TG 2.5-volt, 10 ampere, (Kenyon T-360) Above is shown a front view of the TY 10-volt, 8-ampere (Kenyon T-361) speech amplifier. Below is the rear Chi Filter choke (Kenyon T-154) Ch2 5-18 henry swinging choke (Kenyon T-513) Ch3 10 henry filter choke (Kenyon T-1768) Crystal microphone (Shure Brothers 70-S) Four 6-prong sockets (Hammarlund S-6) Two 4-prong sockets (Hammarlund S-4) Two sockets for 203-Z's (ICA No, 956) Swi, Sw2, Sw3, Sw4, s. p. s. t. (ICA No. view. Tube shields are not shown. 1230) Terminal strips, three 4-terminal (ICA No. 2413) two 2-terminal (ICA No. 2420) one 6-terminal (ICA No. 2404) Fuse mounting (ICA No. 2342) Metal cabinet (ICA No. 3826) Tubes: two Taylor 203% two Taylor 866 two 6B5 (Raytheon) two 6C6 (Raytheon) Milliammeter 0-300 (Triplett) Grid caps (ICA No. 870) Name plates (ICA) Dials (ICA No. 2169) Pointer knobs and dial piates (ICA No. 2240. 2241) PEECH AMPLIFIER CRYSTAL _ MICROPHONE SWITCH 1 DRIVER AND MODULATOR "INPUT FROM. SPEECH AMPLIFIER April, 1938 99

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POWER SUPPLY FOR DRIVERS AND SPEECH AMPLIFIER At right is the power supply for the speech amplifier and drivers. T4 supplies filament power for 6C6’s and 6B5’s. ini former for the 203Z’s as shown in the photographs, is mounted at the rear of the baseboard. Inasmuch as almost eight am- peres is consumed by the filaments of these tubes, the wire used for connections should be fairly heavy, at least No. 14. Leads also should be as short as possible to prevent voltage drop. The speech amplifier was constructed as a separate unit to prevent pickup and re- sultant feedback. Shielded cable should be Sw 4 eo 1200 VOLTS + = At left is the power supply for the 203Z modulator tubes. Ch2, the swinging choke, is next to the plate transformer. The bleeder should be adjustable so that plate voltage can be reduced when desired. 100 . Modern Mechanix

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used for connecting it to the driver tubes. Beside the electrical advantage of having the speech amplifier separated from the rest of the transmitter, the operator will find it con- venient to have it on the operating table, for easy adjustment of the gain control and the tone control. When the gain is turned up high, the tone control will be very useful for cutting out Above is the rear view of the modu- lator showing the 203Z’s and the modulation and driver transformers. When testing, be sure that a load is connected to the output of this stage before speaking into the mi- crophone. At the right is another view showing the 6B5’s just behind the driver transformer. T7 sup- plies power for the 203Z filaments. April, 1938 background noises and unnecessary pickup. The construction details of both the speech amplifier and modulator are simple and little can be said to help the individual builder. The pilot light on the speech amplifier panel is connected in the filament circuit of the 6C6 tubes. If this circuit is connected into the line feeding the rest of the transmitter, it will serve as continual notification that the rig is “alive.” When the audio equip- ment is completed’ and ready for tests, do not apply power and speak into the microphone unless the modulation transformer has a load applied to it. This can be in the form of a bleeder connected across the terminals and a loudspeaker connected across a very small portion of the resistance. The builder then can test for [Continued on page 118] Tias T7 An under view of the speech amplifier. A- : metal panel and cab- inet aré used to insure adequate shielding, The lead from the amplifier to the driver stage should be of the shielded type. By con- necting pair of phones to output connections, -this section can be “tested for quality be- = fore connecting it to the driver stage.. 101

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Electric lights in cellars, closets, halls and other permanently dark places usually burn out just when needed most. A simple way to avoid this inconvenience is to equip the socket with a V-type double bulb holder (above), using two small 15 watt bulbs in- stead of a single 25-watt type. The possi- bility of two bulbs burning out is remote. Flexible electric cords develop bad kinks be- cause the insulation and covering dry out ir- regularly while the cord is kept in a tangled heap in a drawer. Avoid this trouble by hanging the cords up neatly when not in use. A good place is the inside of a broom closet or on the door of a folding ironing compart- ment, as shown in the photograph below. URZ = S FP pes NANM rm i a n QS D Loose wires from floor lamps, radio receivers, etc., should be kept well separated from radiators and connected piping as the latter are well grounded and if the wire’s insulation becomes worn or frayed, the wire will form a dead short circuit against the piping and some unpleasant “fireworks” may result if the house fuses do not blow out quickly Hold wires to floor with insulated staples. enough (above). Wiring held in place with insulated staples often develops trouble because of breakage of the wire inside the insulation. This is usually caused by heavy hammering on the staples. Cushion the blows of the hammer by wrapping tape around ` wire before pounding staples in place (above). The tension of a small spring fastened to a vacuum cleaner cord, as shown below, informs the user when the cord has been stretched its full length, enabling user to stop pulling before the cord breaks, arousing housewife’s ire.

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FIRST PRIZE—$15——"A Friend in Need is a Friend Indeed.” This homeless pup couldn’t reach the fountain, so a thoughtful boy helps him to a drink. A fine ex- ample of story-telling photography by Andrew C. Bruening, 2613 Hebert St., St. Louis, Mo. Rollei- flex 6 x 6 cm. camera, Eastman : S.S. Pan film, 1/50 sec. at f.11. SECOND PRIZE—$10—to Elwood J. Hunemorder, 613 Haley St., Midland, Mich., for catching this deer in such an artistic pose. The hill is a small pile of sand on a board, and the sun is merely a 60-watt lamp! Exposure, 21 minutes at £.4.5 on Verichrome film. THIRD PRIZE—$5.00—'Ghost Writing” by Don Brumbaugh, 191 Castlebar Road, Rochester, N. Y. Taken by waving a lighted candle in front of a 2A Kodak with the lens open. FOURTH PRIZE—35.00—to Joseph å Fred Cornett, 601 Union Avenue, Bronx, N. Y., for ‘Shadows,’ taken : under a beach boardwalk; 1/25 sec. at 6. 6.3. FIFTH PRIZE—$5.00 Sth PRIZE 5 —Spilled milk that isn’t going to waste. Robert Olive, Jr., 214 z = 3 Dobbin Avenue, Fayetteville, N. C., caught pussy at 1/25 sec., £.8, mams 7 with the help of one photoflood lamp, as the natural light was weak. MONEY FOR YOUR PICTURES! Get busy with your camera and send in unusual pictures of people, animals, machines, trains, airplanes, etc. Each month we will pay $15 for the best picture received from readers, $10 for the second choice, and $5 each for the next three selections, Prints should be glossy, as large as possible up to 8x10 inches (although a small, clear photo is more desirable than a big, fuzzy one) and should be accompanied by the following data: make and size of camera, type of film, and how developed and printed, fens opening and shutter speed, and lighting conditions. Wrap all prints cai erally. and include postage if you want them returned. Address al! contributions to Photography Editor, MODER MECHANIX, 1501 Broadway, New York, N. Y 103 “catch?” is that the deer is a glass miniature bought for ten cents, the — a

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How To Make A typical “auto-focus” enlarger taking negatives up to 4x6 inches. It is readily clamped to the edge of a shelf or table in the dark room. This is a good in- strument for the beginner because the automatic focusing action makes it practically foolproof. ONTRARY to general impression, it is no more difficult to make enlargements than - contact prints. Enlarging offers many ad- vantages besides big pictures; you can mask off unimportant parts of the negative and thus give emphasis to the better sections, and also perform all sorts of dodging operations. Many books have been written on the subject, but the fundamentals can be explained in a short article. An “enlarger” is nothing more than a camera turned upside down, with light from a strong bulb made to shine through the ` negative, through a lens, and then onto a sheet of photographic paper of the desired 104 size. Figure 1 represents the in- ternal construction of 95% of the enlargers in use today. Some en- largers made for small negatives (the 35 millimeter size used in “candid” cameras) have one or more condensing lens placed be- tween the bulb and the negative, to concentrate the light. The only real mechanical differences that will be found between various enlargers is that some are “auto focus” and others aren’t. In the former type, a cam device moves the lens closer to the negative as the whole enlarger head is raised to make bigger prints; in the lat- ter, this adjustment must be made by hand as the operator judges the sharpness of the image pro- jected on the enlarger easel. The self-focusing type of course is more convenient, but then it costs more, Most present day enlargers are of vertical construction, the lamp housing, with its attached nega- tive holder and lens, being mounted on a heavy pipe or other standard. However, horizontal arrangements work just as well and some people prefer them. Their bad feature is the large amount of table space they oc- cupy. The accompanying pictures show representative enlargers of popular’ styles. The dark room set-up for enlarging is very much like the one shown on page 108 of the December, 1937 issue of Mopsrn MECHANIX, modified as in Figure 2, As most amateurs rarely make prints larger than 8x10 inches, three trays of this size should be used. The first contains developer, the second the acetic acid shortstop bath (114 ounces of acetic acid and cold water to make a quart), and the third the regular hypo fixing bath. The tank in the back is filled with water for washing the print tongs. The safelight is fitted with an OA (bright yellow) filter as recommended in the December article. 2 The most successful and widely used paper developer undoubtedly is “D-72,” which is

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Enlargements available in prepared dry form, requiring _ Fix, 1: Gross-sec: only mixing with water. The “stock solu- larger, showing ; x . : À ers s e arrangement tion” is diluted 1:4 for enlarging paper, so Sern a single can will last quite a while. An manner in which 8x10 tray will require at least a quart of age Pred m ee solution; so measure out 61⁄4 ounces of stock by the lens i -SDIFFUSING GLASS solution and add cold water (70 degrees is a Se ee NEGATIVE - the ideal temperature) to make 32 ounces. It is not advisable or economical to save this stuff after use. If it looks brownish, throw it away and mix a fresh bottle-full. The “HINGED RED FILTER a z ; LENS chemicals are cheaper than wasted prints and : : wasted time. By the way, don’t fail to filter a ee PATH OF the solution before use. ee LIGHT RAYS Cleanliness and absolute freedom front dust in the dark room are the real secrets of n enlarging success. One writer says that BROMIDE PAPER EASEL almost surgical cleanliness is E F : necessary, and he isn’t exaggerat- ing much. A tiny speck of dust or lint on the negative looks like a baseball on the print with even medium size blow-ups. Clean the negative holder glasses (if a glass sandwich is used) by breathing gently on them and wiping again very gently, with a soft cloth. If you rub too hard you will electrify the glass and make it attract infinitesimal dust Fig. 3, above: A simple siphon attachment converts an ordinary tray into a very effective print washer. The tray is placed on the edge of a washtub or sink, Fig. 2, left: Chemical set- up for making enlarge- ments, Left tray, developer; ` center tray, acetic short- stop” bath; right tray, hypo. Tank in back is for rinsing print tongs after prints have been dropped in the hypo. Safelight is fitted with “OA” yellow filter. 105

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Above: A small circle of card- board, attached to a piece of stiff wire, makes a good “dodging” tool. This is very useful in pre- venting overexposure of dark parts of the print, and for local control in general. The stunt requires Practice, but once mas- tered, it will save many other- wise unacceptable pictures. Right: A popular low-priced en- larger of the horizontal type, which can be folded up and kept in a drawer when not in use. Prints up to 8x10 inches in size can be made with it. Note how the paper is kept flat during ex- posure by two spring bands. particles that you can’t even see! Place the negative emulsion (dull) side toward the easel, and you are ready to start. Practically all enlarging paper is known as “bromide” paper, as distinguished from the “chloride” type used for contact printing. It is much “faster” than the latter, this speed _ being necessary because the light projected through the enlarger is more diffused than the direct, close light in a contact box such as described on page 109, December, 1937 issue. Dozens of different finishes are available. The most popular paper is “semi-matte,” which has a soft, smooth appearance. Most camera fans develop a liking for one finish or another and stick to it; this is entirely a matter of experimenting. As for size, it is a good idea to use small sheets for the first trials; 5x7 is quite respectable and also quite inexpensive. Don’t invest in bigger sheets 106 until you have mastered the operations and are sure that your negatives are good enough for that much enlargement. An easel for keeping the paper flat during exposure is quite necessary. Get one with adjustable bands and margins, and large enough to take 11x14 paper. It will thus hold anything up to and including 8x10 very com- fortably. ‘Adjust the height of the enlarger head and the position of the lens so that a clear, sharp image is projected on the white surface of the easel. Keep the bromide paper well covered so that it will not be fogged by stray white light from the lamp housing. For the beginner a small device known as a focusing magnifier is a big help. This is placed on the easel and throws a magnified section of the image to the operator’s eye. If the enlarger is auto-focus, this of course is not necessary. . There are contrast, normal and medium types of paper. The exact one to suit each particular negative is a matter of judgment growing out of experience. Slightly thin, flat negatives require contrast paper; normal, contrasty negatives take normal paper. A peculiar diffusing effect takes place in en- larging, and negatives that take normal paper for contact prints may need contrast paper for enlargements. As a matter of fact, con- trasty negatives are not desirable for enlarg- ing purposes. In general, better results are obtained with slightly thin, not-too-contrasty ones. For this reason contrasty film de- velopers like the MQ, originally recom- mended in the November issue, should be [Continued on page 124} Modern Mechanix

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Wie You Be My BY ALENTINES These “before and after” pictures illustrate the possibilities of the simple and easily fers silver-print process. The lettering in the “balloon (above) was drawn in by hand. ANY novel T AA can be obtained by means of a simple process of converting ordinary photographic prints into black-and-white or colored line drawings. For engineering and other technical purposes, unnecessary or unimportant parts of machinery can be eliminated from a picture and the main structure thus given increased em- phasis. For purposes of general illustration—serious or humorous—the faces or figures of people can be exag- gerated or caricatured, double pictures built up, extra features inserted, etc. Comparatively little drawing ability is required, as the original print serves as a guide. The accompanying illustrations show two typical trick drawings made from photographs. The beach chair was selected as a simple exercise because its lines are straight and were readily drawn in with T square and triangles. If this drawing were required for a construction project, the actual dimensions could be ruled in very easily, and the finished illustration would be a complete and easily followed perspective. The second pictures show how an otherwise formal and dignified portrait can be turned into a comic Valentine card, with a “balloon” coming out of the pipe. The possi- bilities in this direction are practically limitless. [Continued on page 134] TRICK Drawings - From PHOTOS | April, 1938 : i 107

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Right — The same scene when taken with 3-power - binoculars and a K2 filter placed before camera lens. r IS the purpose of this article to` dispel a little of the awe. and trepidation with which the average amateur approaches the subject of camera lenses and auxiliary lenses, and to show how most of the effects: obtained with extremely expensive equip- ment can be duplicated satisfactorily with ordinary everyday lenses of various types. There are very good reasons for the high cost of the regulation auxiliary lenses, but 90% of this goes for extreme speed, accuracy and ultra-correction which the average ama- teur does not need in order to achieve the effects he has in mind. Portrait work par- ticularly, and its second cousin, table-top photography, certainly do not require speed, extreme accuracy or correction, for the reason that portraits are preferably taken with diffusers, or are diffused slightly in the printing or enlarging process, while table- top work is usually of such a nature that aberrations go unnoticed. The commonest desire of the camera addict is to be able to work closer to the camera, for portrait, table-top or other purposes, and this requires the simplest type of auxiliary lens. Amazing as it may sound, practically any type of lens under the sun may be used for a portrait-lens, and mounted in practically any manner conceivable, at any distance from the camera, direction booklets to the contrary notwithstanding. This may sound like a very broad statement, but the photos submitted herewith prove it. In the first series (on the opposite page) 108 Was A Y9709399947 nnn a Seer : 44 aa SS Seal Above — The Empire State building tower taken with an ordinary camera on a hazy day. Right — The best photo of the three, taken by binding a 10-power navy tel- escope and a K2 filter over the cam- era lens with tape. is a shot of a package of cigarettes made with a small reflex camera, with the ordinary lens as close as it will normally work. In the successive shots, the object approaches closer and closer until we have nothing but a por- trait of Sir Walter, half-tone dots and all, at a distance of two inches from the camera. The most convenient type of lens to use for this purpose is an ordinary ten-cent store spectacle lens. These are marked with various numbers, from 8 to about 30, which refer to the focal length. From 20 to 30 is a good length for portraits, while lengths down to 8 inches or even less can be used for closer work. Lacking this type of lens, any ordinary hand magnifying-glass lens will do. These are practically all 8-inch lenses or there- abouts, and are possibly better for this use than spectacle lenses, even if not as con- venient, for the reason that only the center portion of the lens is being used, which cuts out most of the aberration, although, as stated above, it.is hardly noticeable. For working at shorter distances than the lenses on hand will permit, it is only neces- Modern Mechanix

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sary to “double up,” i. e., hang still another lens in front of the one you are using, or two or three for that matter. If conditions per- mit, the lens may be merely held up against the camera-lens by hand. If a more perma- nent rigging is desired, the lens may be stuck to the camera with Scotch tape, as shown in one of the photos, or a regular lens-ring may be made, of the proper dimensions for ready removal and attachment, by winding kraft- paper adhesive tape around the camera lens. Wrap the first layer with the gum side out, stick it to itself, and then wrap as many layers as needed on top of that, then bind the auxiliary lens to that ring with more tape. When this assembly dries, it will be as con- venient to use as a regular portrait attach- ment. The supplementary lens can be mounted in direct contact with the camera- lens, or any distance away from it. The field automatically moves away from the camera the same distance, but conditions are not altered eenase. for all practical considera- tions. There is only one requirement and one caution in using hay-wire lens assemblies such as this — you must have a Binoculars placed on a book before the camera, Grandma’s spectacles held in place by hand, and an ordinary 20 to 30 focal length lens taped over the regular camera lens, as: shown: ‘in above photos, serve well as auxiliary” lenses. ; April, 1938 Proof of the effectiveness of tbe simple auxiliary lenses is. shown by these photos, gebed in cútline below: Top Hikes A ciga ` rette package snapped with an ordinary camera | placed as near as it will work. Center— Photo taken with two 8-inch spectacle lenses. “bound: together before | camera lens. Left -The front half of cam- ‘era lens was removed. to make “this photo: camera with ground-glass focusing facilities, either back or reflex such as the one pictured, as depth of focus at such short dis- tances is extremely shal- low; a quarter of an inch may throw your picture out of focus, the latitude varying with the lens stop used and the distance from the camera. If your camera is not a reflex, you can. calibrate it by removing the back and attaching a piece of waxed paper, thin tissue or ground glass in the posi- tion ordinarily occupied by the film, while you focus and measure. Then, when your camera is loaded with film, you can do your focusing with a ruler. If anything other than a small flat surface is being photographed, particularly when working under two feet, it is best to stop down as far as your light and other factors will allow. Another common method of “working close,” suitable only for certain types of cameras, is to remove the front half of the [Continued on page 128] 169

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MIRROR REFLECTS LIGHT OF DARKROOM LAMP. With but one safelight in the darkroom, you can avoid carrying it about by using a small mirror mounted on a wood block, as shown above. This will reflect a spot of red light to any part of the darkroom. The angle at which to hold the mirror is determined entirely by experiment. VEST POCKET DARKROOM LAMP. A red safelight that you can carry ~ s z in your pocket is an advantage when you wish to change films while -. away from your own darkroom. Use a pen-light of the type shown above (right), dipping the concentrated-filament buib in red lamp coloring, obtainable at any neighborhood electrical supply store. n-cent kitchen an ordinary te use, will LL FILM. not in R DRYING CUT OR ROUI oo th nee HANGER FOR Pnicn fits conveniently Agre dryi towel Pozen or so fine AN Saer with a hold a arm of the 4 ir can sock Srey wail ‘dry more quickly if air fims as one. circulate freely around eack p : INDICATOR FOR DARKROOM WATCH. Point one end of a small strip of tin, bending the point over so it touches stop- watch dial (circle). Turn watch until the tin point rests over the number of seconds required for your enlarging job. UNBREAKABLE LENS SHADE. Secure a five-cent rubber ball and cut an : opening in one side for the lens and a larger opening on the other CARDBOARD STRIP KEEPS DEVELOPER TEMPERATURE side. Blacken the inside completely with waliboard paint (below).. EVEN. A piece ef cardboard, placed under a tray of developer solution, wiil help to keep the developer temperature even by eliminating contact with table or bench (below). 110 Modern Mechanix

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SHELF ATTACHMENT FOR TRIPOD. An oblong piece of one-quarter inch Prestwood, or similar material, attached to the top of a tripod (left), will provide a shelf at the back of the camera for holding ground glass, film pack, slides, and spare parts. Only one hole need be made in the small shelf, as shown. AARON a oeenn enoa mra nenna: SHORT CUTS eeu TAPE MEASURE AIDS IN FOCUS- ING. A spring-type tape measure (above, left) clipped to the front of a camera so that the case is on the same plane as the lens will enable you to take advantage of auxiliary lenses for copying and portrait work by providing method of measuring distance from the lens to the object being photographed. MAGNIFIER AIDS IN READING DISTANCE GAUGE. A small mag- nifier attached to front of camera with meta! clips shows tne figures and pointer greatly enlarged, as shown in photograph at the left. CONVERTING A FLOOD LAMP INTO A SPOTLIGHT, Cut a baffle from a piece of 14-inch Prestwood, placing bolts at the edges for hook- ing it over flange of flood lamp re- flector, Cut a hole in center to accommodate a five-inch condensing lens and mount the latter, with convex side out, by means of Prest- wood rings glued in ptace (left). CLIP ATTACHES THERMOMETER TO TRAY. Waterproof a spring- type clothespin by dipping it in hot paraffine and use it to attach a ther- mometer in one corner of the de- veloper tray, providing a means of checking temperature accurately. April, 1938 111

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__ KITCHEN CABINET A second-hand kitchen cabinet (right) can easily be converted into a compact photographic labora- tory, providing space for supplies of chemicals, scales, graduates, etc. The left-hand upper com- partment can be made into an efficient enlarger, as described in the text below. Above-—The enlarger, with lens removed, being used as a light source for making contact prints. A built-in safelight with colored glasses serves to illuminate working area. HANDY compact photographic laboratory can be arranged by the amateur from an ordinary kitchen cabinet. As most modern homes now have built-in cabinets, discarded movable types can be picked up second-hand for as little as $5.00. Placed in the garage, spare room, basement, or wherever the photo- graphic work is usually carried on, such a cabinet provides adequate storage for ma- terials and equipment as well as space for printing, developing and mixing solutions. The photographs accompanying this article show how space is provided for chemicals, scales, graduates, trays, solution bottles and jugs, enlarger, cameras, lighting apparatus, and photographic literature. The original flour compartment was altered to make a vertical enlarger. Four lights were mounted near the top with a piece of opal or ground glass several inches below. Holes in the back were necessary to provide the ventila- tion for the light compartment, which is painted white or lined with tinfoil. Below the diffusion screen are a series of slots in which the glass negative holder slides. 112 BECOMES This is merely a sheet of glass which forms a shelf on which the negative is placed, dull side down. It is covered with a clean piece of glass to hold the celluloid flat. By moving this glass shelf closer or farther from the lens, different degrees of enlargement can be obtained. The lens is mounted at the bottom of the compartment and should be adjustable for focusing. With the lens removed, a printing frame can be substituted for the paper holder and the light then used for printing contact prints. P This compact photographic laboratory is particularly adaptable and valuable to the man living in a small apartment. It will please the housewife, too, for it means that her photo fan husband will now have a “place for everything and everything in its place.” Modern Mechanix

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Buile with two or three drawers, this chest holds photo supplies and provides support for enlarging camera track. COMPACT chest of drawers, built into the space under an enlarging camera, can be used to store photographic equipment. Build This Two-Purpose DISCARDED picture frame, some bronze paint and enamel and a few pounds of glass beads are all that are required to make a novel back-of-the-door projection screen for showing home movies. The picture frame should be hinged at one corner, as shown in the accompanying sketch, so as to enable the cardboard sereen to be slid into position. The screen should be sil- vered on one side by applying silver bronze paint with a small brush. When dry, turn the cardboard over and spread white enamel paint on the untreated side. While this surface is somewhat sticky, sprinkle the entire surface with tiny white glass beads. Make sure the beads cover the entire surface smoothly and when the enamel has dried, turn the cardboard on edge and lightly brush off the superfluous beads. The silvered side is useful for the projec- tion of motion pictures in an ordinary man- ner, while the beaded side will create a novel effect. because it provides better luminosity April, 1938 ENTIRE CHEST 374" PINE LARGE DRAWER L_PARTITIONED FOR ENLARGING PAPER HANDY DRAWER FOR ENLARGING PAPER ENLARGING CAMERA TRACK RABBETED FOR 174" PLYWOOD iza” PLYWOOD RONT 4" BOTTOM RABBETED IN Making one of the drawers deep, with re- 7 movable partitions, solves the problem of. where to store large size enlarging paper. The chest can be made to dimensions to suit the builder, using 34-inch pine for all sides. ‘The drawers can be made of lighter material, such as %4-inch. plywood, for the. sides, bottoms and front, but use %-ineh pine for the backs. - The enlarging camera track can be attached to a wooden T and screwed to the side of the chest as shown in the sketch. Movie Projection Screen and greater depth to the projected pictures or lantern slides. Legs can be attached to the base of the screen so that it can be set up on a table, instead of being hung on a wall | or door, if desired. CARDBOARD As explained in the 113: text, a home-movie screen is easy to make.

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HOTO booklets of various kinds make many references to the “color sensitivity” of different kinds of films. This is very con- fusing, not only to beginners but to some experienced amateurs as well, because of the word “color.” We must remember that no matter what the colors of a scene or object are in natural life, ordinary cameras and films reproduce them only as different tones of black on white paper, or as black images on a white movie screen. This is why some people who have very: vivid and interesting coloring in their hair, faces and eyes sometimes look dull and unattractive in a still picture or in the movies, and also why some people who look quite ordinary in the flesh express re- markable personality in pictures. Depending on the kind of film and the ‘design of the filter (if one is used over the lens), the colors of an object will register with varying shades of blackness. Films of the “orthochromatic” type, in general, are sensitive to yellow-green light in addition to 114 Believe it or not, but: these: two. pictures ate of the same books! The difference is. that the one =- above (SA?) was taken with orthochtomatic film, the one at the left (B?) with panchromatic. blue and violet light, the latter being strong colors in the pho- tographic sense. These colors show in the final print as variations of gray. However, red does not register at all, and any part of a scene that is red doesn’t affect the film and therefore shows up as dead black in the print. “Chrome” type films can, for this reason, be developed safely under a red light. “Panchromatic” films are sensitive, for practical purposes, to all colors that the human eye normally sees. “Super-sensitive panchromatic” film, now very popular with camera owners, is extremely sensitive to yellow, orange and red light, as well as to green, blue and violet. For this reason it can be developed only in total darkness. Reds and oranges no longer “blank” out, but register very nicely. The remarkable difference between ortho- chromatic and panchromatic (don’t let the words scare you!) film is illustrated by the two accompanying pictures. These were taken with the same camera and under the same light conditions, “A” with chrome film and “B” with super-sensitive panchromatic. [Continued on page 130]

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Think of the pleasure of owning an outboard that weighs no more than a. pair of oars... think of a 14-pound fishing pal that will drive your boat steadily, tirelessly, as Jong and far as you want to go! A motor that is equally at home on canoe, fishing boat, row boat, resort boat—or any craft you wish to put it on! Three cents an hour is the operating cost ...a single gallon of fuel is an ordinary day’s supply! Note the many features of advanced construction that have made this one of the world’s most popular outboards. INSTANT, DEPENDABLE, EASY STARTING Most important of all features, the Pal offers amazing starting ease... even a young child can start it with an easy snap of the wrist. The simple, conveniently Flaced controls give finger-tip ease of handling. The Evinrude-built Elto line offers three other popular models . . . write for full details on these, and the come plete line of Evinrude models. ELTO ACE Weighs only 22% Ibs., gives speed up to T | miles an hour, $47 50 HANDITWIN World’s lightest “twin’= weighs only 29% Ibs. Speed up to 8% miles an Sour -see $67.50 FREE! Write today for Evinrude and Elto Catalogs — Boat Guide, and Handy Boat Chick E Motor Selector. With these handsomely illustrated Evinrude and Elto catalogs we will send Boat Guide of leading builders and new Boat-and-Motor Selector. FREE! Address, EVINRUDE MOTORS, 5407 N. 27th St. Milwaukee, Wis, EVINRUDE When Answering Advertisements Please Mention Aprit Modern Mechanix 115 SEND THIS COUPON— EVINRUDE MOTORS, 5407 N. 27th St., Milwaukee Send me Evinrude and Elto catalogs, Boat Guide and Boat & Motor Selector. Pree. Namo .essseesassasusseapensesor E A Address .esesosasae sessesosecoesao besssosasosacssa

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| Amateur ġ Photo Puzzlers In this department the Photography Editor will answer any question or problem relating to cameras of all types, enlarging, printing, developing, taking pictures, and the various phases of home movie making. D When sending questions to this department, be sure to include a stamped, addressed envelope, so that we can answer directly in case space does not permit publication of the question on this page. Send all inquiries to the Photography Editor, Modern Mechanix, 1501 Broadway, New York, N, Y. RECOVERING SILVER Please tell me how to recover the silver in hypo solutions. I understand some photographers make quite a bit of money this way.—E, S., Sturgis, Mich, The recovery of silver from old hypo solutions is not worth the trouble and the cost of the necessary apparatus unless very large quantities of the chemical are available. The amateur photographer who uses perhaps a gallon or so of hypo per month should not bother with the idea. SPOTS ON PRINTS My negatives appeat to be clean, but my enlargements invariably are full of little spots and small white lines. I wipe the rolls of films very carefully after washing, by means of a viscose sponge rung out in water. I also filter the print developer carefully before use. Can you offer any sugges- tions? —A, A. D., Long Island City, N. Y. This trouble is probably due to tiny specks of dust and lint picked up by the negative after it has dried. Sometimes this dirt comes from the inside of the enlarger itself, If your enlarger negative holder uses a glass “sandwich,” breathe on its surfaces lightly and rub them off just once with lens tissue before putting the negative in place. FILTERS ON SMALL CAMERAS Is there any reason why I cannot use filters on a small folding camera that cost about ten dollars, in order to obtain those beautiful sky and cloud effects I see in many exhibition prints?——R. S., Atlanta, Ga. Certainly not! The size or price of a camera has nothing to do with its ability to use filters. By all means buy several filters of the correct size to slip over the lens cell, ENLARGEMENTS FROM PRINTS? I have a small but very clear picture of a group of chil- dren taken at a summer camp. Is there any way of making an enlargement from this, so that the picture of my own child stands out better? I do not have the negative, as the picture was taken by another visitor—Mrs. D. B, H., Wood- side, N. Y. Enlargements can be made only from negatives, not from prints. However, if the print is clear, it is a simple matter to have it “copied”; that is, photographed by another camera so that a engative is obtained. From this copy negative, enlargements of any size and in any quantity can be made by ordinary methods. Any commercial photo-finishing estab- lishment will do this work at a reasonable price. PROJECTING PICTURES ON THE WALL I am interested in projecting large images on a blank sheet of paper tacked to a wall, so that I can sketch in the outlines and thus make a unique kind of photo-poster. I rigged up my camera with a light reflector, so that it acts as a sort of enlarger or projector, and used my regular negatives, but the images appear to be reversed; that is, what should be black is white, and white, black. What's wrong? I thought I had fixed up the equivalent of a movie projector, but for “stills.’—-H- L, S., Los Angeles, Cal. 116 The image produced by a negative on white paper through an enlarger or projector of any kind is still a “negative” in the sense that the light values are reversed. In actual pho- tographic enlarging, this image on sensitized paper becomes a “positive” only after the paper has been developed by chemical means. If you want to project an actual “positive” image, you must use a “‘positive negative,” or, more correctly, what is known as a positive transparency. This is made by printing the negative on transparent film instead of on ordinary paper, so that light will shine through it. All motion picture film, whether used in home or theatre projectors, is positive transparency film, What probally confuses you (and many other people) is the fact that 8- and 16-mm, amateur films are first developed as negatives, an:l then turned directly into positives by a trick “reversal” process. The film you get back for projection is the same roll you took originally in the camera. However, in com- mercial 35-mm. movie work, the original negative ‘‘shot’’ in the camera is developed only as a negative, and from this, duplicate positive rolls are made by simple contact printing. Many owners of 8- and 16-mm, movie cameras attempt to make enlarged prints from individual frames, and are puzzled when they obtain reversed prints. This is to be expected, as the film is a positive. A contact negative must be made first, and this used in the enlarger to produce a positive print. ENLARGER FOR BATTERY SERVICE I work in a camp removed quite a distance from 110-volt power lines, We make our own electricity with a gasoline engine driving a 32-volt D. C. generator. This is very satis- factory for general purposes, but I want to do all my own developing and enlarging and all the machines I see in the catalogs are designed for 110 volts. I intend to make a contact printer like the one described in your December, 1937, issue, and also an enlarger. What changes are neces- sary to adapt these to 32 volts direct current?—-A, Co Denver, Col. None whatsoever, A 25-watt bulb working on 32 volts gives as much light as a 25-watt bulb working on 110 volts. You can use safelights, contact printers and enlargers with- out change. You will not be able to use an electric clock for timing purposes, but there are many spring-operated photo timers that serve the purpose very nicely. WASHING PRINTS I see many conflicting instructions about washing prints. Some say let them wash 15 minutes, others 30 minutes, an hour, even two hours. Which is correct? —W., L., Pearl River, N. Y. Washing time really depends on how fast the water is running, and how well the prints move around in the basin or tray. Prints that are not thoroughly washed start to fade, sometimes only a few months afterward. About the minimum washing time is thirty minutes, An hour of vigorous washing is better and will produce prints that will never fade. MODERN MECHANIX AWARDS $40 EACH MONTH FOR BEST PHOTOS SUB- MITTED BY READERS The editors of Modern Mechanix distribute $40 in cash awards each month to the five persons who, in their opinion, submit the best pictures suitable for publication in the Modern Mechanix Photography section. Full particulars regarding these awards will be found in this issue on page 1Q3.

