RADIO CONTROL of MODEL AIRCRAFT NEWNES This Is NOT an S 0 S It Is NOT an A.R.P

RADIO CONTROL OF MODEL AIRCRAFT NEWNES This is NOT an S 0 S It is NOT an A.R.P. Call It is an Appeal It is a genuine appeal to all men and women to do just that little bit extra; to make that extra effort which will make the difference between efficiency and stagnation.It is not enough to merely earn a living; we must make the best of whatever abilities we possess. We cannot wait for those abilities to develop themselves unaided; they must be trained. By becoming efficient in your vocation you can give the best service to your country and to yourself. The more you increase your earning power the better it is for the country, and for yourself personally. War or no war, earning power always brings its possessor to the front.It is no use waiting for better times. The ideal opportunity never arrives. We have to make the bestof existing conditions Therefore, delay is useless; it is worse, it is harmful. YOU CANNOT MAKE MONEY BY SAVING. If you save 10s. per week for 10 years you have only £260, but it you spend 2s. 6dper week for 12 or 18 months on a correspondence course, you give your brains a chance to earn thousands of pounds,then there is no need to save. Savings are likely to vanish, but earning capacity is a permanent investment. DO ANY OF THESE SUBJECTS INTEREST YOU? Accountancy Examinations Engineering. All branches, subjectsPumps and Pumping Machinery Advertising and Sales Management and examinations Radio Communication Agriculture General Education Radio Service Engineering Fire E. Examination. G.P.O. Eng. Dept. Road Making and Maintenance Applied Mechanics Heating and Ventilating Salesmanship. Army Certificates Industrial Chemistry Sanitation Auctioneers and Estate Agents Institute of Housing School Attendance Officer Aviation Engineering Insurance Secretarial Exams. Banking Journalism Sheet Metal Work Blueprints Mathematics Shipbuilding Boilers Matriculation Shorthand (Pitman's, liook-keeping. 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EVERY DEPARTMENT IS A STUDY AT HOME IN LET ME BE COMPLETE COLLEGE: EVERY YOUR FATHER STUDENT IS A CLASS TO HIMSELF YOUR SPARE TIME Let me tell you how to make a success co your career. JOURNALISM If your futureisun- Short -Story, Novel and Play decidedor appears Writing unsatisfactory,letus Therein money and pleasure in Journalism and in Story talk it over together. Writing. No apprenticeship, no pupilage. no examine time, no outfit necessary.Writing for newspapers, I want to help, and it novels or pictures is not a gift; it Is a science that will cost you nothing can be acquired by diligent application and proper CAN YOU CHANGE guidance. It is the most fascinating way of making MY EXPRESSION? to get my help; you pastime profitable.Trained ability only is required; will be under no we do the training by post. Let ue tell you all about it. IFSO, YOU MAY BE obligation whatever. DEPARTMEN rOF LITERATURE 16 THEARTISTTHAT COMMERCE IS It you attend to this now, it may make WAITING FOR I HAVE HELPED THOUSANDS a wonderful difference to vour future. 1 listtrytforyourself OF OTHERS Trace or draw the outline COUPON- and then put inthe features And when I say thousands, I do not exaggerate, CUT THIS OUT --...111111141k There are nunareds of openings in connection with asI can produce well over 10,000 unsolicited Humorous Papers, Advertisement Drawing -- To - Dept. - 76, THE BE N NETT Posters, Calendars, CataloguesTextileDesigns testimonialsfromgratefulstudentswho, COLLEGE LTD., SHEFFIELD Book Illustrations, etc. through our Postal Train- Please send me (free of charge) 60 per cent. of Commercial Art Work is done ti " Free Lance Artists " who do their work at ing, have achieved their Particulars of home and sell it to the highest bidders. Many Your private advice about Commercial Artists draw " retaining fees " from life's ambition (Cross out line which does not apply various sources others prefer to work full-time employment or partnership arrangement. We teach you not only how to draw what is wanted but how to make buyers wan' what you draw. Many 01 our students who originally took up Commercial Art as a hobby have since turned it Into a full-time paying profession with studio and stall of assistant artists; there is no limit to PLEASE WRITE IN BLOCK LETTERS the possibilities.Let its send full particulars for a FREE TRIAL and details of our course for your Name Inspection Youwiltbeuncle,no obligatiott Andress whatever

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ti November, 1939 NEWNES PRACTICAL MECHANICS 49 Deciding Factors... The DLP Vice -Screwing Machine should occupy a central position in YOUR workshop. Parallel Vice Pipe Vice Adaptability Tube,RodandStrip ENGINEERING Bender The DLP Machine Cable,Rod andPin WORKSHOP PRACTICE combinesthefunc- Cutter tions of all these tools, Screwing Machine without loss of indi- Punching Machine This up-to-date book provides a complete practical vidual efficiency. Cable Stripper Flat and Conical Anvils course of instruction in every important branch of The space required on your engineering workshop methods, materials and equip- Compactness benchisonly12'x 18". ment.It deals with the underlying principles, crafts- The purchase price is but a manship, machines, tools, measuring processes and fractionofthecostofthe machining methods of to -day, and it will prove indis- Economy separate tools listed above. pensable to the engineer, draughtsman, mechanic, apprentice and engineering student. Its scope extends £5 . 176 from simple hand tools and machines to the latest Illustrated elaborate machines and methods employed for mass - Folder

on Application. ' production purposes. SOME OF THE SUBJECTS Files, Chisels, Scrapers, Shears, Punches, Burnishers, Hand Screw -cutting Tools, Spanners, Vices, Various measuring . methods.Verniers, Micrometers, Gauges, Optical Devices, Fluted and Twist Drills.Grinding Angles, Drilling Data, Patent No. Small and Large Drilling Machines, Electric Drills, Practical 418,829 Lathework in allits branches, Machining of Metals and Synthetic Materials. Tungsten -carbide and Diamond Tools. Lapping, Honing, Cleaning, Polishing and Rust -protection ofvariousmetals.Grinding Operations and Machines, Milling Operations, Cutters and Machines. Planing, Shaping, Slotting and Broaching Operations.Special Machines for SOLE DISTRIBUTORS FOR THE BRITISH ISLES Production Purposes.Plate and Bar Machines. Gears and BUCK & HICKMAN LTD. Gear Cutting Methods.Templates,Jigs andFixtures. 2 WHITECHAPEL RD., LONDON, E.I. Overhauling and Adjusting Machines,Millwright Work. Overseas Enquiri:s toDeLaPr3 Components Ltd., Northampton Welding, Brazing and' Soldering Metals.Forging Work. R52.46 Sheet Metal Work. Foundry Work. Patternmaking Practice. Press Work.Engineering Steel and other Metals; their Something toDoin the BLACK -OUT ! Properties, Testing.Hardening, Tempering and Annealing. Engineers' Drawings. Workshop Calculations, Data, Hints YOU CAN and Recipes. STILL GETS11131U1DiS THE ILLUSTRATIONS The book is lavishly illustrated so that the explanations SOLID AND FLYING MODEL are rendered very clear with examples taken from actual AEROPLANES AND ACCESSORIES. works practice in many instances.There are 24 full -page These goods are ALL BRITISH MADE. plates and 877 line and photographic illustrations in the Prices are slightly advanced owing to war conditions, text. BUY NOW whilst you can obtain at reasonable prices. ENGINEERING POCKET BOOK We keep in step with the times! In order to make the work even more comprehensive, we SKYBIRDS new model is one of the latest FRENCH FIGHTERS- have brought out a pocket book, which is supplied free to all ' THE MORAINE S.403. Present price 3/ - purchasers.It contains many useful tables of Screw Threads, EveryAccessory to make the Complete Hobby. Tapers, Angles, Drill Speeds and Sizes, etc. These Models have achieved World-wide Reputation Send stamps lid. for Free 4 -page illustrated Price List and specimen copyof theSKYBIRDSLEAGUE mon:hly BULLETIN. Address :- A FREE BOOKLET SKYBIRDS (Desk P.M.), 3 Aldermanbury Avenue, LONDON, E.C.2 To the Caxton Publishing Co., Ltd., 119 Clun House, Surrey Street, FOR ACCURATE WORK AND PERFECT FINISH London, W.C.2. Pleasesendme,freeofcharge,IllustratedBooklet A "MILNES" LATHE is Essential describing "Engineering 'Workshop Practice."

Natr.e 7 in. Jcilu this form in unsealed envelope (hd. stamp) diameter or a postcard. Centre Lathe Address

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If you are earning less than £10 per - EiN.F? OFF HERE - week you cannot afford to miss reading -ENGINEERING OPPORTUNITIES." In your own interests we advise you to write (or forward the coupon) for your copy BRITISH INSTITUTE OF of this enlightening guide to well -paid postsI ENGINEERING TECHNOLOGY -NOW. 410a, Shakespeare House I There is no cost or obligation of any kind. I 17-19 Stratford Place, W.1. Please forward, Free of cost or obligation of any kind, you, I 268 -page Handbook."ENGINEERING OPPORTUNITIES.' BRITISH INSTITUTE OF I ENGINEERING TECHNOLOGY I I I Add res, I 410a, SHAKESPEARE HOUSE, 17,18& 19, STRATFORD PLACE, LON DON,W.1 =NI NMI November, 1939 NEWNES PRACTICAL MECHANICS 51

SUBSCRIPTION RATES Inland and Abroad 7s.6d.per annum Canada - - 7s. per annum PRACTICAL Editorial and Advertisement Office,:" Practical Mechanics," George Newnes Ltd. Tower House, Southampton Street, Strand, W.C.2. 'Phone: Temple Bar 4363. Telegrams: Newnes, Rand, London. Registeredatthe G.P.O.fortransmissionby Canadian Magazine Post. MECHANICS Copyright in all drawings, photographs, and articles published in "Practical Mechanics" Editor:F. J. CAMM isspecificallyreservedthroughoutthe countries signatory to the Berne Convention and the U.S.A. Reproductions or imitations of any ofthese are therefore expressly forbidden. VOL. VII.NOVEMBER, 1939.No. 74. FAIR COMMENT