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Your present camera "ugg" Film Two or three Photoflood lamps in Kodak. Handy Rete è your jpidure- napshots at Night ALL YOU NEED- loaded with Kodak NAPSHOOTING indoors aiter dark, you discover scores of new and fascinating picture chances. You get good results from the start, and really great snapshots as you become increasingly skillful in placing your subject, ar- airing your lights. ‘The equipment is both sim- pleand inexpensive. Youdon’t need a high-priced camera. Any camerathat can beloaded n P ë ° S with Kodak “SS” Film will do the trick—even the sim- plest Brownie. With “SS” Film, you use two or three of the new No. 2 Mazda Photoflood lamps, which last for hours, together with inexpensive Kodak Handy Reflectors. If your par- ticular camera is equipped with an f.6.3 or faster lens, then No, 1 Photoflood lamps are quite powerful enough. FREE BOOKLET... Suggests a variety of picture opportunities ... shows you how to arrange your lights ... how to place your subject ... tells you everything you need to know about two ways to make night pictures—snapshots with Photoflood lamps, fast exposures with Photoflash lamps. (You can use Photoflash lamps, each good for one picture, if your camera can be set for “time.”) Get a copy at your dealer’s today... Eastman Kodak Company, Rochester, N. Y. When Answering Advertisements Please Mention April Modern Mechanix 117

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Follow The Fleet [Continued from page 52] to operate their cars is because they do not enjoy sufficient mileage. Once a car is warmed up and ready for action it operates more efficiently and thus more cheaply. Taxi companies long ago found out that it paid them to keep the engines running all day, especially in cold weather. Heavier oil could be used, and there were none of the usual periods of cold starting, over-chok- ing and overloading. Traveling men seldom need to have the head removed and the valves ground, because most of their mileage is done at peak efficiency. Carbon is built up largely in around- town driving, especially when there are frequent stops and periods of parking. The question of when to trade in for a new car is no problem to the fleet operator. One form for reaching this decision gives something of a case history of the car as well as of its driver. On the reverse side of the report of the total cost of the various expense items is a place on which the driver lists all repairs, accidents and other points in connection with the car. Mileage on present tires is also recorded. If the car appears to have reached the point where it needs an engine overhaul, a new clutch, a new rear end or some other major work it is likely to be traded in im- mediately. Repairs are tolerated only so long as they represent an opportunity to increase or maintain efficiency. The cost of accidents shows up plainly on ex- pense records. This is one reason why fleet operators are noting an improvement in their accident experience. Safety students claim that defective mechanism accounts for only a small percentage of automobile accidents, but the ex- perience of fleet operators indicates that where cars are better cared for they are better driven. Personal contact is one of the reasons for the success of fleet management. Someone usually goes with the car to the service station and follows it through the work, This not only assures better work, but helps to lessen the chances of an over- sight. Many worthwhile savings are also effected when the mechanic can discuss the matter with a representative of the fleet management. Be- cause all service of importance has to be given the approval of the management there are no opportunities for costly experiments. Fleet operators warn of the importance of draw- ing a distinction between operation and main tenance. Most drivers try to reduce operating costs, even though they may fail to do this properly, but in aiming for such savings they are apt to be “penny wise and pound foolish.” Only through spending the necessary amount of money on maintaining the car in good condition is it possible to keep operating costs from going out of bounds. New spark plugs every 8,000 miles is an item of maintenance needed to keep gasoline mileage up. New breaker points also illustrate [Continued on page 132] 118 War Machines Needed, U. S. [Continued from page 39] The Air Corps now has about 1,000 modern fighting planes. The present program calls for bringing this force to 2,350 planes by 1940. This number should be adequate, but more trained pilots will be needed. The Air Corps is already taking steps to train these pilots. The common soldier can be trained in a few weeks, but trained officers to lead them, and the trained technicians needed to handle modern weapons and technicians cannot be produced in a hurry. We already have the R. O. T. C., which gives officers their basic training, but funds should be provided to give at least half of these reserve officers training every year. An enlisted reserve of at least 150,000 should be provided as a reser- voir for trained technicians. The Army has no enlisted reserve now; though one is maintained by the Navy and Marine Corps. And finally, the factories which are to manu- facture the intricate mechanical equipment needed for modern warfare should be given small sample orders, so that the machinery and tools will be on hand, and that at least a few men be trained in their use, MM Short-Wave Transmitter [Continued from page 101] quality with no fear of insulation breakdown. After tests are completed and quality is found to be satisfactory, the modulator can be con- nected into the Class C circuit. Here again, apply a load to the tank so that the Class B output impedance will match that of the Class C input. The builder will save considerable trouble by reducing plate voltages to the final and modulator during these tests. The builder will do well to keep in mind that before power is applied to the transmitter, some provision must be made for taking up the resultant energy. When 400 watts or more go into an amplifier, to say nothing of when it is plate modulated, each watt will ac- count for itself in some manner, It is the builder’s problem to see that they are sent along the right path. When tests are completed, connect the antenna, and give the rig the greatest test of all, a QSO. NOTICE Changes in the make-up and title of this magazine, designed to make your favorite publication better than ever before, will be announced in our next issue. Be sure and reserve your copy now.

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A WORLD CHAMPION TELLS HOW TO BUILD A POWERFUL BOD THE SECRET’S OUT: Well, fellows — here’s the low- down. Don’t think I always had this swell physique—and don’t think it just naturally grew on me. When I first started boxing, Í was tipped off that a champion must be able to take it — as wall as dish it out. The fighting game is hardly a ping-pong contest. You have ¢ to meet not only scientific boxers but human gorillas. To stand up and swa punches for twelve and fifteen rounds oe an enormous amount of energy and stamina—That is why it was neces- sary for me to first build up a sturdy frame work for my body before I could ever amount to anything as a fighter. And that is just what I did. A NEW LIFE 7227" first impor- tant fight was nothing compared tothe “Gass joys I experienced from possessing this strong, healthy body. Troa that day on, I decided I would possess a perfect phy- sique as well as be a boxing champion. My record speaks for itself as to whether I accomplished my ambition, TOMMY LOUGHRAN Undefeated World Champion Photo taken Feb., 1938 All these years while I was working my way to the top, I kept investigatin, and studying every known method of physical development unti I finally discovered the secret of “PUISSAN. T POWER.” Learn from a Champion Tt took me years of study and research — also thousands of dollars to acquire thia knowledge of building muscles which possessed the power of an ox, but the speed and agility of a panther. These are the only typo of muscles which enable you to engage in active sports or to really accomplish anything. It was not long until Í was receiving offers galore, if I would only impart ‘thie knowledge and train others through this short but certain method of body building. Days were all too short to satisfy the demands on my time. [ decided to have duplicates made of my apparatus and put the instructions into printed form. In this way J am now enabled to spread the joyful message to the world. Send For My FREE Book, “Puissant Body Building” This contains numerous photos of some of the athletes and atrong men J have trained. It will be an impetus and an in- spiration to you. I don’t ask you to buy it.I want to spread the glad news. It ia absolutely free. Yours to keep. Don’t delay. This does not obligate you in any way what- ever. It is merely an inspirational talk and will show what I have done for so many others. 227 jie TOMMY LOUGHRAN 18 years Dept. 14 4 So. 15th Street, Philadelphia, Pa; That’s COME TO ME fos aienak SSS a a eS Do you wish these mighty 4 ynamic muscles for your- rle power, self? Would you like to feel TOMMY LOUGHRAN, Dept. 14 I do it? the joys of a strong, healthy 4 So. 15th Street, Philadelphia, Pa. That’s m: I ety epee a howe goa ant Dear Tommy: —Please send that book “Puissant Body secret. I’ not on! bethe ae a cue Building.” I want a strong, active body like yours. This reveal it friends onan OGAN qd Tyas book is absolutely FREE with tbe understanding that I to yon: ical viewpoint but I will also am not obligated in any way. build up those inner muscles around your vital organs. You will feel the thrill of a new life pulsing through your veins — you will Feel like shouting to the world “I am a man and I can prove it.” When Answering Advertisements Please Mention Abril Modern Mechanix 119

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The household “utility-man”. For craftsmen and manual training. Use for fixing and repair work. ‘In bottles, tubes and cans. WHY RENT A BOAT? MAKE YOUR OWN Even a child ean build at least one of the many Boats cs are described Wa the big new 146-page book, HOW as LD 20 Edition, Send Soc lor your copy, ni MODERN MECHANIN PUBL. CO., Fawcett Bldg., ‘Greenwich, Conn. IN 5 MINUTES LEARN TO FHROW YOUR VOICE! Be the hit of every sare Amazing easy method shows ou in 5 minutes HOW TO HROW YOUR VOICE. EN $ a (N k Everything Complete The Mac Method of Ventriloquism is so easy, anyone can become an expert quickly. No skill or experience need ded to throw your voice and fool everyone. Talk, whistle, sing, make funny noises. Full size 30-inch Ventriloquist Dummy and special Ventriloquist Mouth-Piece included at no extra cost. Dummy’s head made of double cast material with movable mouth. Easy to operate. Dummy alone worth more than $1.00. SEND NO MONEY—WRITE! Order complete Mac Method of Ventriloquism” today with Full Size Dummy and humorous dialogues. Send no money —just mail name and address. Pay postman only $1.00 plus few cents postage for everything—complete. Nothing else to buy. Rush order NOW. MAC METHOD, Dept. G-2053, Cincinnati, Ohio 120: Pocket Electro Plating Outfit [Continued from page 80] Small pieces of solid gold or silver can be cut from pieces of old jewelry. Only a small quantity will be required, and to “recharge” the electrodes with more of the precious metal all that you have to do is to pull the glass tube from the cork and drop in some more pieces, When you replace the glass tube in the cork cemented to the bottle cap, the carbon rod should make contact with the pieces of anode metal. When the electrode is dipped into the bottle of plating solution, the latter will soak the flannel and cotton, and wet the silver or gold anode metal. This makes an electrical circuit. To proceed with your first plating job, the article to be plated must be clean and free of grease, otherwise the work will be uneven and streaked. Professional workers use a strong caustic solution, but with small articles you can do very well by scrubbing them with strong soap solution. If the surface is not absolutely smooth, it must be polished beforehand. You can then grip it with the spring clip connected to the negative (zinc) side of the battery, and rinse it in clean water. If the article is of copper or brass it should first be given a coating of mercury, to serve as a bond- ing agent for the gold or silver to be deposited. Merely swab it with the mercury solution until it has an even, silvery appearance. Then rinse it in clean water again. Connect the wire from the positive (carbon) side of the battery to the connector on the gold or silver electrode, and remove it from the bottle. Holding the electrode by the bakelite bottle cap, gently swab the wet flannel at the end of the glass tube over the surface to be plated. Keep it mov- ing slowly. Almost at once you will see the de- posited gold or silver “flow” onto the work in a brilliant film. Continue until the plating is as heavy as you wish it to be. The plated article should then be well rinsed, dried, and burnished by rubbing it with a rouge-treated polishing cloth. If the gold or silver deposits very slowly, it is [Continued on page 133] Flower Pot Shell [Continued from page 71] cutoff to meet it from the other. When you see light through the intervening wood, turn off the motor and finish the turning by hand, using the point of a knife for the final cut to prevent throw- ing the piece onto the floor, Place a bit of glue in each groove, then assemble the strips one at a time, spacing them as evenly as possible. The shell can be painted any suitable color or colors, or it can be made of walnut or gum and finished in natural with lacquer or var- nish A bit of felt can be glued to the bottom, For pots of other sizes, vary the file tang grooves and strip lengths accordingly. Accept No Substitutes! Always Insist on the Advertised Brand!

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guard ... four-speed efficient V-pulley drive with double- row indexing Check the proper square in the coupon below and you will be sent the special circular giving full details and prices on the new Utility Lathe. If you have not received the 1938 Delta Catalog showing the complete line of latest Delta motor- driven tools—send the coupon for your copy as well as special circular on new Utility Lathe—and the latest Delta Project Book No, 4—packed full of new and different things to make, with many photographs, working drawings and complete instructions, Enclose 10e for Project Book, Catalog will be mailed postpaid, DELTA MFG. Co., Dept. M438, 600-634 E. Vienna Ave., Milwaukee, Wis. Read the Sworn Statement: With New Delta Utility Lathe Here is the ideal general utility lathe—for the school shop—for the general woodworking shop—for the home workshop—you will find it in this new lathe, Can be adapted for metal-turning. A heavy, rigid bed of fine-grained cast iron, with accurately machined and polished ways ...a substan- tial cast-iron headstock, with built-in, removable belt require lubrication . . . exceptionally handy, free-moving universal tool support, locked to bed at any angle by convenient handle at front, and fitted with two tool rests .. i tailstock, locked by front lever, and with self-ejecting center actuated by large, convenient ball-end crank handle. Get the full story of this remarkable new lathe! The undersigned be- ing duly sworn says: “5 MILES MORE PER GALLON” F. L. Van Ness, y JACK SMEAD Service Manager gf IN GASOLINE” _,., mechanism for dividing, fluting, ete... heavy steel hollow spindle, threaded front_and rear for faceplates, etc., and with No, 2 Morse-taper centers ... carried on pre- loaded New Departure self-sealed bearings which never . substantial cast-iron G CO., Dept. M J 4 enna | Milwaukee, Wis. o enclose 10¢ (S or coin) for which please send me one copy of the new 1938 Book No. 4 of ‘‘Practical Delta Projects.” Also place me on your mailing list to receive 1938 Delta catalog of quality motor-driven woodworking tools. O Send me special circular on new Utility Lathe. Write for More Statements The undersigned be- ing duly sworn says: “4 TO 6 MORE MILES TO GALLON” D. C. Brame, Ont. The undersigned be- ing duly sworn says: “B MILES TO GALLON MORE” G. K. Marman, Pa. 1938 SAVINGS ON MOTOR TRIP SAN FRANCISCO to CHICAGO Mich. Says: AMAZING Improved GAS ECONOMIZER When you get MORE MILES per gallon of gas you get money paving results, YOU SAVE UP-KEEP COST. Hundreds of letters in our files from auto owners of every make tell us our wonderful gas economizer has saved money for them and reduced auto running expense by getting MORE MILES PER GALLON OF GASOLINE, Note a few in this ad and write us for complete revealing detalls of this world famous inrention and our trial plan whereby YOU can try one on your own car and if you don’t think it’s wonderful, the trial costs you nothing. Anyone can attach to any auto—as inexpensive as a good wrench— absolutely automatic and self-regulating. New Improved Gas Economizer SENT .2N. TRIAL Costs Nothing if it Does Not Save Gas Yes, you may try this new improved gas economizer on your own car under our Iiberal 30-day trial offer—check your gas mileage BEFORE you install it, CHECK it again AFTER you install it—then, you be the Judge, and if it does not save gas, Save money for you, and you are willing to return it under our liberal guarantee within the 80-day trial perlod, it costs you nothing—but, that’s not all, we will even pay, rou a bonus for testing It If not dellghted—so, ou can’t jose. Ithout obligation, send name and address on coupon elow—or paste on lc postcard and mail NOW. When Answering Advertisements Please Mention April Modern Mechanix SALESMEN, BIG MONEY AG E NT MAKING OPPORTUNITY Startling demonstrator. Convinces motorists—makes sales quick, easy. T. M. iley says, ‘‘Cleared $39 in 3 hours—on previous Saturday I cleared $18.” Get unusual money making plan and offer of NO-COST SAMPLE to salesmen for a rte work, spare or full time. Write be first in your locality — check below, now, J. A. STRANSKY MFG. CO., D-600, Pukwana, $0. Dak. Ses BER RE Se J a a J. A. STRANSKY MFG. CO., D-600, Pukwana, So. Dak. E E Without cost or obligation, send your TRIAL @ a fl OFFER and GUARANTEED BONUS OFFER. E a 1 » O 4 - Name „uaan a e d a a a e a a e a a : CHECK HERE i if interested 1 l in no-cost i i Address -----~2-~~.200----- anne .------ I SAMPLEH | i and money i I g making plan, g y Bn u a M U M a 121

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Think of getting, for only $19.75—not only amore accurate time piece, but ALSO:- A STOP WATCH that at the touch of a e lever checks off the time in seconds and fifths of seconds ! 2 A TACHOMETER that gives you at a è glance the exact speed at which any moving object is traveling over a measured distance! A TELEMETER which tells the distance ə you are away from any simultaneous source of light and sound! WRITTEN GUARANTEE Smart, trim and compact, the Pierce 4-in-1 Watch is simplicity itself to operate. And it’s unconditionally guaranteed against any mechan- ical defect for one full year! See this amazing Pierce Watch at any good dealer today. If he cannot supply you mail order direct. SEHSSSHHHHHHTHHHSSHHHHHHH HHH HTHHETHSEAHRASEERSESTESESESEOZESS PIERCE WATCH oe Dept, 14, 22 W. 48th St., N. Y. O Please send me E literature describing the sensational new Pierce 4-in-1 Watch, I understand there is no obligation. O Enclosing check or money order for $19.75. Please send my Pierce Watch at once, the major toc! of science, is a fascinating and educational home hobby for thousands. You, too, can explore che mysteries of the un- seen world, chrough the magic of the microscope. Bausch & Lomb precision amateur microscope Model R (left), 75 to 300 power; with 455-page book, $21. Other models, $14.50 up. SEND FOR FREE BOOKLET (right). Bausch & Lomb Optical Co., 242 Bausch St., Rochester, N. Y. BAUSCH & LOM B Documentary Evidence [Continued from page 88] a mere signature, as on a will or check, and and may be done freehand or by the method of tracing. The crook procures a genuine signature from a letter, cancelled check, autograph, ete. If he is an accomplished penman he may decide on the freehand method, whereby he will school him- self by hours of copying the original, practicing until he can dash it off without effort or hesitation. Detection here involves relatively high magnifi- cation so that the slightest characteristic may be thrown up in bold relief in an endeavor to find something the forger overlooked. In the tracing method the culprit employs a frosted glass plate with a light beneath, place the genuine signa- ture on this illuminated plate and the document he wishes to forge on top, centering it so that he can directly trace the signature upon the space provided for this purpose. He may execute the tracing very carefully and the finished piece of work may very closely re- semble the original, but when enlarged the spuri- ous name will show certain features that go along with this method. There will be evidence of tremor, the lines wavering ever so slightly because of the slowness of execution and the effort to trace accurately; the tracing lacks the boid sweeps, free from tremor, of the natural signature. There will be retracings, where the pen has been lifted dur- ing a pause and again applied to the paper, leaving slight blots and tails of lines that only the micro- scope can detect. And there will be evidences of hesitation, with tiny spots of ink where the pen has rested, be it ever so fleetingly, when it should not have paused at all. The binocular microscope, : especially, is the bane of the forger. Here too you can arrange an entertaining ex- periment by having a friend sign his name to a card, and another person copy this signature ky the tracing method. The two cards are given code numbers unknown to you and your job is to study the two and state which is the genuine, which the forgery. With the foregoing explana- tions and the accompanying photographs, can you do it? The once-common crime of check raising has been greatly curbed by the use of mechanical check writers, which punch the amount into the paper as well as ink it into the fibers, and by new types of paper so treated that any alterations, by mechanical or chemical erasers, rub off the com- plex colored or printed pattern of the surface and leave glaring white blanks in their place. How- ever, not everyone owns a check writer and there are ways of raising amounts without recourse to erasures. Two illustrations show how this is done. As an example, write the amount “one hundred” on a card. When this is dry, make a C-shaped loop on top of the capital O, converting this letter into a [Continued on page 133] 122 Accept No Substitutes! Always Insist on the Advertised Brand!

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NEW 1938 MODELS DE LUXE 4—the only American-made 4-cylin- der motorcycle. CHIEF 74—a peerless “top speed” performer. SPORT SCOUT =a winner all around. FREE! Getthis RIDER'S HELMET and INDIAN PIN MAIL COUPON TODAY! The lowest priced “twin” in America! There’s a real thrill in its easy riding, peppy power and 70-miles-to-the-gal- lon economy. No wonderit's the great- est motorcycle “buy” in all the world! PAY AS YOU RIDE = The Indian Junior Scout— and any of the new 1938 Indian models, for that matter—can be bought on an easy, pay-as-you-ride plan. Ask your Indian dealer to demonstrate these magnifi- cent machines for you today. SREARSSTREERBESVPRSSTETSSBeeeetew EGE worn MOTOCYCLE CO., Springfield, Mass. Please send me at once, without obligation, your illustrated Folder showing the new 1938 Indian Motocycles, and CERTIFI- CATE of VALUE entitling me to FREE RIDER'S HELMED. and INDIAN PIN, as illustrated, when 1 place my order. Name seers Steennvee! seeysenecessevenacasatacserovememamssngamiensenvenes rae Please be sure to check your age group: MM43. O 16-19 years 020-30 years 041 yearsandup O under 16 years FREE WOOD CATALOG NEW 1938 100 PAGE BOOK No. 10 WITH ANY ORDER SO¢ OR MGRE i {Otherwise send dime or stamps) Every home crafisman should have this fine book crammed full § trom cover to cover with beautiful things you can easily make. valuable information, and belps for professional and ‘amateur woodworkers. 24 pages in color, lists and illustrates 76 blue print designs for scroll patterns, inlay table tops. ete. . . . hard to find K woods, lovely crotch, butt, burl, fiddle back, etc. Veneers. 1 Solid woods, ete. These woods cost you less . . . much ess... yet give you just what you want. Full of BARGAINS Like These: DEAL NO. 16 ONLY sq. tt., Ye” Walnut, 51/2” and wider 00 sq. ft, e” Mahogany, 51/2” and wider sq. ft., Lg” Satinwood, 31⁄2” and wider —q sq. Ft., Ye” Benin, 51⁄2” and wider F. 0. B. sq. ft., 1/g Holly, 4” and wider CHICAGO sq. ft., 1a” Plain Maple, hall and wider Shipping Weight We will ship about 36 inches long. 10 pounds Make your own at 14 store VENETIAN BLINDS ake your orm at ta store tapes, cords, etc. Easily assembled with simple home tools. (2 Pages of Specially Priced Solid Woods and Veneers from All Over the World New Process of Intaying Make this beautiful wall plaque In striped Mahogany , . . Walnut . . . Lacewood. ete, Complete Kit includes intricate border all ready to fit together. Requires no tools or clamps. Makes beautiful 61/2 x 9 wall orna- Ment in 1 hour complete. Easily worth $3.00. Sent postpaid—only $1.00. DOWEL CENTERS Complete set 7 sizes—14" to 54” Indispensable to cabinet builder: Special, postpaid, 40c. 2 sets 75 ms ORDER TODAY DIRECT FROM THIS AD OR SEND DIME FOR CATALOG! CRAFTSMAN WOOD SERVICE COMPANY Money Back Guarantee—We ship all over the world 2731 Mary Street CHICAGO “Over 200 five-stroke words a minute’— that’s what speed experts can do on this,up- to-the-minute machine. See its beauty, its completeness ...try its quiet, easy Operation «..and nothing else will satisfy you. Famous Floating Shift, Touch Selector. Free case and touch chart; free trial. LC Smith & Corona Typewriters Inc Desk 4, 733 E. Washington Street Syracuse, N. Y. O Send free Corona book and terms D Tell nearest dealer to call When Answering Advertisements Please Mention April Modern Alechanix 123

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ALL winter long, rust and sediment have accumulated in your radiator. Fine scale is choking the cooling system of your car. Clean it out! It’s easy and inexpensive. Do it yourself in a few minutes. Use Sani-FLusu, There is nothing in Sant-FLusH that can injure your motor or radiator-fittings. It is a scientific powder that removes damaging dirt from the cooling system. Just pour 10c worth in the radiator. (25c for the largest trucks and tractors.) Follow directions on the can. Run the engine. Drain. Flush. Re- fill with clean water. Your motor will run cool. You save fuel. You don’t take chances on costly repairs. You'll find Sani-FLusH in most bathrooms for cleaning toilets. Sold by grocery, drug, hardware, and five-and-ten- cent stores. 25c and 10c sizes. The Hygienic Products Company, Canton, Ohio. Sani-Flush «1% KEEPS RADIATORS CLEAN "UWAG cost your own. ence or advanced edueation necessary. Life- time Employment Service. Write for Big Free Electrical Book Today! No obligation. We supply you 20 separate outfits of Electri- | eal Equipment and Apparatus at no extra to help you learn Practical Electricity in ome Shop. No previous exper’ ELECTRIC INSTITUTE, Dept. 48D, Hinsdale, Il, Be 124 How To Make Enlargements [Continued from page 106] avoided if the negatives are to be enlarged. Be- sides, the contrasty developers are mostly also. rough-grain in action; for enlarging, fine-grain developing is necessary or the pictures will look like rough sand. The popular D-76 film developer is highly recommended. Never start immediately with a whole sheet of paper. Cut a sheet into five or six strips about an inch wide, and try test pieces first. Until you develop “timing sense,” make any wild guess as to the exposure, and see how the test strips work out. The standard bromide papers start to show an image after about 20 seconds of immersion in the developer, and reach their full depth in 99. After determining what appears to be the correct exposure time, put a whole sheet of paper on the easel, turn the red filter over the enlarger lens, snap on the light, and move the easel around to center the image properly. Turn off the light, swing the red filter out of the way, and make the exposure, Immerse the whole print quickly in the de- veloper and swish the latter around by tilting the tray. After about 80 seconds, pick up the wet print with the print tongs and examine it under the safelight while it drips. When it is fully de- veloped, swing it through the acetic acid bath for about five seconds, and then transfer it to the hypo. NOW, wash the tongs in the water tray, [Continued on page 138] How To Train Your Dog [Continued from page 60] | onto the other, he is placed in a sitting position. Stepping a few feet in front of him, the trainer calls the dog by name. If the dog does not respond to the order, “Come Max” the rope can be jerked gently. The dog at first does not know you have the power to pull him by tugging on the rope and he will be astonished the first time you do so. However, after three or four lessons he will realize what is expected of him. The Hollywood trainer. says it is a good idea to reward the dog either with praise or a meat scrap when he has answered the command, Unless you want a shy, disobedient dog, he should not be let outdoors without this long rope being attached to his collar, Spitz believes. This lesson should not be given more than five times in one day. Don’t wear a dog out with training and do not try to teach him everything at once. Walking without a leash can be conveyed to a dog in the same manner as was shown above. At the first sign of any independent spirit, however, the leash should be put back on and the dog reprimanded. The best way to teach a dog to “heel” is to place him on a short leash and walk with him beside a high board fence. (See illustration). The dog is [Continued on page 139] Accept No Substitutes! Always Insist on the Advertised Brand!

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PRINCIPLE G : a aa P i oe T LAST! Automotive engineers have smashed down che A barriers to perfected combustion! The new VACU} MATIC solves the secret of greater power! With almost magical action, this amazing invention instantly puts new life and pep in any motor. It adds mileage to every gallon of gasoline . . . produces split-second pick-up, sensitive accelerator fesponse, quicker starting, greater speed and smoother running. GiGmaLd ~ Nothing Like It! The self-scarter — four wheel brakes — knee action — stream- lining . . . and now VACU-MATIC! The sensational money- Guaranteed Gas Savings saving invencion! With it, engineers have achieved a practical means VACU-MATIC proves itself on every car. Ie is guaranteed of cing ait and gasoline aucomatically for all speeds. to give worthwhile gas savings, quicker pick-up, and’ more VACU-MATIC is entirely different! It operates on the supercharge í i ; tinciple by automatically adding a charge of extra oxygen, drawn Iree power or it costs. you nothing. You can instantly tell. the From The outer aif, into the heart of the gas mixture. Ir is entirely difference in added power and motor performance — you AUTOMATIC'and allows the motor to “breathe” at the correct time, quickly notice the cash savings on gasoline, opening and closing automatically as required. No idling troubles—. no carburetor adjustments necessary. It is so simple it will amaze you Fits All Cers so practical it will save you many dollars on gas costs, VACU-MATIC is constricted of six parts, assembled and y fused into one unit, sorcery adjusted and ed at the r =æ — = — FREE OFFER COUPON = = = a 7 factory, Nothing to regulate. Any motorist can auach (ere antic in ten minutes. Once in, its only reminder I THE VACU-MATIC COMPANY ! is che surge of instant power and speed 7617-372 W, State St, Wauwatosa, Wis, it gives to the motor and the savings [| i ; i fut pocketbook. Gentlemen: Please send me full particulars conceming the VACU- at abords your k ( MATIC and details of yous Free Offer. This of course docs not Free Details obligare me in any way, VACU-MATIC offers a | splendid opportunity for 1 You owe it ro yourself to know all N unusual sales and profs aboue this remarkable discovery. Mail BING a ak eR Re Hee eed RRR E reer ee . its. Valuable terri- f j tories now being J the coupon below. Start saving gas assigned. Check with VACU-MATIC and enjoy a new I Address PEEVEEN Ei bashed E OA ERAS 2 og: iT and mail driving cheill! There's no obligation— Koad gal so get the facts now! Write roday! l Energa SrA NERE Slate AEE LL EA TIELAS TTA l O Check here if interested in selling proposition The VACU-MATIC Co, Wauwatosa, Wis. L m n = — = = — — — = — =- =- KNOCKOUT BLOY without using fib! © a 6 Learn American Police Jiu Jitsu w SCIENTIFIC BOXING HOW TO BE A DETECTIVE bt spot ar a light Also many o Ronbwest cupune use premen i. system. -Men must u-Jitsu experts. e persone By a Fistic Expert By Acthut H. Farrar ally taught mary in U, S. Army, Navy, Marines, Siustrated with Slow G-Man Mastery, Shadowing, | National Guard, Coast Guard, Immigration, Border ‘Motion ‘Pictures Criminal Code, Cross- Patrol, police. ete and pertormed for nearly all This is the greatest in- | Examination, Case Analysis, a eT for new Taung or qla, man structor in the Art of Self- Fingerprint Studies FULL PRICE 15c, Size or strength mean noth- Defense ever published. Ex- i Ing. Fear no man, gun, knife or club, pert guidance in How to This Easy-Instructor S. J. JORGENSEN Train, How to Land a | Method will give you the 721 Maritime Bldg. Punch, How to Dodge. Slip, | needed elementary informa- Hook, and Feint a Blow, | tion that will set your feet How to Receive a Murder. | on the Road to the Career ous Punch Without Hurt. of a Scientific Detective. Price 35c Postpaid. Price 35c Postpaid, Seattle, Wash. AUTOPOWER TURN SCRAP INTO MONE “PW AUTOPOWER tells you how in plain, easy, simple and illustrated instructions oe that rone can follow. Change auto generators into useful, practical A Ç and DC generators and motors with voltage from 2 to 1,000 volts, for power, light, welding, radio, sound. ete, No previcus experience nor special tools needed. Generat can be driven by wind, water, fan belt, etc, INSTRUCTIONS FOR BUILDING AN AC WELDER THAT ACTUALLY WORKS UP TO A 3/168 ROD. ALSO COMPLETE PLA? FOR WIND AND W E p PLANTS. Send for your copy of ‘‘AT'TOPOW Already used and en- dorsed by thousands. Only $1.00 posipaic. A S. W. DUNCAN, Publisher 412 $. Hoyne Ave., Chicago When Answering Advertisements Please Mention April Modern Mechanix 125

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GREATEST BARGAIN IN TEN YEARS NEW REMINGTON NOISELESS PORTABLE TYPEWRITER Money Back Guarantee 10-Day Free Trial Offer T LAST! The famous Remington Noiseless Portable that speaks in a whisper is avail- able for only 10c a day. Here is your opportunity to get a real Remington Noiseless Portable equipped with all attachments that make for complete writing equipment. Standard key- board. Automatic ribbon reverse. Variable line spacer and all the conveniences of the finest por- table ever built, PLUS the NOISELESS feature. Act now while this special opportunity holds good. Send coupon TODAY for details. YOU DON’T RISK A PENNY We send you the Remington Noiseless Portable for 10 days FREE trial. Jf you are not satislied, send it back. WE PAY ALL SHIPPING CHARGES. @ FREE ryvpine course With your new Remington Noiseless Portable we will send you—absolutely FREE—a 19-page course in typing. It teaches the Touch System, used by all expert typists. It is simply written and completely illustrated. Instructions are as simple as A, B, C. Even a child can easily understand this method. A little study and the average person, child or adult, becomes fascinated. Follow this course during the 11- Day Trial Period we give you with your typewriter and you will wonder why you ever took the trouble to write letters by hand. @ FREE carrvine case Also under this new Purchase Plan we will send you FREE with every Remington Noiseless Portable a special carrying case sturdily brilt of 3-ply wood. This handsome case is covered with heavy du Pont fabric. The top is removed by one motion, leaving the machine firmly attached to the base. This makes it easy to use your Remington anywhere—on knees, in chairs, on trains. Don’t delay ... send in the cou- pon for complete details! SEND COUPON WHILE LOW PRICES HOLD m yc ee Remington Rand Ince., Dept. 141-4 465 Washington St., Buffalo, N. Y. Please tell me how I can get a new Remington Noiseless Port- able typewriter, plus FREE Typing Course and carrying case, for only 10c a day. Also send me new illustrated catalogue. | Naim: ge) A OEE ode ok Baw along Sei Le Mie aia ee ee | Add reas i333 445 eee eee BS de Sey eee AAS AT i City oTe EEE EEN Er BIAR SUNE a aane 126 Water Treasure Hunting [Continued from page 44] of cutting out, at the bottom of the well, the great pit that is to act as a filtering plant for the well, and the repacking of it with graded gravel from the top. Let Mr. Sweitzer tell of this operation, the most distinctive and valuable in deep-well creation. “The cutting or reaming out of this pit is ac- complished,” says he, “with a hydraulic reamer , that works under pressure in the manner em- ployed in hydraulic mining. This reamer is made i up of a series of jets and nozzles placed at the ends of direct rods in positions opposite the water-bearing strata. Water forced down from the top of this reamer spreads upward and out- ward from the jets at the bottom of the drilled well and washes out the formation there. The refuse is floated to the top and sluiced away. “In the meanwhile, from another pipe, parallel- ing this one but not connected with it or its jets, graded gravel and water are pumped down into the pit hole from the top. This operation we call ‘gravel-walling’ or ‘gravel-packing. It is a new idea in deep-well construction and is designed to-assure more water from the well than other- wise. From two to ten times the volume of water that is obtained from other types of wells is ob- tained through this new type. The hydraulic reamers work under pressure of from 100 to 200 pounds per square inch and the volume of water forced through the reamer during the excava- tion process is about 700 gallons per minute.” When the outer casing has been placed and the contaminating seep water from the surface cut off by running a concrete shell around it, the inner casing is put down. This inner casing is very important, for it is through this casing that the water from underground is brought to the tcp of the well. It has a shutter screen at the bottom through which the water enters from the gravel filters. This shutter screen extends from the bottom of the well to the top of water-bearing strata and wherever else, in the course of sink- ing the well, water-bearing strata is encountered. This bronze shutter screen also represents the ' very latest ideas in deep-well construction. The slots in it are arranged cross-wise around the tubing so as to insure against sand-locking of the well. It is made of silicon bronze, 95 per cent copper and 5 per cent other alloys. It will not corrode, rust away or build up mineral de- posits on itself. Its hardness is so great that an acetylene torch can scarcely faze it. The forcing of concrete up the outside of the outer casing is the most particular job of all in modern deep-well construction. This is because the concrete is pure and sets so quickly that, should enough time elapse from running it that it hardens before it reaches its destination, the well is “done for.” Running this concrete shell is accomplished as follows: The outer casing of the well is put down with a wooden plug in the bottom. This plug Accept No Substitutes! Alscays Insist on the Advertised Brand!