THE firstsix weeks of war have96 -page book isfully illustrated, andnot be necessary to reduce it. Itis indicatedthereadiness and thecosts1 s. or1 s.2d. by post from theabsolutely essential, however, for the speed with which British people canPublishers,GeorgeNewnes,Ltd.,paper supply to be conserved, and for change from the comforts of peace to" Tower House," Southampton Street,this reason, if for no other, you must the rigours of conflict.Motorists haveStrand, W.C.2. place an order for its regular delivery been restricted as to the supply of petrol The informationdoes,ofcourse,with your newsagent.You must not and tens of thousands of them haveapply equallyto motor cycles. rely upon buying an odd copy, for returned to the pedal bicycle.Enter- newsagents are not allowed to return tainment has been restricted, and mostPractical Instructions unsold copies, and thus will only order of us are now compelled to find our DURING the past month I have beencopies for which they have received firm evening entertainment at home. We approached by some hundreds oforders from customers.One or two shall profit by it.A war throws intoreaders and a considerable number ofreaders who have not placed a regular sharp relief the liberties we enjoy withmanufacturers to publish in this journalorder have written complaining that peace. Fortunately, most readers ofa series of practical articles dealing withthey were unable to obtain last month's thisjournalhavepracticalhobbiesmethods of manufacture and workshopissue.Thus, they have had to apply which keep them keenly occupied inprocesses. Accordingly, I have arrangeddirect, and this means that their copy their workshops and at home. for the publication of a series of articleshas cost them 9d.Will you therefore This is the time for home study. Andealing with the Lathe, the Planer, the(presuming you have not already done inspectionofthelistofreservedShaper, the Milling Machine, Boring,so),please order your newsagent to occupations indicates the value whichDrilling,Screw -Thread Cutting,thedeliver PRACTICAL MECHANICS to your theStateplacesuponthosewithDrawing Office, the Tool Room, Dyesdoor regularly each month ? practical knowledge and training.Thisand PressTools,Gauges,Jigs and A form is given in this issue to enable can be rendered more valuable if youFixtures, Foundry Work, Pattern Mak-you easily to do so. can superimpose upon it a theoretical ing, etc., etc.It is pointed out to meIndex for Volume 6 knowledge. Such can be obtained in athatso many technicalclasseshave number of ways, and notwithstandingceased to function that I should make NDEXES for the last volume, which the fact that many technical classes have good the omission.These articles will Iconcluded with the September issue closed down.Correspondence Coursesstart in the next issue in which I alsoare now available complete with title to day have reached a high standard ofhope to be able to make an announce-page for7d. each. Only a limited excellence. The moment is ripe to takement of interest to all those engaged innumber are available and applications up a course in one or other of the manythe engineering trades.These shouldshould be made at once.Binding cases subjects offered.It will bring a returnnot overlook our two practicalcomplete with index andtitlepage out of all proportion to the modest cost.volumes, the " Practical Mechanicscost 3s. 6d. Handbook " 6s., by post 6s. 6d.; and "More Miles Per Gallon" " Workshop Calculations, Tables andThe Wheels of Chance BEARING in mind thatalargeFormulae " 3s.6d., by post 3s. 10d. G.WELLS'classic cycling number of motorists use their carsA catalogue of our technical books isH.novel entitled " The Wheels of for business and only to a minor degreeavailable free of charge. Chance," is appearing in serial form in for pleasure, I have just written a special In this issue I commence publicationour companion weekly THE CYCLIST. book entitled " More Miles Per Gallon."of a " Dictionary of Metals," which willCharmislenttothisentertaining In it I deal with all methods of securingbe of greatvaluetoengineers andnovel by the fact that it deals with real petrol economy, including the factorsstudents. roads and real inns.It deals with the affectingmilespergallon,engineOur War -time Policy adventures of Mr. Hoopdriver and the efficiency, the use of Pool petrol, tuning Lady in Grey. the carburetter, jetsizes and m.p.g.,I REITERATE thatitis the inten- Now that so many readers are riding fuel consumption and driving methods, tion for this journal to carry on duringbicycles, they will find this journal of decarbonising, adjustments, the effectthe war.Owing to the paper shortageparticular interest. It contains the latest of lubrication on petrol consumption,it may be difficult to give exactly thenews of the pastime, and a great amount makers'economy recommendations,same number of pagesashitherto,of technical information on bicycles and petroldopes,runningonparaffin,although at present the size of the paperaccessories. Itispublishedevery and the use of alternative fuels.Thishas been maintained. We hope it mayWednesday at 2d. 52 NEWNES PRACTICAL MECHANICS November, 1939 RAD CONTROL F Controlling aModelby Radio Reduces mon to the Usual Practice of Allowing a Fly and Land by Itself

model is at the mercy of the breezes. Theybut the rudder is used.The first effort, may cause it to drift into overhead wires,then, was to develop a complete control fences, or perhaps cause it to land in thesystem simplified by being limited to the water. With control from the ground madefunction of operating the rudder, so as to possible, the engine may be allowed to runkeep the weight within reasonable limits. until the fuelis exhausted-the average tank carrying fuel enough to last from five toThe 'Plane Receivers ten minutes. Since the rudder may be A type 30 valve seemed logical to start operated at will, the ship may be made towith because it had a filament drain low stay over the field. enough to allow operation from a very small battery.It was decided to operate on an Basis of the Contro. ultra -highfrequency, sothe transmitter Motor torque effect, or the reaction Iron)radiating system mould be compact and the turning of the prop., causes a tendency Fig. 2.The portable field transmitter, control easily handled.For simplicity. the super - box, and the aerial tubes for 56 -Mc. operation for models to lower the left wing and turnregenerative type of 'receiver seemed the to the left more or less slightly, depending onlogical choice. the model and the engine.All commonly The signal response of such a detector rOR many years the writerhas hadused engines are made to rotate in thewould not ordinarily operate a relay from more or less of an ambition to operate by the plate current change available.. The radioremotecontrol some form of outstanding characteristic of this detector, movini, vehicle.But it has been only in that of causing an audio hiss when idling recent years that the ambition has been and losing this sound upon reception of a realisedintheformof radio -controlled model aircraft. L, Tice growing popularity of petrol -engine - C1-25-mmfd, air pad.R3-500,000 ohms, 4 d ri venmodelaeroplanesinfluencedt lie der condenser watt decision to apply some form of control to TO C2-.00025-mfd. micaR4-100,000 ohms. STEERING watt reduce the hazards common to the usual MOTOR C3-3-30-mmfd. mica 3 TURN trimmer R5-2 megohms, practice of allowing these models to take watt off, fly and land themselves. Many a proud r. c C4-.006-mfd. midgetR5 -6 -ohm midget CA I mica rheostat owner has released his five- or six-foot wing - C ,-.003-mfd. midgetL1-13 turns no. 16, pan model, only to be forced to stand Mica in. i.d., tapped 3 helplesslywringinghishandswhileit NOcormccnoxr -- -1. Ca-.004-mfd. midget turnsfromplate CE, 1F4 1 finisheditsflightin s 955 1,- mica end a bunch of electric R1-2megohms; RFC-21-mh.,125-MA wires, or crashed in a mass of wreckage after watt choke a long and losing argument with a carelessly R2 -200,000 -ohmRelay -8,000 ohms, placed pole or tree. rheostat s.p.d.t. Powered with tiny two-cycle petrol engines of from A to A. horse -power, according to the size of the 'model, these 'planes are not carrier, was used to change the bias on a capable of carrying very much weight in 45 V. following audio stage through a grid leak addition to that of the engine and ignition and condenser. This principle of operating a .ITO,,, HEATERS .01119 accessories.A number of radio -controlled v relay from the audio -stageplate -current modelshavebeenmade,allover the change was borrowed from earlier experi- country, but the usual practice has been to Fig.I.The three -valve acorn receiver used in menters.The valve used for the amplifier build a comparatively large 'plane of from the model plane stage is a high -mu typethe American 11.4 .8 ft. to 12 ft. wing -span, or even larger, to or its English equivalent works excellently accommodate the necessary apparatus fordirection which causes a left turn.If this-whose bias from thegridleak and steering and otherwise controlling it fromturn is allowed to affect performance of thecondensercombinationlimitsitsplate the ground. model, it will climb.Opposite rudderingcurrent to a very low value when no signal It occurred to the writer that the develop-will usually have the reverse effect.Theseis being received. When a received carrier ment, if possible, of equipment capable ofeffects may be used to control the height ofsignal reaches the detector the hiss stops, being carried in the more prevalent size ofthe model's flight, even though no controlthe bias of the audio stage drops, and its model would be of more general interest and importance. The aim, then, became to make possible the ground control of model 'planes Fig.3.-Groundcontrol having a span of about 6 ft. equipment TO DIPOLE ANTENNA - HUI.KEY RIGHT The " flying weight " complete of this size RUDDER model is usually around 3 lb. This loads the Oscillator Unit Lz RR 34 CLOSED wing to about 10 oz. weight to the squareC1-35-mmfd. midget vari foot of wing area.It was soon apparent able that models would fly very well with a C2-.003-mfd. midget mica R1-10,000 ohms, 2 watts -;neater wing loading than this.However, I.1-4 turns no. 14, d in. i.d. this is not generally done, since the common L2-1 turn no. 14, d in. i.d. procedure is to limit the engine run byL3-6 turns no. 14, 4 in. i.d. RFC 21.mh., 125.mA TO HEATER timers which cutcif the ignition after choke 'WitiTERRUPTER 10 to 30 seconds, after which the model should glide around for a considerably Control Box R1-(Series resistor toin- greaterlengthof timebeforelanding. terrupter) 30 -ohm rheo. SOCKET PLUG 5, Loading them more heavily would result in stet their gliding a somewhat shorter time afterSi-Heater on -off switch OSC IL,LATOR UN IT CONTROL BQS, S5-Dynamotor primary the engine was shut off. switch It is during this gliding time that the I-Filament on -off indicator November, 1939 NEWNES PRACTICAL MECHANICS 53 MO EL LANES the Hazards Corn - Model to Take -off,

plate current rises to from three to five times the no -signal value. The writer's experience with the type 30 valve on ultra -high frequencies has not been too good.The valves seem to reach a condition altogether too soon where their emission is too low to super -regenerate at high frequencies.This is particularly true as the plate voltage used is limited to 45 volts maximum to avoid having to carry too much weight in the form of high-tension batteries.The filament voltage has to be raised again and again, and the valve is soon useless. For this reason the acorn type 955 was next tried.The detector stage was coupled to the audio with resistance instead of transformed coupling to eliminate the weight of a transformer.The 955 super - regenerates easily at either 56 or 112 mc. througha200,000 -ohm plate -coupling Fig. 10.-The 5 -ft. biplane model which is equipped with radio control.The tuning resistor which serves also as regeneration meter whichisremoved for flying can be just seen above thelanding gear control. It was found that varying the heater voltage through a range of several voltsthem and they must be easy to transport.get very good service from them.Their from normal had little effect on performance. The receiver using the acorn valves, asshelf lifeis guaranteed at 6 months, but In the receiver used, shown in Fig. 1, adescribed above, was the fifth form of setthere is so little demand for them that the 955 detector, followed by a 955 first audiowhich was constructed while efforts weredealersupplyingthemfrequentlyhas stage fed a 1F4 second stage having abeing concentrated mainly on producing athem in stock for some time before their sale. sensitive relay in its plate circuit. Thepractical, sensitive receiver. The drawback The weight of the set may be decreased practice of earlier experimenters of adjustingto the set described was that the filamentby the use of the new acorn valves recently the detector for maximum hiss was followedrequirements were 6 volts for the 955's andbrought out, with a filament rating of 1.4 This is not the2 volts for the 1F4. Total current require-volts at 50 mA. These were not available at first with fair results. ments for the acorn heaters and the 1F4when the above discussed set was being are 360 mA. This drain necessitates the useworked out. This would reduce the filament By E. L. ROCKWOOD WEBB of about eight penlite dashlight cells inbattery weight requirements. series parallel in order to get any satisfactory life out of the lir ater battery. ThisLight H.T. Batteries most sensitive condition of the detector, There are a number of light 45 -volt H.T. however, so an experiment was made withbank of penlite cells anu unts to a weight of about 4 oz. batteries available, but in the main their the detector just barely super -regenerating. The acorn receiving set weighed aboutshort life and the difficulty of obtaining In this case the last audio stage plate them makes their use impractical. current was lowest instead of at a maximum.7 oz., the relay 3 oz. more, and the H.T. The line of Bantam valves produced by When a carrier was received, the currentbattery from 9 to 10 oz., varying in individual batteries.If fresh when first pur-the Hytron Laboratories might be used to was decreased, instead of increased, causingchased, the batteries will give better thanadvantage. They are very small, and their a normally pulled -up relay to drop out to a100 hours' service life in these receivers.filament drain is about 70 mA. at 1.4 volts. back contact with signal. The first batteries purchased were dated atThe line includes a detector triode, a high - With this arrangement the reception of aor before the date of purchase, so I didn'tgain pentode suitable to replace the 1F4, signal causes the plate current of the relay all designed to operate at 45 volts. stage to change in a ratio of over 2i- to 1. The sensitivity is such that a 6L6 trans- Relays mitter at a 33 -ft. distance, with no aerial There seems at present only one type on transmitter or receiver and only 42 volts which is really practical for this use, the of plate on the transmitter, operates the American Sigma 2A or 3A. Theonly relay stage through its full range of current difference between them is that the 3A change. Sensitivity seems to be at a operates on 4 milliwatts power and the 2A maximum when the H.T. plus leadis calls for 6 milliwatts.Either one has been tapped down from the grid end of the coil found practical,as they both included about three-quarters of its length, rather means of adjustment offering a response at than having this lead connected directly to quite a range of different current values. the grid end, as is usually done with self - The 2A type was used by the writer, as that quenched detectors for 'phone reception. type happened to be the most easily avail- Fig. 4 shows a receiver of this type. able.It responds satisfactorily at as low a The primary object of the writer was to current as mA. The adjustments allow control models of the size usually flown, settings which will cause the armature to rather than to build a special model to carry pull up and drop back with a current change the control. The usual petrol -engine -driven of as little as mA. model varies in size from those of 46 in. to 48 -in. wing -span to the rather more un- Control Transmitter Design usual sizes of 8 -ft.to 9 -ft.span. The The transmitter for field use offers quite smallest ones were impractical to carrya a bit of latitude for variation on the part of control, so it was decided to concentrate on the constructor.Sixteen watts for output those of about 6 -ft. span. With the wings seems a good value for reliable control, and removed these may be carried fairly con- this may beobtained from an RK34 veniently in a car ;there are, of course, Fig. 4.-Top view of the diminutive chassis of operating at 300 volts.The power supply only certain places where it is practical to fly the throe -valve acorn receiver may be obtained from either a vibrating 54 NliWNES PRACTICAL MECHANICS November, 1939 reversed at will, no matter in what positioncontrolled for most satisfactory operation it -in Ay be. by a series rheostat. The armature exten- The instrument on the left of the slopingsion is weighted at a point near the contact panelis an indicator showing when thein a fashion similar to that employed on a filamentoftheoscillatorison. InVibroplex key.The weighting is done to the centreis.. a millimeter in series withcontrol the natural period of vibration of the oscillator plate circuit.Above it is thethe assembly.A speed of contact as low rheostat controlling the interrupter.Theas two per second may be obtained.The car dashboard ammeter to the right showspurpose of this interrupter will be explained the total battery drain.Above itis thelater. knife switch controlling the 6 -volt input to the high -voltage supply.On the rightThe Steering Mechanism end of the cabinet is a five -prong radio One of the surprising facts that become socket into which plugs the rubber -coveredevident to the builder of radio -controlled cord whose other end plugs into the oscil-models is the fact that getting the actual lator case on the tripod.The aluminiumreceiver working correctly in the 'plane is tubes shown standing against thecase. only the beginning from the standpoint of plug into feed -through insulators on theproblems involved. The attitude that it is all rear of the oscillator case.The case wasright to spend the time on the receiver and fitted with a nut underneath which fits thethen only work on the steering mechanism threads of the standard camera tripod. Theas a last-minute job must soon be corrected aerialisa horizontal dipole inductivelyor there will be a batch of trouble in store coupled to the oscillator tank, and is tunedfor the experimenter. The steering mecha- by means of telescoping sections of thenism must be foolproof, absolutely reliable, aerial. unaffected by the vibration set up by the The circuit of the ground equipment islittle one -cylinder petrol engines, and be shown in Fig. 3.As mentioned before, acapable of reasonably rapid response-not vibrating reed rectifier, or any source ofto mention one of the most important 300 volts D.C., may be used in place of theconsiderations, that of lightness in weight. genemotor. A method the writer has found The steering engine (top view, Fig. 5; Fig. 5 (Above).-Top view of the steering control satisfactory is to use two 200 -volt gene -front view, Fig. 6I is made up of a balsa showing the double worm reduction.Fig.6 motors with the high -voltage windings inframework upon which is mounted a Knapp (below).-Front view of thesteeringcontrol series and the 6 -volt connections in parallel,model railroad electric motor of the size showing the balsa -wood scotch yoke arrangement or even a smaller vibrating reed rectifier inknown as " HO " gauge.This drives a reed rectifier or a 300 -volt motor generatorseries with a 150 or 200 -volt genemotor. Inworm -and -pinion gear train with a ratio of operating, of course, from a 6 -volt storagethis connection a word of caution-watch500 to 1, ending up with a disc 1 in.in battery. out for difficulties arising from the practicediameter on the second jack shaft. A pin While acrystal -controlledtransmitterof some .manufacturers of bringing thenear the outer edge of the disc drives a could be used-perhaps with one section ofnegative high voltage and one side of thescotch yoke.This converts the high speed RK34 a 10 -meter crystal oscillator and the6 -volt lead to a common earth on the frame.of the little li-oz. motor into a compara- The negative high voltage must not hetivelylowhorizontalto-and-fro motion other half as doubler, followed by a final which may be linked to the rudder through amplifier-it will in general be found more a length of stiff No. 16 piano wire.The satisfactory to make final adjustments in motor is reversible by changing the polarity the field for resonance of the receiver with of the armature current, the field being a the transmitter by tuning the transmitter to permanent magnet. the receiver rather than vice versa.So a Fig. 7 shows the diagram of the late self-excited oscillator transmitter has been receiver using an RK62 thyratron detector. used for most satisfactory all-round results. When a radio signal is received and the The stability of a TNT circuit using the relay falls back, a contact is made by the RK34 has been very good for this purpose Sigma relay which sends, current through as far as the writer has found. Any combi- STMEMNG nation of valve or valves delivering about OTO. the steering motor in one direction, the WE *Ur) motor increasing the rudder turn in a right- 16 watts to the aerial and operable from a hand direction as long as the signal con- reasonably portable . power supply will be tinues. A release of the radio carrier allows foundsatisfactory,providedthatfair the relay to pull up, reversing the current stability of frequency may be obtained. No throughthemotor by transferringto modulation is necessary, hence the practic- Fig. 7.-RK62 receiver used in the model biplane another motor battery.The motor then ability of self-excited oscillators. moves the rudder to the left as long as the C1-25 'mmfd. air pad - Li -10 turns no.14, signal is absent, until the limit is reached, The Ground Control Unit der in. int. dia. At firstit was planned to build theC5-.00025-mfd. mid- LRFC-Midgetu.h.f. when the frame of the scotch yoke opens ground control equipment into a car as for get mica choke switch S, turning off the current and stop- C3-3-30.mmfd. mica Relay -8,000 -ohmping the motor. portable mobile work.A slight practical trimmer experience inflying petrol models soon .05-infd., 400 - s.p.d.t. To stop the rudder at any desired point showed this to be impractical in a good volt tubular 131-Penlite cell along its travel, it is only necessary to move R1-4 megohms. I B9-Midget 45 -voltthe key switch intoneutralorcentre many cases due to the difficulty of driving watt battery the car close enough to the flying area of theR_ -15,000 -ohm mid- B5, B4-2 penlite cellsposition.This position cuts in the inter- field, and to the fact that a car too close get rheostat in parallel rupter incorporated in the transmitter unit, to the models constitutes a flying hazard. and the effect is to send out a pulsing signal Hence the portable battery: earthed, since it is to be connected to thewhich repeatedly reverses the steering motor Referring to Fig. 2, the case on the leftpositive high -voltage lead of the other unitat a speed such that rudder is prevented topped by a carrying handle contains theused in series with it.Using the RK34from moving in either direction.To get battery, an interrupter to be described, theoscillator of Fig. 3, 80 mA. at 300 volts willthiseffectproperlytheinterrupteris 300 -volt genemotor and a filter.The keybe required. adjusted by the value of weight on the switch at the left end of the top is the armature extension until the pulsations of control key which turned forward givesThe Buzzer Interrupter signal are just fast enough to keep the right rudder control, turned back gives left The interrupter shown in the cathodesteering motor from making any appreciable rudder, and left in neutral causes the ruddercircuit of the RK34 of Fig. 3 is made from aprogress in either direction, though it will to hold whatever position has been attained.medium -size electric buzzer by soldering anrapidly move a slight amount first one way This method allows the use of right or leftextension about 4 in. long to the armature.and then the other.The rheostat in the rudder to any amount desired, not in steps,A contact is placed at its extreme end tointerruptercircuitisusedtogetthe and without a step. by -step selector systemmeet another contact on a piece of lightsmoothest action of the unit, but it has little which would necessitate putting the modelshims brass. The shim is fastened parallel toeffect on the actual speed of interruption, through successive unwanted positions tothe armature extension and secured at thethis being determined by the weighting of reach the one desired. Any position of theenf opposite to the contact so it will springthe vibrating arm. steering mechanism may be reached fromslightly when contact is made. The buzzer (By Courtesy of "Radio") any previous position-the rudder may he is *rated from the 6 -volt battery and (To be continued) November, 1939 NEWNES PRACTICAL MECHANICS 55 How High Can WFly ?

A stratosphere 'plane which hasreachedaheightof nearly 50,000 feet

T0 the question, " What is the altitudedevoid of sufficient oxygen to sustain humantions he came to the conclusion that after a limit of human flight ? " the answerlife, but it is, also, far too rarified to impartcertain height has been reached (a height of is that, in all probability, there is nothe necessary amount of uplifttotheapproximately seven miles) the tempera- such limit, for if we had available a suitably -normally -designed aeroplane. ture of the air no longer shows a steady designed aerial -rocket capable of carrying Indeed, an ordinary gas galloon has adecrease with increase of height, but that passengers, we could fly practically as highfar better chance of taking a man up intoit remains practically constant at about as we wished. As matters are, however, atthe mid -stratosphere than any of the usual50 degrees Centigrade below zero.It was the present day the greatest possible heighttypes of lower -level' aeroplanes, for, afterfrom these observations that Teisserenc to which it is possible to ascend by meansall, a balloon filled with hydrogen gas, thede Bort discovered that region of the upper of a specially -designed balloon or aeroplanelightest of allmaterial substances,willair which we now term the stratosphere, is represented by the lower regions of thecontinue to rise to an enormous heightthe region which commences some ten stratosphere. before eventually it bursts owing to themiles -above the earth's surface at the The earth's atmosphere, as most aviationexpansion of the gas within its envelopeequator and about six and a half miles amateurs are aware, reaches upwards to aconsequent upon the increasingly reducedabove the earth at the poles. height of nearly two hundred miles.Menair -pressure without. Of very recent years, an enthusiastic of science nowadays divide the atmosphere For many years previous to the inventiongroup of Russian scientists have utilised into four different regions :The Tropo-of the aeroplane, the exploration of highthe sounding balloon method of obtaining sphere, which is our " ordinary " atmos-altitudes by means of the balloon had pro -records of the earth's upper atmosphere. phere consisting of the air we breathe, with its winds, clouds, mists and water vapour. Next comes the Tropopause, which is a sort THE PROBLEMS OF ULTRA -HIGH of bufferlayer, some two miles thick, between the troposphere and the Strato- ALTITUDE AVIATION OUTLINED sphere. The latter is the vast region of` ratified atmosphere consisting ye ncipally of nitrogen, which extends upwards aboveceeded apace.Little scientific data, how-They have even gone so far as to cause auto- the tropopause to a height of between fiftyever, had been accumulated, first of all onmatic radio transmitters to be taken up in and sixty miles above the earth's surface.accountof lackof sensitiverecordingsounding balloons in an endeavour to obtain Finally,comestheUpperStratosphereinstruments, and secondly in view of thean accurate indication of the maximum extending above the stratosphere properfact that the early high altitude observersaltitude reached by these balloons. and reaching to about two hundred milesin mid-Victorian times found it impossibleMaximum Height Reached above the surface of our globe. The upperto retain consciousness at altitudes much above five or six miles. Up to the present date, the maximum stratosphere is believed to consist mainly Scientists and meteorologists, therefore,height reached by any sounding balloon of light gases such as hydrogen and helium,evolved what is now known as the " sound-is twenty-three miles, that is to say well and its upper reaches constitute that ill-ing balloon," a balloon which is equippedinto the stratosphere proper. Temperature defined and still somewhat problematicalwith various types of registering instru-records obtained with these balloons all boundary betweentheearth'sgaseousments and which is sent up into the higherbear out the fact that in the stratosphere envelope or atmosphere as a whole and theregions of the atmosphere without anythe temperatureispractically constant. gasless, matterless void of outer space. human occupants whatever.When theOther records show, also, that in the strato- The Upper Stratosphere balloon reaches a certain height, it bursts,sphere thereis no moisture, very little No human being has ever attempted towhereupon a parachute automatically comesoxygen and that the region is one of abound- voyage upwards intothe upperstrato-into play and allows the instruments toing ultra -violet light and cosmic rays. sphere, but many have been the endeavoursdescend to the ground unharmed. Modernstratosphereexplorationby to sail into the stratosphere proper and to means of lighter -than -air craft was estab- explore its many perplexing and mysteriousSounding Balloons lished by the renowned Dr. Piccard and conditions.With an ordinary aeroplane, The instrument -equipped sounding bal-his companion, Dr. M. Cosyns, who, on no matter how well -powered and speedy itloons werefirstused near Trappes, inMay 27, 1931, ascended toa height of may be, it is, of course, impossible to get upFrance, in 1894,byanindividualabout nine and three-quarter miles.On a substantially into the stratosphere, sincenamed Teisserenc de Bort.By analysingsecond voyage (August 10, 1932) Piccard not only is that region of the atmospheretwo or three hundred instrument registra-reached a height of ten and a half miles, 56 NEWNES PRACTICAL MECHANICS November, 1939

neither man norenginecouldbreathe without artificial aid. Air Supply The problem of the air supply of an engine at great heights has brought back once again into the realm of aviation the suggestion of the steam engine as a power unit for high -flying 'planes.Despite the greaterweight of a steam power unit compared with that of an internal-combustion engine of approximately ecu d horsepower, itis a simpler problem to supply oxygen or air to a steam boiler at great heights than it is to a petrol engine. Hence. when thenowadaysprojected" strato- planes " come into practical being, it is quite possible that the engines of -some of them may be steam -driven instead of petrol - propelled. The firms of Farman inFrance and Junkers in Germany have, even at the present juncture, constructed experimental aircraft for lower -stratosphere flight. In both instances sealed cabins have been provided in the 'planes for the pilot and his observer, whilst in the case of the Farman 'plane an engine of some 400 h.p. was used, the carburetter taking air normally up to about 13,000 feet. Above this leVel and up ----- Stevens and Anderson in their stratosphere 30 balloonin which theyreached a height of nearly 73,000 feet 29 28 whilstinthe followingyear a Russian observer, one M. F'rokofief, attained an 27 altitude of practically twelve miles. 26