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is securely fitted in place with screws from the side of the casing. In the center of it is a “V- shaped” vent. ; When the concrete is ready to be poured, a pipe is dropped down into the well with a V- shaped nozzle on the end of it that fits snugly into the V-shaped vent in the wooden plugs at the bottom. Concrete and water are now forced down this pipe under pressure. They pass through the vent and are carried back up along the outside of the casing to the top of the well. Thus a concrete shell is formed about the entire cuter casing. The purpose of this shell is to ward off seeping surface water from the pure water rising from underneath the ground. The tendency of this seepage is to trickle down the casing’s outer- side to the bottom of the well, contaminating the reservoir supply there. This system of pro- tecting a deep-well water supply is now virtually required by all hospitals, cities and municipali- ties using deep-well water. “There is a popular belief that rivers and streams supply the underflow of water in the earth,” says Mr. Sweitzer. “This is not the case. The supply comes from rainfall. The rain per- colates down through successive strata until it reaches a porous formation underlaid by an ‘impervious one. This porous stratum thus be- comes a storage reservoir. “Another source of underground water supply is limestone. This stone is very porous and water permeates it readily. Whole areas of the United States are underlaid with this water- bearing formation. A notable section is that found around Savannah, Georgia. “Water is also found trapped in underground _ rock where, through crevasses, it has seeped, remaining there until it is brought to the surface by the deep-well driller. It is also found in low, flat plains, immediately on top of granite rock beds located at depths from 35 to 4,000 feet. The water collected in a porous stratum is ecatrolled by gravity and flows at a velocity dependent upon the inclination of the stratum and the voids or openings in the actual water-bearing material.” Interesting facts in connection with the flow of underground water have been gathered by Dr. Slichter of the United States Geological Survey. The facts relate to the Arkansas River Valley at Garden City, Kansas, and the survey showed that the average flow of underground water was eight feet in 24 hours. Using these figures and taking a river valley five miles wide. with a river in the center, it would take water coming from the hills through porous strata about four and one-half years to reach the river. This computation shows how dependable and constant the underground water supply is. An average supply is always on hand. NOTICE Changes in the make-up and title of this magazine will be announced in our next issue. Reserve your copy now. When Answering Advertisements Please Mention April Modern Mechanix Treet Topics UO MAKE RA THIN DIME ~ END TO MAKE A FACE LOOK ~~ = A S LIKE | Ce. ih DG; 4, Ne 2 BLADES/ \ -AND TREET yoursELF TO A PACK OF PERFECT SHAVES/ Edge | FOR GEM AND EVER- READY. RAZORS Treet Salety Razor Corporation, Newark, New Jersey 127

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PILOT 6 A Reflecting Miniature Camera At A Roll-Film Price Do you want a reflex camera that provides razor-sharp definition, Dy means of a clearly visible, film-size Image on the focusing ground-glass finder—would you like a miniature camera that gives you sixteen pictures, slze T3 x 214 inches on standard economi- tal 120 roll-flm? Do you desire both? Well then—your Instrument is Pilot Q—the reflecting miniature camera series obtainable at prices that compare favorably with those of the roll-Alm type. A high hood prevents side-light and glare from penetraling the focusing screen: an auxiliary magnifier enables ultra-fine focusing, It has five shutter speeds ranging from 1/20th to 1/150th second as well as time and bulb and many other precislon camera con- veniences, With f/8.3_ lens $17.50 #/4.5 lens #/3.5 lens $23.50 $30.00 FREE TRIAL GLADLY GRANTED Literature on Request 6 BURLEIGH BROOKS INC., 127 West 42 Street © New York WEAT ARE YOUR NEEDS! Write us today—Get our low down Prices. Bring your Equipment up- to-date Cheaply. Specialists in Fine Grain Developing, Enlarging and Print- ing. Send us your rolls. NEW YORK CAMERA EXCHANGE 109 FULTON ST., NEW YORK CITY, DEPT. MX4 SINCE 1890 CANDID BARGAINS ENLARGE OR REDUCE DRAWINGS— COPY PHOTOGRAPHS Jecta-Scope! Like magic, cam take a small int illustration and m et an enlarged image Full-Size Patterns on 4 sheet of paper So that the operator can in a Jitfy quicitly trace the i ge and obtain a perfect renroductjon in any required size. No skill POST PAID is required. Anyone can use Jecta-Scope pro- $ ficiently the very first tlme, Installation of (Less Gord) light cord and bulb make jt ready for use. s Gor Nothing will take its place, and no work- shop owner will ever part With it after he has tried it out. Silhouette objects, lathe turning patterns, scroll saw designs and hundreds of other pris. of illustrations are casily reproduced. size designs can be projected and traced directly on Wood to save valuable time making, things in your workshop. Jecta- Scope is as essential to every workshop as hammer and plane. Enlarges and Reduc į cluding telescop i curate ad, ducing. Cons colors ructed of § and equipr ished magnifying le: watt bulb. Emerling and Educational @ Derelops Arr Talent Quicke: yay FREE Suhouelte Patterns A ee di ficient in drar As a special offer to “dis to draw fror Keadere a thie magazine, jections every Jecta-Scope ordere Ma aian x from this announcement tracing method of ins active Sihouelie designa Reproduces Objectsin Color Without charge. This fres Objects can be projected in full, enlarged quickly and ac- natural colors wiih the Jecta-Scope curately with Jecta-Scope, by simply placing a sheet of glass and the designs can then he Lop opening and laying the on the sheet of glass, Flet s can he projected easily, inary truction, be used for making many Book over« appealing projects. ends, lamp shades, lays for furniture, nursery su v Ww ne cutouts, and wall plaques a: hee ola sen ae i are only a few of the pos- sible uses. JECTA-SCOPE Model No. 70 is quickly converted {rom a vertical projec- tor to a horizontal pro- jJector for throwing clear images on wall or sereen up to five feet In dla- meter. Takes less than one minute to change. PROJECTS Silhouettes Postcards Patterns Drawings Turnings Chbijects Fretwork Snapshots Photos MAIL COUPON TODAY Federal Stamping & Eng. Corp. Brooklyn, N. Y. VEE EB ERE R ERR ERE Federal Stamping & Engineering Gorp, 1 Brooklyn, N. fo in full pay int for Model No. 70. Please C Send mac hine C.O.D. plus postage. I wili pay posman, 128 | New Uses For Rubber Heels [Continued from page 91] any surface, use either shellac or bicycle rim cement. It is best to coat each surface with the shellac, allow it to dry, then recoat the rubber lightly and press it in place. If the use makes it desirable that the rubber have a pleasing finish, use a coating of shellac to which dry color has been added. When the cushioning legs under your type- writer became hard from age, cut new ones from a rubber heel and notice the difference. Thin discs cemented to the bottom of table lamps, book ends and similar articles will protect the finish of the furniture; likewise, a larger block or a small-size heel under each leg of the furniture will protect the floor from becoming marred; unlike glass “sliders,” they are unbreakable and non-sliding. By squaring up a heel and attaching it to a wood or metal handle, it is a practical pan scraper for kitchen use; when the edges are worn, square them with a knife. Two blocks of the material screwed side by side to the kitchen wall will hold the handle of a broom, and it can also be cut into plugs to replace worn sink stoppers when the manufactured article is not readily available. The automobile radio will receive less vibra- tion if it is mounted on blocks of the rubber, and small blocks make suitable replacements for the soft rubber cushions under the automobile hood clips, to eliminate noises. Tricks With Lenses [Continued from page 109] camera Jens. The easiest way to determine whether your lens is of the type that will work this way is to try it. A jeweler’s loupe, which has a focus of about 4”, is very good for close-up work, particularly since its construction includes a barrel which acts as a lens-hood. Jumping from one extreme to the other, the telephoto is the most expensive type of auxiliary lens, and one of the rarest to be found in the ama- teur’s kit-bag. Prices run from fifty to five hun- dred dollars, so unless you make your living by taking wild-animal pictures in tree-tops or some- thing of the sort, you are likely to pass this one -up. You need not, however, for any field-glass may be used for the same purpose. Even the 98c ones will do, but of course these are seldom over 3 or 4~power, and hardly worth the effort. Never- theless, there are such things as irreducible minima in photography, and the number of grains of silver as well as the resolving power of a small lens are limited by this fact. A small house a mile away might only show up as a half-dozen grains of silver with the finest camera, but when that distant landscape is divided optically by a 32- power glass, and that 32nd of the horizon en- dlcccpt No Substitutes! Always Insist on the Advertised Brand!

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larged to cover your whole film, you have a pic- ture, instead of a fly-speck. The difficulties involved here are slightly greater than in close-up work, for the reason that errors of all kinds are greatly magnified. In fact it is practically impossible to get perfect focus, but the examples shown will prove that satisfactory work can be done. The first picture shows the Empire State Build- ing tower taken from the writer’s window with the ordinary camera lens on a typically smoky and hazy New York day. The second shows the same view, with the aid of a 98c pair of opera glasses, about 3-power. The third picture was taken with the same camera, but using one of the bargain 10-power navy telescopes now avail- able on the market for ten or twelve dollars. Any telescope or binocular can be used in this way, and the better the instrument the shorter the ex- posure. A k-2 filter is practically a necessity on a hazy day. Best results are secured by removing the camera lens entirely. The binoculars are bound to the camera with Scotch tape, with the forward end supported on books or wooden blocks. The camera stop is left wide open, the focusing done on the ground-glass, and then a piece of black paper is pasted over the front end of the large binocular lens. This has a circular hole in the center about one-fourth the diameter of the lens, thus serving as a stop and sharpening the focus and cutting out some of the color aberration. The focusing is done before this stop is pasted on, for there is little enough light at best. Naturally a longer exposure is needed, and absolute lack of vibration. The safest method is to hold a piece of black paper in front of the binocular lens, not touching it, then open the shutter, wait for vibration to cease, and then time the exposure with the paper. Here again, a more permanent rig can be made by removing the lenses from the binocular and mounting them in wound kraft-paper tubes. painted black inside, with the rear tube At camera lens, and the front tube sliding over th rear tube, telescopically. Various other well-known lens tricks might be mentioned again, for the benefit of chose who may not be acquainted with them. One way to increase the speed of a cheap box camera is to cut out the “diaphragm.” This results in a slight haziness in the picture at all distances except one, and it usually trebles the speed of the lens. The hazi- ness is hardly more than the equivalent of a “soft focus” effect, however, and the negatives will still stand enlargement in most cases. Still another method of working closer with your camera, if it has a bellows extension, is to file off or bend the metal stop on the focusing scale, thus permitting the bellows to be extended beyond the usual last stop. Frequently this opera- tion will permit you to work as close as three feet without any kind of portrait lens. If your camera has no ground-glass you will of course have to im- provise one. When Answering Advertisements Please Mention April Modern Mechanix AMERICA’S 7222 MOVIE Richard Arlen, star of Columbia’s “No Time To Marry,’ i With F:3.5 Lens . . . $19.95 UNIVEX CINE “8” Over 200,000 enthusiastic UniveX owners will tell you why this amazing movie camera, in one short year, outsold those of all other makes combined! Compact, lightweight, easy to load and operate, and always dependable—it’s the only movie camera in the world that uses the inexpensive 60¢ UniveX Cine Film and takes theatre-quality movies at less cost than snapshots! See it at your dealer’s today, or send for booklet 27. View! UNIVEX MINICAM The lowest-priced precision- built Miniature ever offered! Uses UniveX 10¢ roll film. The only one taking six exposures, thus eliminating unnecessary picture-taking and delay! Fitted with new-type Achromar Precision Lens — individually focused, adjusted and tested. Shutter speeds for time exposures and 1/50-of-a-second snapshots; spy-glass-type view-finder. Self-opening. Antique bronze finish. Clear, sharp, negatives 114” x 1144” that make excellent 3” x 4” larger-prints. See it at your dealer’s, or send for booklet 28. Universal Camera Corp., New York, N.Y. 129

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Do you like RADIO? Does the future of TELEVISION Interest You? ie Vee a EYN Cz “N K Send for your FREE COPY of this book of FACTS Full of Instructive Information on Employment Opportunities and Requirements You men who are sincerely ambitious to m related industries will want a copy of this new L opportunities and requirements, Written in pl language with no exaggerations and no mis-statem. gives you facts you want to know about these pr dllustrations. Major subjects include Television Theor; tion, Plek-up Systems, Amplifiers, Transmitters, Hecei Tubes, Sound-Recording on disc, Loud Speakers, Ta Projection and Radlo Communication, NATIONAL SCHOOLS is the oldest trade institution in ti: Established in 1905. Occupies its own modern three-story t exclusively devoted to training ambitiouns men, Latest equip Selected, experienced staff of engineers and instructors, Man) 3s can earn room and board while learning. Natlonal students ar allowed coach railroad fare from any point in the United States. NATIONAL SCHOOLS Los Angeles Request for FREE BOOK of Details NATIONAL SCHOOLS Dept. MMR-4 4000 So. Figueroa Street, Los Angeles, Calif.. NAME... AGE irs ADDRESS CITY “Color” In Black And White [Continued from page 114] To appreciate the effect shown, it is necessary to know the coloring of the three books. The left hand one has a background of bright red; the three large lines at the top are deep blue, almost purple. The emblem in the lower left corner has yellowish gold letters against deep blue. The center book is entirely maroon red, with dead black lettering. The smallest book is deep orange, with a black panel across the center. The small lines of type are black; the trade name in the center is orange like the background. Notice in photo “A” that the orthochromatic film registered the bright red, the maroon and the orange all about the same tone of blackness. The smallest book is all dead black, and not a word on it can be distinguished. It is hard to believe that photo “B” is of the same books. The reds are now distinctly light, and the type stands out perfectly, and other differences in the “color” values are also evident. These effects could have been exaggerated greatly through the use of filters, but this wasn’t necessary. Filters prevent the passage of certain bands of light, thus giving the effect of greater emphasis to the light they do transmit to the film. The selection and use of filters is a highly inter- esting phase of photography, and the camera who masters their properties can produce un- usual, prize-winning pictures. Fishing For Distant Quakes [Continued from page 75] recording arm. Now prepare the stirrups at the ends of the recording arms, folding strips of aluminum as shown in Fig. 5 and punching small holes in the sides of the stirrups to accommodate the recording needles. These needles consist simply of two ordinary sewing needles run through a piece of cork at right angles, one serving as an axis while the other traces a fine line on the recording drum. The arm is now ready to mount on the pier. Hang the weights from the two 14-inch bolts at the top of the pier, using light. strong wire and cutting in small turnbuckles for adjustment. Now place the points of the phonograph needles in the punch marks and adjust the wires until_the magnifying arms come to rest parallel to each other, This construction is clearly detailed in Fig. 6. If the arms and weights are exactly alike they will have the same natural “period”? of vibration. Set them in motion and time each one’s movements, shifting the wire on the 34-inch bolt until they have exactly the same rate of vibra- tion. Moving the wire toward the pier lengthens the period; away from the pier, shortens it. The recording drum, also shown in Fig. 6, is a cardboard roll 6 to 8 inches in diameter and 20 inches long and may be secured for the asking at a furniture store. Linoleum is shipped on such rolls of various sizes. A drum of these dimensions will run a week’s record without renewing the record sheet. From your neighborhood plumber, get a brass tube about 30 inches long and a brass rod that will slip snugly into the tube for a distance of 2 or 3 inches. This brass rod should be about 14 inches in length and threaded, 12 or 16 threads per inch, for a distance of 10 inches. A square-hole washer now should be soldered in one end of the brass tube, which forms the axis for the recording drum. Mount the drum securely on this axis, leaving the 10 inches of threaded brass rod projecting from the end of the drum. The threads run in the “V” of one of the knife-edged supports made from metal strip. so the drum will move horizontally the width of one thread for each revolution of the drum. The other support. of course, carries the opposite end of the drum, as pictured in Fig. 4. 130 Accept No Substitutes! Always Insist on the Advertised Brand!

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Make a square shaft which will slide smoothly in the square hole in the washer of the drum’s axis. Connect one end of this square shaft to the hour shaft of the driving clock (preferably an electric or 8-day instrument so as not to stop at inopportune moments) and insert the other end in the washer. , For connecting the driving rod to the clock a universal joint of some sort must be used to allow for friction that may develop through mis-alignment or temperature changes. Fashion this universal joint by using a square washer with holes on four sides, or a small block of rubber will suffice. The instrument may be refined somewhat by mounting the clock on a rubber-tired toy cart which moves horizontally with the drum, thus eliminating the sliding driving rod and reducing friction. Use a sheet of wrapping paper for a recording sheet. Wrap it smoothing around the drum and glue the edges tightly. Revolve the drum slowly as you now smoke the recording sheet black by use of a coal-oil lamp minus chimney. With recording sheet in place, carefully check over the apparatus. See that the magnifying arms are parallel; that the instrument is protected from air currents; and that the needles rest lightly on the recording drum. When every- thing is ship-shape, start the clock. As the drum slowly revolves a fine line will appear on the stnoked record cylinder. To make a really accurate record it is well to provide some kind of time clock. A simple scheme is to wind two tiny coils and place one on each magnifying arm in such a position that when the coil is energized by current from the light socket, it will attract the needle and lift it momentarily, leaving a minute break in the seismogram. Fig. 7 and the accompanying photos show details of magnets. A second clock, preferably an alarm clock with a sweep- second hand, should be fitted with contacts so that each hour the contact will be made and the magnet coil energized, producing an hour mark on the drum. A small bell-ringing transformer will step down the 110 volts from the lighting service to the right voltage. When the drum is filled with a record, remove the sheet and slip it into a trough containing shellac diluted in 50 percent alcohol, then hang it up to dry. The alcohol not only thins the shellac, but also gives a dull finish to the record and protects it against blurring. Don’t expect immediate results—you may register a quake five minutes after starting the instrument, or you may have to wait several days. But on the average, there is a distinct earthquake somewhere on this earth once every hour and some of them will register e i When studying your Àr seem to come in bunches. T 1 l of at least three distinct groups of shocks—a prin a secondary wave following a little later, and a ! cession of minor shocks. The spreading of the wav they travel through the earth’s crust gradually separates these groups, and for a quake 8000 miles away, they may be as far as twenty seconds apart. By noting the time between these wave groups you may form a rough idea of how far away the shock originated. In the study of seismograms you will doubtless find of interest two booklets that can be bought from the Superin- tendent of Documents, Government Printing Office, Wash- ington, D, C. The first is a 61-page booklet with a map of the U. S. and is entitled, “Earthquake History of the U. S., Exclusive of the Pacific Region’’—Special Publication No. 149, and costs 15 cents. The other, “Destructive and Near Destructive Earthquakes in California and Western Nevada, 1796 to 1933, —Special Publication No. 191—is priced at 5 cents and is a 24-page booklet, Funnel On Lock Guides Key No more fumbling for the key-hole in the dark! For Ralph A. Ringseis of San Francisco, Calif., has just been granted a patent for a key-hole guide which unerringly sends the key on the first try into the key-hole no matter how dark it is. The guide is a key-hole-finder de luxe. It amounts to a funnel that clamps on to the lock. The funnel has a big mouth, so that any lunge you make with the key is bound to land the key in the funnel. After that it’s simple. The funnel just guides the key—and in the proper position, too —tright into the key-hole. Mineral wool is favored hy many architects for insulating houses against heat and cold, but it is too bulky to be trans- ported far by rail economically. Television cameras, to be tried in Fogland. are several times more sensitive than those previously used. When Answering Advertisements Please Mention April Modern Mechanix Fine Work Begins with a Disston Saw » «+. The Disston DeLuxe is the finest home workshop saw you can buy. Disston steel! Disston workmanship, of the highest standard! On any job you do, Disston DeLuxe means easier cutting. On something that is a real challenge to craftsmanship, you will realize that the easy, accurate cutting of this fine blade is the beginning of fine work. Ask your dealer for this saw by name: “Disston DeLuxe’’, etched on the blade. See the high, smooth finish...accurate fitting... keen teeth, that hold their cutting edge. Own- ership of a Disston DeLuxe Saw is of itself inspiration to build pieces of which you can be proud. Cross-Cut— Rip— Combination 6" (14" hole) $2.70 8” (33. 35". 32“ hole) $3.50 7” 24" hole) $3.10 10” (24",34"hole) .. $4.50 Hollow Ground Combination 6” (4" hole) $4.30 8" (34", 44", 4" hole) $5.10 7” 4" hole) $4.90 10"( age 34“hole) . . $6.90 Use Disston Saws, Tools, Files in your home workshop. How to choose, use, care for, these better tools and do better work — all is shown in this Disston Manual sent FREE. MAIL COUPON TO: HENRY DISSTON & SONS, INC. 408 Tacony Philadelphia, U.S. A. Check the Hardware Store for Value and Varlaty

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This MACHINISTS’ Home-Study Course — helps men get ahead Newly assembled—specially priced—these five recent books give you the practical facts on modern machines, up-to-date methods you need to advance in machine shop work, Take advantage of the other man’s experience as found in books, to solve your problems, increase your efficiency, with The New AMERICAN MACHINISTS’ LIBRARY 5 volumes—2014 pages—1853 Ulustrations (A combined home-study course and reference library) This library of machine shop practice was written for practical men. It gives you the best methods for every kind of machine shop work. It deals fully with lathes, drills, and other machine tools and their operation, automatie serew machines, speeds and feeds, gear design and production, puneh and die work, inetal surfacing, ete., ete Plainly written—coumletely illustrated—the best kind of help to the machine-shop man who wants to advance himself, No money down—special priceeasy payments FREE EXAMINATION COUPON McGRAW-HILL BOOK CO., inc., 330 W. 42nd St., NEW YORK, N. Y. Send me for 10 days’ free examination the new, American Ma. $ n } j chinsts’ Library, If satisfactory I will send 0 days and $3 monthly untill the special price of $16.50 is paid. nas wanted, I will return the books postpaid. (To insure prompt ship- ment write plainly and fill in all lines.) Name -sesses nce a a a e City and State...-_- am. Position -_-------- pingeid ain gag inp gee peng apa Explains latest inventions, methods of Photography stil : d movie Cameras, Lenses, Films, etc. Used equipment accepted Central Gamera Co., 230 S. Wabash, Dept. J-4, Chicago, U, S. A. Let millions of tiny, living plants help to the curse of youth—a pimply skin. They velop, Your system is upset. Poisons may pol- and purify your blood. active, living yeast plants will help keep poisons or less. Start eating Fleischmann’s Yeast now. y and Home Movie Making, for fun in haa Satisfaction guaranteed! keep blood free of skin irritants know what happens between the ages of 13 and lute your blood stream and bubble out on your Let Fleischmann’s Yeast help remove these from the blood and help to heal your broken-out Buy some tomorrow! | Company. ..-.--------------------+--------+-- MMs-4-33 i FREE! ©? i hundreds of amazing money-saving Bargains in WRITE GOR [REE BARGAIN BOOK! SCHOOL-AGE PIMPLES? a Thousands of young people have said good-by 25, the time of life when important glands de- skin in ugly pimples. Then you need to cleanse impurities the natural way. Millions of tiny, skin. Many report amazing results in 30 days Copyright, 1938, Standard Brands Incorporated 132 | | zl | { and profits. Offers j | The Flood Of New Stamps [Continued from page 70] 1937 issued a series for Pushkin’s centenary, six stamps in the perforated series. Only two designs were used on the six stamps. Thus the “type col- lector” saves but two stamps; the two designs are shown, which are sufficient. The other values merely repeat the designs, or types, and in this sort of collecting are unessential. “Type collecting” has taken hold these days, of innumerable new stamp collectors. It is one of the most satisfactory ways of collecting, because we may have every type without every value of stamps. Therefore the cost is materially lessened. Also, an album does not become so bulky. Of course, when an issue appears and all the designs are different, it is necessary to retain every value. In the general collection, following the “type method” the expense will be found materi- ally decreased, and the stamp deluge immeasur- akly lessened. Follow The Fleet [Continued from page 118] this relation between the two items of car ex- pense which are so often misunderstood. Fleet operators suggest to the car owner the im- portance of aiming for hidden savings. Keeping the oil filter in working order, for instance, not only saves more frequent oil changes, but lessens the tendency toward sticky valves. This, in turn checxs lowered gas mileage. Keeping the shock absorbers well filled with the right kind of fluid will not only save the springs but, by controlling the bobbing action of the car, will save extra wear on the front tires. Often a little service on the generator will go a long way toward sparing the battery overcharge or discharge. Service stations will give the owner a great deal of consideration if they find that he is tak- ing his car management seriously. Tire com- panies often will rotate tires without charge, if | the customer is aiming for better mileage. It is naturally good business for the company to point to examples of high mileage with its products. Such tire changes should be counter-clockwise, and the spare or spares always should be worked into the picture. Pressure is very important. To- day, most tires are wearing prematurely along the edges of their treads as a result of under inflation. Inflate the tires at least once a week. Every two weeks is not often enough. Take into consideration where the car is to be used, and vary pressure accordingly. Tires need more air around the city, especially if the car is parked for long periods. Follow the fleet for genuine savings in motoring. If you know someone whose car is owned by a large firm, follow him to the service station and get acquainted with the system he follows. Accept No Substitutes! Always Insist on the Advertised Brand!

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Pocket Electro Plating Outfit [Continued from page 120] probably an indication that the distance between the work and the carbon rod of the electrode is too far. Some of the cotton can be removed from the electrode and a longer carbon rod used. The resistance can also be overcome by wiring the batteries to deliver 3 volts. Do not use too high a voltage, however, as the plating would then have a dark or “burned” appearance. In order to make the polishing cloth, moisten a strip of flannel with benzine and rub it well with a piece of jeweler’s rouge. The mercury solution is merely a saturated solution of mercury nitrate in distilled water. All three bottles should of course be marked “poison.” To make up the gold and silver electrolytes, first make a stock solution of 160 grains of yellow prussiate of potash and 80 grains of sodium car- bonate in 8 ounces of distilled water. In 4 ounces of this dissolve 40 grains of silver nitrate, and add 4 grains of gold chloride to the other 4 ounces. Place each in separate test tubes or beakers and bring them to a boil over a bunsen burner. On cooling, the precipitates will Have settled and you can pour off the clear gold and silver solu- tions. Half-fill the 1-ounce bottles, and store the remainder for replenishing purposes. Documentary Evidence [Continued from page 122!

capital E. Place a dot above the first upstroke of the letter n, making it an i; connect the top of the second upstroke of the n with a curved line over to the top of the e, then continue from the e down- ward with a loop to make the e into a g. The “One” has now become “Eig.” Add “ht,” and “One Hundred” now reads “Eight hundred.” The cor- responding numerals on the right side of a check are similarly altered, “100” being made “800” by simply connecting top and bottom of the “1” with an S-shaped loop. Experts can do this sort of thing so that it will escape detection by the unaided eye, but the microscope will show up the added work by the same principles as explained above under forgery. There are a great many different brands of ink on the market, the blue tint predominating. While many of these different inks appear to have ex- actly the same hue to the eye, a comparison micro- scope will quickly disclose even slight variations in tint, and the same principles apply in com- paring the inks of typewriter ribbons as seen in typed material. This constitutes another way of detecting checks raised by the method of addi- tion, as very often the new ink will not exactly match the original. The comparison microscope has two tubes, each with its own objective, but only a single eyepiece, the two images being directed by prisms so that [Continued on page 135] When Answering Advertisements Please Mention April Modern Mechanix

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a once. INVENTORS [e= 5 TO OBTAIN A PATENT YOUR IDEAS Titan ! SEND FOR FREE BOOK === aly ap ; HOW TO OBTAIN A PATENT phie | Written by a Former Member of the Examin- ing Corps (1922-24) of the U. S. Patent Office. lf you want to profit by your idea, you should take steps to apply for a U. S, Patent at = Your first step is to get this Free Book. This 9 interesting illustrated book contains valuable information $ you should have. It tells you fully how to obtain a patent on your idea in the quickest way. With this Free Book you will also receive a “Record of Invention’? form on which you can easily record your idea. Personal and Confidential B Service: Your case will be personally handled only by a Registered Patent Attorney who is also a Former Member of § the Examining Corps of the U. S. Patent Office. AH com- munications confidential. MAIL COUPON TODAY for FREE PATENT BOOK and RECORD OF INVENTION Form Gi CARL MILLER. i REGISTER ED PATENT ATTORNEY FORMER MEMBER EXAMINING CORPS U. S.. PATENT OFFICE i Woolworth Bidg., 35th Floor, Dept. 48B, New York City a MILLER BUILDING, Dept. 48B, WASHINGTON, Please send me your Free Book, How to Obtain a Patent,” ‘and | | i your “Record of Invention" form, i] : NAME noores wusuaveeasaccakyee E eeeeeaeen I L] : ADDRESS „.oossssereerere esnesaresesssoasereeserreasen. D 1 Dun Le ee 8 MAKE MONEY IN YOUR WORKSHOP | Build furniture, auto trailers, canoes, iceboats, cruisers, sailboats and aegris refrigerators described in REE BLUEPRINT BOOKLET MODERN MECHANIX PUBL. CO., Faweett Bldg., Greenwich, Conn. in9 Months _ with the FOLEY LAWN MOWER SHARPENER “A subslantlal inerease in grind jobs cach year, proves beyond any doubt that Foley Grinders do very satisfactory work, We hare ground 723 mowers since February 1 to date, November 9. Our total receipts on lawn mower service alone during that period hag grossed us $1,025.00, The prevalling price of grind- ing and adjusting service ls $1.00 and $1,25—vepairs and parts extra.’—W, A. Tulip, Phoenix, Ariz. You Too Can Make Big Money Free plan tells you how to start. The Foley Lawn Mower Sharp- enes turns out ‘perfect work quickly and easily, no experience needed. Simply put the mower in the machine and turn on the power. Uses same system as lawn mower factories. Sharpens all sizes and types in 15 or 20 minutes. Special Offer: Attachment for grinding axes, hatchets, knives, etc. included FREE with Foley Lawn Mower Sharpener on our Special for, brings Soe ar Ss 3 Offer, ri brings you ausiness th the year! ground Seng coupon, today FOLEY MFG. co. ~~ 408- 8 Main St., N. E. Minneapolis, Minn. | Send Free Plan for making money sharpening lawn mowers, and | Special Offer on the Foley Lawn Mower Sharpener, DDRESS so 2seneeeGecesasemesea ce case eae seen Ba ee ee eee eee eee 134 Trick Drawings From Photos [Continued from page 107] The most important requirement is that the print be on smooth or semi-mattie paper. Glossy paper is absolutely unsuited for the stunt. Pin the print to a drawing board, and use ordinary drafting or art instruments. The ink can be of any color, as long as it is the waterproof kind. Simply ink in whatever you want to remain in the picture, or add lines wherever desirable. Use T-squares, triangles, French curves, compasses, brushes, ete., as aids. You can even do good work with an ordinary fountain pen. Be careful to let each line dry before you run the T-square or triangle over it. If you attempt to make erasures, you are likely to remove the thin layer of emulsion that constitutes the picture image. Use as many different colors of ink as you like. However, if you are preparing an illustration for reproduction for printing purposes, use black only. Two chemical solutions are required. The first is for bleaching, the second for fixing. The bleach- ing bath consists of the following: Iodine crystals (NOT tincture of iodine sold for antiseptic purposes)—60 grains or 7}4.gm. Potassium iodide—180 grains or 23144 gm. Cold water—20 oz. or 592 ml. Iodine crystals are sold in small glass-stoppered bottles. Don’t let any of it touch your fingers. The mixture becomes deep red in color with the addition of the potassium iodide, and must be stirred thoroughly with a glass rod until all the crystals have dissolved. A quart bottle is handy as a container. f The fixing bath consists merely of 4 oz. or 113.4 gm. of ordinary photographic hypo in 20 oz. or 592 ml. of cold water. Pour the solutions into two trays. Immerse the inked-in print in the iodine bath and keep it there for about two minutes. The entire image will ap- pear to be blotted out with red, but don’t be alarmed. Pull out the print with a pair of tongs, let it drain for a second or two, and then immerse it in the hypo tray. In about a minute the red tone will fade out, and in about five minutes the photo- graphic image will disappear completely. All that will remain will be the inked lines, appearing against a perfectly white background. Let the print “fix” in the hypo for about fifteen minutes. Then wash it in running water for about 30 minutes, and dry between blotters just as with regular photo prints. This entire “silver printing” process is carried out in full room illumination. No darkroom is necessary. NOTICE Changes in the make-up and title of this magazine, designed to make your favorite publication better than ever before, will be announced in our next issue. Be sure and reserve your copy now. Accept No Substitutes! Always Insist on the Advertised Brand!