Air -Tight Gondola 25 All these ascents were made possible by means of a very light, air -tight aluminum 24 STRATOSPHERE gondolaofsphericalshapewhich was attachedto theballoon,theobservers 23 taking up their own oxygen with them and 22 HIGHEST SOUNDING - bringing back with them a considerable BALLOON ASCENT number of scientific records. 2/ High as thesealtituderecordswere, however, they were greatly eclipsed on 20 /4"aiagy ik...I' November 11, 1935, when Captain Stevens STRATOSPHERE and Anderson; of the United States Army /9 ''-OmILE.5__- Air Colys, ascended in their stratosphere balloon, Explorer II. to a height of no less /8 than72,395feet,ornearly 14miles UPPER STRATO.), above land level.This constitutes the 17 ,200 MI LE5 highest altitude to which human beings 16 haveeverascended, and althoughno doubtthisrecordwillinitsturn be /5 HIGHEST POINT REACHED BY MAN (Above) The four components (72,395Fr) STEVENS E. ANDERSON of the earth's atmosphere. exceeded, the feat of Stevens and Anderson NOVt. HT" /935 The in ascending without mishap to that un- /4 highest altitudeatpresent precedented height is one which will not reached by man or his instru- lightly be forgotten. ments corresponds to the region of the lower stratosphere American Balloon /2 PROF: PICARD'S BALLOON Explorer II, the American stratosphere 11 balloon, had an envelope whose area was no less than 2f acres, and whenfully 10 inflated at the highest point of its ascent 9 h1412/0 PEZZ1 LOWER LIMIT the envelope was distended with 3,700,000 HIGHEST AEROPLANE AT EQUATOR cubic feet of helium gas, which gas, at 8 RECORD ground level, occupied a volume of 300,000 cubic feet. 7 The ordinary aeroplane cannot, of course, hope to reach these colossal heights, for, in the first place, the air at those altitudes is so LOWER LIMIT AT EARTHS MOUNT EVEREST rarified thatitis unable to impart the (29./4/ FT necessary degree of upliftand,again, because of the lack of oxygen at such 4 extreme heights. 3 The height record for an aeroplane is approximately ten miles, a record which was 2 achieved by the Italian airman Mario Pezzi in October, 1938. This height, of course, was rendered possible by the employment of an enginesuper -chargerandalsooxygen apparatus for the pilot, for at that height Illustration showing the comparative heights reached by different types of aircraft November, 1939 NEWNES PRACTICAL MECHANICS 57 to 25,000 feet a compresser was brought No Danger of Ice into action to feed air to the cylinders, a At the lower stratosphere levels, despite second compresser functioningsimilarly the great cold prevailing, there will be no between 25,000 and 60,000 feet, whilst a Astratosphere danger of ice forming on the 'plane, since third compresser was arranged to operate rocket which was the air in those regions is perfectly dry. At at altitudes above 60,000 feet. designed torise these levels, also, the air is still and wind- - The designof theGerman Junkers to an altitude of less, although, towards the upper limits machine ran on similar lines, and by either more than 300 of the stratosphere it is now considered that of these planes it was intended that a miles in less than violent storms rage and circulate. The lower minimum height of some 12 miles would five minutes stratosphere is, of course, perfectly cloud- readily be attained and maintained. less and the sun is visible uninterruptedly Variable Pitch Propellers from its rise to its setting.Many of the brighter stars are visible in the day -time, Suchmachinesweredesignedwith also. Hence, a commercial service of strato- variable -pitch propellers, the " cut " of the planes operating, say, between England and propeller being made more acute as the Australia or betwixt Europe and America machine ascended to stratosphere levels. would experience no navigation difficulties, Telescopic wings were alsodesigned in for the only " blind flying " which such order to give the machines huge wing- pilots would be requiredto undertake spreads at high altitudes, these ultra -large being that involved in flying upwards or wings being necessary in order to enable downwards through dense cloud -belts when the machine to ride on the intensely rarified ascending into or descending from the lower air at heights of ten miles or more above stratosphere. sea level. Unfortunately for scientific research, war The Upper Etratosphere preparations in several countries prevented Th, upper stratosphere,that entirely themakingofsustainedtrialswith unattained region of the earth's atmosphere specially -designed machines of this type. existing at a height of from approximately Hence it would appear that all ultra -high fifty to two hundred miles above sea level, flying and stratosphere research must neces- will,perhaps,neverbeconquered by sarily be postponed until times of peace methods of flight as we know them at again return. present.No ordinary hydrogen or helium Although no ordinarily -designed plane balloon has ever reached the upper strato- can hope to attain the height of a stratosphere, so far as we are aware, and it is, of sphere balloon, it may, in the future, be course,impossibleforany present-day possible to design mechanically -propelled powered flying craft to attain that enormous aircraftwhich willtravelat enormous height. speeds at heights well above the present- It would seem, therefore, that if man is day limit for aeroplanes.After all, strato- ever to lift himself up to the level of the sphere or lower -stratosphere travel, quite upper stratosphere he must await either apart from its enormous scientific interest, the coming of the rocket projectile or else would, if made practicable, possess much the ultra -light plane which, propelled by commercial value.Owing to the rarity of the as yet undiscovered atomic power, will the air at stratosphere levels, friction thereat be capable of journeying upwards to the isgreatly diminished. Consequently a extreme boundary of the earth's atmosphere plane can be propelled at a far greater and of cruising thereat by means of energy speed for the same effort than it can be at supplies which are, at present, not merely ordinary air levels. unknown, but also wholly undreamed of

New Generator The generator to which this Interesting An Engineering Miracle principle has been appliedisthe third 110,000 kilowatt unit to be placed on the line of the world's largest industrial power- Producing Power from "Thin Air" house at the Ford Rouge plant.Official FOR startlingeffectsof legerdemain,out any increase of input energy. Althoughstarting of the new generator was accom- engineersofFordMotor Companythe magician's rabbit may not legitimatelyplished recently when William Clay Ford, and GeneralElectric Company feelbe a creation of " something from nothing,"grandson of Henry Ford, turned a Mer- that they have pretty well surpassed thethis feat of the engineering profession cer-cury 8 steering wheel to open the starting -magician who produces a whole live rabbittainly is. valve.Companion unit to its two pre- from the apparently vacant atmosphere The armature of the generator is encloseddecessors, installed in 1931 and 1936 res- somewhere to the right of and above hisin a sealed casing mounted on the armaturepectively,the new generator embodies right ear.Instead of a mere rabbit theseshaft throughoil -sealedbearings.Thisengineering improvements which markedly engineers have produced some 2,500 tocasing, or jacket,is provided with con-increase its efficiency over the other units. 3,000 extra horsepower before the verytrolled valves at top and bottom.TheWith the new unit in service the capacity eyes of all present, and to make the analogyfirst step in filling the jacket with hydrogenof the power house has been raised to complete they have produced these horsesis taken by opening both valves and pump-462,000 horse -power. from what may wellbe called" thining carbon -dioxide gas, which is heavier air." than air, through the bottom valve untilHydrogen Cooling all the air has been displaced. Both valve Efficiency of the generator has been Trick of the Trade are then closed and the jacket is readyincreased by hydrogen cooling along prin- Unlike the prestidigitators of old, thefor charging with hydrogen. ciples almost identical with those under- engineers are glad to explain the clever lying the increase of automobile efficiency trickof theirtrade which dispels theInlet and Outlet Valves through streamline styling. In other words, mystery.It is the substitution of " thin Hydrogen being lighter than air,theboth are problems in which the resistance air," or more properly, hydrogen, for airselection of inlet and outlet valves for theof a moving body to the medium through as a cooling medium for the armatures ofchargingisreversed.The top valveiswhich it passes must be reduced. In the the new 110,000 kilowatt turbo -generatoropened and hydrogen is pumped in, carboncase of the automobile the solution has atthe Ford Rouge Plant Powerhouse,dioxide being allowed to escape through thecome through careful wind -tunnel tests to Dearborn, Mich.Weighing only 1/14 asbottom valve until the concentration ofdetermine changes of external design which much asair,hydrogenoffersfarlesshydrogen in the jacket reaches 97 perwill allow it to move through the air with resistance. to the turning of the giantcent. Both valves are then closed. Stabilitya minimum of wind resistance. A similar armature, effecting a gain of 2i per cent.of the hydrogen content of the jacket isprocedure could not be followed in the in power output at the 80,000 kilowattensured by automatic gas analysing devicescase of the generator, but an identical normal " cruising speed " of the generator.which flash warning lights and audibleresult was obtained by the substitution of That amounts to an output gain of fromsignals in the event the concentration ofthe much thinner medium through which 2,500 to 3,000 horse power per hour with-hydrogen falls below 90 per cent. the armatures must move. 58 NEWNES PRACTICAL MECHANICS November, 1939 THE MONTH IN THE WORLD OF- SCIENCE AND INVENTION the sun so that the shadow falls down its Television in War'Planescolumn. The higher spot will be reachedPost Office Under the ANEW YORK newspaper states thatby noon, and the lower at 9 a.m. and 3 p.m. Italy has now fitted a squadron of Sea war 'planes with television sets.Previous difficulties due to the weight of the televisionHunting For Cosmic RaysSEATED inaglobular,glass -walled installation and necessity for very strong DR.ROBERT A. MILLIGAN, of the chamber in the heart of a marine fairy- light have now been overcome. California Institute of Technology, hasland asmall company of officials and They state that the installation has beenrecently set out from Los Angeles on a cos-privilegedguestsrecentlywitnessed an reduced to " flying " weight and that themic ray hunting tour of the Equator andevent unparalleled in history-the opening television set will now work in ordinaryadjacent countries.His equipmentwill of the Bahamas Sea Floor Post Office, the daylight. include the world's smallest radio station,world's first undersea postal depot.The The first experiments carried out wereand 225 balloons. The balloons are capableactual size of the post office is 6 ft. by 10 ft., limitedtothetransmissionofcloudof reaching a height of 20 miles and theyand it is a well yentilated chamber at the formation pictures to a ground station, butwill be released in Australia, New Zealand,bottom of the sea. itis now claimed that itis possible tothe East Indies, India and Egypt. The Known as the Williamson Photosphere, recognise the make of a car travelling alongballoonswillcarrydelicaterecordingit will also be used for broadcasting from the road from an aeroplane flying at ainstruments up to altitudes which receive height of 6,000 ft.It is possible to attain the ocean floor, a powerful radio telephone a television range of 100 miles.Experi- ments in this field of television have been ,Aft in progress inother countries for some FIRST DAY COVbiZ, "4/111.--- time. England's Oldest Watch F LO DURING the recent alterations to the 3.0 103 Cloister Garth of Canterbury Cathedral, a Saxon 10th century pocket sundial of jewelled gold and silver was discovered.

A specimen postPl packet sent from the undersea Post Office, "Sea Floor, Bahamas"

making it possible to describe the wonders of the undersea as the sphere cruises through coral forests abounding in colourful sub- marine life.Mr. Ernest Williamson's sub- marine tube and Photosphere can thus be truly said to make the visions of Jules Verne come true.The mother ship for the photosphere is the " Jules Verne III," a strange craft from which is lowered the flexible tube and spherical chamber into the sea. A Gas -driven Car illustration is shown on this page of ANwhat isclaimed to be the first coal gas -driven car in England since the start of the second Great War. It has been The first coal gas -driven car in England since the start of the second Great War converted for use with coal gas and Leeds Corporation have installed a special 4 in. gas It is considered to be the oldest watch inthe full force of the bombardment of thismain at their depot in readiness for users. the English-speaking world. The workman-planet by the mysterious rays from outer The car can be used for either gas or petrol. ship is excellent and it consists of a silverspace. A switch has been installed in the petrol tablet with a cap and chain of gold. circuit and when gas is being used you just The gnomen, which consists of a gold switch off the petrol, or if you run out of gas pin, is surmounted by a delicately chasedWorld's Broadcastingyou just switch on the petrol. The owner of animal head with jewelled eyes. The head the car is having a crate made to fit on the has a ball in its mouth which when not in Stations roof so that the gas carrier will not sway use rests in a pocket at the lower end of the ITisestimatedthatthereare aboutabout too much. tablet. Abbreviated names of the months 36,000broadcastingstationsinthe Bags have to be used as the Government are inscribed in pairs on the faces and atwhole world, of which about 8,000 are landwill not pass the use of cylinders for a life the top of each of the three columns is astations, and the rest are mobile installa-of more than five years and the cost is too hole for the pin when in use. Two spots aretions in ships, etc.Of these 8,000 landgreat as they are made of drawn manganese marked below each hole. stations, 1,800 are regularly used for enter-steel. There is also the estimated outlay by To find out the time, the pin must betainment, and the rest for communicationsthe gas companies of approximately £10,000 inserted in the hole appropriate to thepurposes.Moreover, over two-thirds ofto instal gas compressors and in present month, and the dial must hang free facingthese are American Stations. conditions this is out of the question. November, 1939 NEWNES PRACTICAL MECHANICS 59 MASTERS OF MECHANICS Instead ofjourneys,people now of metal tubes twisted roughly into the May go upon a Gurney, shape of a figure -eight. This boiler was only With steam to do the horses' work partiallysuccessful,butbeforelong a By power of attorney. second boiler was forthcoming, the tubes of which were not welded but butted Tho' with a load it may explode together so that if any great internal steam And you may all be undone, pressure arose, the tubes simple came apart, And find you're going up to Heaven attheirjunctions.By means of such, Instead of up to London ! tubular boilers, Gurney was able to get up with safety steam -pressures of some 800 lbs., THUS Tom Hood, the comic poet of despite the fact that the average steam - acenturyago, characteristically pressureinhislaterroadlocomotives epitomised the credulous, suspicious seldom exceed 120 lbs. sq. in. andhalf -humorousattitudewhichthe In 1825, Gurney obtained his first patent London public adopted towards the pioneer- for a road locomotive propelled by steam. ingtrialsof Goldsworthy Gurney, the It was a somewhat curious contraption, for' engineer and steam -coach inventor, to make its inventor endeavoured to work it without practicable a steam vehicle which would be a crank, utilising a pair of oppositely -placed of service for ordinary road use. "legs," which, in the words of the inventor, There were, of course, plenty of people "are set in motion as the carriage ascends who were ready to say that a steam - a hill and move like the hind legs of a propelled road -vehicle was impossible, that horse,catchingtheground andthus such an invention, even if it did materialise, forcing the machine forward."Such a could be nothing other than a highly steam -coach seems actually to have been dangerouscontraption,andthatsuch run on the public roads in 1827, but a vehicles ought to be prohibited by Act of couple of years later, Gurney completed Parliament. But Goldsworthy Gurney and another steam carriage capable of accom- his few contemporary inventors heeded modating twenty-one passengers.It, also, them not. Instead, they concentrated upon Sir Goldsworthy Gurney,who invented a road had "legs," but it possessed pistons and the problem of designing and constructing carriage driven by steam cylinders, these driving the two rear wheels. No. 5o. Sir Goldsworthy Gurney and theeginDlings of Road Locomotives

a steam -driven road vehicle of such powerface of all obstacles and eventually createdA Successful Carriage to enable it to ascend all ordinary roadtherailwaylocomotiveandtheroad Thislatter road -carriageof Gurney's gradients fully laden and withoutdiffi-locomotive. wasreallysuccessful.Itmade many culty. appearances in the environs of London, and, Heating Coloured Water on one occasion, it actually made a journey His Early Career Gurney, at the outset, began by heatingfrom London to Bath and back at an average Sir Goldsworthy Gurney-for he wascoloured water in a circular -shaped glassspeed of 15 m.p.h., a feat which, con- knighted by Queen Victoria later on in histube provided with an outlet vent for thesidering the times in which it was made, is career-was a Cornishman, being born insteam.He showed that the convectiontruly astonishing. the Dutchy of Cornwall in 1793.Of hiscurrentscausedbytheheatedliquid Just, however, as the pioneer railway early education and training we know nextenabled the latter to circulate, and, fromconstructors encountered severe opposition to nothing. He seems, however, like manythis observation, he constructed his firstto their labours, so, also, did -Goldsworthy' other Cornishmen of his generation, to havetubular boiler which consisted of a seriesGurney experience the same narrow par-' been attracted to engineering at a very early age, for in his youth he made mechanical models which really worked, models of Cornish beam engines and the like, which power units had at that time attained a very important status in the engineering world of the day. Although Gurney, during his younger days, was not actually the first to hit upon the now universal idea of the tubular boiler, he was one of the first to construct a light boiler made up entirely of tubes. In a tubular boiler, of course, the water is circulated through a series of heated tubes, an arrangement which permits of rapid and high-pressure steam -raising. Quite a number of engineers of Gurney's day had been against the principle of high-pressure steam when it was first introduced for locomotive purposes by Richard Trevithick, another contemporary Cornish genius. James Watt, for instance, whose present measure of fame is, to say the least, out of all proportion to the true facts concerning his career, was strongly opposed to all high-pressure steam systems.So, too, was his unscrupulous partner, Matthew Boulton. But Trevithick, Gurney and a handful of other locomotive pioneers and inventors persevered in the Gurney's steom-propelled road coach built in1839 60 NEWNES PRACTICAL MECHANICS November, 1939 tisanship which arose and threatened toOther Branches of Engineering workings became the scene of an under- make an end of all his carriages.Indeed, As,however, we haveseen,Gurneygroundconflagrationwhich,foryears, on one occasion when Gurney was drivingrefused to remain dismayed. He turnedrefused to become extinguished. his steam carriage along a road near Bath,his attention to other branches of engineer- an attack was made upon the vehicle. Itsing, and, having more or less washed hisAn Underground Fire occupants were actually stoned and Gurneyhands of mechanical road vehicles and Much damage was caused to underground himself was so badly manhandled that helocomotive construction, he took up othercoal seams by this" burning waste of lost consciousness and had to be conveyedlinesof engineeringinterest,becomingClackmannan," as the area became known, back to Bath for attention. eventuallyrenownedasaconsulting engineer of high repute, and ultimatelyuntil Goldsworthy Gurney, the engineer, " Gurneys " was approached in the matter, he having meriting for himself the honour of knight-previouslysuccessfullyextinguishedan Gradually, however, Gurney's activitieshood. underground fire at the Astley Collieries in in the construction of road locomotives Gurney attained some measure of fameYorkshire. prevailed. His vehicles-" Gurneys " theyas a mining engineer and as an ingenious Gurney'splanwastouseahigh- were popularly called-came, for a time,inventor of a variety of mechanical devices.pressure jet of steam and, by means of into regular usage. For instance, in 1831,About the year 1854, for instance, a numberthis, to force down into the mine workings aregular toadserviceof" Gurneys " a largevolume of" choke damp "of between Gloucester and Cheltenham came Gurney's experiment on the heating of Water in sufficiently low temperature to cool down into operation four times per day.The 7 , z the burning mass and at sufficient pressure average speed of these journeys, stoppages a circular tube. Upon to keep out the intlowing air. these experimentsWas included, was approximately 10 miles per h To this end, a furnace was constructed hour. based Gurney's inven- STEAM VENT above ground and over it was erected Other similar road -locomotives ran on tions ofhis tubular :!!' a high-pressure boiler.Flues and pipes regular services in London, and, for a boilers conveyed the steam and gas to the under- relatively short time, Gurney appeared to ground workings. Carbonic gas, generated be heading rapidly for the utmost success by the furnace, was flooded into the mine- in his pioneering activities. workings under steam pressure for several Powerful interests, however, combined hours every day, until, eventually, after together and eventually thrust the Gurney several weeks of these operations, it was road -carriages and others from the roads. found that the subterranean inferno had Such vested interests were by no means been entirely cooled down and permanently only those of the horse -owning and agri- extinguished. cultural fraternities.Rather, the greater As an engineer pure and simple,Sir amount of opposition to Gurney's sch( me Goldsworthy Gurney has long been for- came from the railways, who, having, a', gotten.Indeed, it is only his pioneering thatperiod,hardlyestablishedtheir steam -coach activities which has kept his position in the country, saw in the rise of memory alive.In such respects, however, the road -carriage a powerful competitor Gurney undoubtedly exhibited many of the which would, if uncombated, defeat their traits of genius.His tubular boilers, for interests and destroy,their coming monopoly. instance, contribute greatly not merely to the making of road locomotives in general Extortionate Road Tolls but also to rail locomotives.Stephenson, it is said, took several hints from Golds- And so it was that all these interestsof illicit distillers were worthy Gurney in respect of steam boilers combined together to pass through Parlia-plyingtheirunlawful for high and maintained steam pressures, ment certainActs which,by way ofactivities in the neigh- and,doubtless, many another inventor imposing extortionate and numerous roadbourhoodofStirling. became similarly indebted to this nowadays tolls, made it quite impossible for the roadThey erected their plant little-known Cornish engineer. carriages of Gurney or anyone else to carryin a lonely part of the Goldsworthy Gurney died in Cornwall, on with any commercial measure of success.estateoftheSouth the land of his birth, in March, 1875, at the Steam carriages and, indeed, all forms ofSauchieColliery,near ripe age of 82. He had lived a retired life mechanically -propelled vehicles were drivenStirling town.For a considerable periodfor some time, but to the last day of his off the English roads until, towards the endthis" whiskygang "operated secretlyexistence he evinced an amazingly keen of the century, the invention of the internal-andsuccessfully,butonedaytheirinterest in all things mechanical. combustion engine and its adaptation tostillboiledover,thealcoholvapours- What judgment posterity will accord to a road -vehicle resulted in the rise of thecaught fire, and the burning liquor flowedthe life and inventions of Sir Goldsworthy modern motor car and the rapid removalin a stream down into the colliery workings.Gurney is difficult to prophesy. The earlier of the various Parliamentary Acts whichHere it met with fire damp. An explosionportion of his career is, of course, the one for more than sixty years had kept allresulted, the illicit distillers flew from thewhich most entitles him to a niche in the power -propelled vehicles off the highwaysplace. and the result was that the collieryFfall of Engineering Fame. of Britain. Disappointedas Goldsworthy Gurney undoubtedly was at the eventual lack of commercialsuccessofhissteam road vehicles, their failure did not break him. He ceased to construct steam engines at his own expense in1832, although for some years afterwards he made efforts to float a public company for the construction and operation of such vehicles. This project failed, however, as, also, did the efforts which Gurney made to bring together a " ring " or association of contemporary road -vehicle inventors and steam -carriage proprietors, as, for example, the renowned Walter Hancock, who ran steam carriages in London, Francis Maceroni, the Manches- ter -born Italian who operated mechanically - propelled vehiclesin the East End of London and many others.Gurney even made petitions to Parliament on behalf of his inventions, but the forces, opinions and interests of his day were entirely against him, and, so far as his road -locomotive activities were concerned, little else than unbelief and bitter opposition greeted his efforts at every turn. Another contemporary steam coach November, 1939 NEWNES PRACTICAL MECHANICS 61 SOFT SOLDERING HINTS A Practical Article on the Elementary Principles THIN STRIPS OF ZINC of Soldering DROPPED INTO ACID lamp bodies and petrol pipes, which arejob carrying off the heat when the iron is " tinned " before soldering. applied. The larger the iron the better, as Don't try to solder chromium plating, asit must hold more heat,also repeated it cannot be done. The chromium must beapplication of a small iron means that the applied heat is flowing away whilst the second heat is being added. Hold the iron still when once applied and watch the effect PIPE SOLDERING of the molten solder around it. The solder HYDROCHLORIC IRON cannot be rubbed in-it must flow of its ACID own accord. Solder has little strength as a metal, therefore always remember it as the " glue " that holds the work together only. SOLDER Piling it on the job in the hope that it will FILLET - overcome the difficulty or your poor work- manship is no use and only failure will result. Suppose a nipple is to be soldered on a NIPPLE copper pipe :first, the end of the pipe must be clean and really fit the nipple. The pipe WOODEN should just slide into the nipple with slight Fig. 1 .-Chloride of zinc can be made by dissolving BLOCK pressure. Dip the end of the pipe into the strips of zinc in hydrochloric acid. A porcelain liquid flux and apply some solder with the vessel should, for preference, be used hot iron. It will now be " tinned " and will have cooled off somewhat. Again clip the OLDERING is an easy process if one is end in the flux and tap on the nipple. This skilled to the rules, but even so-called " tinned " end will act as a small iron and decent mechanics fail hopelessly on save the trouble of having to " tin " the many soldering jobs.Cleanliness is the Fig. 2.-The correct method of soldering a nipple small interior of the nipple. Hold the pipe great thing, but not more important than a to a pipe vertically on a piece of wood with one hand hot " iron and the right' flux."It is and apply the iron with the other hand. natural that the parts to be united shouldremoved before the solder will take, what-As the iron has again been charged with be clean, and unreasonable to expect hotever the flux. Aluminium is only success-solder, it flows from the iron on to the pipe, fluxtoremoverefractoryfully soldered by the professional, and thenwhere it is already tinned, and so passes solderand with special solder and flux. It is not easy,down between the nipple and pipe. material whose melting point is above thatand is often unsatisfactory. An excellent of the iron or at once oxidises when heated. A Bad Joint Oxygen is the enemy of all forms ofpreparation based on zincchloride isa uniting metals, as nearly all metals absorbgood solderingfluid.Itisbetter and Should the pipe have been a bad fit in the oxygen readily on the temperature being nipple, the hot solder will not only have raised, and it is to protect the metals from penetrated between the pipe and nipple, being oxidised that fluxes are used. An POINTS TO REMEMBER but up the inside of the pipe also, not being excellent flux for one metal is not so effective Make sure that you are using the able to run out at the bottom on account of on another, or for some reason cannot be right flux. the wood acting as a washer. Should this used owing to after effects which cannot happen, the pipe must be drilled and the be eliminated. As an instance, acid fluxes Chloride of zinc, resin, Fluxite and shavings from the drill blown out.If too must not be used on electrical connections. Baker's Fluid are the main fluxes. much solder is applied, it is possible to wipe The electrical flow sets up some form of it off before cooling, but it leads to " blobs," electrolysis definitely aided by the minute where they are not wanted, such as on the imprisoned particles of acid, which particles Many failures are due to the iron cone of the nipple, and perhaps a leaky are never entirely removed, however efficient cooling off before it can 4o any effective union. With practice, the right quantity the washing of the part in question. work. of solder can be gauged, and if not enough, the iron can, in this instance, be applied The Main Fluxes Always keep the iron well "tinned." again the second time, such process doubly Chloride of zinc, resin, and Fluxite are the assuring a tight soldered joint. main fluxes used on repairs.The former A patch on a tank is also an excellent is a liquid and resinis used powdered.cleaner than the home-made product andexample of heat transmission by the solder- The easiest way to make up chloride of zincequally as cheap in the long run. ing iron. As usuaL,clean the place on the is to dissolve thin strips of zinc in commer- Resinisa difficultflux atall times,tank thoroughly and " tin " the place to be cial hydrochloric acid. Do this slowly in antherefore Fluxite (a paste) is far better open porcelain basin until the acid will nofor general use in every way, and is men- longer " act " on the zinc. When cool, thetioned because it is based on resin and is TANK UNDER solution is ready for use, and it should notideal for all electrical joints. REPAIR be adulterated with water.The action of this flux not only helps to clean the job, butWhen the Iron Cools the moment the hot iron touchesit,it Many failures are due to the iron cooling entirely covers the spot without furtheroff before it can do any effective work, the trouble. When cold, it rests on the surface in isolated globules, but the heating trans- forms it into a liquid coating, thus excluding ------oxygen from the air, that is unless the heat is too great and the flux is evaporated. As an iron too cold will not run the solder, so , - - - an iron too hot will counter the effect of PATCH the flux. A small iron over -heated will not, and cannot, take the place of a larger iron which, if anything,is on the cold side. Fig. 4.-When soldering two wires together, an Fig. 3.-When patching a tank make sure that This flux is used on all tinned goods and efficient joint can be made by using sleeving both sides of the patch are "tinned," thus ensuring articles,such as petrol tanks, autovacs, over the two ends as shown an efficient job 62 NEWNES PRACTICAL MECHANICS November, 1939 operated upon about half an inch all round FLUXES FOR SOLDERING the patch to be applied.The patch should be tinned both sides, as the hot solder on Metals Fluxes Fluxes generally used the outside helps to convey the heat from the iron to the patch proper, and so to the Iron Chloride of Zinc Chloride of zinc (killed solder under the patch.The hot iron, Steel Sal -ammoniac spirit) supplied with solder, should be slowly and Copper Chloride of zinc systematically moved over the whole of the Brass Resin patch so that it sticks to the tank at every Sal -ammoniac Resin point, and towards the end the ironis Zinc (new) Chloride of zinc applied to the edges, when, if there is still Zinc (old) any air under the patch, it will be seen to Lead (with fine solder) Hydrochloric acid bubble out through the molten solder. The Lead (with coarse solder) Tallow and resin iron should only be applied to the edges Tin Tallow last of all, mainly to Make a neat job and to Pewter Resin and sweet oil prove the exclusion of all air.Again, the largestironpossibleshouldbeused, COMPOSITION OF SOFT SOLDERS especially as it is not always possible to do the job with one application. Solder Composition Melting point