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Documentary Evidence [Continued from page 133] they make up halves of a single field of view, divided by a hairline. Not only ink colors but many other forms of documentary evidence are directly compared by means of this ingenious in- strument, a modification of which, used in study- ing bullet scratches, appears in one of our photo- graphs with this article. Specimens of hand or typewriting, pen and pencil points and slants, type faces, paper surfaces, erasures, added ma- terial in the form of interlineations or overwrit- ing—these are but examples from a long list which are but grist to this microscope. Operating on a similar principle, the colorimeter is an optical instrument borrowed by criminolo- gists from biochemical laboratories. It has two cups in which liquids can be placed for a direct optical comparison of a known with an unknown solution. The fluorescence microscope is yet another weapon in society’s war on the criminal. This ma- chine employs lenses and prisms of quartz, which will transmit ultraviolet light to be recorded pho- tographically, though such rays are invisible to the human eye. They cause substances to glow or fluoresce with hues that are characteristic for different kinds of materials and may be extremely valuable in identifications. As an example, there ‘was a case where it was alleged that notations on a certain document were written in 1868, but when the red ink under dispute was examined by the fluorescence microscope it was proved to be made from the synthetic dye eosin, which was not dis- covered until 1874. When the microscope is put to work on a simple piece of typewriting, as an anonymous pcison-pen letter or demand for blackmail. it is seen that every typewriter has its-own’distinctive peculiarities and that the product of one may be told from that of another just as surely as the ex- perienced operative can distinguish between two different fingerprints or sets of bullet scratches. Marks and imperfections on type faces, smudges from unclean and clogged characters, deviations in slant from the perfectly vertical, minute diver- gencies from a theoretically perfect horizontal alignment, slight discrepancies in spacings, letters which do not strike the platen evenly but are instead heavier in one portion than another— these examples will give an idea why it is easy, under magnification, to identify a specified piece of work with the machine that wrote it. The police consider all possible suspects in a case and the proposition is then to “cherchez la typewriter” instead of “la femme!” Samples are taken from every machine to which any of the suspects could have had access, and compared with the criminal document, with certainty of identification. Working back then from the type- writer, an arrest most often follows. [Continued on page 137] WET CELLARS MADE DRY from the Inside! Damp musty cellars are unsanitary, a danger to health and a poor place to store valuable material. Where ground water or moisture seep in through cracks or porous spots in the floor or walls, you can make and keep your cellar dry and sweet—a fit place to work, free from odor, mold and rust—by filling the cracks and coating the moist surface with Smooth-On No. 7. This is the one practical waterproofing that you can apply yourself, easily, from the inside, to wet or dry surfaces and with every as- surance of thorough water- tightness, even in the wettest seasons, Excellent also for patch- ing concrete floors, water- proofing boiler and machinery pits, pumps, garage, stable and washroom floors, brick walls, cisterns, septic tanks, water troughs, 'fountains, fish ponds, swimming pools, manure pits, etc. Working Smooth-On No. 7 into the original construc- tion is economical procedure, but where this has been overlooked, Smooth-On No. 7 can be applied to the existing structure quickly and at low cost and is entirely dependable. Specifications, working directions, diagrams, and typical examples of what may be accomplished will be found in the Smooth-On Home and Auto Repair booklet, Get the booklet by returning the coupon and get Smooth- On No. 7 in 1 or 5-ib. can or 25 or 100-lb. keg from sour supply house or from us. About 25 Ib. required for cach 100 sq. ft. of sur- face covered, HOME ars AUTO REPAIRS SMOOTH-ON MFG. CO. Dept. 69 574 Communipaw Ave. Jersey City, N. J. Write for FREE BOOK. Please send Smooth-On Home Repair Book. SMOOTH-ON NO 7 When Answering Advertisements Please Mention April Modern Mechanix 135

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Why Not Subscribe? Save the cost of two issues by becoming a regular subscriber, Only $1.50 per year in the United States and Canada—-$2.00 olse- where. Your copies will arrive punctually every month and you won't miss any of the | fine articles that are making MODERN MECHANIX "America's most popular me- chanical magazine.” Here's a big, convenient blank to fill out. Write your full name and address clearly and play safe by remitting by money order or check, Don't send cash, please! G Message Ns Man OOE, Dared to Write ! FAWCETT PUBLICATIONS, Inc., Greenwich, Conn., U. $. A. Furtive glances. Whispered words. or ene pets as. aie Cee Chak ie oe Concealed remarks, Who ever would einen two years; elsewhere, $2.00 for one year, $4.00 have been so foolhardy as to commit them to writing would have signed his own | | Name ........ death warrant. What were these communi- cations which for generations could only be transmitted from mouth to ear? It was the rare wisdom of the ancients; age-old eee ee ee ee rrr) Street and Number............ pees truths which tyrants and selfish rulers |f 0 UU" oe ees sought to suppress, knowledge which they , knew would give man power, independence, scuisieiviele eases TAEA TEEPE . mastery of life and the ability to attain z his highest ideals. Today, these secret principles, once withheld from the masses, —Every deaf person knows that= are available to the sincere, to you if you naay pade hirmolf hear hia watch tick after seek the fullness of life. ficial Ear Drums. He wore them day and night, | They stopped his head | noises. They are invisible SEND FOR FREE BOOK t andcomfortable.no wireg FO aieh Gane sd FAVE TON ales ad . 60 the Rosicrucians have tor centuries, in booklet on Deafness, Artificial Ear Drum distant lands, preserved this knowledge, at 3 THE WAY COMPANY kept it in secret archives, They have always 741 McKerchey Blag. Detroit. Michigan Sought progres ia fe ty making de | RE-STRING RACKETS AT HOME utmost of their natural talents and abilities. They offer you a free copy of “The Secret Heritage,” which explains how you may receive these startling facts. Address; FREE | and silk strings for your selection. Scribe T.B.O. Write for our 1938 Illustrated Catalog Every item highest quality, Write 7 J and Instruction Book. for complete details. The ROSICRUCIANS W. A. BICKEL & CO., Dept, B4, 137 N. Marion, Oak Park, III. TAMORC} San Jose California 60 POWER TELESCOPE $2.19 (Not a religious organization) VARIABLE EVEPIECE. 20X—40X—60X near the money. Closes NEW! Three telescopes In one, 3 different mag- ® nifications. 20 power for ultra-bright Images with 40 and 60 power for extra long range. Guaranteed to bring istant i : = Tl to !ées than a foot In length. Multipia 4 —— lene aystem. 30 mm. objective, In heavy Cow brasawmount. Directions [Included foe ualng as a compound 4 lens microscope. American made, We pay the postage. 4 7 Only $2.19. Catalog of Microscopes, Binoculars, etc. FREE on request. B oO | B) & ¢ BROWNSCOPE CO., Dept. 74, 5'W. 27th St., New York, N. Ye EA. Amazing rubber mold-making outfit makes perfect objects, people, sports evente, Operator eaa FOLLOW THIS MAN flexible molds of plaques, ash trays book-ends, cte. ships, moon, stare, etc. 6f times as close, Noe 38 Secret Service Operator No. 38 is on the jobi Running down dangerous Counterfeit Gang. Telle Molds cost from 6e to 25c each. Each mold makes hundreds of novelties and gifts to sell up to $1.00 tale finger prints In murdered girl’s room, apiecet No experlence necessary. Everything fur- ‘he Confidential Report ree erator No. 38 made to his chief. Write for tt. nished. Start profitable business In your home... sell to stores, friends, resorts, road stands or by Earn a Reguler Monthly Salary mail—NOW! Make BIG MONEY full or spare time. YOU can become a Finger Print Expertat home, Write for complete FREE details and easy Instruc- in your spare time, at small cost. Write for con. tions, SO-LQ WORKS, Dept, D-834, Cincinnati, It’s pleasant, profitable work. No experience or skill required. Easy to Learn, Full line of guar- anteed stringing tools, frames, gut Most power fidential full report and details. Literature will Ə eent only to persons aiating their age. INSTITUTE OF APPLIED SCIENCE 20 Sunnyside Ave. Dept. 2354 Chicago, Sit. frai aan aaa Ohio, 136 Accept No Substitutes! Always Insist on the Advertised Brand!

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Documentary Evidence [Continued from page 135] This project can be worked with ease as an exercise in evaluating evidence. Have various friends copy the same material upon separate cards, using as many different typewriters as can be pressed into service, marking their contribu- ticns with code numbers. The cards are shuffled and one is handed to you to represent a black- mail note. First study the characteristics of this specimen thoroughly, then endeavor to secure samples of all the machines that you can associate with these friends. After making com- parative studies you finally pronounce your ver- dict as to the guilty party. This can be made into a thrilling game among a group who own microscopes or as a club program, perhaps even cfiering a prize to the one who solves a given problem most rapidly, or who makes the best score in a series of puzzlers. Low magnification, up to 20X, is best for this werk and the binocular microscope much the best of all. While spuricus ccins or bills are not available for comparison with real ones, the points involved may be explained. Examine a dollar bill care- fully under low magnification and see how many separate items you can pick out as to composi- tion of the special paper used in printing bank- notes. The engraving itself is exceedingly intri- cate, but even granting that what the skill of one man can produce, the ingenuity of another can reproduce, the counterfeiter cannot have access to the correct paper and inks, the ingredients and manufacture of which are closely guarded secrets. Nor can he make a plate so exactly like the origi- nal as to defy detection under a comparison micro- scope, Ncte the elabcrateness of the engraved design and instances of cverprinting in separate colors. See the colored threads in the paper—reds. and greens and blues, not visible without magnifica- tion, and the very fine grain and composition of the paper itself. Those trained in looking for definite features with a lens can quickly pro- nounce a given bill as genuine or otherwise. Examination of coins is similar. It is impossible for two dies to be exactly alike in all microscopic detail, no matter how clever the workman. Stamps toc are carefully executed. Paste a postage stamp on a blank slide, add xylol, cover and study by transmitted light; mount another one dry and examine by reflected light. These observations will make clear how Uncle Sam safeguards the peper, ink and workmanship of all replicas hav- ing monetary value. The binocular and comparison microscopes are cf greatest service in work on spurious moneys, with the colorimeter or fluorescence microscope alsc occasionally asked for a verdict. The micro- scope, like that hero of our small boys, Dan Dunn, preaches that crime never pays! When Answering Advertisemcuts Please Mention April Modern Mechanix i You can turn out pro- | fessional-like work with Driver machines—they’re engineered for accurate, clean-cut results. Build trellises, garden furniture, porch furniture, flower boxes—yes, a myriad of projects— in less time—with greater economy; no waste motions or material. Your friends will be surprised at the beauty of line in your work—you’re bound to get greater satisfaction out of your hobby. MOST COMPLETELY EQUIPPED BAND SAW BUILT! BN730 12” BAND SAW $34.95 less motor, belt and motor pulley. Here’s a lot of machine for little money—made possible by efficient Driver factory methods. Guards, ripping guide, table extension, improved cushion-type spring tensioner, are all part of this great value. Ball bearings throughout. Geared control mechanism for tilting table. Handles big, little and difficult jobs with the ease of a champion. BN560—10” Model Band Saw with bronze bearings, $19.95, THIS BENCH SAW HAS EVERYTHINGI s B737 8” BENCH SAW $27.95 as shown, with self- indexing mitre gauge — 72- bage manual. One home craftsman says, “I’ve looked everywhere and I can’t find a machine to compare for the money.” 19”x15” machine-ground iron table tilts to 45 degree angle. Ball bearings. Saw blade raised by precision worm gear. Maxi- mum depth of cut, 244”, B575—same superior work- manship, 7” size, $12.35. Ask your local Driver dealer for a demonstration—write today for catalog containing complete details on these and other Engineered Power Tools. Walker-Turner Co., Inc., 548 South Ave., Plainfield, N. J. DRIVER RON EROS 137

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© THE rustle of leaves in a whispering breeze, with the light of a moon for your mood. An Old Town Canoe is a world of your own... your passage to peace and contentment. The dip, dip, dip of a Redskin’s pad- dle takes you through quiet enchant- ment. Paddling or resting, it’s steady and strong. It’s sturdy and easy to own. FREE CATALOG shows all kinds of Canoes for paddling, sailing or out- boards, Also Outboard Boats, including big all-wood family boats. Rowboats. Dinghies. Write today. Address Old Town Canoe Com- pany,464 Main Street, Old Town, Maine. Auto, Diesel, Aviation Mechanics— Body, Fender répair, Painting, Welding. Learn with a few weeks practical train- ing. Write for FREE BOOK, low tuition rate, and course interested in. McSWEENY SCHOOLS, Dept. 11-52 Detroit, Mich., or Kansas City, Ma. FRee | 800K 3-IN-ONE OIL KEEPS GOOD For cleaning and oiling tools, for adding smoothness and speed to action points “triple-action’’ cleans, oils, prevents rust. Athardware, drug, groceryand 10¢ stores. Ene “ONE OIL 138 How To Make Enlargements [Continued from page 124] so that no hypo will be carried back to the developer. At no time should you get a drop of any liquid on your fingers. Keep a towel around for emergency use, anyway. Agitate the prints in the hypo every time you add a new one. Keep prints “fixing” here for not less than 15 minutes, and then transfer to a wash- ing tray. Any ordinary tray can be made into a very efficient washer by the addition of the siphon type attachment pictured in Fig. 3. This costs about $5.00 and is well worth it. Improperly washed prints will fade in a few months, so keep them in the water at least 30 minutes, and preferably an hour. Glossy prints are best dried on chromium plated “squeegee” plates. These are prepared for use merely by being washed with soap and then rinsed in hot water. Put the wet prints on the plate face down, place a piece of blotting paper over them, and roll them flat with a small print roller. Don’t roll directly on the print; the paper is weak when wet and tears easily. Any prints other than glossy are dried between blotters, under pressure. Remove the surface moisture by rolling them out a couple of times between one set of blotters, and then put them under a fresh, dry set. The blotters must be squeezed together pretty tightly to prevent the prints from drying in a wrinkled condition. There are many simple print presses on the market; or you can make one yourself in an hour out of a couple of small drawing boards or pieces of five- ply veneer, College Glider Fan Devises Home-Built Altimeter A University of Michigan glider enthusiast has invented an ingenious “home-made” rate of climb indicator for the use of soaring fans. A thermos bottle, a glass U-tube, glass tubing and a calibrated scale constitute the device de- scribed by its inventor, L. D. Montgomery. Water and a small “leak” are the essential features of the instrument. Changes. in atmos- pheric pressure, which are proportional to the height of the plane, are registered by changes in the height of water in the U-tube. This device, essentially an altimeter, is converted into a rate of climb indicator by controlling the flow of water by means of the “leak,” a fine capillary tube from the thermos bottle used to store the water. The thermos bottle is used to minimize changes in the temperature of the water which might throw the readings off considerably. Chemists have tried to make diamonds in the laboratory ever since 1880, but have succeeded only in producing tiny crystals. Accept No Substitutes! Always Insist on the Advertised Brand!

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How To Train Your Dog [Continued from page 124] put on the inside so that he is walking between the trainer and the fence. The command “Heel” is given and if the dog attempts to walk ahead, the instructor can turn his leg inward and block the dog’s passage, thus making him retreat. After a few walks, he will remain at his master’s heels. With this groundwork mastered, the dog is ready to learn a few stunts. Every dog-owner would like to have his dog retrieve objects, bring in the evening paper, or go upstairs and bring down house slippers when commanded to do so. In giving a lesson in retrieving objects, the dog’s play ball should riot be used. To his mind this ball is associated with play and he will not regard it seriously. In its place a stick of wood or a wad- ded newspaper should be utilized. The dog should be kept on a clothes line while he is being taught to retrieve and the same is true when he is learn- ing to carry a basket or a newspaper in his mouth. The paper wad should be placed a few inches in front of the dog’s mouth and the command “Hold” given. Lengthen the distance gradually and then place the object on the ground. From this point his progress will be rapid and he will be a good retriever within a short time. In teaching him to carry objects, the newspaper wad should first be placed in his mouth with the command, “Hold” and removed after a minute or two. The procedure is repeated until he is ready to walk with the object. All you have to do is walk with your hand under his chin to prevert him from dropping the wad and coax him forward. By using the command “Carry” he will walk with the object in his mouth until he is told to put it down or into your hand. For the best results the daily training periods should not be more than a half hour in length. Consistent, day-to-day work is necessary. Every- thing a dog has Jearned should be reviewed in each subsequent lesson. With the proper amount of patience and concentration, the average dog can be taught this primary course in a month’s time, and from there, the trainer can write his own ticket. Photographs Flame Cutting High speed motion pictures of flame cutting have been made by H. R. Bullock of Massa- chusetts Institute of Technology. The pictures indicate that the oxygen stream of the oxyacety- lene cutting process behaves very much like a stream of water from a faucet. The split second of contact between oxygen jet and steel was photographed. In the camera a prism rotating at high speed acted as a shutter and at the same time permitted continuous film motion. The film was exposed at the rate of 1,200 frames a second. When Answering Advertisements Please Mention April Modern Mechanix ARE YOU DOUBLE-CROSSED BY GLUES THAT “DRY LOOSE? oe ESSESI ESS OS Here’s why CASCO makes permanent home repairs: © It sets chemically...forms a heat-proof, damp- proof boad. CASCO joints can’t be weakened by eat and moisture changes in your home like old-style liquid glues that set merely by evapora- tion. CASCO saves you time and trouble, because you need make a CASCO joint only once. EASY TO USE. Just mix one part CASCO powder in one part water. No mess. No heating. And no waste...you mixit as you need it. ECONOMICAL. CASCO plus cold water makes a full- strength glue artless cost than ordinary liquid glues. CASCO has many household uses. (Send for the free book offered below.) HERE'S PROOF OF CASCO’S STRENGTH World’s Largest Wood Airplane Propeller is Made with CASCO 16 feet long... weighs 194 pounds! Built up of 13 plies... made to stand terrific strain under all weather con- ditions. One of hundreds of CASCO’S industrial uses that require a glue with utmost strength and proof against moisture, heat and cold. FREE! NEW 1938 EDITION-CASCO GLUING GUIDE Fully illustrated, tells how to make lifetime home repairs... also how to make water-resistant paint, wallpaper paste... tile cement..,crack filler...Swedish putty, New methods for erecting fibreboard...flush door ee construction... veneering ... inlays. Send request on penny postcard to CASEIN COMPANY OF AMERICA Dept. MM 438 350 Madison Avenue, New York, N. Y. CASCO WEATHERPROOF POWDERED CASEIN GLUE = BLUES EVERYTHING] RESMANEATEE 4 Handy Sizes —10c to 65c— At Your Hardware Dealer’s 139

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Build Your Own Engine $5 a ONE DAY TAE DELIVERY | Over 6,000 of these same, famous G.H.Q. gasoline engine kits have been sold at $8.50 during the past year E P alone. Mass production g methods and enthusiastic re- i Pg ception have enabled us to re- duce the price from $35 each orig- fo to the NEW LOW PRICE of $5 Identical with the original higher-priced kit and with the same Guarantee. New 7 1938 High Compression Piston and Cylinder. All parts finished—quickly assembled. G.H.Q. “tncine $10. Now offered at a new low price. The famous G.H.Q. Engine, completely assembled and guaranteed to run. Send only $1.00 and we will ship Express Collect C.O.D. for the balance, DISCOVERS PHOTO-FACTS Send 3c for Catalog—DEALERS WRITE | © Basil Rathbone, as Sir Guy, on the set. of TAC SUr TT TW Taryip | Robin Hood, reads 854A East 149 St. New York, N. Y. PHOTO-FACTS or Th, K: sf i NEW! œ@ 3- WHEEL SIDE-KAR e Pocketbook of Knowledge : Au fo- G, Ji ide because he finds USEFUL KNOWLEDGE Carries Extra Person or 250-Lb. Load and at the same time gets iNew Speedy Slde-Kar model AUTO-GLIDE} R “Ble pas” load, Tor sefiveries. Meavy steal REST AND ENTERTAINMENT Kar rah on ae awe 5 nan Powerhal (aes 0h? EP. peine, Ciuten. “Brake. YOU, TOO, WILL ENJOY OSE! Drüg *. teased dabas | fascinating, dramatic stories of the world and 3 i" people of past and present—science, art, re- mine BOOK the Peete ligion, history, folklore; economics, ete. i rd Dowt Miss The Current -=n PHOTO-FACTS Correspondence! Courses in ki Only 25c at all newsstands DO ELECTRICAL ENGINEERING $25 If your newsdealer is sold out send 25c to “ ELECTRICAL ENGINEERING Set good, grasp Puoto-Facts, 22 W. Putnam Ave., Greenwich, eal field. ae eeate yourself, at Low Cost, for secure future. Modern Toa course, lifed anyone can understand quickly Conn, for the next issue. RADIO ENGI EERING Extra fine course In Tadlo, public address, Photo-electric work. Trains you to be Buper-service man, real vacuum tube technician. Experimental kits furnished. Diploma given on completion. Tultlon, ONLY $25, either course. Deferred payment plan available. § Send name quick for free coples of school catalogs s student magazines, complete details. SEND NOW. LINCOLN ENGINEERING SCHOOL, Bex 931-72, Lincoln, Nebr. MOVIE STAR 35 tess BATTERY Ovouit NEED / ~ THIS POWERFUL ELECTRIC LANTERN 80 to 100 hours light ona 6-volt dry battery. 2 ree flectors give either 800 ft, spot beam or big floods light. Unbreakable lens. ‘ 6 1-2 in. tall, At ha Parion Teel ana ri i Dept, 450 a” dry batteries, 7 1-2 tall Big, sturdy light, Less batteries $1.95 GENUINE 140 Accept No Substitutes! Always Insist on the Advertised Brend!

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Engineer Reveals Resulis Of Lightning Studies Lightning may strike a tree, travel to the ground, but if the soil happens to be of gravel or of a poor conductor type, it is liable to bounce out again and do further destructive work until it finds a ground of less resistance. This an- nouncement was made by K. B. McEachron, in charge of General Electric’s artificial lightning and high voltage labor- atory. who has observed several occurrences of this character in connection with his recent investigation of lightning. In one of these cases, lightning came down a 90-foot pine tree aud plowed up a furrow in the ground until it reached a pole supporting telephone wires. It went up the pole leaving some splintercd wood behind, and finally found its ground connection after passing through the telephone wires. In another case, in New Hampshire, lightning followed down a tree, traveled a distance of approximately 50 feet over the earth to pass up another tree, then jumped approxi- mately one foot to a 110-volt lighting circuit, from which it dissipated itself in lightning arresters connected to the power circuit, In a case but a month ago, the lightning discharge traveled through devious paths to Anally reach the ground by way of an apple tree, 37 feet of earth, two metal beds, the body of a boy, a radio aerial, a secondary power line, and finally a telephone circuit. The boy was killed, several of the electric light circuits were put out of commission, and some damage was done to the telephone system. The boy was standing in a bunk house between two windows, apparently watching the storm. His body showed burns on his chest and one foot. How the accident happened was a mystery until Mr. McEachron made his investigation and determined the bolt had first struck a tree 37 feet from the bunk house, stripped off the bark as it traveled down to the base, fol- lowed a root of the tree for a few feet, then a small stream of water caused by the rain which carried it to the foundation of the bunk house. Here it tore off a patch of tarpaper along the foundation, came up through the floor and a bed, and passed through the boy’s foot, up his body and left by way of his chest to an aluminum cooking pan hanging from a shelf but an inch or two from his body. It next jumped to a radio antenna strung under the eaves and then to an electric light lead just inside the building. From this, the lightning traveled over the electric light wires out the build- ing to a nearby building in which the cord from a desk telephone was hanging over the metal part of a bridge lamp. Burns on the insulation of the wires and on the metal of the bridge lamp at this point indicated the lightning entered the telephone system and gradually dissipated itself to ground over the lightning arresters connected to the telephone system. “If you are familiar with lightning, it is not difficult to trace its path,” Mr. McEachron explained. “It generally leaves ils mark wherever it goes. Our years of experience with artificial lightning, with voltages as high as ten million, have supplied us with much informati i of natural lightning and how to s it is liahle to do. That is ore r failures during electrical storms in 7 learned its habits and have beun able to dev protecting electrical apparatus against it. In the case of the boy, the lightning discharge was seeking a good ground convection, and was only partially satisfied by the ground at the base of the tree. It followed the path of the least resistance, which was by way of the boy, antenna, light wires, and finally the telephone conduc- tors to ground. “When providing grounds for transmission towers, power stations, or lightning rod systems on buildings, grounds are provided by driven rods, buried wires, or pipes. often cover- ing a considerable area. Lightning is discharged into such a system without damage.” This illustrates again the three main hazards of standing under a tree, which according to Mr. McEachron are: 1, the discharge may side-Aash from the tree; 2, the dis- charge in passing through high-resistance soil at the base of the tree may pass considerable current up one leg of a person and down the other. This is often the reason why cattle are killed under trees. 3, the tree may explode and a person may be injured by the flying debris. , “Well-grounded lightning rod systems will protect build- ings against damage from lightning in the majority of cases, and persons in such buildings will in general be safe,” Mr. McEachron declares. We have means for The great planet Jupiter is now about 590 million miles away from the earth. Glass textiles are being made both from staple- length glass and from continuous thread. When Answering Advertisements Please Mention Abril Modern Mechanix d- Ẹ : Jor Would you invest less than one day’s pay to learn Diesel? Thousands of big Diesel opportunities are waiting for trained men—why not prepare yourself for your chance? Here, at last, is a complete pelt Tasfrietion Course that R may mean the beginning of a secure and ha future for you. FLASH!! Big corporation has just announced vast Podu tion schedules for Diesel “packaged power” units! FRACTION OF USUAL COST S=N Now is the time for you to learn Diesel— SS while the industry is new and growing at LEMENTS. RN an amazing pace, Get in on the ground SEEL RA floor, This Course—complete within the ES RING NN covers of one large volume—is easy to own. NS See our astonishing offer below! A If WITILILITITLES VIILEE New edition, just published contains simple yet comprehensive instruction on every phase of Diesel Engineerlng—in- stalling, repairing, operating, selling, manufacturing, 478 pages (size 6 x 9). 332 illustrations, Written expressly for self-instruction by beginners and those with only a little knowledge of Diesels. Covers all practical points, compression, ignition, fucl injection, lubrication, ete., ete. AN EASY WAY TO GET STARTED IN THIS BIG MONEY FIELD You don’t have to interrupt your present work or disturb your budget, You can get started in the Diesel field thls easy, inexpenslve way. Everywhere you turn you see Diesel engines replacing old equipment. Train yourself for this new, fascinating and highly profltable work ELEMENTS OF DIESEL ENGINEERING prepares you by easy stages, Total price for the complete course is only 95¢ down and then $2 per month for two months, (Total—$4.95—noathing more to buy.) SENT ON APPROVAL. Get your examination copy now—no obliga- tion, no expense to you, Don’t miss this chance! See how you car earn real big pay, Also, if 25 x 38 Inch DIESEL ENGINE “TROUBLE SHOOTING: l WALL CHART ' m ingeniously arranged chart that explains Diesel Engin Fore a masr ata Ziance! Nothing else like it. ‘This large chart is just what every man learning or operating Diesel Engines needs. Shows cross-section of the latest model. ete., polnting out by illustra- tions and quick-view tables all operating difficulties, where and how to locate and correct them. Yours absolutely FREE with each copy of ELEMENTS OF DIESEL ENGINEERING. SEND NO MONEY You owe it to yourself, to your family and your future to examine a copy of this Rook-the most up-to-date, Most complete self-instruction course for beginners. o money is required now. Just mail the if you act promptly! on for an ‘ton a ** copy. But do It today! Diesel will pay generousi:” for tr g ana PYnowledge—but it as nothing to offer to those who ‘m ve learned.” LIFETIME OPPORTUNITY? GARGOYLE PRESS, Dept. 4A 70 Fifth Ave., New York, N. Y. nd me ELEMENTS OF DIESEL ENGINEERING for ten days examina- font I Swill pay postman 95e (plus postage charges) with the under- standing that if I keep the volume ï will pay you $2 per month for 2 months (total price §4.95). If I return the book you will refund my down payment. Send also a FREE copy of the DIESEL ENGINE TROUBLE CHART. Occupation. ...-.--------------- -- ne ene eee If you enclose $4.95 with this caupon we will pay carrying charges, Same 10 aay examination privilege with full refund if not satisfacto. y. p a a

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Sound Engineers Produce “Stereophonic” Movies N EFFECT entirely new in talking pictures was recently demonstrated before a large gathering of motion picture engineers. It was a demonstration of “stereophonic” or third-dimen- sion sound in which dialogue’and sound effects come directly from the point of origin on the mo- tion picture screen. The demonstration was given at the Bell Telephone Laboratories in New York City before members of the Society of Motion Picture Engineers. In the demonstration, a ping pong game was shown on the screen and the sound of the bounc- ing ball followed the exact path of the ball itself. So accurate was the “sound path” of the ball as it traveled from one side of the net to the other, that it was easily possible to close the eyes and tell at any instant which side of the net the ball happened to hit. At one point of the game, the player missed the ball and it bounced off the table and disappeared behind the player. The sound of the bouncing ball likewise went to the floor and appeared to recede beyond the line of vision on the screen. The development of “stereophonic” talking picture recording and reproduction is the result of a number of years of research carried on by engineers of Bell Telephone Laboratories and Electrical Research Products. The demonstration was described by J. P. Maxfield of the latter organization. “In present-day talking pictures, we obtain only an illusion of sound coming from the point of origin on the screen,” Mr. Maxfield said. “Ac- tually. it comes from a fixed point behind the center of the screen with no direction or space- relationship. If for imstance we see someone playing a piano on the screen, our ears and our eyes tell us that the sound of the piano is coming from the keyboard of the piano because we see the pianist strike the keys. There is no effect of sound motion on the screen. Stereophonic re- cording and reproduction provides this sound motion or direction.” “In ordinary talking pictures of today, sound is picked up with one microphone amplifier channel and recorded on only one sound track. The con- dition is actually similar to hearing with only one ar,” Mr. Maxfield said, in explaining how third- dimension sound is produced. “In ‘s.ereophonie’ talking pictures sound is picked up by two chan- nels and the output of each is recorded on a sepa- rate sound track on the film. In other words, there are two separate sound tracks on the film each of which is a recording of just one channel. In re- producing the two sound tracks in the theatre, the output of each track is fed to a separate set of loud speakers at the sides of the screen. The effect on the listener is that he is actually en- joying “two-ear hearing” (binaural) instead of “one-ear hearing.” Accept No Substitutes! Akcavs Insist on the Advertised Brand!

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Chemical Cure For Wounds The cure of ulcers and stubborn wounds with allantoin, brought about through research work in the U. S. Department of Agriculture, has re- sulted, the department says, in wide interest among physicians and the public. Favorable re- ports have come in to the department from physi- cians, hospitals and patients throughout the coun- try. The story of allantoin goes back to the obser- vations made during the world war by the late Dr. William S. Baer of Baltimore that maggot in- fested wounds frequently healed more quickly than wounds kept clean. Later, when maggots were used in treating stubborn wounds, the De- partment of Agriculture entomologists for a time supplied some hospitals with blowfly maggots. Then the Bureau of Entomology set about learn- ing new facts about these insects so long consid- ered undesirable and odious. Dr. William Robin- son of that bureau learned how to grow clean maggots—free of any infection—something much desired by the medical profession. He then began research to find out what the insects produced in wounds that might explain the stimulation of healing. He found they produced, among other things, allantoin, a substance occurring in some plants and animals and which long ago had been suggested as a healer of ulcers. At the time he made this discovery allantoin was known only as a rare chemical and was pre- pared in small quantities. With this new use of allantoin the demand for it grew. Now at least six concerns are making it. The maggot is out of the picture. In fact, the insect provided only the basis for a start with this new healing agent as even the early tests were made with the artificial product, which is almost snow white. More recently Dr. Robinson has shown that the maggots produce urea, and collaborating physi- cians have shown that this substance, the first organic chemical ever to be made synthetically, is much like allantoin in its effect on ulcers and sores. It also is a crystalline substance which under the microscope resembles tiny splinters of sparkling ice. It is cheap and the commercial grades are manufactured in huge quantities for fertilizer and for various uses in industry. Both allantoin and urea are being used exten- sively by physicians. A single manufacturer of allantoin reports a regular output of the chemical sufficient to treat 1,000 average cases each month. Some pharmaceutical companies are now putting out allantoin—and in some cases urea—in various forms, including ointment, jelly, dusting powder, in addition to the original crystal form and water solution. NOTICE Changes in the make-up and title of this magazine will be announced in our next issue, Reserve your copy now. “evervtuine Zz Write today for ALLIED'S big cot Fe aden off the press. 164 pages packed with everything NEW in Radio! 62 sensational new “Knight” Radio sets: advanced Push-Button Tuning models at new low prices, new inex- pensive Auto Radios, Phono-Radio combinations, 6 volt-110 volt farm radios, latest portable models, new radios with Hush-a-Tone attachment, and others. Radios from 5 to 16 tubes for every purpose. Models for AC, AC-DC, 6 volt, 32 volt, battery, and auto operation. Set-Builders’ Kits of all types, including new simple transmitter kits, Electric Fence Control kit, and other new circuits. Amateur Gear— all leading lines; latest transmitters, receivers, transceivers. Amazing new Public Address equipment—portable, mobile, permanent—from 10 to 80 watts. All standard lines of test equipment, books, tools, replacement parts, ete. Everything you need in one great book—arranged for instant selection. ALLIED’S FAST SERVICE and COMPLETE STOCKS save you tine—ALLIED’S LOW PRICES save you money. That's why thousands find their radio dollar buys more at ALLIED! Send coupon now for ALLIED’S new Spring and Summer Catalog. It’s Free! FREE PARTS LISTS—We supply matched kits for any radio circuit described in this or any other magazine. Write for Free Parts Lists. FREE senn couron LIED RADI ALLIED RADIO CORP. 833 W. Jackson Blvd, Chicago, Ilinois | l NANE sicaceretenuecnscrora casa tare OEE e aaa a se eink vis l AMOLESS, setcrsrir ntek kke n AEO A REK KEE E l When Answering Advertisements Please Mention April Modern Mechanix 143

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A. C. GENERATOR PRACTICAL changes for automobile generators, A. C. and D. C. generators, motors and welders, Complete wind and water power plants. See our ad- vertisement at bottom of page 125. Antopower. A. C. Generators, hand-driyen, gen- erates 110 volts, original price $5.50. Special 98c. Electrical Salvage, Box 524-76, Lincoln, Nebr, Rn a a a. ADVERTISING AGENCIES ADVERTISE: Get mail-order business, avents. Pree assistance. Free Ad- Guide of newspaper, magazine, circula- tions, rates, mailing-lists, Chicago Ad- vertising Agency, 22 West Jackson, Chicago. ADVERTISE: 24 words in 250 news- papers $10. Lists Free. Advertising Service Bureau, 4515-B Cottage Grove, Chicago. 33 WORDS, 25 Magazines, Months, $2.00. Goodall Agency, Market, San Francisco. FREE NEW advertisers rate guide. Brown Advertising Agency, 140 South Dearborn, Chicago. AGENTS WANTED AERIAL Eliminator—Tiny instrument equals 75 foot outside aerial. 10 days free trial. Tone, volume, sensitivity, reception improved or money back. Makes radio complete—move anywhere. Send $1.00 or C.O.D. plus postage. Three 742 Agents write V&R Electro, Detroit Lakes, Minnesota. AGENTS Santos I : Smash go prices! Coffee 12c 1b. 4-oz. Vanilla 814c. Razor Blades 10 for 814c. 100 Sticks Chew- ing Gum 12c. 150 other bargains. Premiums. Experience Unnecessary. Carnation Co., MN. St. Touts. Mo. PROFIT with new products. M sell, repeat. Analysis. Research. G anteed formulas. Biggest catalog ive Special prices, leads. Gibson Labora tory, Chemists, CE-1142 Sunnyside, Chicago. BIG MONEY Taking Orders; Shirts, Ties, Hosiery, Underwear, Raincoats, Pants, Uniforms, etc. Sales Equipment FREE! Experience unnecessary. Write NIMROD, Dept. 132, 4922-28 Lincoln, Chicago. BIG Money applying initials on auto- mobiles, Easiest thing today. Free samples. Also, sideline salesmen for name plates and tire cover transfers. “RALCO”, 1305 Washington, Boston, Mass. LARGE Profits in your own bu Sell new and used clothing, bank upt stock. Experience unnecessary. Every- & thing furnished. Details free. Publix, 558-KA Roosevelt, Chicago. NO PEDDLING—free booklet de- scribes 107 money-making opportunities for starting own business, home, office. No outfits. Elite Co., 214-G Grand tı New York. 1000 BARGAINS, Drygoods, Notions, Drug Sundries, Specialties, Novelties. Agents undersell stores. Free catalog. Jobbers, Dept. 2898A, 930 W. Roose- velt. Chicago. BIG Money Applying Initials on Auto- mobiles; $1.45 profit on each sale. Write for particulars and free samples, Ameri- can Monogram Co., Dept. 11, Dunellen, New Jersey. 144 Classified Advertisements Rates for classified ads, 18c¢ per word (include name, address and all numbers), per insertion. accompany order and be received in this office March {st for the May issue (on sale April 6th). Modern Mechanix Hobbies & Inventions, (501 Broadway, New York City, Rotary Dial Clock Shows Day, Month Shown above is a new clock which features rotary dials that indicate not only the time in hours and minutes, but the date, day of the week and the month as well. WHERE To Buy At Wholesale 500,- 000 articles, Free Directory and other valuable information, Maywood MM. Publishers, 925 Broadway, New York. 500% PROFIT Selling Gold Leaf Letters for Store Windows. Free Samples. Metallic Co., 445 North Clark, Chicago. ATLAS W S P EEE AGENTS—Make biz profits supplying hulk perfumes to family routes. Leffler & Co., 741 Walton, St. Louis, Mo. MEXICAN Curios, tremendous money- makers! Samples 10e. Marquez-M, Apartado 1176, Mexico City. AMERICAN POLICE JIU JITSU 13 KNOCKOUT Blows without use of fists, by internationally famous Jiu Jitsu instructor. Send 15 cents. S. J. Jorgensen, 293 Maritime Building, Seattle, Washington, ARC WELDER 200 AMPERE arc welder from Complete plans and 5c. 100 other gen- LeJay Manufacturing, z., Minneapolis, Minn. AUTOMOBILES ECONOMY! Pe Semi-diesel conver motors, $5.00 up. written guarantee, Learn basic facts from free literature. Houston & Logan Conversions, 1719 Addison, Berkeley, California. SEMI-DIESEL fuel oil conversion units for auto, truck, other gas motors save 75% fuel cost. Units low as $5 guaranteed on Free Trial Offer. Agents rmance: Mileage! cus for gasoline Manufacturer’s Wanted. Free details. Dies-L-Gas, Fee Foothill Blvd., Oakland, Cali- ornia. Minimum 10 words. Cash must Address Classified Mgr., AVIATION GET INTO AVIATION. Air trans- port pilots get up to $7,000 per year; mechanics, $2,500, Learn at this Gov- ernment approved school. Write for complete information, State age. Lin- coln Flying School, 4002 Aircraft Bldg., Lincoln, Nebr. AVIATION Apprentices. Good Pay— Big Future. Write, immediately, en- stamp. Mechanix Universal Aviation Service, Strathmoor Station, Dept. A2, Detroit, Michigan. INEXPERIENCED workers, apply for aviation jobs now. Fall salary while learning. Details for stamp. Airploy- ment, Box 553, West Los Angeles, Cali- orma. FLY Original Very Best Flying Ex- perimental Sets 35c. Alexanders, 1965 Muskego Ave., Milwaukee, Wis. SLED Propellers, $2.50 while they last, N. Marsh, Colby, Wisconsin. BABY CHICKS SEX- LIN KED Chicks, famous Austra- whites, 5 other Hybrids aud 52 pure- breds. Beautiful catalog Free. Mrs. Berry’s Farm, Rt. “F,” Clarinda, Iowa. BLUEPRINTS METAL TUBE Midget Radio, the last word in compact radio receivers. You can construct this set even though your knowledge of radio is limited by. follow- ing the large pictorial blueprints avail- able, from Modern Mechanix Publ. Co., Greenwich, Conn., at 50c postpaid. BOATS T ATEST Boat Sensation: New 20 Ib. tsmans Ki-Yak assembled at E quickly from complete ctory-cut kit, $6.00 paddle now given pn yours—if you hurry! Rush dime or vlog with pictures, description i e “ead Gliders, Dept. MC-48, Chi- cago, TI FORD and Lincoln Marine Conyer- sions. Send 10c for information. Lehman Engine Co., Newark, N. J BOOKS & PERIODICALS 'SPORTSMEN’'S MANUAL—The out- doors man’s guide containing scores of practical articles by America’s leading outdoor writers, covering every phase of fishing, hunting, camping, and trap- ning. This book, edited by Robert Page Lincoln, will make that next vacation a dozen times more enjoyable. Price 50c at your newsstand, or order directly irom Modern Mechanix Publishing Co., Fawcett Bldg., Greenwich, Conn. NEWEST radio, electrical experiment books, 20c up. Amazing values. Cata- log free. Electronic Publishing Co., Box 323-AF, Lincoln, Nebr. BUILDING MATERIAL BUILDING Material Bargains. Buy direct from mill and save! Low prices on everything needed to build, repair or remodel .. , lumber, roofing, flooring, screens, windows, hardware, barn sash, paint, etc. Free estimates on_lumber hills. Guaranteed materials. Building Materia] Catalog Free. Gordon-Van Tine Company, Dept. B10, Davenport, Iowa. Accept No Substitutes! Always Insist on the Advertised Brand!

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BUSINESS OPPORTUNITIES PLASTEX Industry needs manutac- turers on “small scale and for big pro- duction of Art Goods and Novelties in Plastex and marble imitation. Cheaply and easily made in our guaranteed rubber moulds. We cooperate in selling goods. You are just in time for big 1938 wholesale season now starting. Interesting booklet mailed free. Plastex Industries, Dept. R, 1085 Washington Ave.. New York. MAKE Big Money in floor surfacing with electric sanding machines. Get inte something for yourself and be your own boss, Start with as little as $75.00. A tried and proven money- maker. Learn to run one in an hour. No previous experience required. Write D. C. Wing, Box R, Central Station, Toledo, Ohio. FASCINATING business. Repair, Ad- just typewriters, adding machines. Learn casily at home from factory expert. Earn up to $15.00 daily. Com- plete instructions covering all makes $3.00 postpaid or sent C. O. D. Adding Machine Equipment Service, 3001 Michigan, Dept. 2044, Chicago. MAKE Photo Rings At Home! New easy way to big money! | Everyone wants Gold or Silver Plated Rings with picture of loved one enshrined in gem- like setting. We supply everything. Low cost—tremendous profits. Photo Jewelry Company, Dept. A-201, Cin- cinnati, Ohio. WE START vou in business, furnish- ing Outfits and Instructions, operating “Specialty Candy Factory” home. Men and women, earn $25.00 up to $60.00 weekly, all or spare time. (Our 29th year.) Booklet Free. W. Hillyer Rags- falc, Inc., Drawer 110, East Orange, SQUAREKNOTTERS! Make belts, handbags, etc. Quality cerd sample with catalog, free. Be : catalog and samples. Regular $1 bock with outfit, all for $1. P. c? Herwig N Dept. R, 121 Sands St., Brooklyn, N. FAS MAN in Each Town to Plate Auto Parts, Reflectors, Bicycles, Fixtures, Mirrors, by late method. Simple plan of manufacturing at home starts You in Good Paying Business. Free par- ticulars and proofs, Gunmetal Co., Ave. A, Decatur, Illinois. MAKE artificial marble, glazed tiles, uncanny. Tabletops, plaques, floors, hones, novelties. Hard, fireproof, in- expensive, cement secrets. Brilliant tile and liquid rubber samples 3c. John H. Payn, 945 Grande Vista Avenue, Los Angeles, Calif. LIKE To Write? Earn extra cash! Clipping and preparing newspaper articles for publishers. Simple, fasci- nating, profitable. Stamp brings details. Division 76, National Press, 3923 West Sixth. Los Angeles, California. COLOR Concrete Surface with chemi- cal solutions. Beautiful pottery with- out moulds. Garden wishing wells. Glazing concrete. Sample 10c. Holly- wood CementCraft, 8528 Wonderland, Hollywood, California. FREE circulars describing hundreds of money-making opportunities by mail. Newest methods. Pleasant surprise. Write Now. Progress Publishing Com- pany, 2513B N. 9th Street, Milwaukee, Wisconsin. PROFIT with new products. Make, sell, repeat. Analysis. Research. Guar- anteed formulas, Biggest catalog free. Special prices, leads. Gibson Labora- tory, Chemists, CE-1142 Sunnyside, Chicago. When Answering Advertisements Please Mention April Modern Mechanix Flashlight On Shovel Facilitates Work A handy application of a standard automobile flashlight holder is shown above. The holder, attached to a shovel, enables the user to direct the flashlight beam directly on the work at hand and is ideal for firing furnaces in derk cellars, shoveling snow at night, ete. The holders are manu- factured by a Freeport, Illinois, firm. MAKE Rubber molds that need neo greasing. Castings come out with glass- like smoothness. Beginners outht $1.00. faction guaranteed. Details free, 1-D Beech, Holyoke, Mass. "a oe to reépare tor X tic-S, Station D, Los Angeles. SUCCEED With Your Products. Make: S Them, Formulas. Processes. Catalog free. A. W ashington, D. Ĉ extremely profitable, cperate_a Collection- Credit Agency. Free Folder. Cole Associates, S we N. Y. FREE LITERATURE describes hun:- dreds plans fcr making money locally or by mai Gilbert Supply, 1107-M Broadway. New York. AGENTS—To mail our literature. Gocd prefits. Home business. M. Mayweed. 149 Fifth Ave., New York. SELL Ly Mail! Books, Novelties! Bar- gains! Big nrofits! Particulars Free! H. Elfco, 438 North Wells, Chicago. EARN cash income, copying and dupli- cating simple cartoons for advertisers. 3-N Service, Argyle, Wisconsin, HOW And where to obtain fully cxplained, free particulars. Service. Wapakoneta, Ohio. FREE details on Mail Order Business, lifetime tv capital Star Better Joh, Promotion. Holmes, Box 453, Rranford, Conn. CLERICAL DUTIES, Spare time Proposition, Wilsons, 2408 Pine, Ever- ett. Washington. OPPORTUNITIES. Men, women. Silvester & Co., MM, Old Bridge, N. J. ‘RUBBER LI.atex. CAMERAS & PHOTO SUPPLIES CAMERAS and supplies. Free illus- trated catalog listing everything phcto- graphic—still and movie cameras, film Jenses—at tremendous savings. Hu dreds of bargains, new and used. All guaranteed, We take your old camera or equipment in trade. Write now for your free copy of our newest moncy- saving bargain book—just out! Limited edition. Hurry! Central Camera Co. (Photographie Headquarters Since 1899), 230 South Wabash, Dept. 4-J, Chicago. MAKE money in photography. Learn quickly at home. Spare or full time. Easy plan. Previous experience un- necessary. Common school education sufficient. Interesting booklet and re- quirements free. American School of Photography, 3601 Michigan Ave., Dept. 2049, Chicago. INCOME From your camera instead of expense. Low cost home course teaches you to make photographs for magaziues, newspapers, advertisers. Tremendous demand. Earn good money wherever you live. Free book. Universal Photog- raphers, Dept. A, 10 West 33rd St. New York. MAKE MONEY Selling Snapshots— Dime brings hundred-page book com- plete instructions, buyers, real informa- ‘tion. “Photomarket, » 402-M Evans Building, Washington, D. C. CHARTERS DELAWARE Charters: Complete in- corporating and organizing service $35., Submitted forms. Chas. G. Guyer, Inc. Wilmington, Delaware. CHEMISTRY Dime Brings Litera- ture, 20 Experiments. astern Latex Lab., Box 53. Dept. M, Canton, Mass. CORRESPONDENCE COURSES 500,000 USED Technical and business books. Sold, rented, exchanged. All subjects. Satisfaction guaranteed. Cash . paid for used books. and Send Complete details illustrated bargain catalog free. name. Nelson Co., 3228 Man- Bldg.. Chicago. DETECTIVES DETECTIVES. Make vestigations. Experience unnecessary. Detective Particulars Free. Write, George Wagner, 2640-V Broadway, Secret In- LEARN HANDCUFF Secrets, Earn Big Salary. FREE circular. Box 8363, Pittsburgh, Pa. EDUCATIONAL & INSTRUCTION MEN—Women, Get 1938 Government Tobs. $105-8175 month. Dependable. repare immediately for next examina- tions. Experience usually unnecessary. Full particulars—list positions, Free. Write today. Franklin Institute, Dept. P59, Rochester, N. Y MEN Wanted—Learn Tool & Die Making. Automatic Screw Mach. Machinist Trade. Big Demand. Actual Experience. Expert Supervision. Write for Free Book “M”, Allied Screw Machine Co., Inc., School Div., 603-9 Lake St.. Chicago. WANTED Immediately, Men-Women, age 18-50, qualify for Government Posi- tions. | Commence $105-$175 month., Common education sufficient. Valuable information free. Write, Instruction Service, 234. St. Louis. Mo. INSTRUCTIONS. Hardening and Tempering Steel. $50.00 Course Sent You $10.00, Demonstrated from Coast to Coast for over 50 years by H. Wheeler. and Son, Lock Box 132, Moline, Tl. 145

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FLECTRIC FENCE MAKE Electric Fence. It's easy w ih our simple plans to convert Ford T coil No further costs. Complete plans 350. LeJay Mfg., $14 LeJay Bldg., Minne- apolis, Minn. ELECTRIC PENCIL ELECTRO-SCRIBE: Electric Pencil Writes—Engraves all Metals. $1.00 postpaid. Details Free. Beyer Mig. Co., 4515-Y Cottage Grove, Chicago. EMPLOYMENT SERVICE EMPLOYMENT Guidance. Successful Job Hunting. Employment Counsellors, Milwaukee, Wisconsin. ENGINES, MOTORS, ETC. GENERAL ELECTRIC motors slight- ly used, 1/25 H. P. Speed 1800, 110 Volts A. C. 60 cycle. Special bargain $2.95. Money order only. Arnold E. Ristau, P. O. Box 71, Kaukauna, Wis. WINDING Data, 225 motors, single and three phase. Price $1.00. Motor Data Service, Box 7631, Kansas City, 0. Booklet. 25¢ coin. Box 1283B, FARMS 40 ACRES, Near White River, un- improved; poultry land. $175, $5 down, $5 monthly. Free list and literature. Hubbard, 224 Grossman Bldg., Kansas City, Kansas. FEMALE HELP WANTED WEAR fine hose I send without cost with outfit while taking orders for amazing new hosiery. Replacement guaranteed against holes, snags, and runs. Rush name and hose size. Wil- knit, Desk 34-D, Greenfield, Ohio. FENCING FENCING equipment. Foils, swords, masks, etc. Low price. Free catalog. Industrial Products. Dept. MM4, 48 W. 48th Street, New York. FOR INVENTORS PATENTS—Before too heavy an out- lay of time or money is made on an invention, a search of the Patent Office records should be made to determine as nearly as possible whether or not the same idea h d before. The cost of th i the value of the i often considerable. We and manufactors a thorough. confidential search service—plus perienced counsel and assistance every phase of Patent and Trade-Mark practice. Write for our new free book containing valuable information relating to patent procedure. Clarence A. O’Brien and Hyman Berman, Regis- tered Patent Attorneys, 28-W Adams Bldg.. Washington, D. C. PATENT Your Idea. Write imme- diately for two free books, “Patent Protection” and “When and How to Sell an Invention.” Fully explain many interesting points to inventors and illustrate important mechanical principles. With books we also send “Evidence of Invention” form. Prompt service, reasonable fees, thirty-nine years’ experience., Avoid risk of delay. Address: Victor J. Evans & Co, Registered Patent Attorneys, 42-D Vic- tor Building, Washington, D. C. INVENTOR’S Universal Educator; contains 900 mechanical movements; 50 perpetual motions; instruction on pro- curing and sclling patents and selcecting an attorney, etc. oe í new ideas. Price $1 postpaid in U. S. Address Albert E. Dieterich, snk Colorado Bldg., Washington, D. È. 146 Electric Light Switch Operates Noiselessly | A newly developed electric light switch is absolutely noiseless in operation, the contact being made and broken by the movement of mercury. More im- portant to users than the matter of its sileni operation is the fact that the switch has literally no parts that can wear out, The actual switching ele- ment is composed of two metal disks sealed within glass, completely enclos- ing the mercury make-and-break of the switch. The switch casing is made of special composition material. INVENTORS: Send for my free 72- page book. Conscientious, prompt per- sonal service on all patent matters. Registered Patent Attorney, L. Randolph, Dept. 341, Washington, D, C. WE SUCCESSFULLY sell inventions, patented and unpatented. Write for proof, and tell us what you have for sale Chartered institute of American . Washington, D. C. ETC. guar- aluy free. . Gibson Labora- CE-1142 Sunnyside, for Self! For Profit! la and Business In- v cash, 6c stamps, Jerz New Haven, Conn. Your Products. Make- Formulas. Processes. Catalog free, A. Thaxly Ce i ton, D. C. MONEY mal formulas. Dime, stamps brings list. Paul Bumbal, 735 East 163rd Strect. Bronx, New York. FORMULAS—Latest money makers. Literature free. D-Belfort, 4042 N. Keeler, Chicago. FORMULAS—AI! kinds. Guaranteed. Catalog Free. Kemico, 67, Parkridge, Tllinois. 100 BEST Formulas 25c. Cherokee, Fountain City, HYPNOTISM HYPNOTISM. Complete 20 Method Course 25c. Western Institute Hypno- tism, MM-2984 North Ridgeway, Chi- cago. Tindell, 206 Tenn. : Amaze, Mystify friends. ;ı booklet, INVENTIONS e Write today for free i book clearly explaining how to obtain patent protection by paying only Gov- ernment filing fee. American Vateuts Sorporatigtis Dept. 5-E, INVENTION S—Patented, Unpatented. Bought outright, royalty. Write Arel- lano-Power Comnany, 1 North La Salle St Chicago, Illinois, INVENTIONS WANTED SMALL inventions wanted by manu- facturers. I'll help you sell your in- vention. Write for free circular. S. aa 7829-L, Euclid Avenue, Cleveland, Jhio. Washington, INVENTIONS Commercialized. Pat- ented or unpatented. Write Adam Fisher Co., 582 Enright, St. Louis. Mo. MACHINERY & SUPPLIES | THREADING dial indicator for South Bend Workshop lathes, $3. _Cireu‘ar free. Unique Manufacturing Company, 4807 No. 31 Ave., Omaha, Nebr. MAGIC TRICKS & NOVELTIES FREE! Magic Catalog 500 Tricks. Write today! Lyle Station A-3, Dallas, Texas, WE SUPPLY every noted magician, Large Professional catalog 25c. Holden, 222 West 42nd St., New York. MAIL SERVICE Douglas, NEW YORK mail address; business, personal; forwarded daily; $1.00 month- ly. Mail-Order Service, 954-8th Ave. MALE HELP WANTED MAN WANTED—by shoe manufac- turer established 35 years, for sales work. Ready cash daily. No experience needed. Your own shoes at factory prices. Complete line of almost 300 styles for men and women, including famous Velvet-Eez air cushion nailless insole shoes, sent free. Write Mason Shoe Manufacturing Company, Dept. R27, Chippewa Falls, Wisconsin. STEADY Work—Good Pay—Reliable man wanted to call on farmers. No experience or capital required. Pleasant work. Home every night. Make up to $12 a day. Wonderful new proposition. ‘ticulars Free. Write McNess Co., ent. 136, Freeport. Illinois. “HALE AND FEMALE HELP WANTED M. M. earned $267, three weeks, raising mushrooms in cellar! Exeeptional, but your cellar, shed perhaps suitable, We buy crops. Book free. United, 3848 Lineoln Ave., Dept. 88, Chicago. MIDGET AUTOMOBILES BUILD a Midget Miller Racer. Com- plete plans for constructing this authen- tic midget automobile appear in the new 1938 edition of How-To-Build-Tt along with many other interesting home and workshop plans. Send 50c for this 148 nage book to Modern Mechanix ` Publ. Co.. Greenwich, Conn. MIDGETS! Motors! Parts! Used, ‘new; sport, racing. Over 20 midgets, 60 motors, $5 up. Latest lists, 20c. Shipps Midgets, Box 543-B, Zanesville, Ohio. MISCELLANEOUS BURIED TREASURE, Minerals, free photographs. Fisher, Palmer Hollywood. MODEL RAILROADING BUILD a Model Railroad in 00 gauge ¿34 inch between rails). A complete vatalogue of parts, construction kits, and completed units, One Dime. Nason Railways. P. . Box 9, Mt. Vernon, N. Y., Dept. 4X. Bldg.. Accept No Substitutes! Always Insist on the Advertised Brand!

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Automatic Tweezers Pull Hair Without Breaking the Skin Pulling the hair at the same angle that it grows, a new type tweezer is said to practically eliminate all pain and pre- vents breaking of the skin. The op- eration of the tweezer is entirely automatic as an inward pressure on the outer spring “wings” pull the hair out. MODEL Railroad Supplies “O” Gauge (144" scale—14" between rails) Freight Car Body Kits $1.00, Illus- trated Catalog 10c. Westbrook Co., Hashrouck Heights, New Jersey. MODELS & MODEL SUPPLIES YOUR Ideas developed into practical working model. 30 years successful experience; thousands satisfied custom- ers. Confidential service guaranteed. Bank references, Send 3c postage for 32 page book “Making Inventions Pay.” Crescent Tool Company, Dept. T. Cin- cinnati, Ohio. ENGINE Catalog 21c. Particu fres Evraymesco, 28 N. Cl sE ia MONEY MAKING OPPORTUNITIES HOME Industries. 10c. forty Melotz, Publisher, MOTION PICTURE & SOUND EQUIPMENT LEARN Motion Picture Theatre Busi- pages. Bensen. Ne! ness. Home Study Training: Manage- ment, Advertising, Projection, Free catalog. Give age. Theatre Institute, 345 Washington Street, Elmira, New York. MOTORCYCLES RECONDITIONED Motorcycles. New | —used parts for all makes. Authorized Harley-Davidson Dealer. Whitman Motorcycle & Supply Co., 405-9 South- west Blvd., Kansas City, Mo. SEND 15c for illustrated used Motor- cycle catalog. Bargains. Largest stock genuine Indian parts and_motorcycles. dadian Motorcycle Sales, Kansas City, 0. MUSICAL INSTRUCTION LEARN Swing Piano! free booklet. Christensen, 768 Kimball Hall, Chicago. When Answering Advertisements Please Mention April Modern Mechanix OFFICE EQUIPMENT TYPEWRITERS, multigraphs, address- ing machines, adders, dictaphones, dup- licators, sealers, folders. Save half, write Pruitt, 553 Pruitt Bldg., Chicago. OLD MONEY WANTED COMMEMORATIVE Half Dollars, Lincoln, Stone Mountain, Oregon, | Texas, Cleveland, Kentucky, San Diego, i Long Island, şi. 50 each. Illustrated | Catalogue No. 14, 25c. Norman Shultz, Salt Lake, Utah. OUTBOARD MOTORS BUILD electric outboard motor from automobile generator. Operates with car battery. Complete plans and valuable catalog 10e. LeJay Mfg., 514 LeJay Bldg., Minneapolis, Minn. PATENT ATTORNEYS PATENTS— Before too heavy an out- lay of time or money is made on an invention, a search of the Patent Office records should be made to determine as ne rly as possible whether or not the same idea has been patented before. often considerable. We offer inventors and manufactors a thorough, prompt, confidential search service—plus ex- perienced counsel and assistance in every phase of Patent and Trade-Mark practice. Write for our new free book containing valuable information relating to patent procedure. Clarence O’Brien and Hyman Berman, Regis- tered Patent Attorneys, 28-W Adams Bldg., Washington, D. C. DON’T tell anybody the secret of your invention. Take steps to protect it be- fore it’s too late! Get our Free ‘“‘Certin- cation of Invention’ and two Free hooks, They answer hundreds of Patent questions and explain our Deferred Payment Plan. _ Strictly confidential service. U. S. Registered Patent At- torneys. Over 62 years’ experience serving inventors all over the world. Postal brings | Write for free books Today! C. A. y @ Patents Division, 4, D.C. Exposure Meter Has Light-Limit Hood Designed for use over a wide range of illumination levels, a new ex- posure meter, shown above, has a special hood to limit more effectively the angle of the light received to approximately that of a camera. This lessens the error of indica- tion caused by strong sky light. The cost of this search is small, while ; the value of the facts it uncovers is j ; PATENT Your Idea. | Particula Shaving Mirror Has Built-In Light In addition to being illuminated, a newly developed shaving mirror has the added advantage of having aa outlet in its back to which an electric razor can be connected. The mirror has a translucent area near the bottom through which the light from a small bulb illuminates the face of the shaver without casting shadows. Write imme- diately for two free books, “Patent Protection” and “When and How to Sell an Invention.” Fully explain many interesting points to inventors and illustrate important mechanical principles. With books we also send “Evidence of Invention” form, Prompt service, reasonable fees, thirty-nine years’ experience. Avoid risk of delay. Address: Victor J. Evans & Co., Registered Patent Attorneys, 41-D Vic- tor Building, Washington, UNPATENTED Ideas can be oid. I tell you how and help ycu make the sale. ith list of manufacturers sent free on re- 1 Holmes, 905 ington. D. C. “INVEN TOR S Guidebook” containing 96 mechanical movements and advice » about patenting, selling inventions, alto “Record of Invention”, Free. Frank A. Ledermann, Patent Attorney-Engineer, 154 Nassau Street, New York. HAVE YOU a sound, practical inven- tion for sale, patented or unpatented? If so, write Chartered Institute of American Inventors, Dept. 5-A, Wash- ington. D. C. PATENTS. Booklet free. Highest references. Best results. Reasonable fees, Watson E. Coleman; Victor Build- ing, Washington, D. C. PATENTS INVENTORS— Time counts— Don’t tisk delay in patenting your invention. Write for new 48-Page Free booklet, “Patent Guide for the Inventor.” No charge for preliminary information. Clarence A. O’Brien and Hyman ‘Ber- man, Registered Patent Attorneys, 28-X Adams Building, Washington, D. C. INVENTIONS Conmercialized, Pat- ented or unpatented. Write Adam > Fisher Co., 582 Enright, St. Louis, Mo. GET Your Own Patents. Legal blanks, complete instructions $1. Cudding Sons, Campbell, California, 147

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Device Clamps Pan To Table, Freeing Hands For Stirring É Shown above is a new household aid which serves to hold a kitchen pan or bowl in place while the contents is stirred, leaving the operator's hands {ree for the job. The device is ad- justable to permit, its use with pans of varying size. PERSONAL STUTTERING and Stammering cor- rected at home. Booklet free. Paul J. Wolfe, Box 52, Pittsburgh, Penna. PHOTO DEVELOPING DEVELOP and print your own pic- tures, Save time, money with our com- plete outfit, $1.95 plus postage, or sent C.O.D. Includes electric ruby lamp, printing frame, photo paper, chemicals and equipment. One of hundreds of amazing hargains in our free, newest, money-saving bargain book. Send for it today! Central Camera Co., 230 So. Wabash, Dept. 14-J, Chicago. FINER Finishing. Rolls developed and printed, with One Colored enlargement, or two professional enlargements. All for 25¢ (coin). Genuine, a onally Known, Moentone Supericr Quality. Moen Photo Service, La Wi ARGUS, Bantam, Leica, ¢ fine grain 25c roll, 3x4 en prints 4c. Send no money. . D. MULSON’S 1491 Strati Avenue, Bridgeport, Conn. IDEAL Photos. 25c per roll, finished with round corner prints. To get acquainted! Coupon and snapshot folder Free! _Ideal Photo, Box 2255, Paterson, N. ROLLS DEVELOPED—Two Beauti- ful Double Weight Professional En- largements, 8 Never Fade Prints, 25c. Century Photo Service, LaCrosse, Wis, ROLLS DEVELOPED—25c coin, Two 5x7 Double Weight Professional Enlargements, 8 gloss prints. Club Photo Service, LaCrosse, Wis. AMAZINGLY Beautiful, Roll veloped, 8 Natural Color Prints, 25c. Reprints, 3c. Natural Color Photo, D-39, Janesville, Wis. LIMITED Time Only. 4x6 Natural Color Enlargement from your negative, Me: Natural Color Photo, Janesville, 15. SENSATIONAL Offer. Five 5x7 ene largements 25c. Cardinal Photo, Sum- mit, N. J. 148 ! High St., Spri PRINTING 2,000 Business Cards neatly printed j $1. 50. Free samples all printing items, ATLA S CO., Bedford Ave., Pittsburgh, 125 LETTERHEADS 84x11 and 125 Envelopes—$1.00 postpaid. Benneville, 907 West Roosevelt, Philadelphia. 500 Letterheads and 500 Envelopes, $3.25 cash. Barry, Babylon, New York. PROPELLERS PROPELLERS Sied-Airplane, Lowest Prices, Catalog 10c. Wooderaft_Pro- pellers, Hillside Station, Wichita, Kans. RADIO & TELEGRAPHY RADIO BUILDERS’ MANUAL—A book of radio set building plans and | kinks for the home experimenter. Everything from a crystal set to powerful 6-tube auto radio is included. Price 50 cents—order directly from Modern Mechanix Publishing Co., Fawcett Bldg., Greenwich, Conn. RADIO Engineering, broadcasting, aviation and police radio, pw: thoroughly. All expenses low, free. Dodge’s Institute, King St., Val. paraiso, Ind. RADIOS PLANS 18 Distance Crystal Sets— SW record 4250 miles, with “Radio- builder” year—25c. Laboratories, 151-K Liberty, San Francisco. RAZOR BLADES 100 FINEST Quality, double edge, blue steel razor blades, $1.00 postpaid. Richard Ashton, 63 Basswood, Lawrence, Mass. TWENTY Surgical Bluesteel double edged blades 25c. Bladeco, 3001—4th Ave., Huntington, West Virginia. RESIDENT SCHOOL LEARN fascinating profitable profes- sion of Swedish Massage in great resi- dent school in Chicago, Short course. Write for free illustrations of massage technique. Low tuition. The College of Swedish Massage, 1601 Warren Blvd., Dept. C2, Chicago, Illinois, SALESMEN WANTED IMMEDIATE openings for ambitious men! Wear, introduce “Fairbanks” individually tailored clothes. Enjoy fine income. Get new suits and over- ecats without cost as c Ccm IONAL money maker! Sell calendar _ business cards to Insurance Companies, Factories. les. T. Pricing Card Co., . New York. wW ANTED “Cosy Distributors. Ex- cellent op ty for earnings. a- tionally ai d product. Large company. Dept. 257, Fyr-Fyter Com- pany, Dayton, Ohio. POPCORN Machines, Carmelcrisp, Crispettes, Cheese Coat, Potato Chips. Write for cata Long Eakins, 2029 eld, Ohio, Sign letters, ATLAS Window Sizes, Penny Each. Beautiful Free . Samples, Atlas, 7941-G Halsted, Chicago. SPECTROSCOPES SPECTROSCOPE with book of 120 experiments, $2.50. Cudding Sons, Campbell. California. TELESCOPES, MICROSCOPES, ETC TELESCOPES, Microscopes, Binocu- lars; 1938 bargain catalog free. Brown- | scope Company, 5 West 27th Street, New York. Machine Puts Gloss On Waxed Paper Shown above is a new paper mill ma- chine which is used to impart a high gloss to sheets of waxed paper. Melted paraffine is put on a sheet of paper by means of a chilled iron roll and rubber roll, working in conjunction with each other at a temperature of 135 degrees Fahrenheit. While the wax is still molten, the sheet is dipped into a water bath of a 38 degree temperature. The water is then removed from the sheet by the new machine and a gloss imparted in the process. TELESCOPES, Microscopes, lars, Mineralogy, Chemistry. free, Teeko, Evanston, Illinois. DUPONT Superior Panchromatic, 35 mm; 25 ft. roll, $1. Optical Lahora- tories, Larchmont, N. Y. Binocu- Catalog 6” REFLECTING Telescope Lense. 52” Fl. 100 power, Price $10. Box 298, Mansfield, Ohio. VENTRILOQUISM LEARN Ventriloquism by mail; small cost, 3c stamp brings particulars, Geo. W. Smith, 125 North Jefferson, Room 5693, Peoria, Ill. LEARN Ventriloquist Art. Easy. Low Cost. Details Stamp. Apex, 221 Ę 31, New York, VIOLET RAY LAMP ULTRA Violet-Intra Red. Health Lamp. Two separate units in Promotes Sun Tan—Vitamin Automatic control. AC-DC current, $3.90 postpaid, Details Free. Beyer Mig. Co., 4515-M Cottage Grove, Chicago. WELDING. CONTROL, 25-200 Home-made from North-East (Dodge) automobile genera- tors, without rewinding armature, New method designed for beginners. Over 3,000 words, real facts, actual welding views. Certified Instructive Plans $1.00 C. O. D. $1.12, Airmail 12c_ extra. Welders Club of America-B, B-3432, M-Mart, Chicago. ARC-WELDER Home-Made from orig- inal North-East (Dodge) 12 volt auto- mobile generator. No rewinding. Plans $1.00. Welders Club of America-B, B-3432, M-Mart, Chicago. WIND ELECTRIG PLANTS your own Windcharger. material plus used car generator. Draw- ings—Instructions 10c. Wesco, Min- neapolis, Minn. Accept No Substitutes! Always Insist on the Advertised Brand!