Electrical Repairs - Fine 1/ parts tin, 1 part lead 334°F. In dealing with all electrical repairs, it is ., 370°F. Tinman's 1 -part tin, 1 part lead _ again pointed out that Fluxite or resin must Plumber's 1 part tin, 2 parts lead 440°F. be used and it is preferable to keep a special Pewterer's 1 part tin, 1 part lead, and 2 parts bismuth 203°F. iron for such repairs. An iron continuously dipped in the liquid flux is bound to impart A mixture of 1parts tin and 1 part lead fuses at a lower temperature than any other some. of the acid to the electrical joint,mixed proportion of these metals. eventually leading to trouble.Smear a little Fluxite on the parts to be soldered, as COMPOSITIONS OF HARD SOLDERS too much is not only a waste, but the surplus paste has a tendency to mess up the nearby Solder Composition insulation.Cleanliness here is a definite injunction, as the Fluxite has no cleansing Hard brazing 3 parts copper, 1 part zinc powers like the fluid, and old wires that Hard brazing 1 part copper, 1 part zinc have become blackened through burned Softer brazing" 4 parts copper, 3 parts zinc, and 1 part tin solder must be cleaned with fine emery cloth until they are bright.Dipping the WOOD'S METAL wires in nitric acid is fatal for the same A special soft solder used for joining delicate pieces.It consists of 1 part tin, 4 parts reason mentioned with the liquid flux. bismuth, 1 part cadmium, and 2 parts lead. It melts at about 60 degrees C. A spliced joint is out of the question owing to the confines of the space allotted,the inside of the sleeve and between thepiece of rag.The iron is now " tinned " also a sleeve -joint is far more efficient fromstranded wires. and ready for use, but thereis another an electrical point of view and occupies less method which is equally as good, and that space. Fig. 4 shows the sleeve, bored out so" Tinning " the Iron is to have a small piece of tinned steel on that the prepared wires just slide into the To " tin " an iron with either acid orthe bench on which to rub the iron instead hole. The ends of the wires will be seen atFluxite, the bit should be cleaned up with aof wiping it with the rag.Both methods the centre of the sleeve, where a slat hasfile until the copper is bright. Heat it onapply to both fluxes.When the ironis been filed so that the hot solder can bethe gas -ring until the copper is about to" tinned," it should still be carefully heated, applied. Place a little Fluxite on the centrechange colour and rub with a stick of solderas a " burned " iron ruins the tin on the of the sleeve where the wires meet, andwhich 'has previously been dipped in thesurface, turning it into a very brittle dark immediately the hot iron and solderisflux.Apply it quickly to all sides, after-mass that will neither convey heat nor hbld introduced, the Fluxite will run freely alongwards wiping the solder over evenly with athe solder. Two Useful Soldering Hints solder into the bole, and it will be found A Workshop Wrinkle that the solder will run down the groove IF when making a soldering joint, difficultyinto the hole. Iis experienced in making the solder run into the seam, the following tip may prove useful. Clamp the bit in the vice, and drillA Soldering Blow -Pipe a shallow 1 in. hole in the middle of the7HE accompanyingsketchshowsa iron. Now, with a three -cornered file make Isoldering blow -pipe constructed from a a groove from the hole to the tip of the irongas bracket. The nipple ends, on the gas and as shown. air tubes, were formed by hammering, the When using the iron, place the stick oftubes being supported on a hollow block duringtheprocess. Whensufficiently reduced, the tube ends are reamered to size, the orifice of the gas -nipple being 18 in. diameter, and that of the air -nipple in. diameter.Flexible tubes connect the gas