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Europe Surpassing America In Aviation Progress Unless America keeps pace foreign aviation expansion will shortly outstrip the present front- running position of the vital military and commercial aeronautical industry in this country, warned Arthur Nutt, engineer of the Wright Aero- nautical Company at a National Aeronautic Association meeting sponsored by the Society of Automotive Engineers. Mr. Nutt, returning from his second trip in three years to the airplane engine factories of European powers, emphasized his warning with the following: 1. Germany has a single airplane engine fac- tory which has more floor space than all the fac- tories of all the American aviation engine com- panies combined. The Reich is concentrating on Diesel engines, with its realization that in war- time gasoline will be curtailed. 2. Russia is producing American engines, under license, in factories that are twice as large as those of the parent American companies. 3. The greater number of mechanics in Euro- pean airplane factories represents inefficient op- eration much less than it does the desire to train men for wartime expansions. 4. Italy has a large expansion program and is overcoming a deficiency of personnel and mate- rials, 5. Political unrest and labor troubles have handicapped France in the last two years but development of liquid-cooled engines continues. 6. England, after its late start in expanding its aviation production facilities, shows phenome- nal progress. Several hundred military airplanes have speed of between 300 and 350 miles an hour. In the Rolls and Bristol engines it has two of the world’s best. 7. Emphasis in Europe on military airplane en- gines puts more stress on maximum, short-time performance and less on the American standard of reliability and durability. 8. Contrary to the secrecy which often sur- rounds American airplane factories the European factories give a warm reception to reputable visi- tors. 9. In experimental laboratory testing equip- ment Europe is definitely ahead of America. The result of this fact is not yet apparent but soon will be as measured by future developments. ADLETS FOR HOBBYISTS (See regular classified sectlon for rates and other Information.) STAMPS SUPER-WONDER Packet offered, containing 60 different stamps from Afghanistan, Transjordania, North Borneo, Manchukuo, Sudan, Guadeloupe, Iraq, Sarawak, French and British Colonies, including natives, heasts, ships etc., all for only 5c to approval applicants. Big illustrated lists free. Kent Stamp Company, Box 87-Z (G. P. O.) Brooklyn, N. Y. STAMP CATALOGUE FREE:— Special Gift Edition— Giant forty-page quarterly listi Albums, Supplies, Ce TO nations, British Col » Ca United States. and Airmails. Illustr ! EMPIRE STAs es Dept. MM., Toronto, 1897 Grande Comore Islands, rare old genui Turks Caicos, $5 U. S., British Colony Mar ‘Western Samoa, etc. Everything 3c with approvals. 1-MM, Hanson Place, Brooklyn, Ea FANTASTIC INDOCHINA, Somalicoast German State, Perak, Selangor, Sembilan, Bicalored Banana Airmail, Siberia—Free with Approvals! Postage 3c—Saxon Com- pany, 3 Dekalb Ave., Brooklyn, N. Y. DIAMOND Airpost Commemorative Issue Complete, Pro- Jetariat Portraits Complete, Dragon Stamp, with 117 addi- tional, cataloging $3.00. only 10c. Friendly Filatelists, Box 4428M, Philadelphia, Penna. NEW Rivera nude stamp! World's largest triangle! Congo, Sudan, South Scas. bicolers, pictorials and many others. Only 3c with approvals, Cactus Junior Approvals, Box 1870-D, Tucson, Arizona. STAMPS! 100 diff. 3c; 500 diff. 35c; 1,000 diff. 90c! Illustrated Album (4000 spaces) 22c. Approvals sent. Tatham Stamp Co. (D9) Springfield, Mass. MONTHLY Stamp Magazine, 6 months and 25 foreign stamps, 25c. American Stamp Journal, Cedar Rapids, Iowa. UNITED STATES—i25 different $1; 75 different 30c; 45 different 10c. Sidenburg, Baroda, Mich. FREE!!! Two Coronation Sets. Postage 3c. 312T Shearerbldg, Baycity, Michigan. Roberts, COINS —— FREE: Foreign Coin, Banknote and Large Illustrated coin catalogue, for 4c postage. Approvals sent. Tatham Coinco, Springfield-9, Mass. —~ COINS, Beadwork, Indian Relics, Minerals, Books, Curios, samp: Catalogue, 5c. Indian Museum, Northbranch, ansas OLD MONEY WANTED E02 TO $300.00 EACH paid for hundreds of Old or Odd rs. Keep all until posted. Send 10 cents for Illustrated ccin value book, 4x6. Guaranteed buying and selling prices. In business 31 years. Stamps, Old gold and silver also bought. Coin Exchange, Box 43, LeRoy, N. Y — ANTIQUE FIREARMS ~ REVOLUTIONARY Indian guns, Wooden Antlers. Photolist 10c. Indians, Museum, Rutland, Ilinois. INDIAN CURIOS — 100 good ancient Arrowheads $3.00. Illustrated catalog 5c. H. Daniel, INDIAN CURIOS. Tomahawk Head 50c. Hot Springs, Arkansas. INDIAN RELICS 12 Arrowheads. Spearhead, birdpoint, wampum $.99. Collection of 20 Indian relics $.99—11,500 Bargains— Spears. Bannerstones, Pipes. Photolist 10c—Museum, Rutland, Illinois. When Answering Advertisements Please Mention April Modern Mechanix 149

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VLL FIX THAT IN A JIFFY! CANNED WOOD MAKES HOME REPAIRS EASY Anybody can do a fine job of repairing quickly ~broken chairs, loose casters, holes in wood, nicks, cracks, screw holes, loose drawer pulls, ete. with this s canned wood that handles like soft putty and quickly hardens into wood you can drive nails and screws into, paint, or carve. Try it, Paint, hardware, and $ stores sell PLASTIC WOODin 10¢ and 25¢ tubes, 35¢ cans. WHY RENT A BOAT? MAKE YOUR OWN Even a child can build at least one of the many boats that are described in the big new 7 850 page book. ee are BUILD 20 BOATS—1938 Edition. Serd for your copy, MODERN MECHANIX PUBL. co, Fawcett Bido Greenwich. Conn.

WORKS ON 110-VOLTSS Electric Light CIRCUIT — Atthis unheard of price, youcanget =Œ this marvelous DYNAMIC Super- “= Charged Welder— this welder is 2 radical departurefrom accepted welding prac- tices. It will dothework of much higher priced types — efficiently cooled — light of weight— easily portable, Will solder and braze on the lightest material. Works on iron, steel, tin, brass, copper and all other metals. WELDS Cylinder Blocks, Bumpers, Fenders, Tanks, Farm Machinery... AG ENTS With this Dynamic Super- Charged W. ER, a man Make big profits selling to ga- without previous experi- ence can make as mael ag 5 on a repair jo! ae fy e tae tories that can be done in less machine shops, Write TODAY \ than one hour. Many x wel ding operators make J a8 mue! as $15.00 - $20.00 day—Go into business — Open a Welding Shop N ow. S DYNAMIC WELDER COMPANY 2226-DA Silverton Road, Chicago, Illinois <P

LOOK WHO'S LAUGHING

a pretty large order. Unless our eyes deceive us, though, Jack Oakie seems to be genuinely amused by the latest issue of FOR MEN ONLY. In fact, we hear from reliable sources that the genial President of Oakie Radio College plans to make FOR MEN ONLY required reading for the students— and faculty. Mra a comedian laugh is generally HE April issue is just ouf—with another two dozen hilarious color cartoons, and twenty-odd lusty, entertaining articles by some of America's favorite authors. Toho) VNU AT ALL NEWSSTANDS . 25c

150 Accept No Substitutes! Always Insist on the Advertised Brand!

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New “Synthetic Rubber” Outside of the technical industries concerned, most people may yet feel that “synthetic rub- ber,” or rubber-like materials, is still a laboratory curiosity. How many know, for example, that six products now on the American market are rivals of rubber? Some are true synthetics, built in the laboratory, while others are derived from natural rubber but have special and desirable properties. Pioneer of the rubber-like substance is Thiokol, which is available in sheets, as a liquid, or as a powder for molding. Like rubber, it can be vulcanized, but has the additional valuable prop- erty of being impervious to gasoline and does not swell and quickly disintegrate. Koroseal is the rubber-like plastic with prop- erties that make it desirable where natural rub- ber fails. It can be obtained in hardness that runs all the way from a soft jelly to hard rub- ber. You can mold it, make sheets out of it or extrude it from openings. Remarkable resistance to light, water, air and certain corrosive chemicals and oils are its merits. Chief use is in the im- pregnation or coating of fabrics, paper and metals. AXF is another rubber-like synthetic organic compound which makes hard rubber flexible and aids in overcoming the deterioration due to ozone. DuPrene is one of the newest and most widely known synthetic products having rubber-like properties, which has greater resistance to oil, grease, gasoline and air and heat than natural rubber. Tires have already been built with it and performed satisfactorily. Leather, fabrics, asbestos and cork have already been coated with i for special service. Plioform is a rubber derivative made from pale crepe rubber. It resists the attack of water, all alkalies and most acids. It has excellent elec- trical insulation properties. This plastic has wide usefulness in the field of sound production. When used as a sounding board it approaches violin wood in producing pleasing tones. Sixth of the rubber-like materials is Tornesite, a rubber derivative, whose present function is primarily in the coating of metals. It shows re- sistance to acids, alkalies, smoke and fumes and can be applied with a brush or as a spray. In the commercial sense there is little reason why the synthetic rubber-like plastics should exactly duplicate the natural products. While the search for synthetic rubber originally had that goal, the present products nave excelled rub- ber in many ways and lack only the price angle to be highly competitive on a wide scala. Astronomers have found nothing so satisfactory for making a system of fine guiding lines on a telescope, as a spider web. Astronomers cannot examine the surface of the planet Venus, because clouds hide it. 180 PAGES OF RADIO VALUES! NOW? Get your FREE copy of this dollar-saving radio catalog. Use it as your buying guide. Compare prices of famous equip- ment listed. 50,000 items—parts, tubes, tools and the famous “line of 70” Lafayette radios. Get ‘the best, FOR LESS. Mail coupon NOW! WHOLESALE RADIO SERVICE €? ME. NEWYORK, N.Y. @ CHICAGO, ILL. e ATLANTA, GA. 100 SIXTH AVE 901 W. JACKSON BLVD. 65 PEACHTREE STREET BOSTON, MASS. « BRONX, N. ri y WHOLESALE RADIO SERVICE CO., INC. RESERVER THENEW r I 901 W. JACKSON BLYD., CHICAGO, ILL. I Rush FREE general Catalog No. 69—22D8 [J SPRING} CATALOG i I Reserve Catalog No. 7!—22D8 J _ WITH TA I Name,.... I Address... World’s Finest Sport F E N C I N G Exciting Fun—Harmless Boys! Become the best swordsmen in your neighborhood. Develops both body and mind. Harmless, because the spring- . steel 3 ft. long foils are equipped with t rubber buttons. Cup shaped hand Complete set cf two foils (swords) and free in- struction bcoklet only 51.98 postpaid. Order Now. INDUSTRIAL PROD. CO., DEPT. 4D, 48 W. 48TH ST., NEW YORK, NY, Concentrate your talents on inventions that will pay, BIG MONEY. New Edition of 1500 NEEDED NVENTIONS by R. F. Yates tells what Inven- tions manufacturers NEED badly. Describes in detail 1500 Needed inventions in these fields: General Problems; Autom 3 Electrical: Me- chanical; Shemical; Aviation; Radio; Marine. Also chapters on the Ten 3 Needed Inventions, and on new scien- tific discoveries important inventors. Simple, practical ideas—one idea from this book may win you a fortune. If you want to invent, know what inventions wlll pay you the most money, This book tells you. Keeps you from working ‘on inventions nobody wants to buy. Large cloth bound bool 5 ‘pages, nine big chapters. Only $2.50. Drop a postal and we w send 1500 NEEDED INVENTIONS Cc.0.D. We pay postage if you send cash with order. If not delighted after 5 days’ examination, return it and get your money back. INVENTORS’ SELLING GUIDE How and where to sell patented or unpatented inven- tions, Inventors’ Selling Guide F. Yates, noted authority on inventions. diassined lst of Nearly 1000 manufacturers who . Tells how to sell unpatented inventions fely, how to sell chain stores, how to price inventions, Selling by correspondence and demonstration, how to find buy- ers. etc. Tells what an inventor must know about Law, Royalty, Contracts, Pee Pending, Financing, Schemes, Selling Methods. Clothbound book, 24 pages, 15 chapters, paa 52 (or C.O.D. plus postage). Satisfaction guaranteed. BOTH BOOKS FOR $4.00 if ordered at one time Write for FREE specimen pages and complete catalog of valuable books for inventors. DONLEY PUBL. CO., 509 Fifth Av., Dept. M4, New York,N.Y. Patents, $1.00 Making Unpat- ented Inventions Pay, 50c When Answering Advertisements Please Mention April Modern Mechanix 151

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` A BACK-GEARED SCREW- CUTTING PRECISION LATHE - S Weight 320 Lbs. 35% Less) Motor Drive # Sold on Easy i g SS ği AVENE No. 415-YA, 914” swing by 3’ bed Workshop Low as $6.00.a Bench Lathe with Horizontal Motor Drive, Month: for 12 hp. Reversing Motor, Switch, Belts and $1 17.00 CPUC tte Adjustable Belt Tension Countershaft...... - ($15 Down—$6 Monthly for 18 Months) THE MOST USEFUL OF ALL TOOLS IN ANY AUTO SERVICE SHOP Ce your investment in shop equipment, and do your work on this profitable all-purpose lathe. 95% of the modern motor service work can be done on the 9-inch “Workshop” South Bend Lathe. With attachments it handles the six most important auto jobs—refaces valves—tinishes pistons—bores re- babbitted connecting rods—makes SOUTH BEND 9-INCH WORKSHOP PRECISION LATHE Used by: MANUFACTURERS. — TOOL ROOMS LABORATORIES ; MACHINE SHOPS - Features—Twin Gear Reverse to Lead Screw, Ball Thrust Bearing on spindle, cuts screw threads from 4 to 112 per inch, 34” spindle hole taking collets up to 15”. Made in 3’, 313’, 4’ and 415’ bed lengths. Operates from lamp socket at less than 2 cents per hour. Write for information about the —Automotive '—Electrical z -——Gun Smiths U.S. GOVERNMENT SCHOOLS- Z HOME WORK SHOPS ; INVENTORS bushings—cuts screw threads— trues commutators. Also get the profits from other machine opera- tions this all-around tool handles. modern motor service shop. Learn how to do many profitable jobs. SOUTH BEND LATHE WORKS 266 E. Madison St., South Bend, Ind. The9”x3' South Bend Precision Lathe does these operations: TURNS—BORES =—CUTS SCREW THREADS—FACES —DOES MILLING, CHUCKING, REAM- ING, DRILLING, -FILING AND HUN- - DREDS OF OPERA- TIONS IN STEEL,. _ TRON AND OTHER $ METALS. LATHES STOCKED IN PRINCIPAL CITIES Chicago—C. B. Burns Mchry., 541 W.W ash. Blvd. New York—A. C. Colby Mchry., 183 Centre Si. Philadelphia—W. B. Rapp Mchry., 132 No. 3rd. L. Angeles—Eccles & Davies Mch., 1910 Santa Fe, Detroit—Lee Mchry. Co., 6318 E. Jefferson Ave. Milwaukee—Voell Mchry. Co., 1533 No. 16th St. Boston—MacKenzie Mchry. Co., 36 Oliver St. Cleveland—Reynolds Mchry., 2034 E. 22nd St. SOUTH BEND LATHE WORKS, 266E. Madison St., South Bend, Ind., U.S.A. ( ) No. 33-G Auto Workshop Bulletin, Free, ( ) No. 33LB "How to Run a Lathe,” 25c, ( ) No. 46, 8” Workshop Catalog, Free, ( ) Easy Payment Plan. Ginsarse Work. eee tant ee cee ee s White FOR THESE BOOKS “How to Run a Lathe’’—~160 pages, over 300 illustrations on lathe operation. Auto Work- shop Bulletin No. 33-G shows how to do auto service jobs. Catalog No. 46 shows, describes 9” lathe in all sizes. Use coupon. There are 5 sizes of - South Bend Lathes— 9”, 11%, 13%, 15” and 16” swing with bed lengths 3’ to 12. In “motor or. counter- shaft drives. Priced $85 to $1500. A D (Precis 152 Accept No Substitutes! Always Insist on the Advertised Brand!

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Depth “Thermometer” Shows Temperatures Within Earth Scientists looking forward to the day when the earth’s insides will be tapped for heat and power have a new tool to aid them in locating the “hot spots” below the earth’s surface. It is a depth “thermometer” for taking the temperature thousands of feet underground. Ernest N. Merrill and George A. Young, both of Long Beach, Calif., are the inventors who have been granted a patent covering the device. More and more, scientists and oil companies have become interested in just how hot things re down under. They know that the tempera- ture increases the further down you go. From readings already obtained, scientists have been able to make a rough estimate of the age of the oldest rocks, and to infer from this result that the amount of heat which is being supplied to the earth from radioactive minerals may be much less than heretofore supposed. They have found, also, that generally the western part of the United States is hotter underneath than the eastern part of the country. This result is in agreement with the conclusion of the historical geologists that the Rocky Mountains are younger than the Appalachians. However, aside from pure research, sub- surface earth temperatures have a present day practical aspect for the oil man. Attached to a long steel wire, he drops thermometers down the wells as he drills deeper, pulls them up, reads the temperature. Should the drill be passing through rock strata where there is liable to be water, he can tell from his temperature readings what precautions should be taken to insure a water-tight cement job under such high temperatures and pressures. Bullet-shaped, the new thermometer, claimed to be more efficient than anything heretofore used, comprises a water-tight metal case. Into this goes a metal box provided with many com- partments. Through the bottom of the box in each compartment and through its cover are small holes. Each compartment contains sharp edged plates of various alloys which are the “mercury” of this thermometer. It is by noting which of the alloys have been melted after the thermometer has been lowered into the bore hole of the well and raised up, that the underground temperature is ob- tained. When sunspots are most numerous, it is pos- sible to use shorter wave lengths in Transatlantic radio reception. An Army aviation expert regards 480 miles an hour as the top speed limit for airplanes, and 409 as the practical limit. When Answering Advertisements Please Mention April Modern Mechanix | AUDELS Carpenters and Builders Guides F T 4vols.$6 {Inside Trade _ Information 1 Ve for Carpenters, Builders, Jcin= erg, Building Mechanics and all Woodworkers, These Guides give you the short-cut instructivns thab you want— including new methods, ideas, solutions, plans, systema and moncy saving suggestions. An easy progressive course for the apprentice and student, A ractical daily helper and uick Reference for the master worker. Cnrpenters every» where are using these Guid? as 4 Helping Hand to Easiot Von Botter ‘Wark and Bete s er Pay, ‘To get this aisi á TaS ance ior yourself, simply fll z a in and mail the FREE COU- Inside Trade Information On: PON below, How to use the steel square—How to file and set saws—How_to build furniture—llow_to use & mitre bos—How to use the chalk line—How to use rules and seales—IIow to make joints—C=rpenters arithmetic—Solving mensuration problems—Ese timating strength of timbers—How to set girders and sills—LIlow to frame houses and roofs—How to estimate costs—How to build houses, barns, gar eges, bungalows, ete—How to read and draw plens—Drawing up specifications—How to exe cavate—How to use settings 12. 13 and 17 on the steel aquare—How to build hoists and scaffolds— skylights—How to build stairs—Ilow to put on interior trim—How to hang doorse—Llow to lath— lay floors—How to paint THEO. AUDEL & CO.; 49 W. 23rd St., New York City Mail Audelg Carpenters and Buflders Guides, 4 vols., on 7 days! free trial. If O.K? Twill remit $1 in 7 days, and $! monthly until $0 is paid, Otherwise 1 will return them» No obligation unless I om satisfied. Occupation.-..sseene Reference... aeee So eveacerencerevacerreceres wee OF TOOLS IN ONE For work on all metals, alloys, bone, resins, plastics, glass, / stone, weod, etc. Uses 209 ¢ dierent accessories to grind, For drill, cut, carve, sand, saw, Faster engrave, sharpen, clean, © oe polish, ete. Saves hours of tedious hand work, Plugs in any socket AC or DC, 110 volts, STANDARD MODEL A sturdy little helpmate. Weighs 1 pound. 13,000 r.p.m, $10.75 postpaid, 3 Accessories Free. DE LUXE MODEL Fastest, most powerful tool of its type and weight, 12 ounces. 25,000 r.p.m. $18.50 postpald, 6 Accessories Free, GET A DEMONSTRATION at your Hardware, Department or Tool Dealer or order either Model on 10- Days, Money-Back Trial. Catalog Free, CRAFTSMAN’S PROJECT BOOK Easy working plans for making many ine teresting and unusual projects, 25¢ stamps f or coin, Chicago Wheel & Mig. Co., 1101 W.MontoeSt., Dept. H, Chicago, II. G $10.73 Model) Project Book D Send ©. O. D. O Send Catalog O De Luxe Model MMI-4 Name Address

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ow eas for Homes Shop Names and addresses of manufacturers of products described below will be sent free to any reader on request. Twenty-nine thousand feet of saw teeth a minute cut through solid beams or through ordinary stock when this sixteen-inch band saw is used. Frame is hollow design, in one piece. An all-purpose material for mending holes, worn spots in shoes, boots, or anything made of rubber, leather or cloth. A concealed fire screen which disappears into Se -~S.° This small back-geared screw cutting lathe has the construc- tional features of an industrial tool scaled down for accurate machining of small work in the home or commercial shop. IN NEXT MONTH’S Its Here—The Radio Newspaper! While television still hides around a distant corner, “facsimile” transmis- sion is making big strides. The new Finch machine. which is simple, rugged and foolproof, automatically delivers a continuous printed roll, bearing news, pictures, maps, fashions, ete. It is fully described in the May issue. . e e How Strong is Our Air Force? An authoritative answer is given by Brig. Gen. H. H. Arnold, assistant chief of the Air Corps, U. S. Army, in a vigorously-worded article of interest to every American. e e e Midget automobiles are the latest rage! Build one yourself in the cellar out of odds and ends of lumber and 154 the housing over the fireplace and provides protection against sparks. A non-breakable weather- proof socket. A tight fit around base of lamp prevents This record changer will play either eight or ten-inch records, and is available for current. water, dust or gas any from entering. A special tape for ammonia, brine air condi- tioning and refrigerating work. It is especially efficient as a wrapping for felt pipe covering. A hand-operated lever punch. The three major parts are drop - forged and heat treated. Weighing eight pounds, the. tool has an adjustable gauge for regulat- ing the distance of the hole from the edge of the sheet. An electric paper cutter which will cut paper of any thickness. Blades are adjustable and operate on 110 volts a. c. It will cut wet as well as dry paper. A thread cutting serew which cuts its own threads in metal or plastics, thus eliminating a separate tapping operation. With this electric MODERN MECHANIX a “one lung” engine from a washing machine. Complete plans and photographs. . e e Spring is painting time. Do you know how to get started? Don’t miss “Choose the Right Brush”, a help- ful, informative article. ° . ° Eliminate the “bugs” from your model planes before you take them to the field. Test them in a model wind tunnel that you can put together in an evening. Every model club should have one. —plus home, shop and garden kinks that will save you time and money, and the best photography section in print today! coffee mill, freshly ground coffee is instantly available by snapping a switch,

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Yeu dant hare lr TEL L ITTO THE MARINES they NOW” wsWRITES HARRY E. REECE, FROM THE U. S. VETERANS HOSPITAL AT MEMPHIS, TENN. “On active duty with the Fifth Marines in the Nicaraguan jungles. I went to our field hospital with fever. One day a badly injured Marine was flown in...it was my buddy! ` “His head had been bashed in by a machete. To save him, surgeons must remove fragments of skull press- ing on the brain...a delicate operation anywhere, it was extra tough in a field hospital. I guess they didn’t have much hope. Just when they started operating... “Our small portable generator had failed! Hospital corps men rushed through the dark ward, gathered up flashlights some of the men had there, and with the light from fresh DATED ‘Eveready’ batteries, the surgeon finished his work, “My buddy returned to duty, is still living and he thanks one swell Marine Corps sur- geon and dependable, dated ‘Eveready’ bat- teries. They were the only kind our canteen sold, the only kind that could have taken what we gave ’em. (Signed) Haru E. Recor” ROR BEST RESULTS NATIONAL CARBON COMPANY, INC., 30 EAST 42nd STREET, NEW YORK, N. Y. eRINTED, IN USB

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= things that add up fo more smoking pleasure. z Chesterfield’s refreshing mildness... good taste... and appetizing aroma . ë e Copyright 1938, LicGeTT & MYERS TOBACCO Co. Ne aa millions $

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uble Page Spreads

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Sty To Determine The Patentability Of Your Invention Before you spend money in making a model, or spend weeks in its design, we advise you first to have a preliminary search made through U. S. Patents in the U. S. Patent Office to see if there are inventions like yours already on record; and, if so, let us give you our opinion as to the patent- ability of what you have We employ experienced searchers to per- form this service for you. From the reports of our searchers we can quickly form our opinion as to whether your invention is con- fronted with obstacles in the form of already granted patents. First get our FREE BOOK and read the chapter on “How Can I Know Whether My Idea Is Patentable?” How We Serve The I t We have secured patents for nventor inventors located in every state in the Union. Our organization is a large and efficient one. Our practice is confined en- tirely to Patents, Trade- Marks. and Copyrights. We have had years of experience in Patent Matters. When you place your invention in our hands, we are in position to proceed at once to secure protection for you. Our fees are reasonable, and, if you desire, we can arrange convenient terms of payment.

CLARENCE A.OBRIEN & HYMAN BERMAN 317-B ADAMS BUILDING, WASHINGTON,D. C. Registered Patent Attorneys bofore U. S. Patent Office

What Help is the Patent Attorney? Your invention may provide your life’s £ ortunity. If it is to bring income id be l

in

lly yours. Upon your patent completely your patent in your invention. € money on his è claimable point would not miss.

cover 1 The inventor invention by that a skilled patent ä What The Inventor Must Know geweeg the inventor must follow certain definite steps that precedent has established as the quickest way to reach his goal. Our FREE BOOK, “Patent Guide for the Inventor,” gives a concrete, logical, and thorough resume for the inventor to follow. It takes him, through 48 pages, from the crude first model to the finished commercial product. It shows the inventor how to avoid mistakes, how to shorten the read in getting his invention ready for market; it also points out how to save money and avoid the errors of inexperience in applying for patent. Get- ting our FREE BOOK should be the first step in definitely declaring yourself an inventor. After you get this illustrated, clearly worded guide of carefully compiled patent knowledge you will know how to proceed without expensive mistakes and discouraging setbacks from ‘“wrong-track” methods.