WORKSHOP CALCULATIONS TABLES AND FORMULIE by F. J. CAMM Details of the blow -pipe A handbook dealing with methods of calculation, solution to workshop problems, and the rules and formulw necessary in various workshop processes. and air tubes to their respective sources of It contains all the information a mechanic normally soft -solderingcan be A useful requires supply. While soldering executed by blowing the flame with the hint From allbooksellers,3;6net, mouth, brazing requires the use of foot - by post 3/9 from the publisher : bellows. When the air supply is derived GEORGE NEWNES 'LTD.(BookDept.), from bellows; a cock fitted to the air tube Tower House, Southampton St., London, W.C.2 will give better regulation of the flame. November, 1939 NEWNES PRACTICAL MECHANICS 63 A DICTIONARY OF Metalsand Their Alloys What this Dictionary Aims At The reader who uses this present dictionary, however, can rely THE history of civilisation, and certainly that of industry, upon having at hand a mass of modern information on the subject follows closely upon the history of metals and their alloys. of metals and their alloys.Whilst the dictionary is no high-flown Our modern age, both in peace and in wartime, is, without a compilation got together for the benefit of advanced students, the doubt, a metallurgical age, an era whose multifarious activities information which it contains will be found of use to even the work- are based to a very large extent upon the production and usage of ing scientist. various types and combinations of metals. It is a remarkable fact that an alphabetical dictionary of metals Yet, although metals have been known and used since history and alloys has never before been published in this present form. began to be recorded, it is a strange and significant fact that it is Many treatises and handbooks on descriptive metallurgy are only within the last fifty years or so that the science of metallurgyavailable, but not one of them is arranged in such a manner as to has arisen.Formerly, the common metals were smelted fromgive straightforward information with the least possible amount their ores by rule of thumb methods which had been known for of trouble. hundreds, and in some cases for thousands, of years, and the few This dictionary, therefore, aims at meeting this need.Its alloys which were of any practical import were, in like manner, object is to enable the busy and mechanically minded reader of produced by haphazard methods. " Practical Mechanics " to put his finger at once on the information Necessity, however, is well known as the mother of indention, he requires.Information which, for the purpose in view, is useless and it was virtually necessity coupled with the rise of applied has been rigorously excluded from this dictionary in order to keep science in the metal and engineering trades which was responsible it within reasonable bounds. Yet every known metal is included for the enormous development in the science of metals and theirin the dictionary and almost every type of commercial metallic alloys which has taken place since even the commencement of the alloy. present century., Many very highly specialised alloys bear no specific name, In spite of this advance, however, the science of metals and their these being simply represented by a series of code letters, as, for alloys is yet, in many respects, an infantile one.By no means example,'P.66/7 alloy."Such alloys have been omitted from have we penetrated anything like completely into the inner secrets this present compilation, but in all cases the general type of alloy of the metals. We do not kiaow exactly why the alloy produced by to which they belong has invariably been included. Thus, mention the admixture of two or three simple metals may exhibit chdrac- is made of the famous " R.R." alloys, yet their various " Code - teristics astonishingly different from any of the constituent metals. number " alloys have necessarily had to be excluded in view of Neither do we know why a variation of as little as a tenth of one their great numbers. per cent. in the composition of steel may create an amazing differ- Sometimes, also, the reader may note that the percentages of ence in the characteristics and properties of the resulting metal. the constituents of an alloy do not- add up to one hundred.In Metals, in fact, are still, in many respects, a mystery to us, andall such cases, the difference must be ascribed to the presence of much of the information which we have garnered about them is impurities which, usually accompany the alloying ingredients and still of the rule of thumb kind. which are not readily got rid of. Nevertheless, slowly but surely the science of metallurgy is The dictionary is adequately cross-referenced.It is, in fact, a creeping on, making new discoveries, nibbling away at the innerhandy and straightforward compilation of salient and useful facts mysteries of metals, so that, in the time to come, we may look for- regarding all the known metals and nearly all the known com- ward to an age in which metals of strength and properties very mercial alloys, and, as such it is presented to the reader in the different from those of our present time are known and widely hope that it will long remain a quick -reference compilation of used. practical use, instruction and interest. Abyssinian Gold. -See Talmi gold. approximate composition: Copper, 4.0; LIST OF ABBREVIATIONS Acid Bronze. -An acid -resisting alloy, some- The following abbreviations are used throffi.hont magnesium, 0.5; manganese, 0.5; silicon, times used for mine pumps. Composition : this Dictionary : 0.6 per cent -remainder aluminium.Is Nickel,1.50;lead,17 ;copper,73.5 ; At. No. ... Atomic Number hard and possesses a tensile strength of At. Wt. ... Atcmic Weight tin, 8 per cent. M.P. ...Melting Point between 25 and 35 tons/sq. in. Actinium. -A radio -active metallic element. B.P. ...Boiling Point Aldebaranium.-A name forYtterbium, Chemical symbol, Ac ; At. No. 89 ; At. Wt. Sp. 1;vay. ...Specific Gravity proposed by Auer von Welsbach in 1906. Sp. Ht. Specific Heat 227 (7)..Discovered by Debierne in 1899 Coef. Ex p. ... Coefficient of Expansion It is now obsolete. in uranium residues.Littleis known Therm. Coml. ...Thermal conductivity Aldrey.-A modern aluminium -magnesium - about it but it is apparently intermediate Elec. Cond...... Electrical conductivity silicon alloy.Composition : Magnesium, in properties between calcium and lan- 0.5;silicon,0.6 percent. -remainder thanum. Aluminium -magnesium alloys and aluminium. In this alloy, the magnesium Admiralty Gunmetal. -A bronze having the aluminium -copper -silicon alloys are and silicon act as hardeners.The alloy composition :Copper, 88 ;tin, 10; zinc, particularly susceptible to age hardening. can be heat -treated.Tensile strength, 2 per cent.Has a tensile strength ofAgeing. -Metallurgical term referring to the 20-22 tons/sq. in. 19 tons/sq. in. improvementincharacteristicswhichAlfenide Metal. -Composition: Copper, 60; Aeral.-An alwninium alloy of the com- some alloys undergo, particularly those zinc, 30; nickel, 10 parts; plus traces of position :Copper, 3.5 ; magnesium, 1.8 ; of aluminium, after they have been kept iron. Similarto Albatametal. Is silicon, 0.6; cadmium, 2.25 per cent - for some time. It is a process of metallic resistant to dilute acids. remainder aluminium.Tensile strength maturing. Alferium.-A French aluminium alloy used approximately 30 tons/sq. in. Aich's Metal. -Average composition : Cop- inaeroconstruction. Composition : Aerolite.-A light aluminium alloy of com- per, 60.66 ;zinc, 36.58 ;tin, 1.02 ;iron, Copper, 2.5 ; magnesium, 0.6 ; manganese, plex proportions.Composition : Alumin- 1.74 per cent. It is hard and tough, and, 0.5 ;silicon,0.3 percent. -remainder ium, 91.93;zinc,0.12 ;silicon,0.45; being resistant to sea -water, has been aluminium. Tensilestrengthabout iron,0.97 ;copper,1.15 ;magnesium, used as a sheathing metal forship's 30 tons/sq. in. 0.38 per cent.Specific gravity, 2.74. bottoms. It has a golden colour. Alger Metal., -A tin -antimony alloy.Com- Aeron.-A modern aluminium alloy con-Air -hardened Steels. -These are alloy steels position: Tin, 90; antimony, 10 per cent. taining 4 per cent. of copper and 1 per in which a certain degree of hardness hasAlgiers Metal. -A tin -antimony alloy, little cent. of silicon.Is hard and strong. been induced merely by air-cooling under used nowadays.Composition: Tin, 90; . Can be heat -treated, in which state it will controlled conditions. antimony, 10 per cent.Sometimes con- develop a tensile strength of 25 tons/Ajax Metal. -An anti -friction bearing metal. tains copper, also.It is white and takes a sq. in. Composition : Copper, 87.24 ; tin, 10.98 ; good polish. Afinide.-French jewellery metal composed lead,7.27 ;arsenic(orphosphorus),Alkali Metals. -This well-known family of of nickel or German silver. 0.37 Parts. .1The arsenic or phosphorus metallic elements comprises the following Age Hardening. -The property which cer- acts as a hardening agent. members :Lithium, sodium, potassium, tainalloyspossessofautomaticallyAlbata Metal. -Composition :Copper, 40; rubidium, caesium.The name was so hardening themselves when left for a zinc, 32 ; nickel, 8 parts. given on account of the strongly alkaline few days at ordinary temperatures afterAlclad.-A metal consisting of duralumin nature of the compounds (particularly the having been quelched in water. Changes with a coat of pure aluminium rolled on. hydroxides)of thesemetals,as,for in the grain structure of such alloys It has good corrosion resistance. example, caustic soda (sodium hydroxide). underlie this phenomenon. Aldal.-An aluminium alloy of the followingAlkalineEarthMetals. -Thesearethe 64 NEWNES PRACTICAL MECHANICS November, 1939

metals, calcium, strontium and barium- silicon.It is ductile and fine-grained, and tendto formblowholes.Aluminium. so-called because they are derived from has a silvery -white colour. however, removes these oxides and so " earths " (such as lime) which are alkalineAludur.-A modern aluminium alloy con- contributes to the homogen-ity and result- in nature. taining 0.6 per cent. of magnesium and ing strength of the steel. Allan's Metal.-A copper -lead alloy (or so- 0.88 per cent. of silicon.Itisheat - Aluminium steels werefirstinvesti- called " tin -free " bronze).Composition: treatable and has a tensile strength of gated by Sir Robert Hadfield in 1890. Copper, 55; lead, 45 per cent.Used for 20 tons/sq. in. With steel containing, say, 0.2 per cent. Diesel engine piston rings. Alumel.-A nickel alloy used in electrical of carbon, aluminium may be added in Allautal.-This consists of the aluminium thermometersand thermo-j unctions. amounts up to 5 percent.without alloy, " Lautal," having a coat of pure Composition: Nickel, 94; aluminium, 2; influencingthetensilestrength.The aluminium rolled on to it.It is corrosion silicon, 1; manganese, 2.5 per cent. brittleness of the steel, however, increases resistant. Aluminac-AnalloysimilartoAlpax, with more than 2 per cent. of alloyed Alloy.-A mixture and/or combination of which see. aluminium. two or more metals forming an apparentlyAluminium. --Metallic element.Chemical There is a curious alloy formed with homogeneous mass.Alloys can be pro- symbol. Al; At. No. 13; At. Wt. 27; iron and about 17 per cent. of aluminium. duced by the simple admixture of the M.P. 657°C. ;B.P. 1,800`C. ;Sp. Gray.' This is non-magnetic and heat -resisting. molten metals, by the smelting of mixed 2.58 ; Sp. Ht. .2253 ; Coef. Exp. .002313;Aluminised Yellow Brass.-A variety of ores, by electrolytic methods or by the Therm Cond. (Silver= 100) 31.33; Elec. brass containing up to 1 per cent. of compression of mixed metallic powders. Cond. at 0°C..(Mercury= 1) 20.97. aluminium. When aluminium is added in Alloys containing mercury arecalled Chief ores : Bauxite, Cryolite and the small quantity to a brass, the zinc con- amalgams. various Felspars. Is a constituent of all tent of the latter can be higher than when When metalsarealloyedtogether clays.Firstisolatedin1828 by F. the aluminium is not added, thus making they (a) dissolve in each other in any Wohler.Given its name by H. Davy for a light-coloured brass. The following proportions but without actual chemical from the Latin, alumen, alum, on account is an aluminised yellow brass made for combination; or (b) chemically combine of its presence in the various alums. saddlery and harness purposes :Copper, with one another, such resulting com- Owing to difficulties in manufacture, the 55.25; zinc, 41.25; lead, 3; aluminium. pounds in some cases dissolving in the metal was not commercially marketed 0.5 parts. excess of pure metal present; or(c) until about 1887. Aluminum.-The American rendering (pro- dissolvein one another to a limited Aluminiumisabluish -whitemetal nounced " a-loo-mi-num ") of our word extent; or (d) remain undissolved in one capable of taking a high polish. Exposed " aluminium."It is, perhaps, the more another, in which latter case they will to air,it becomes covered with a fine logical word, since it more clearly indi- tend to separate out in layers when the filmofoxide.By suitableelectro- cates the fact that the metal is a con- metal cools. chemical treatment it may be " anodised " stituent of alum. The general effect 'of alloying metals or coated with an artificially-prOducedAlumium.-An early name for aluminium together is to lower the melting point and film of aluminium oxide, A1503, of great suggested by Sir Humphry Davy in 1807. conductivity, increase the hardnesa, and tenacity and fineness. This film may thenAmalgam.-The name given to a solution sometimes the strength of the metal. bedyed,thus imparting acoloured of a metal in mercury or to an alloy of Colour changes often are brought about surfacetothemetal.Aluminiumis mercury with one or more metals. Most by alloying, and in many other ways, the fairly ductile And malleable, particularly metals will form an amalgam with mer- propertieff of the alloying metals are pro- above100°C. At 530°C.themetal cury, and often, as in the case of sodium - foundly modified in the resultant alloys. becomes so brittle that it can be powdered. and potassium,theamalgamationis (The word " alloy " is considered to be When ignited at high temperaturesit accompanied by considerable rise of tem- derived from the Latin, alligo, to bind burnsbrilliantly,an extremelyhigh perature.In otherinstances,as,for together.) temperature being attained. Upon this example, in the preparation of tin amal- Alloy Steels.-These are, varieties of steel fact is based the principle of " Thermite " gam, thereisan absorption of heat containing considerable percentages of welding. The metal is electrically posi- during the process of amalgamation. - other metals, such as tungsten, chromium, tive.It disolves in many acids and also Amalgams are much used in modern nickel, manganese, etc., which have been in solutions of caustic soda and potash. industry and arts, as, for instance, in the added for the sake of increasing the Owing to its tendency to forth and retain extraction of gold and for the filling of hardness, strength or corrosion -resistance an oxide coating, the metal is difficult teeth. of the metal, or for some other special to solder. Aluminium forms a largeAmerican Gold.-American standard gold purpose. Such steels are also known as series of alloys with other metals, many as used for 'coinage purposes contained Special Steels." They are detailed under of which are nowadays of the greatest 90 per cent. of gold and 10 per cent. of their individual names. importance. Castaluminiumhasa copper, thus being slightly harder than Alluvial Gold.-Gold obtained from sands, tensile strength of about 5 tons'sq. in ; the English standard gold on account of _ gravels and grits occurring on the beds when rolled. of about 12 tons/sq. in. its increased copper content. of ancient streams.The gold in suchAluminium Amalgam.-This is prepared byAmerican Nickel-Silver.-An old alloy.It localities usually takes the form of small adding fine aluminium filing to a half per contained : Iron, 1 ; cobalt, 1; silver, 2; scales or rounded grains, and is known cent. solution of mercuric chloride for tin, 2; manganese, 4; nickel, 24; zinc, 36; to the miners as " gold dust." two or three minutes, and afterwards copper, 96 parts. Almag.-An aluminium alloy.Composi- washing the product with alcoholorAmmonium Amalgam.-When a quantity tion: Copper,2.5;magnesium.0.7 ; spirits.The resulting amalgam decom- of sodium amalgam is thrown into a dish silicon, 0.6 per cent., remainder alumi- ooscs water at ordinary temperatures. containing a fairly strong solution of nium.Tensile strength about 25 tons liberating a steady stream of hydrogen gas. ammonium chloride_ (sal ammoniac), the sq. in.Is very hard and enduring. Aluminium Brass.-A variety of copper - mercury swells up enormously intoa Almasilium.-A modern aluminium alloy aluminium alloys containing up to 5 per metallic -looking, soft, sponge -like mass. of French origin. Contains i Magnesium, cent.of aluminium.Uses similarto This is often called " ammonium amal- 1.0;silicon,2.0per cent.-remainder those of aluminium bronze. gam," and it has been thought to consist aluminium.Canbeheat -treated andAluminium Bronze.-A classof copper - of a true amalgam of mercury with the hasconsiderablehardness. Tensile aluminium alloys containing from 5 to " ammonium " group or radicalNH.). strength about 22 tons/sq. in. 11 per cent. of aluminium.They are It is now believed to comprise ',rely Almelec.-A recent aluminium alloy con- chiefly of use in circumstances in which mercury, which is inflated by hydrogen taining magnesium (0.7 per cent.) and it is necessary to increase the oxidation gas, for, after a few minutes, the mass silicon (0.5 per cent.) as hardening agents. resistance of the metal. They have ten- sinksdownagain,leavingmetallic Tensile strength about 20 tons/sq. in. sile strengths up to 38 tons,'sq. in. mercury at the bottom of the dish. Alnico.-An aluminium -nickel -cobalt steelAluminium -Chromium Alloy.-AlloyedAmorphous Antimony.-A black powder usedformaking permanent magnets with chromium. aluminium forms beauti- produced by the electrolysis of a solution and magnet cores.It offers a maximum fulneedle -likecrystals.The alloy -is of tartar emetic in antimony trichloride. amount of magnetic energy per unit brittle, however, and has no commercial It consists of metallic antimony mixed mass of metal and, in this respect, con- applications. with from. 4 to 12 per cent. of antimony stitutesagreat advance on the oldAluminium Gold.-A peculiar alloy having trichloride. magnet steels.Composition :Steel. 604 an intense ruby -red colour. Composition : Amorphous antimony is unstable, and aluminium, l0; nickel, 20; cobalt, 10 per Aluminium. 22; gold, 78 per cent.M.P. will return to the more usual crystalline cent. 1,060°C. form of antimony with explosive violence Alpax.-An aluminium -silicon alloy, origi-Aluminium Steel.-Aluminium is not usu- when merely scratched or given a slight nally invented by Aladar Pacz,after ally alloyed with steel in order to form a blow. On this account, it is often known whom it is named.It contains 87 per special alloy, but in view of its deoxidising as " explosive antimony." cent. of aluminium and 13 per cent. of powers.Dissolved oxides in molten steel (To be continued) November, 1939 NEWNES PRACTICAL MECHANICS 65 The Kiel Canal in Peace Time