Ñ Keen competition in every form of industry has put manufacturers feverishly at work try- ing to speed up output, reduce overhead, save on materials, outsell trade opponents. The inventor is the key-man in making advance- ment possible to any business. Upon the in- ventor rests the success of many enterprises, This does not mean that you must have some- thing gigantic to win commercial success. A new way to open a door or button up a shirt may be the very thing hundreds of manufacturers are looking for. If you have something novel—if it is practical to manufac- ture—no matter whether it be an improved rattle for a child or a whistle for a ~ mechanical automobile, there is likely a waiting market. / The Dp elapsed between Elisha Gray’s ap- plication for his telephone patent and the application of Alexander Graham Bell probably cost Gray the rights to the telephone. g a e Prepared “Record of Invention” © G NAUT striae neta semaines ADDRES Biasscsssssicsavissiocenesesvecssensosin

317-B Adams Building Washington, D. C. Registered Patent Attorneys Before U. S. Patent Office 8 a Importance Z : Z a S, Of Immediate © Ma Action A , o. , ly CLARENCE A. O'BRIEN In making application for patent it a is important to be first. Even if TEAR OFF a your application is delayed by a few AND Tà days you may be placed at a dis- MAIL l advantage. The short time that Wow! S Please send me at once your Big Free 48-Page Book, “Patent Guide for the Inventor” and your Specially form. This request

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A frank man to man talk about PATENTS-INVENTIONS -SELLING INVENTIONS HE world of invention moves on. About a hundred years ago people were saying, “There’s nothing left to invent”—today we know that is one of the funniest things ever said. Just think what has happened in the last hundred years! Autos, radios, airplanes, and thousands of useful, practical devices for home, shop and office have been invented and put on the market. Inventors are con- stantly making the world a better place to live in. Did you see a notice in the paper that an obscure worker, Hans Wach, has invented a simple device to utilize exhaust steam on steam boats. Already, the report states, the steam ship lines have saved more than $15,000 in fuel bills with his invention. Almost in the same breath the Dept. of Commerce announces that it will soon test out a new non- crashable aeroplane, which the average man can learn to fly in a day, which will travel at 110 miles an hour and sell at the price of a cheap automobile. An unknown Seattle man has invented a robot to go 5.060 feet under the sea and recover millions and millions of dollars worth of gold lying at the Who Are Inventors? You'd be amazed at the men we con- tact in the course of a busy year. Most of them do not consider themselves inventors at all. During their work or Jeisure they get an idea. They work it out on paper. They get 7 in touch with us about P 4 Did you know that a dentist invented the stock ticker, a school teacher the telephone, a farmer the typewriter, an artist the telegraph? Did you know that the crinkly hair pin—sold by millions now—came about because a husband saw his wife twisting the old-fashioned straight hair pin to make it stay in place? Poor men who have no thought of invention now will be financially well-fixed in a few years because the average man. of a happy thought that the world could use to advantage. steps can I ta he any trouble, or delay. Can You Answer These Questions? Ask yourself these questions: Tow do the Patent Laws protect me? What easy Tor more than forty years, this firm node bottom of the ocean since the days of the early Spaniards. Remember this: For every outstanding big inven- tion there are thousands of small, simple things for use in the home, the office, the factory, on the farm, on every sort of travel conveyance. Little articles like you find on the counters of a 10-cent stores hardware store, drug store, toy and novelty shop. Many Little Ideas Have Big Commercial Poss ies A person finds something he’s using doesn’t work right, or it’s clumsy, or costs too much. He gets a happy thought. He improves the old Article. That’s contribution to human progress. That’s the way that many, many men have reached the goal of financial comfort, independence and even wealth. Most of the things millions of us use didn’t come from the brains of engineers and physicists. They came from the mind and maybe the crude home work bench of Mr. Average Man, busily engaged in earning his bread and butter at whatever chance or circumstance has given him to do. The “little” man’s opportunity as an inventor was never greater than it is today. Our Business Is To Help You. Write Us Today t. ut has been helping men with an inventive turn G I. We maintain a large staff of trained, | experienced specialists—Registered Patent Is a Patent Attorneys, Draftsmen, and Searchers to help Do I need our clients secure all the protection to which Should I try to they are entitled. Fees are reasonable, De- invention before I ferred payments frequently arranged. Ques- hout e to (o it Patented? Is there tions promptly answered. Write us frankly safe, business-like way wiih absolute assurance that what you say will to secure financial help? If be treated with strictest secrecy. But FIRST, I do apply for a Patent send for the FREE BOOKS shown on the op- how shall I reach people who posite page. They are filled with facts, pic- can market my invention? Can I protect and tures and ‘suggestions, They teil you things sell an improvement on some invention that about Patents, Inventions and Selling Inven- has already been patented? These are but a tions that we have learned in our long few of the questions which usually confront experience. They may save you time, expense, You need the answers! EVEN LATER DISAPPOINTMENT. Simply YOU CAN HAVE THEM, without cost, fill in the coupon. No charge, no obligation. Write us today. TO WASHINGTON. D.C 12 Accept No Substitutes! Always Insist on the Advertised Brand! 115 Mechanical Move- ments Like These Besides many other features and facts there are 115 differ- ent mechanical movements and principles in the big, 48-page Book below. Maybe there is just the idea you need to solve some mechanical problem, Use the coupon or write us a card or letter. AAR FREE BOOKS with 68 PAGES of Facts and Pictures! ry, WMV Evans & Co. REGISTERED PATENT ATTORNEYS MAIN OFFICE: 30-D, VICTOR BUILDING, WASHINGTON, D. C. Other Offices; 2610-B, Singer Bldg., New York 1445-B, Monadnock Bldg., Chicago 1010-B, Hobart Bldg., San Francisco Los Angeles WHEN NEW BOOK and About Selling e) INVENTIONS ro Selan So far as we know, the facts in this booklet have | ELAMA never before been pub- lished by any Patent At- torney. You are given very definite suggestions on “When and How to Sell an Inven- tion” It also comes to you FR 514-B, Empire Bldg., Pittsburgh Send me FREE copies of your books, “Patent Protection” and “When and How to Sell an Invention.’ (Note: Same books sup- plied by any of branch offices listed above.) Name ...... ee eee T ere seeeee PePrrer rere rire reer eerens Btrect OAD No, cccpascsnccss sve Ferree ee Oreee rere rere rer t ere City or Town seereeee StBtererersee When Answering Advertisements Please Mention April Modern Mechaniz 13

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Built entirely from salvaged parts of old automobiles by 78-year-old M, O. Stetler. of Kingfisher, Okla., this garden tractor features six forward speeds and a one-wheel brake. AWARDED first prize of $5 in this month's Workbench contest, a letter received trom Bob Stetler, of Kingfisher, Okla., will undoubtedl: interest many of our rural readers. The letter says: Dear Editor: Enclosed is a photo of a home-built yarden tractor made by 78-year-old M. O. Stetler, The parts were all taken from discarded autos and trucks, the engine, frame and transmission being sal- vaged from a 1928 auto. The front axle was taken from a popular car, but was shortened and inverted to give greater clearance. The rear axle is from an old truck. The engine incorporates a centrifugal-type governor, driven by a fan belt and controlled by a choke assembly running through the steering column. Braking is ac- complished by means of a lever and shoe attached to the right rear wheel, Bob Stetler We don't know ¥ Stetler, builder of don’t blame him for being pr craftsmanship. ee Midget racer fans will be interested in a letter received from Charles and Francis Dusch, of Ashland, Pa., which was awarded a prize of $3. The letter reads: Dear Editor: We are sending you two pictures of our midget racer. It was built from plans that appeared in MM quite some time ago, The car weighs 136 pounds and has a four-foot wheel base. It attains a speed of about ten miles per hour, powered with a 34-horsepower washing machine engine. 8 T Due to the size of the car, we were forced to change the position of the engine, which is connected to the rear wheels by a combination belt and chain arrange- ment, as shown in the photos. We will gladly answer questions from MM readers if they enclose a stamped return envelope with their letters. Charles and Francis Dusch. Here is a chance for you midget racer “bugs” to correspond with two brothers who undoubtedly are good craftsmen. eet A letter from Howard Allen, of Hammond, N. Y., describing his home-built outboard motor boat was also awarded a $3 prize. He says: Dear Editor: Tam enclosing a photo of “Buzzer”, built from plans in tae MM book—“How To Build 29 Boats”. I built the boat a little heavier than called for in the book, but it goes 27 m.p.h. with a 22 horsepower outboard motor. The boat handles very nicely and I have been out during some of the strong winds that sweep the St. Lawrence River, shipping very little water, Several people have admired the boat and said they were going to send for the plans. Please print more boat plans In the future. Howard Allen. Charles and Francis Dusch proudly pose with the midget racer they consiructed from MM plans. The close-up shows details of the tiny car which is powered with a 7⁄4 -horsepower engine. Modern Mechanix Boat fans will readily admit that Allen’s “Buzzer” has trim lines and the strong winds and rough water evidently proved its sea-worthiness. How about it, fans? Why not get a copy of the MM boat book (price 50c) and build a “Buzzer,” too. Make summer time boating time. ak Model plane enthusiasts are usually prolific builders of solid and flying models, but how many can equal Marshall Anderson, of North Warren, Pa., who, in his letter which was awarded a $3 prize, states that he has built 35 models? He writes: Dear Editor: I am sending you a photo show- ing a few of the 35 airplane models I have con- structed. I would like to see plans for a compressed air model in MM. I am 16 years of age and would like to hear from fellows who are interested in model plane build- ing, Please men- tion this if you print my letter. An unusual overhead view of “Buzzer,” built by Howard Allen. Good work. Marsi models is quite an achieven that other MM model plane correspond with you. Marshall Anderson, a prolific MM model plane builder, is shown here with a few. of the 35 flying models he constructed. April, 1938 This splendid action “shot” was sent in by Tom Griberg. It shows the MM “Sunray” sailboat he built at a cost of $84.01. Tom Griberg, of Moline, Ill, sent in a letter which was awarded a $3 prize. The letter reads:. Dear Editor: Most of the pictures you print of sailboats built by M readers show the boats either moored or sailing fl closing a real action photo of “Sunray”, era unc that even with a 170- ne mar ting on the low side and the water run- ning along the top of the cockpit coaming, the boat is still stable. My “Sunray” was built in five weeks of spare time at a total cost, including sails made from airplane fabric, of $84.01, For the second season of sailing, I replaced the centerboard with a metal fin. Tom Griberg. We try to get action photos of all boats built by MM readers, Griberg, but most of the photos submitted show the boats moored, as you say. Remember this point when sending in photos of your boats, readers. EES An interesting letter received from Charles Fottler, of Dorchester, Mass., was also awarded a $3 prize. His letter reads: [Continued on page 31]

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Certainly we would defend Alaska. Then there is the Panama Canal which, in addition to its enormous commercial advantages, saves us the expense of main- taining two fleets. We would fight to pre- vent the canal from being destroyed or falling into foreign hands. And the Hawaiian Islands! We would never permit a foreign power to seize them _ and thus establish an important base off our Pacific Coast. Getting out of the realm of fact, into that of political speculation, would we en- force the Monroe Doctrine in case of an aggressive move by a foreign power in either Central or South America? Would we feel obligated to defend the Philippines, shortly to attain their inde- pendence? Would we defend our trade and citizens in foreign countries or traveling on the high seas? Would we again attempt the role of defenders of democracy throughout the world, as we did in 1917? “The continental limits of the United States are not in much danger of being in- vaded—as long as we have our fleet, now the second largest in the world. The time may come when an invasion by air is possible, but we need not worry about that now. Planes can now fly the Atlantic in one jump, but none can make the round trip, carrying a worthwhile load of bombs one way. Any troops that could be flown -across could be handled by the local police. Invasion of the United States, it is gen- erally conceded, would have to come by sea. And no such invasion would ever be at- tempted as long as our fleet was in existence, unless it should be caught in the wrong ocean and held there by destruction of the Panama Canal. The Canal, for this reason, needs to be made impregnable. Its present defenses consist of a mobile brigade to repel landing parties, our air force, anti-aircraft artillery, and coast defense guns, which are adequate to protect it from a raid (unless it should be a surprise raid made before a declaration of war). Its major defense is the Navy itself, which alone can prevent a major operation against it; since such an attack would have -to be made. by sea. It could, however, be effectively. b eked by the simple expedient _of blowing ‘tip as ip passing through it ha to be done before hi ve bases where it can retire Realizing the-value of aircraft as fighting and scouting auxiliaries, the U. S. Navy has added another carrier, the U. S. S. Yorktown (be- low), to its fleet. Ciele aking off from the flight deck of the U. S.-S, Lexington. mnot remain -afloat indefinitely. It -~ an aerial bomb. nai 2 - they cannot stand up as well against versy is in the same category. No -) capital ship has ever been sunk by plenish its ammunition supply. Such bases must be strongly defended by anti-air- craft and coast defense guns, and a land force strong enough to repel surprise raids aimed at their destruction. We have four such bases at New York, Norfolk, Puget Sound and Pearl Harbor. We have an undefended base at Guantanamo Bay, Cuba, which should be fortified, for it is vital to the defenses of Panama. Since the Key West —Havana route is the line of supply for Guantanamo, Key West should also be strongly fortified. We also need another base on the west coast. Complete docking facili- ties are all that is necessary to make San Diego. such a base. It has been frequently asserted that a navy is obsolete, since an airplane bomb can sink any ship. This has yet to be proved, for no first line, battleship has ever been sunk by In the Battle of Jutland, 50 capital ships hurled big caliber shells at each other for hours, yet only one battleship was sunk (there were 24 other ships sunk, but all were cruisers or lighter craft). 14-inch shell and a one-ton bomb are about equal in destructive effect, the shell having a greater armor-piercing quality. Long- ` range shell fire falls almost vertically, and decks are armored to withstand such fire—there is no reason to suppose — bombs. A well-placed bomb can, of — course, sink any other type of ship. © The submarine battleship contro- ~ - a submarine. Battleships have “blisters” (false sides) below the -a waterline to omer: ode torpedoes _. ‘ke wa Although it is claimed that submarines have never sunk a capital ship, their ability to observe enemy ports and coasts unseen while operating against merchant marine vessels has resulted in the building of more underseas craft by foreign nations, as well as by the United States. One of Uncle Sam’s sub- marines, the P-1, is shown below. Circle— ` Obsolete World War equipment is still used by the U. S. Army Signal Corps for training purposes due to lack of modernized apparatus. before they can do serious damage, the hulls are minutely subdivided as well to localize the damage of any penetration. Besides, battleships never operate without their protecting screen of destroyers, which, with their hydrophones, depth bombs, and great speed, are more than a match for any submarine. So the Navy needs battleships because they are the only type of ship that can fight other battleships. It needs cruisers —fast long range ships—to fight off lighter craft, and to scout and locate the various components of the hostile fleet. The Navy also needs destroyers as pro- tection against submarines, to make fast torpedo attacks against the hostile line (too many torpedoes, just as too many shells or bombs will sink even a battle- ship), and to lay smoke screens in front of the big ships to prevent accurate, aimed fire from the enemy’s surface craft. Because of such smoke screens, as well as because of the extreme range of big guns, battleships must have airplanes for

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spotting their own shell fire. To protect the spotting planes, fighting airplanes are needed, and for this reason we must have enough air- plane carriers to transport these planes, which ean also be used for bombing and scouting operations in co-operation with the fleet. ‘Although submarines aren’t much good in fleet operations, they are needed for ob- serving enemy ports and coasts unseen, for helping to locate the enemy fleet, and for operating against lone ships of inadequately protected convoys. Various types of auxiliary ships, such as airplane, destroyer and submarine tenders . are needed. Such ships operate with the fleet and are capable of performing almost any repair, no matter how great, for the craft they are designed to service. Other ships, . such as oilers, ammunition ships, store ships, ocean tugs, hospital ships, mine-layers and mine-sweepers are also needed. Our Navy is said to be particularly deficient in these auxiliaries at present. Any one or several of these types of ships > Used for reconnaissance by officers, armored cars like the one © shown at left are helping to modernize our army. However, x equipment, | is needed to fully modernize the Regular Arm could be dispensed with, if other naval powers dispensed with theirs, but to be deficient in any one type would invite defeat in case of war. There is no such thing in warfare as second prize. “You either win or lose. Our Navy should be strong enough to win within its own operating range. This operating range is the distance from the base in which it can operate as a complete unit, and is limited to the range of destroyers, which is . 2,500 miles. Though the Navy is the first line of defense, we cannot afford to depend upon it alone. Should it be defeated, should it be afloat in the wrong ocean through the blocking of the Canal, or should we be attacked simulta- neously by a European and Asiatic power, we would have to count on our other arms. The Air Corps would be the first to. see action. Highly mobile, our entire fighting force could be assembled at one point within 24 hours. In an action near our shores the long range bombers (of which we now have the best in the world) could patrol the seas, either alone or in conjunction with the Navy. Having discovered an approaching force they would attack with bombs, but it is doubtful J Corps alone could prevent a land- "on our own shores or in adjacent ‘Canada or lees. ‘A landing force would then have to be expelled by adequate forces aS representing all service arms great numbers of these cars, as well as other mechanical se oleh; anal naval operations, this batter; : pore uns (lower left) would play af awaii in event of war. Belaw— Soldier with a new type zaop 3 miles an‘ hour, Much more likely than this sort of a war, though, is an invasion of Alaska or the Philippines. There is little question that we would fight in either event, yet we are now inadequately prepared to resist such an in- vasion. Our Naval base at Hawaii is 5,000 miles from Manila and about 2,000 miles from southern Alaska. If we plan to hold Alaska, we need a naval operating base at Dutch Harbor, and an Air Corps base farther inland, with the necessary coast and anti-aircraft defenses, plus enough ground troops to resist any landing attempts near these bases. We do not need a large army, but the one we have should be highly trained, and equipped with the best weapons available. While our Springfield rifle is the best military rifle in the world, the fire power of the infantry could be increased five times, by equipping them with semi-automatic rifles. We now have only 3,000 such rifles. We should have at least 50,000. Until recently our Army had only six modern tanks—not nearly enough for train- ing purposes. This amazing deficiency has been remedied, but we still need more. Two _ hundred would be a conservative mini- mum in view of world affairs, We have four thousand °75’s left over see the World War. An excellent weapon in its day, we have since developed a field piece that weighs the same, yet fires twice as far; and it can be towed at fifty miles an hour behind trucks. The old tees maT. gun is. damaged if towed faste a We need Designed. to provide nary support for advaricing infantey, 75 3 unted on modern guns and this is rapidly being done. : Anti-aircraft artillery, surely a defensive weapon, has been wonderfully improved since the World War. We need to equip our anti-aircraft Regular and National Guard regiments with the latest in these types of defensive weapons. In short, all of our Regular Army and National Guard units should be supplied with enough of the latest equipment to enable them to take the field at once, as a modern force. There will be time enough to equip a large wartime army while we are training the men, but our permanent force should be- the best trained and best equipped force of its size in the world. Only if it is so can we afford to keep it small, There should be enough ammunition of all calibers in reserve, to last our regular forces for 30 days. [Continued on. page 118]

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f- oe SAND AND WATER PUMP OFF >. g Ss ENTER WATER NTER WATER ND GRAVEL Deep-well digging ranks as one of the most marvelous of 20th century en- gineering feats. IPERVIOUS CLAY not an oil ANDY CLAY = well, but— NO GRAVEL ATER BEER T NG SAND” i -Paul Sweitzer, who is rated as [the world’s foremost authorities rn scientific deep-well digging. Ea Cross-section drawing showing con- struction of a deep-well reamer. Its operation is fully described in text. OU probably have been thrilled by stories of the big game hunters of the world, by the experiences of horror and death in the frozen North; you may have shuddered over the escape of adventurers penetrating the depths of unknown forest jungles, sur- rounded by tropical disease, deadly insects and poisoned, hostile arrows, but have you ever thrilled to the story of that tiny stream of water which comes trickling from the tap in your bathroom—the romance) of finding it and bringing it into your home? Roughly a third of the people of the United States use underground water. The agricul- tural and industrial uses of it are enormous. Daily these uses are growing and modern methods of searching out this water, guaran- teeing an ample supply at all times, are among the most marvelous of twentieth cen- tury engineering accomplishments. Imagine, if you can, a 60-inch hole running straight down into the earth for a distance of 400 feet. Sixty inches in diameter means five good feet of earth. In this circular space 42 a deep-weil being “flushed” by forcing water into its depths by means of a hydraulic reamer fitted with jets. Right—~A huge slab of clay that became wedged between the cutting blades of the reamer. April, 1938 No wonder Mr. Sweitzer (wearing hat) and his as- sistant are smiling—the water pouring from the pipe during a test indicated that the new well in the background would yield two million gallons daily. Modern Mechanix os ATER Treasure Hunting , by John L. Coontz four men could stand) with comfort. But more than this. Imagine, at the bottom of this black shaft a great)mass of earth mowed out, a huge pit created, and created neither by hand or steel shovel. Imagine the filling up of this pit or hole again with gravel and stone from the earth, packed symmetrically ‘and in accordance with certain engineering specifications. “Modern deep-well| digging accomplishes this—and more,” says Paul Sweitzer, one of the world’s foremost scientific deep-well diggers. Mr. Sweitzer, has dug wells for the Federal government in Washington, giving to the great St. Elizabeth’s Hospital in that city, millions of gallons daily of the purest water in the world; for the cities of Sa- ` vannah, Georgia, Houston, Texas, Annapolis, “Maryland, Jamaica, Long Island, St. 13

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The installation of self-clean- ing oil filters, such as the type shown below, enables fleet owners to saye hundreds of dollars annually in reduced oil bills alone, to say nothing of the savings in engine wear and tear. Some filters feature renewable clarifier cartridges which keep the oil so clean that many operators instruct their drivers to change oil only every 5,000 to 8,000 miles. OW would you like to cut the cost of operating your car from 25 to 50 per cent? Or do you think that is an idle dream? Believe it or not, this pleasant reverie can come true, if you will merely put your mo- ` toring on a business-like basis. It is a matter of adopting the sort of management that is helping large companies save sizeable sums in the operation of their traveling employees’ cars, trucks, buses ete. Follow the fleet owner, if you want to enjoy more miles to the dollar. His rules are fairly simple, yet they produce results that seem incredible. The fleet owner does not think there is anything exceptional about the lowered cost of operating his cars. He ex- pects it. The savings are yours, too, if you will handle the subject as you would your own business. By rotating tires (switching from one side of the car to the other, and shifting the rears to the front in a counter-clockwise direction) it is possible to double their life. One firm 50 Have your car tested regularly with modern equip- ment (above) if you want to keep repair bills down and efficiency up at economical operating levels. found that by insisting that their men rotate tires every 6,000 miles, working in the spare, mileage jumped from the usual 15,000 to 30.000 or more. Tests showed that, although in some cases it was better to switch tires in the way I suggest, it was the mere changing of the tires that produced the real savings. A tire that stays in one position too long may be punished for any irregularity of the brakes or misalignment of the wheel on which it is mounted. Since bringing all of its cars under one management the motor vehicle department of an eastern state has raised gas mileage four miles per gallon in individual cases: Tests show that most carburetors are adjusted too rich, providing extra acceleration which drivers do not actually need. Operators are being educated to realize that in emergencies better acceleration can be obtained by drop- ping into the modern fast second gear. In many cases it is found that the automatic choke is not properly adjusted, or that it isn’t Modern Mechanix Applying the suggestions made in this article may reduce your auto operat- ing costs as much as 50%. Bus line operators regu- larly check their vehicles for wheel misalignment (tight) because they know it causes premature tire wear and faulty braking. THE FLEET =": Russell working properly. Drivers also are cautioned against allowing the engine to idle for warming up purposes where an automatic choke is used. Under such conditions an engine merely loads up, not only wasting gas but diluting the engine oil as well. Since 1928 the operating cost per mile for several hundred cars op- erated by an insurance company has dropped from 8.6 cents per mile to 3.4. This has. been accomplished despite the fact that the company uses a large percentage of cars which do not provide high gas mileage. The management was unable to lower the cost materially until it discovered that there is a very definite period beyond which it is more economical to trade in for a new car. This point is found to be just before the owner is faced with the necessity of having major re- pairs performed on the car and can Unbalanced wheels may easily cause rapid tire-tread wear and front wheel “shimmy,” so thrifty drivers check them regularly. April, 1938 on

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A high board fence can be used effectively when teaching a dog to “heel”. By pressing inwardly with his leg, as shown above, the trainer blocks dog’s passage, forcing him to retreat until it becomes habit to walk at his master’s heels. OUR dog may not be cut out for the movies but he can become an obedient, well-mannered pet if you adopt the training methods suggested by Hollywood’s ace canine instructor. His name is Carl Spitz and he has spent more than twenty years in preparing dogs for police and Red Cross work, “Seeing Eye” duty, the stage and motion pictures. The effectiveness of his methods may best be shown by the success his dogs have achieved in numerous motion pictures, At the film studios, Spitz is an institution and whenever a script calls for a dog, one of his pupils generally gets the assignment. 58 rain Breaking a dog to a leash is the starting point in the ani- mal’s education (sketch). Shown in the circle below is Jane Withers, popular juve- nile movie star, with “Buck”, famous canine screen actor. They have appeared in more than fifty-five motion pictures. The stars of his troupe, Buck, a St. Bernard, and Prince, a Great Dane, move from one set to the next in the manner of busy human stars. They are products of the film training school operated by Spitz and his co-worker, Fritz Bache. It is one of the most complete layouts in America and the kennels are modern, to say the least. They are even equipped with radios to provide music, which, Spitz says, they enjoy. But one radio also serves a more practical purpose. It is con- nected up to a microphone at the trainer’s bedside, and when a dog starts barking during the night he can be silenced by a blast Modern Mechanix Your Dog , by Marty Soden Daily lessons will make your dog an obedient pet. Above—"Buck”’, fa- mous’ St. Bernard dog of the movies, engaged in practice drill at a Hollywood e school under on a whistle or a sharp rebuke from the reclined -trainer. Spitz believes a dog’s education should parallel a human’s and consequently his pupils are separated into three divisions— grammar, high school and college. A film contract usually awaits the college “graduate.” Once in a blue moon a student completes his academic work with flying April, 1938 a pasiak KAn A canine “pupil” can be taught to sit down on all fours by grasping his two front paws with right hand and stretching him out with the other, as shown above. Exerting a small downward pressure on a dog’s hind quarters while holding leash, as shown below, teaches the animal to sit. The lessons must be repeated daily until the dog asso- ciates the actions with your orders.

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p Electric magnets attached to the recording arms of the seismograph are automatically raised each hour to provide a time check on the record itself. A sweep second electric clock; with face removed, is provided with electric contacts that close magnetic circuit. o ’ with a OmMmeée-macke Designed for the ama- i Gj p - teur scientist, this easily- built instrument records him from their big, complicated machines costing hun- earth tremors occurring dreds of dollars. tated a whole section of : R RICT AND A seismograph is nothing but a large pendulum with in all parts of world. MES a pointer which scratches a fine line ona eae drum. D A Strangely, when a quake comes, it moves the drum itself SHOWN IN —not the pendulum, which swings freely and whose inertia keeps it at rest, while the ground and everything hi attached rigidly to it quivers and shakes. The vibration | PIER OF ee ve ee = oeny a ea a = arm Sonat | o the pendulum bob, so that the record may be more by Don Murphy oe easily studied. Simply by changing the length of the LIRON pendulum, the machine may be “tuned” to far-away VERY few minutes, an earthquake i quakes much as a piano is set to a tuning fork. vibrates through old Earth’s rocky manaka . To build a simple, yet effective, seismograph, first cut — crust. On an average, more than 9,000 of i a triangular piece of scrap plate % or 44-inch thick and these shocks occur every year—some of | 18 to 20 inches on the side, as shown in Fig. 1. Your them sending buildings crashing to the 34" local blacksmith will help you out on this for a small ground and leaving ruined cities in their ae charge. Drill a 4~inch hole through the plate near each S Eoo ga es ol eae “Fishing” for these tremors with a home- | Ve Near the top of the angle iron, drill a %4-inch hole mede npea. eae oe Bis a fae | through each face and fasten a % by 1%2-inch bolt. at little or no cost, is a sport wii al | its own. Using an instrument similar to | Sars y that described below, j z Martin G. Murray, its | ; designer, bagged com- SENTER KIA plete records of the r A “VaR, disastrous March, 1933, “i FIG.3 LEAD earthquake that devas- | WEIGHTS | southern California. So ` l KOEN ; PHONOGRAPH NEEDLE good were his ’grams 2" PIPE FLANGE 8" 3/8" DIAM. WOODEN DOWEL . : BOLT OR WELD TO that seismologists of na- BASE PLATE COPPER TUBING FIG. 2- SUSPENSION z FOR tionally known observa- E | | aE, ARMS—2 REQUIRED tories were glad to á p ANCHORAGE HOLE exchange records with In the picture above, Martin G. Murray is seen examing a seismogram made on his earthquake recorder. A close-up of seismo- graph appears at left. Note that it in- CUT FROM corporates such special refinements as a BOILER IRON rubber tired drum carriage and vanes submerged in oil to dampen vibrations. Details at left show the pier suggested by the designer as well as a simpler pipe column which may be substi- tuted. Fig. 3 shows the method used in casting lead pendulum weights. Smali tin cans serve as molds for molten metal. FiG. DETAILS OF THE DRILL FOR 73 1/2" BOLT PIER & BASE PLATE SALMON TIN OR SMALL CAN

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The seismograph is prepared by smoking a sheet of wrap- ping paper, attached to the drum, with a kerosene lamp. Finished seismograph is pro- tected by dipping it in a so- lution of shellac and alcohol. The operation of the sliding spindle on which the record- ing drum revolves is clearly shown in the plans above. “SLIDING DRIVE SHAFT —>= 3/8" BRASS ROD 12-16 THREADS PER INCH DRIVING FIT se = BRASS NUT A INTOTUBE = OR WASHER an WIRE WASHER SOLDERED & FIG.4 DETAIL OF DRIVING ROD AND : x5 4 DRUM SPINDLE ( > Detait below shows how a large s a E aa nut may be converted into a R RASS WE “DIAM, universal joint for connecting oY HOLE SQUARED TO SLIDING FIT the drive rod to clock mechanism. (N A i ; ig l SHAFT ABOUT Approximately 7 inches above the base, make ` A va T ABOUr 1/8" SQ. DRIVE three or four center punch marks, one above 38) BRASS a i ee pe another, on each face of the angle iron. SS This frame comprises the pier or support X for the magnifying arms. It is now ready E HOUR SHAFT OF CLOCK INTO END OF TUBE

DETAIL AT "A" UNIVERSAL JOINT

to be bolted to some firm, stationary founda- tion such as the garage floor. Care should be taken in placing the base (see Fig. 6), so that the faces of the angle iron will be ina true east-west, north-south position, so that you may determine the direction of a disturbance registered by the instrument. By using double nuts on the foundation, you are able to level the base and so keep the recording arms, to be mounted later, parallel to each other. These magnifying arms should be made of some light metal beam, thirty inches long. Strips from an old Venetian blind or other light wood may be used instead, provided cross members and wire braces are attached to stiffen them. Fashion two wooden shafts, as indicated 74

CORRECT SETTING FOR PIER REGULATE PERIOD OF OSCILLATION WITH BOLTS < Dp y in Fig. 2, about 34-inch in diameter and from 4 to 8 inches in length. Into one end of each, insert an old phonograph needle, pointed end out. The other end of each shaft is later fitted with the lead weights. Referring to Fig. 3, make two lead weights, exactly alike in heaviness, by pouring lead into two small tin cans. The weight of each should be between 5 and 10: pounds. Before pouring the lead, fasten in place two lengths of cop- per tubing such as used for automobile oil lines. One tube should run down the center of the tin can; the other should be run diagonally through the can, forming an angle of 45 degrees with the center tube. After the lead has cooled, PROJECTS 4" FROM WEIGHT WEDGE ARM i me iNTO TUBE OR DIRECT INTO WEIGHT

Fig. 5, below, shows as- sembly of the recording needles. Magnets for rais- ing needles hourly are op- tional and may be installed to end of magnifying arms by wiring them as shown. A DETAIL AT WEIGHT

SUSPENSION WIRES == -——

REST POINTIN CENTER PUNCH INDENTATION

CROSS-PIECE OF WOOD

CARDBOARD DRUM 20" X

NUT ABOVE AND BELOW TO ADJUST BASE LEVEL RECORDING OR I/2"BOLTS MAGNIFYING ARM. IMBEDDED 30" LONG IN CONCRETE

CLOCK DRIVE BLOCK UP TO SHAFT LEVEL

SEE FIG.4 FOR SHAFT DETAIL LIGHT METAL SHAFT SUPPORT The completed seismograph is depicted above in per- spective. A careful study of the details will insure the builder of an instrument of precision accuracy. remove the tubing and insert in the resulting holes the 38-inch rods, leaving the needled RECORDING end protruding about 4 inches. Into the SHEET diagonal hole is fitted one end of the PLANK BASE [Continued on page 130] FIG. 6 PRINCIPAL ASSEMBLY 75

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The ends of the glass tubes used in making electrodes are flared over a bunsen burner flame (below). ERE is a complete electroplating outfit —batteries, chemical solutions, applica- tors and polish—which is contained in a case no larger than your hand, and small enough to easily fit in your pocket. An even smaller outfit, for the vest pocket, can be made by using tiny “penlite” size batteries, and by substituting glass vials for the 1-ounce plat- ing solution bottles chosen for this model. Despite. its miniature size, this is a thor- oughly practical outfit and with it you can electroplate:a thin or a heavy deposit of gold or silver on any small article. It is particu- larly suited to the plating or refinishing of A home-built out permanent, low-cost jobs. Plating articles of jewelry with the compact electroplating outfit, shown above, is an easy and simple process, but the objects must be clean and free of grease, otherwise the job will appear streaked. small pieces of jewelry, on which it does first- class work in a remarkably short time. As for larger work, it will handle the replating of silverware, and you can gold plate the handles of knives and forks and similar ar- ticles if you wish. Automobile head-lamp reflectors can be resilvered when the finish becomes dull, and other automotive parts can be gilded, if you wish, at a cost of only a few cents, The work done by the outfit is as durable and permanent as that done by professional, large-scale plating methods, First construct the case, using pressed wood and following the dimensions shown in the accompanying drawings. Although for purposes of illustration the case is made of CARBON FROM FLASHLIGHT. ‘unit that turns PARALLEL CIRCUIT 1% V GOLD SOLUTION (POISON) SERIE 5- PARALLEL ELECTRODE FOR GOLD AND SILVER SOLUTIONS A polishing cloth, for burnishing the plated - BATTERY WITH CONNECTOR =a silver or gold, is made by rubbing a strip SOLDERED TO TOP of flannel with jewelers’. rouge (below). BOTTLE CAP SILVER METAL ACT JAS ANODE: ——— = PIECES OF GOLD OR | “CLASS TUBE GLASS ROD. WITH || Corton PEGE OF FLANNEL Right — Complete We CEMENTED TO END! construction de- tails of the carry- ing case, the bottle- “cap electrodes and APPLICATOR’ fhe applicators. corron-euieo FOR MERCURY WAD OF FLANNEL: SOLUTION ~ CIRCUIT 3V. pressed wood in the natural finish, you can also build it in ebony black, which presents a very fine appearance. Small brads, cut %- inch long, are used for riveting the hardware hinges and lock in place. Four brass up- holstery tacks maybe attached to the bottom to serve as rests, if desired. You will notice that the battery space, or USE BRADS FOR RIVETS TN ASSEMBLE WITH CELLULOSE CEMENT ‘The compact’ carrying case (above) holds everything you need for electroplating with gold or silver. On opening the lid of the ‘case (left), the plating solutions and current source are readily available. Left, above—Wiring diagram ‘showing how change ‘of circuit can be made to in- crease voltage delivered by the batteries. ~ lower compartment, is just large enough for small flash- light cells. The method of making contact is shown in a photograph on page 80; two strips of thin spring brass, each 14% by 4 inches, are given a slightly convex bend so as to make good contact with the positive and negative poles of the batteries. Small tabs left on the ends are rolled around a piece of wire to receive the tinned leads which con- nect with the electrode and the spring clip with which the work is held. This circuit will deliver about 11 volts to the electrode, which is usually sufficient. According to the amount of resistance in the electrode, as will be mentioned later, it may be desirable to use a series-parallel circuit, delivering about 3 volts, in order to speed up the deposition of plating metal. The method of wiring the batteries for a series- parallel circuit is shown in one of the ac- companying drawings: In order to make the combined electrodes and plating solution container units, get three 1-ounce wide-mouth glass bottles from your 79

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FARM _ KITCHENS LINOLEUM LINOLEUM ——s, y HARDWOOD pien x MOLDING 7 u T P INSTALLED AFTER SINK wa Á WALE 18 PLACED CLEATS SIDE E t CABINET FLOOR

PETER [DRAWER '

PLAN OF CABINET BASE - \| 1 DETAILED SECTION THRU SIDE & SINK.

It is not necessary to change the location of the plumbing, water heater, windows or any other features, because the new cup- board and sink are designed to fit the space occupied by the old ones, Linoleum in a solid color will give a striking effect. Lighting arrangements can vary with individual requirements. SIDE VIEW

FRONT VIEW HE possibilities in improving the appearance and convenience of old, out~ moded kitchens are so great that one will not begrudge the time and cost of materials in making the change. A typical example is illustrated in these photographs. This case is interesting because originally it was a lean-to built on to the house in the manner of an enclosed porch. It is not necessary to change the location of the plumbing, water heater, windows or any other feature because the new cupboard

and sink were designed to fit into the space occupied by the old ones. Dimensions given in the drawing are general and can be adapted to the indi- vidual case. Construction throughout is of pine and since it is to be painted, the most expensive grade is not required. Construction of the cabinet follows stan- dard practice, with the usual drawers, rails, cleats, door stops, sink compartment, etc. In this job the sink bottom rests on boards instead of being suspended by the rim, permitting installation after the cabinet top is put on permanently. Cabinet doors are simply four mitred and rabbeted frame-members as- sembled upon a plywood panel, and secured with casein glue and cor- rugated fasteners. Drawers and bread-board are provided, the former fitted with drawer pulls, the latter having a strip across the front. The top is covered with tile-pat- tern linoleum bound with aluminum or, if you care to go to the extra ex- pense, chromium-plated angle-strip.

METAL BINDING STRIP LINOLEUM SSS GRES Above—A typical example of outmoded kitchen cabinet and sink in many farm homes. Below is shown the same kitchen after a little work and small amount of material have changed the old style into a kitchen as modern as those in many new homes. While actual placement of original features has not changed, the kitchen as a whole has taken on an entirely new appearance and gives added convenience to the housewife.

CORRUGATED FASTENERS

CABINET FLOO! cave COOR 1-4” PLYWOOD PANEL

BASE

Details of the cabinet construction. Cabinet doors are mitered and secured with casein glue and corrugated fasteners. Although adding to the cost, chromium angle strips will improve the ap- pearance of completed project. Careful drawer con- struction will prevent sticking and frayed nerves.

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aired, Fert eacy: CHAINS SECTION OF INNER TUBE TIE MOUTH OF BAG TIGHTLY When tire chains are carried in the car, they often cause con- siderable noise when the car is driven over uneven road sur- faces. This noise can be eliminated by carrying the chains in a bag made from an old inner tube.—H. V. Tracy. me CUP GREASE INSPECTION PLATE OPENING 2 STRIPS OF QUARTER- ROUND NAILED ONTO EDGE OF e DWITH LASTIC WOOD AROUND DGE AND MAKING SAME OIL TIGHT mp An old stove board makes an ideal drip board for use under a car in a garage. When a quantity of oil has dripped on it, it is a simple matter to wipe it off with a dry rag. If desired, old newspapers can be spread on the board and when they have soaked up all the oil possible, they can be disposed of by burning. Strips of quarter round should be fastened to the edges of the board.—Bob Poulson. BROKEN NUTS, “CHIPS, ETC. Occasionally broken bolts or small pieces of metal fall into the flywheel housing and are difficult to get cut. They can be re- moved by opening the inspection plate and placing a large lump of cup grease on the flywheel gear. By turning the flywheel slowly the pieces of metal will stick to the grease as it passes around the housing. HINK WELL MAKE, HE NEXT WATERING TROUGH, CASS? IN 1900 AN INVENTIVE PLOW-MAK: BUILT A STEAMER WITH A ROTARY = ENGINE ~ BUT THE STEAM WOULDN'T STAY IN THE BOILER UNTIL CALLED FOR. ~ EVERY TIME IT AMBLED DOWN MAIN STREET THE NATIVES WERE TREATED TO ATHREE DAY RAIN AND FOU PIECE oF f HOSE ABOUT 5" OR 6" RUBBER LONG STOPPER HOSE TO FIT TIGHTLY | OVER THREADED END OF PLUG Z PLUG IS PRESSED TIGHTLY IN ONE END OF HOSE 5 CENT PACKAGE OF SEWING NEEDLES PLACED IN HOSE WITH POINTS TOWARD PLUG HOLD VERTICALLY AND SHAKE A short piece of hose, a cork and a few needles make a handy s and efficient spark plug cleaner. The hose should have a diameter slightly smaller than the spark plug so that it will fit tightly. After the spark plug is in place, put in the needles and cork up to the other end. 2X4 ABOUT 12 INCHES LONG A 2 by 4 fastened to the rear wheels of a car as shown in the drawing will greatly speed the process of freeing a car when it is in a sand or mud hole. When starting be sure to do it slowly so that the wood will not strike the fender—A. H. AUTO KINKS "Crankshaft Chronicles” «(Tis 1S THe THIRTY \{ FOURTH TIME AROUND AND 1 DON'T BELIEVE, IVE GAINED AN INCH = Sl S zi Thiet years aco cart Shuey OF SOUTH BEND WAS ATTACKED IN HIS OWN GARAGE BYA LITTLE ANIMATED TEAKETTLE CALLED A "MOBILE STAN- HOPE” IT HAD BEEN LEFT STANDING WITH A FULL HEAD GF STEAM WHEN AN INQUISITIVE STRANGER OPENED THE THROTTLE, SPACE FOR PENCIL MARKS The drawing shows a home-made measuring stick for measuring the toe-in of an automobile. Two wooden curtain rollers are spliced together. One end is cut square. A piece of wood is shaped as shown in the drawing, for the other end, from which the spring is removed. The small piece should be free to move in or out of the Jong strip, and can be marked when toe-in is checked.—A. C. Hill.

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in use at id, A pinocuias o ES A e sS camera Calif. Under P pouble microscope print ne os For bullet compa in ceni ice oscOPe, Leon Ma ootd ji Mo Be a 237. 7 senei p~ corn fane t note ocent ri owing an F is ¢ handwriting hen an attemP) o) ritin t Samet Some banda elare mea e same Jow is the inn is ses f the d Fe gbt UPPOSING you had done a successful job of kidnaping—successful, that is, up to the point where you were about to sit down and write the note demanding ransom. How would you go about this ticklish part of the procedure? Would you write it out long- hand, print it by hand, or use a typewriter? If you were very, very stupid, as so many criminals are, you might not even give a thought to this part of the business, or might 86 The microscope shows glaring differences while naked eye sees duplicates. loa eor D Qoue Ieee DP are AIE ot} conclude that the police could not possibly be smart enough to trace your handwriting; in either case you would be likely to write or print as best your limited education per- mitted. If you were a trifle less stupid but still far from wise, you might decide that handwriting is a give-away but that anonymity resides in the typewriter, and hence you would use such a machine should you have access to one. The really intelli- gent malefactor knows that, as a matter of fact, it actually doesn’t make any difference— the scientific detective can easily trace any of the three forms of communication. Documents comprise one of the major di- visions in modern crime detection—a subject introduced in the preceding installment (in the March, 1938 issue) by detailing the fingerprint system of personal identification. There are still other chapters in criminology that are fascinating, but scarcely any more interesting than that having to do with trac- ing and identifying all forms of written or printed material, and entering nearly every type of crime from homicide and kidnaping through embezzlement and forgery to black- mail and poison-pen letters. We all get a big kick out of newspaper accounts telling how Modern Mechanix Ou r D wai a C428 d MILLY ray from the jOO0 in fives and what Lica EVIDENCE tOo d0, The been filed G-men traced a ransom note or ran down a notorious band of counterfeiters. Just how are these marvels of scientific sleuthing ac- complished, and can we perform some experiments with our own microscopes that will simulate real cases and teach the methods? Many channels of communication are open today, but handwriting is still one of the chief resorts of the criminal and its study forms a necessary part of training in criminology. It would be out of place here to describe indi- vidual traits of penmanship, but aside from constant differences in the shaping of separate letters, there are charatteristic methods of spacing, punctuation, sentence formation, ehoice of words and the like that are as diag- nostic as the Bertillon system of physical measurements. Most of these points are discernible with the unaided eye, but low-power magnifica- tion—as with a reading glass, fingerprint reader, hand lens or binocular microscope— brings out the differences much more force- fully. Such aids to vision are constantly in use in examining documents and those who wish to study applications of the microscope April, 1938 ‘teats TOLe 18 2l are being watchs COD: u hear from us i for the Pol Smith t ype f the A S€rifes. be As rs =x ar fr. id + POm Wea owen ~ us U Above lef, 7 AB = ; Notice È the same st of a & acteristics Y SOm fal bu S Pewritt a : Rich sh e letters h, Bteater enjoa Note, clearly (distinguish m nent. ma; Char. Cation, ieg Ce he P 3 teq, 7 a a al on o'er Another E0 a ofa 2 oliterea typen aple o O. © simila; ities Piten on th, the e le y Ote wein in is Itten e letter tena machin ma ample A ote sam mples, Below—An enlargement of the work of a machine having clear individual characteristics. Note top of letter “a.” The line is unusually heavy. Also, the dot on the “i” runs into body of letter. Bottom—-Same sample, greatér enlargement. on a machine of oproximately the 1d in the suspec s time for all g the aid of their 1 on a Bachi ipproximatel ind in the gs e time for the aid of?

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i REGULAR SANDING SLIDING d ENDBLOCK : SUPPORT ADJUST AND SET - CLAMP COLLAR TO i a OBTAIN THE FREE WORKING HEIGHT a 5 INDICATED HERE | { SEE DETAIL FiG.1 SIDE ELEVATION (BRACKET CLOSED) ERE is a home-made, motor-driven tool ` which will appeal to every cabinet maker and home-workshop enthusiast. It solves the problem of machine-sanding large sur- faces. It is powered with a 1⁄4 h. p. or 4h. p. motor and will turn out excellent sanding jobs on big table-tops, dresser-tops, large panels, wide boards, etc. It eliminates the laborious task of hand sanding, which is prob- ably the most unpleasant part of woodwork- ing. f 92 ARM by Dick Cole The construction and operation of the sander are visualized in Figs. 1, 2 and 3. It will be seen that the sanding disk is mounted directly to the end of the motor shaft. The motor itself is mounted verti- cally at the end of a parallelogram type extension bracket, which, in turn, is free to swing on the tubular supporting column. Thus the sanding disk is always parallel to the surface to be sanded and ean be moved over a wide area. An objection to a disk-type sander— that it leaves circular scratches on the job—is overcome by using a bevel-face disk to finish off the work. The disk is moved with the grain of the wood and produces a first-class job. The swinging arm sander is intended to be mounted directly to a drill-press column. When not in use, it can be swung to the side, and will not impede any of the usual drill-press operations. If one does not have a suitable drill- press, then a column must be made as shown in the drawings. This consists of a 48” length of 234” iron pipe, dressed down to 24%” outside diameter, and tightly screwed into a 244” floor flange. This is mounted on a 16” wooden disk, which, in turn, is secured to the floor with lag-screws. The base is actually built up of two 34x16” disks glued together with grain opposed. Hardwood is recom- mended for the base, but ordinary pine will serve. We now come to the construction of the ex- tension bracket itself. If the prospective builder will check each individual part against the plans and the photographs, he will glean a complete understanding of the construction of the assembly. Now let us start building the bracket from the column end outward. First we have the sliding end-block. It will be seen that this is built up of select maple into a composite unit (Fig. 3). It is well to Modern Mechanix Easily constructed tool solves problem of sanding large areas with little effort. SANDER bore the holes on a lathe for accuracy. If desired, these holes can be bushed with a brass ring, but the bushings will serve very little purpose. The maple alone is amply strong and, when polished and greased, makes an excellent bearing surface. In any parallelogram type extension bracket one end of the arms at ENTIRE ARM FREE TO eee each end of the bracket ee SUPPORT COLUNN ABOUT ROLLERS Ke CHANNEL M must be free to have ver- i. a \ R tical movement. On this 4 bracket the end arms are au | attached to a cross-shaft | with rollers which travel ‘|| in a channel made of J 3” x134”x134” angle iron. e% The formation of these channels is clearly shown il in the detail of the sliding li. | ee | zA Right—Drawing of the sander | WEIGHT OF MOTOR BALANCED se Serma assembled. Note that Da | SOFT COMPRESSION SPRING. TILT THU! when the bevel-faced disc is used, | Yé VERTICAL MOVEMENT aa j CORR RKING ei > ty Af a ECT the mounting is tilted to correct | TAINED BY PARALLELOGRAM R SAOS = Vie iat j] `N A a angle for flat contact with work. RRANGEMENT OF SHACKLES Below — The completed sander mounted on a drill press column. BOLT BASE TO FLOOR FIG. 2 - SIDE ELEVATION BRACKET EXTENDED DETAIL OF BEVEL-FACE DISC HOOK- UP end-block. The elevation of the bracket on the column is set with the simple clamp collar shown in Fig. 3. The middle arms of the bracket are of select maple. Fig. 3 shows the special arm used at the column end i i of the bracket. It will be seen that a 3;” rod, with a ee ` 5 roller on each end, passes through the arm. The rod April, 1938 mE

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NOTE DIRECTION GLUE AND a" SCREWIN PLACE TO END BLOCK MAKE 2 SLIDE BLOCKS THUS OF HARD MAPLE LUGS WELDED ON SPLIT AFTER WELDING i 400. Pe gt a SHELBY TUBE MAKE | CLAMP COLLAR THUS DEEP FOR SLIDE BLOCKS INNER END-BLOCK SLIDE BLOCK: INNER END- BLOCK CLAMP ~ COLLAR SPECIAL END ARM OUTER ARMS 3716" X 3/4" CRS, OR DURALUMINUM BAR DRILL 1/4" DIAM. 8 PIECES NEEDED. SUPPORT COLUMN 22" RON RIPE (TURN DOWN To 2%4"0.D). (4 DIAM. oe X s 12 BOLTS THU. pe z 22 FLOOR FLANGE REQ'D. FOR ARMS CLIPS AND SHACKLES 3/16" X 3/4" STOCK BASE- 16" 1am. BY =A 3/4 WOODEN DISCS GLUED TOGETHER ~ GRAINS OPPOSED. FiG.3 THE COMPLETE ASSEMBLY is a press fit in the wood, and the rollers turn on the rod. This is mentioned because at all other points in the bracket construction, the cross-rods turn freely in the wood. Similar rollers are used at the outer end of bracket, so four rollers are required, all of them 7%” diameter and not more than ;” wide. The other three middle arms differ but slightly. The pattern can readily be cut out onascroll saw. Care must be taken in boring the holes. If these are inaccurately spaced, or not exactly parallel, it will cause binding in the operation of the bracket. A reasonably accurate jig can be made of hard maple, which will serve in boring the metal arms as well as the maple arms. 94 J CUTFROM 3/32" CHANNEL IRON * USE SELECT MAPLE THROUGHOUT * 7/8" DIAM. ROLLERS: SPECIAL ENO ARM THUS |) MIDDLE ARMS SIMILAR AT BOTH ENDS 3" 4 ALL HOLES 5/16" DIAM. S k— ar i DETAIL OF INNER ARMS (1 f END ARM, 3 MIDDLE ARMS) 7/6" CAP SCREW F 178" DIAM. ROD RECESS FOR SPRING ( —9 A ad ANEA H 3 1/8" STEEL 1 h Gare OUTER END-BLOCK SEE DETAILS OF THE OUTER END BRACKET BLOCK ~ BRACKET AND Dorns Y AEI FOR HINGES ig 3" ELECTRIC MOTOR BASE:exacr MOTOR DESIGN TO SUIT MOTOR SION BERD GRINDING ARBOR ROLLER CHANNEL SANDER. FLEXIBILITY TO HEAD SANDER HEAD x AND DISCS, NN 1 K pa fA 2 A A WS Above is shown the construc- tion details of the arm support- ing the motor and disc sander. By careful study of each part before work is started, the final assembly job will be simplified. DETAIL OF OUTER END BRACKET BLOCK Hight outer arms are required. If 7x34” dural bar is readily available, its use is recommended. Otherwise use cold rolled steel. It is well to refer at this point to the outer end roller shaft. Fig. 3 presents the plan cross-section of the bracket block, outer end. Again Modern Mechanix $5x134”x134” angle iron serves as a chan- nel for the rollers. The outer block is really a composite of three blocks held together with shackles and hinges, so that the motor has a limited vertical and tilting movement. By checking each individual part against the complete assembly, the construction will be obvious. Novelty and practicability are incorporated into the sanding disk assembly shown in Fig. 3. The attachment to the motor shaft is made with a standard arbor. The spring brass “spider” is held between the flanges of the arbor and the ends of the “legs” are bolted to AREA COVERED BY EXTENSION MOVEMENT ALONE DRILL FOR ayign a p STOVE BOLTS le #8 SC! SAL an To PROUERS SUGHTLY TOENTER IA] BAND COUNTERSin, HOLE; i orua FOR Laying ee "LEGS" EQuatiy on SPACED 2-1/4" DIA. į RETAIL OF SPIDER f Hi SPRING Bras i 4 TO ARBOR EUASGEACH | : SANDER Woop (BOLT To Sree Í ver sa X 1 STANDARD S4, FASTEN THUS To 4 5/8" #6 screws NDER Disc REGU, LAR o fn ISC UNIT Fici 5 ES SANDER pisc [10° Cy = DETAILS HARDWoop j #OGARN E ET PAPER BEVEL-Face Discs MADE THUS the sander head. The sanding disks proper are made of 12” plyboard with a 1” metal band around the circumference. Twenty - two gauge brass or monel metal is recommended for the bands, but galvanized iron can be used. The sanding disks attach to the head disk with bayonet type fasteners. Obviously, April, 1938 PLAN VIEW-PARTIALLY EXTENDED f Above is shown the sander in operation. At left is a plan view of the arm partially ex- tended. Below are construc- tion details of the sander disc. BRACKET CAN BE SWUNG THROUGH AN UNLIMITED ARC the bevel-face disk is merely a modifi- cation of the regular disks. It is well to make about three regular disks and fit them with a variety of sand-paper. Any motor capable of withstanding nominal end thrust can be used with this tool. A 34 h. p., 3400 r. p. m. motor is especially recommended for this tool, but a 1⁄4 h. p. or 42 h. p., 1750 r. p. m. motor will serve satisfactorily. The small cost involved in building this useful tool should commend it to every home workshop fan. It will save hours of time and plenty of “elbow grease” when large surfaces must be smoothed. Those who have had to sand down a table top, particularly a large one, know that considerable effort was necessary before the desired result was obtained. With this tool, all the work is done by the motor, the operator merely moving it over the area to be smoothed. If a coat of enamel is applied to the tool, the finished job will not only be useful, but will present an attractive appearance. As shown in the photograph, the sander can be attached to a drill press column without disturbing the drill. This is particularly helpful when extra space is not available in the workshop. When the sander is not in use, it will take up very little room. 95

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PARTS REQUIRED R1 50,000 ohms (IRC BY-2) R2 4 megohms (IRC BT-2) R3 1,000 ohms (IRC BT-2) R4 2 megohms (IRC B-2) RS 500,000 ohms (IRC BT-2) RG 500,000 ohms ton control (IRC 11-133} R7 500,000 ohms volume control (IRC 11-133) RB 1.000 ohms (IRC BT-2) RS 100,000 ohms (IRC BT-2) R10 150 ohms (IRC BT-2) R11 60 ohms center tap (IRC M-832) R12 40,000 ohms (IRC EPA) R13 100,000 ohms (IRC HOA) €i .5 mf. (receiving type) C2 25 mf. 50-volt working (Aerovox) C3 .1 mf. receiving type CA .02 mf. (Aerovox receiving type) €S .005 mf. (Solar receiving type) C6 .1 mf. receiving type C7 25 mf. SO-volt working (Aerovox) C8 25 mf. 50-volt working (Aerovox) C9 2 mf. 1,000-volt working Cornell-Dubilier TJ-£0020) C10 2 mf. 1,000-volt working (Cornell-Dubilier TJ-10020) C11 2 mf. 2,000-volt working €12 2 mf. 2,000-volt working Ti Driver input transformer (Kenyon T-52) T2 Driver transformer (Kenyon T-263) T3 Class “B” output transformer (Kenyon T-465) T4 425-0-425-volt, 6.3 volt, 6.3 volt, S-volt secondaries (Kenyon T-244) TS 1460-0-1460-volt (Kenyon T-666) . . T6 2.5-volt, 10 ampere, (Kenyon T-360) Above is shown a front view of the T7, 1ovolt, B-ampere (Kenyon T-3601) speech amplifier. Below is the rear Ch1 Filter choke (Kenyon T-154) iew. i are not shown. ch2 18 henry swinging choke (Kenyon view. Tube shie T-513) Ch3 10 henry filter choke (Kenyon T-176) Crystal microphone (Shure Brothers 70-5) Four 6-prong sockets (Hammarlund S-6) Two 4-prong sockets (Hammarlund 5-4) Two sockets for 203-Z's (ICA No. 956) Swi, Sw2, Sw3, Swd, s. p. s. t. (ICA No. 1230) Terminat strips, three 4-terminal (ICA No. 2413) two 2-terminal (ICA No. 2420) 240 Fuse mounting (ICA No.’ 2342) Metal cabinet (ICA No. 3826) Tubes: two Taylor 203% two Taylor 866 two 6B5 (Raytheon) twa 6C6 (Raytheon) ammeter 0-300 (Triplett) caps (ICA No. 870) Name plates (ICA) Dials (ICA No. 2169) Pointer knobs and dial piates (ICA No. 2240. 2241) LMOST every amateur at some time finds A ide yie y SRA himself with a desire to go on phone. CRYSTAL i mitter. The two Those who constructed the transmitter de- MRE ONE epee e scribed in the February and March issues Bee i river a gd will find this modulator and speech amplifier u i 3 7 the third shelf. The ideally suited to the rig. t ives 5 : £ Baid the radio fre- The tube line up shown will permit the : ‘ i - eBay a modulator to “loaf along” and still give 100 : : SWITCH I Ai i ing unit is at the er cent, or the more correct 95 per cent, DRIVER AND P i p MODULATOR E e ols modulation. With no need for working the > Bous transmitter, All equipment up to its limit, the quality will be dials are insulated E oa from the condenser excellent, with a minimum of troubles to shafts by flexible couplings and short insulator rods. clear up. Two power supplies were used; one for the speech amplifier and driver, and one for the modulator. The small supply should deliver 400 volts to the drivers, with approximately 275 volts for the speech amplifier. This can be obtained either by tapping off the bleeder, * ‘ INPUT FROM SPEECH or by a dropping resistor. AMPLIFIER The modulator was laid out to give plenty of room between parts. The filament trans- _ 98 Modern Mechanix April, 1938 99

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used for connecting it to the driver tubes. Beside the electrical advantage of having the speech amplifier separated from the rest of the transmitter, the operator will find it con- venient to have it on the operating table, for background noises and unnecessary pickup. The construction details of both the speech amplifier and modulator are simple and little can be said to help the individual builder. The pilot light on the speech amplifier panel easy adjustment of the gain control and the is connected in the filament circuit of the 6C6 tone control. tubes. If this circuit is connected into the When the gain is turned up high, the tone line feeding the rest of the transmitter, it control will be very useful for cutting out will serve as continual notification that the rig is “alive.” When the audio equip- ment is completed’ and ready for tests, do not apply power and speak into the microphone unless the modulation transformer has a load applied to it. This can be in the form of a bleeder connected across the terminals and a loudspeaker connected across a very small portion of the resistance. The builder then can test for [Continued on page 118] Sw2 POWER SUPPLY FOR DRIVERS AND SPEECH AMPLIFIER At right is the power supply for the speech amplifier and drivers. T4 supplies filament power for 6C6’s and 6B5’s. SW 3 former for the 203Z’s as shown in the K y a photographs, is mounted at the rear of the {ator showing the 2032's eoe 7 baseboard. Inasmuch as almost eight am- modulation and driver transformers. A a When testing, be sure that a foad peres is consumed by the filaments of these is connected to the output of this or i $ stage before speaking into the mi- a aa a for e. should crophone. At ithe right. is another e talr. eav t 7 A view showing the "s just behin Iwa y wa east o. 14. Leads also the driver transformer. T7 sup- should be as short as possible to prevent plies power for the 203Z filaments. voltage drop. The speech amplifier was constructed as a separate unit to prevent pickup and re- sultant feedback. Shielded cable should be An under view of the speech amplifier. A- ‚metal panel and cab: inet aré used to insure” adequate shielding, The lead from the — amplifier to the driver stage should be of the shielded type. By con- necting pair of phones to output connections, — ‘this section can be “tested for quality be- = fore connecting it to the driver stage. 1200 VOLTS + At left is the power supply for the 203Z modulator tubes. Ch2, the swinging choke, is next to the plate transformer. The bleeder should be adjustable so that plate voltage can be reduced when desired. 100 Modern Mechanix April, 1938 101

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A typical “auto-focus” enlarger taking negatives up to 4x6 inches. It is readily clamped to the edge of a shelf or table in the dark room, This is a good in- strument for the beginner because the automatic focusing action makes it practically foolproof. ONTRARY to general impression, it is no more difficult to make enlargements than contact prints. Enlarging offers many ad- vantages besides big pictures; you can mask off unimportant parts of the negative and thus give emphasis to the better sections, and also perform all sorts of dodging operations. Many books have been written on the subject, but the fundamentals can be explained in a short article. An “enlarger” is nothing more than a camera turned upside down, with light from a strong bulb made to shine through the “negative, through a lens, and then onto a sheet of photographic paper of the desired 104 To Make size. Figure 1 represents the in- ternal construction of 95% of the enlargers in use today. Some en- largers made for small negatives (the 35 millimeter size used in “candid” cameras) have one or more condensing lens placed be- tween the bulb and the negative, to concentrate the light. The only real mechanical differences that will be found between various enlargers is that some are “auto focus” and others aren’t. In the former type, a cam device moves the lens closer to the negative as the whole enlarger head is raised to make bigger prints; in the lat- ter, this adjustment must be made by hand as the operator judges the sharpness of the image pro- jected on the enlarger easel. The self-focusing type of course is more convenient, but then it costs more, Most present day enlargers are of vertical construction, the lamp housing, with its attached nega- tive holder and lens, being mounted on a heavy pipe or other standard. However, horizontal arrangements work just as well and some people prefer them. Their bad feature is the large amount of table space they oc- cupy. The accompanying pictures show representative enlargers of popular” styles. The dark room set-up for enlarging is very much like the one shown on page 108 of the December, 1937 issue of Mopern MECHANIX, modified as in Figure 2. As most amateurs rarely make prints larger than 8x10 inches, three trays of this size should be used. The first contains developer, the second the acetic acid shortstop bath (144 ounces of acetic acid and cold water to make a quart), and the third the regular hypo fixing bath. The tank in the back is filled with water for washing the print tongs. The safelight is fitted with an OA (bright yellow) filter as recommended in the December article. The most successful and widely used paper developer undoubtedly is “D-72,” which is Enlargements, available in prepared dry form, requiring only mixing with water. The “stock solu- tion” is diluted 1:4 for enlarging paper, so a single can will last quite a while. An 8x10 tray will require at least a quart of solution; so measure out 61⁄4 ounces of stock solution and add cold water (70 degrees is the ideal temperature) to make 32 ounces. It is not advisable or economical to save this stuff after use. If it looks brownish, throw it away and mix a fresh bottle-full. The chemicals are cheaper than wasted prints and wasted time. By the way, don’t fail to filter the solution before use. Cleanliness and absolute freedom from dust in the dark room are the real secrets of enlarging success. One writer says that almost surgical cleanliness is necessary, and he isn’t exaggerat- ing much. A tiny speck of dust or lint on the negative looks like a baseball on the print with even medium size blow-ups. Clean the negative holder glasses (if a glass sandwich is used) by breathing gently on them and wiping again very gently, with a soft cloth. If you rub too hard you will electrify the glass and make it attract infinitesimal dust Fix. 1: Cross-sec- tion view of anen- larger, showing — the arrangement ofthe partsand the manner in which an enlarged im- age is produced by the lens f LENS PATH OF “LIGHT RAYS Fig. 3, above: A simple siphon attachment converts an ordinary tray into a very effective print washer. The tray is placed on the edge of a washtub or sink, Fig. 2, left: Chemical set- up for ing enlarge- ments, Left tray, developer; © center tray, acetic “short- stop” bath; right tray, hypo. Tank in back is for rinsing print tongs after prints have been dropped in the hypo. Safelight is fitted with “OA” yellow filter. HINGED RED FILTER

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Right — The same scene when taken with 3-power binoculars and a K2 filter placed before camera lens. T IS the purpose of this article to dispel a little of the awe and trepidation with which the average amateur approaches the subject of camera lenses and auxiliary lenses, and to show how most of the effects’ obtained with extremely expensive equip- ment can be duplicated satisfactorily with ordinary everyday lenses of various types. There are very good reasons for the high cost of the regulation auxiliary lenses, but 90% of this goes for extreme speed, accuracy and ultra-correction which the average ama- teur does not need in order to achieve the effects he has in mind. Portrait work par- ticularly, and its second cousin, table-top photography, certainly do not require speed, extreme accuracy or correction, for the reason that portraits are preferably taken with diffusers, or are diffused slightly in the printing or enlarging process, while table- top work is usually of such a nature that aberrations go unnoticed. The commonest desire of the camera addict is to be able to work closer to the camera, for portrait, table-top or other purposes, and this requires the simplest type of auxiliary lens. Amazing as it may sound, practically any type of lens under the sun may be used for a portrait-lens, and mounted in practically any manner conceivable, at any distance from the camera, direction booklets to the contrary notwithstanding. This may sound like a very broad statement, but the photos submitted herewith prove it. In the first series (on the opposite page) 108 Above — The Empire State building tower taken with an ordinary camera on a hazy day. Right — The best photo of the three, taken by binding a 10-power navy tel- escope and a K2 filter over the cam- era lens with tape. is a shot of a package of cigarettes made with a small reflex camera, with the ordinary lens as close as it will normally work. In the successive shots, the object approaches closer and closer until we have nothing but a por- trait of Sir Walter, half-tone dots and all, at a distance of two inches from the camera. The most convenient type of lens to use for this purpose is an ordinary ten-cent store spectacle lens. These are marked with various numbers, from 8 to about 30, which refer to the focal length. From 20 to 30 is a good length for portraits, while lengths down to 8 inches or even less can be used for closer work. Lacking this type of lens, any ordinary hand magnifying-glass lens will do. These are practically all 8-inch lenses or there- abouts, and are possibly better for this use than spectacle lenses, even if not as con- venient, for the reason that only the center portion of the lens is being used, which cuts out most of the aberration, although, as stated above, it-is hardly noticeable. For working at shorter distances than the lenses on hand will permit, it is only neces- Modern Mechanix sary to “double up,” i. e., hang still another lens in front of the one you are using, or two or three for that matter. If conditions per- mit, the lens may be merely held up against the camera-lens by hand. If a more perma- nent rigging is desired, the lens may be stuck to the camera with Scotch tape, as shown in one of the photos, or a regular lens-ring may be made, of the proper dimensions for ready removal and attachment, by winding kraft- paper adhesive tape around the camera lens. Wrap the first layer with the gum side out, stick it to itself, and then wrap as many layers as needed on top of that, then bind the auxiliary lens to that ring with more tape. When this assembly dries, it will be as con- venient to use as a regular portrait attach- ment. The supplementary lens can be mounted in direct contact with the camera- lens, or any distance away from it. The field automatically moves away from the camera the same distance, but conditions are not altered otherwise, for all practical considera- tions. There is only one requirement and one caution in using hay-wire lens assemblies such as this — you must have a Binoculars placed on a book before the camera, Grandma’s spectacles held in place by hand; and an ordinary 20 to 30, focal length lens taped over the regular camera lens, as- shown in above photos, serve well as auxiliary lenses. April, 1938 Proof of the effectiveness of the simple auxiliary lenses: is shown by these photos, described in cutline below. Top eho A ciga- rette package snapped with an ordinary camera placed as near as it will work. Center— Photo taken with two 8-inch spectacle lenses bound together before camera lens. Left— The front half of cam- era lens was removed to make this photo: camera with ground-glass focusing facilities, either back or reflex such as the one pictured, as depth of focus at such short dis- tances is extremely shal- low; a quarter of an inch may throw your picture out of focus, the latitude varying with the lens stop used and the distance from the camera. If your camera is not a reflex, you can calibrate it by removing the back and attaching a piece of waxed paper, thin tissue or ground glass in the posi- tion ordinarily occupied by the film, while you focus and measure. Then, when your camera is loaded with film, you can do your focusing with a ruler. If anything other than a small flat surface is being photographed, particularly when working under two feet, it is best to stop down as far as your light and other factors will allow. Another common method of “working close,” suitable only for certain types of cameras, is to remove the front half of the [Continued on page 128] 109

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MIRROR REFLECTS LIGHT OF DARKROOM LAMP. With but one safelight in the darkroom, you can avoid carrying it about by using a small mirror mounted on a wood block, as shown above. This will reflect a spot of red light to any part of the darkroom. The angle at which to hold the mirror is determined entirely by experiment. VEST POCKET DARKROOM LAMP. A red safelight that you can carry . in your pocket is an advantage when you wish to change films while p” 3 away from your own darkroom. Use a pen-light of the type shown ae above (tight), dipping the concentrated-filament bulb in red lamp P coloring, obtainable at any neighborhood electrical supply store. -cent kitchen t in use, wi FOR Attach HANGER towel holder, a push-piny with a dozen holder Wil irculate free! each fim 39 Siu ary a A ateria HE air oaa otee INDICATOR FOR DARKROOM WATCH. Point one end of a small strip of tin, bending the point over so it touches stop- watch dial (circle). Turn watch until the tin point rests over : the number of seconds required for your enlarging job. films as they Wi UNBREAKABLE LENS SHADE. Secure a five-cent rubber ball and cut an opening in one side for the lens and a larger opening on the other CARDBOARD STRIP KEEPS DEVELOPER TEMPERATURE side. Blacken the inside completely with wallboard paint (below).. EVEN. A piece of cardboard, placed under a tray of developer solution, will help to keep the developer temperature even by eliminating contact with table or bench (below). 110 Modern Mechanix SHELF ATTACHMENT FOR TRIPOD. An oblong piece of one-quarter inch Prestwood, or similar material, attached to the top of a tripod (left), will provide a shelf at the back of the camera for holding ground glass, film pack, slides, and spare parts. Only one hole need be made in the small shelf, as shown. SHORT CUTS TAPE MEASURE AIDS IN FOCUS- ING. A spring-type tape measure (above, left) clipped to the front of a camera so that the case is on the same plane as the lens will enable you to take advantage of ry lenses for copying and pertrait work by providing method of measuring distance from the lens to the object being photographed. MAGNIFIER AIDS IN READING DISTANCE GAUGE. A small mag- nifier attached to front of camera with metai clips shows tne figures and pointer greatly enlarged. as shown in photograph at the left. CONVERTING A FLOOD LAMP INTO A SPOTLIGHT, Cut a baffle from a piece of 14-inch Prestwood, placing bolts at the edges for hook- ing it over flange of flood lamp re- flector, Cut a hole in center to accommodate a five-inch condensing lens and mount the latter, with convex side out, by means of Prest- wood rings glued in place (left). CLIP ATTACHES THERMOMETER TO TRAY. Waterproof a spring- type clothespin by dipping it in hot paraffine and use it to attach a ther- mometer in one corner of the de» veloper tray, providing a means of checking temperature accurately.

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