The great lock, Brunsbuttel standpoint a voyage through then In Kiel Bay. canal is very interesting. Whensailingtherefrom IN peace time the Kiel Canal England I entered the canal at was a very importanten- the western entrance. This is gineering achievement Brunsbuttel. Harbour with four worthy of comparison in size, huge locks, in one of which but not in usefulness, with such our small steamer seemed com- great ship canals as Suez and pletely lost like a doll in a swim- Panama. When war broke out ming -pool. The locksare it was instantly transformed into necessarybecausethereisa a strategic waterwayof the variation in tidelevel at the utmost importance. During the west end of ten feet, but as the Great War it almost doubled Baltic is practically tideless the the strength of theso-called Coming out of Brunsbuttel Lock into the canal maximum variationthereis German " High Seas " Fleet, by only 1.7 feet, and this is due to offering a safe refuge with exits wind.It is thought that if our on two seas.Our cartoonists By G. Long, F.R.G.S. gallant airmen could destroy the dubbed it the " Kiel Kennel " lock gates at both ends just and 15ved to picture it as an elongated funk -this the Suez Canal shortens the journeybefore a high tide with a western gale, there hole in which a frightened daschund wasfrom England to India by six thousandis a chance that the rush of water through cowering. It is highly probable that itmiles. The Panama Canal shows even morethe canal might sweep the whole German will assume still greater importance in thestriking results.The voyage from NewFleet out of its funk -hole once and for all. present struggle. York to San Franciscoisshortened by It is very significant that the Germans5,262miles,and from New York toThe Canal Approach did not begin the Great War until theGuayaquil by 7,405 miles.Some other The approach to the canal is through the widening and deepening of this canal hadcomparisons may be of interest.The Kielnarrow channel of the River Elbe for fifteen beencompleted. The datesareveryCanal is 61 miles in length. Panama is 42,miles, which makes the Canal safe from important. The canal was first built duringand Suez 104.The locks on the Kielnaval attack.The shores areflat and the years 1887 to 1895, but when completedCanal are 1,082 feet long, as against 1,000muddy, and the waterway is protected by wouldonlyaccommodatesmallcraft,at Panama.They are said to be thelow earth banks.About four miles from When the Kaiser planned to attack us, helargest in the world, and this for a canalBrunsbuttel we passed under the first of firstdecided to widen and deepen thewhose legitimate commercial traffic consistsseveral remarkable high level bridges which canal, and replace all low bridges by loftyof small coasting craft under four hundredvary between 130 and 140 feet above surface viaducts 131 to 140 feet above the water,tons ! level.At nineteen miles we passed under or by swing -bridges.This work was the Grumental high level bridge which finishedby June1914,and GermanyA Simple Job carries the road, and a single line of railway started the War in August ! The Kiel Canal was cheaper to buildacross the canal at a dizzy height.During than the others, because the job was athe whole voyage we scarcely saw a ship, Small Craft simple matter of digging a ditch at sea -but a few motor boats and sailing yachts It is interesting to observe that the smalllevel through soft soil-not rock as atwere encountered, and they-like the cyclists commercial canal as first constructed wasPanama, with a lofty mountain ridge toon the road beside the canal-all carried amply large enough to accommodate allcut through. swastika flags. the ships which desired to use it, and cost The cost of the original Kiel Canal was Five so-called sidings were passed, these only £7,800,000, but widening and deepen-£125,300 per mile, Suez cost £245,785 aare deep widenings of the canal, where two ingitforbattleshipscostoverelevenmile,andManchester£516,547. Thebig ships could pass, but were really made millions more. Actually more than half thePanama Canal was very expensive, thefor the German battleships to hide away commercial ships using the canal are smalltotal cost being $539,200,000, which at thefrom Admiral Beatty. coasting craft of four hundred tons andprogent rate of exchangeisabout one At forty miles we entered Audorf lake, under.Big ships cannot afford to use ithundred and thirty millions sterling. which is used as a turning -place for ships. at all because the saving in distance by As against this the Suez and PanamaThis is the first of a chain of small lakes using the canal is so slight.The greatestCanals, by saving shipmasters thousands ofwhich extend for about five miles.The saving on any voyage is from Hamburgmiles, are able to charge large tolls, butcountry now is more undulating and the to Bornholm, which is 250 miles by canal,Kiel can only exact small dues, and iscut of the canal passes through a number and 610 by going round the Skaw, a matterunable to increase them, or to pay ,its way.of low hills which are much prettier than of only 46 hours longer.As compared with From an engineering and mechanicalthemudflatsandmarshespreviously 66 NEWNES PRACTICALMECHANICS November, 1939 encountered. AtLevensauwe passedRemarkable Facts were surmounted in typical Hitler fashion. under another highlevelbridge, which The building of the Kiel Canal links upIn 1864 Prussia, in alliance with Austria, carries a single line of railway, and a road.with some remarkable facts in Germanmade an unprovoked attack on peaceful Three miles more brought us to the Baltichistory.The German militarists had longlittle Denmark, and stole the southern exit of the canal at Holtenau, and afterplanned its construction, as a checkmate-portion of the country.Two years later passing through the mighty locks we sailedas they believed-to theBritish navy.the robbers quarrelled and Prussia fought into the sparkling waters of Kiel Bay.But two things stood in their way, firstlyAustria, butthatis another story.There The whole voyage took about twelve hours,the line of the canal must pass throughremained the problem of British Heligo- as steamers are not allowed to travel fastDenmark, and secondly the western outletland, whose red rocks rise from the sea in case of damaging the canal banks by thewas commanded bythe-then-Britishlike a miniature Gibraltar opposite the wash from their propellers. island of Heligoland. These difficulties-approach to the Kiel Canal. A New Pattern -Makingnethod _1 Simple Method of Making Small Jlodels ivith Plasticine as the Mould- making Compound

box is removed and we have a plaster mould in two halves which will produce the original Fig. 1.-The moulded pattern made in plasticine shape.The slanting grooves at the sides will have formed corresponding projections WH EN a number of small parts ofaway so that its upper surface is level withon the top block of the plaster.All that somewhat intricate design have tothe top of the box and half the height of theremains iscarefully to drive (from the be cast in any non-ferrous alloy,plasticine pattern, as shown in Fig. 2, andinside to prevent the drill breaking through as is often the case in model making and inthe plaster is allowed to set hard and theinto the mould) a runner hole for pouring small light mechanical arid engineering jobs,pattern lifted out. the lead, and two vent holes to allow the it becomes necessary to snake a pattern. It The mould is next taken from the card=gases to escape and ensure the lead filling is advisable that the pattern should be asboard surround, carefully so that the latterthe mould. exact aspossibleinordertofacilitateis not injured, and at each side and at each We now have a plaster of paris double, machining, and in order to give a goodend a slanting half -circular groove is cutmould (Fig. 5) with side lugs which locate appearance to the finished model or machine.down from the top surface as shown inthe two halves accurately in position, and The maldrig of small wooden models isFig. 3.The top surface (which will becan weight down the top half, or clamp it delicate and a tedious process. The methodthe parting surface) and the four slantingwith a clamp, and pour the lead in to form here to be described avoids the troublesside grooves are varnished with a shellaca strong lead pattern, an exact replica of connected with such small wood working, the plasticine model, and can obtain as many and enables awkward shapes to be made as desired and send them to the foundry easily and quickly ready for the foundry for casting the part we want, in any metal moulders.The plan is to use plasticine- desired. the clay -moulding compound. The lead pattern will stand up to the The part is fashioned with the plasticine foundryman's handling, and since we can to the size and shape of the finished article, supply several and easily cast new ones if and is allowed to dry thoroughly. This they get damaged or out of shape, we have clay " pattern .",(to use the founder's term) - a means of getting as many castings as we could be used directly to make the sand want, while the supplying of several pat- mould in the foundry, but it would not Fig.3.- ternstothefoundryfacilitateswork withstand continued use. It would be frac-(Above) Details enormously when a good many of the sune tious and would also bend and become dis- of the half - pieces are required, for the. plaster mould torted with the ramming, and probablycircular grooves remains intact.The same procedure can could only be used for one casting. Tocut in the mould of course be followed whatever the first overcomethisdifficultytheplasticine Fig. 4.- pattern is made of, and since the wood is at pattern is used to make a plaster of paris (Left) The card- times awkward because of its grain making mould, from which is easily cast a lead boardbox is it friable in small intricate pieces it is often replica of the plasticine pattern, and this replaced on the an advantage to cut out a rough wooden lead replica can be used as the pattern to plaster block model with no great accuracy but of ample be sent to the foundry and from which any size. It can be used in the manner shown to amount of other pieces may be moulded get a lead casting. The lead casting should and cast in the metal intended for the job. next be trimmed with files, etc., and used as The Pattern a pattern for the foundry or as a pattern In Fig.' 1 we have a supposititious case, from which to make another plaster mould which shows the pattern moulded in plasti- as described. Thus several patterns can be cine.A box (it may be of cardboard) is made at little extra work and expense. filled to the -level of the top with soft plaster of paris, and the plasticine pattern is laid in it while soft to a depth which will bring VENT FILLING HOLE the plaster to a level a little higher than half Fig. 2.- of the depth of the pattern. The plaster is(Left) The Pat- then, when nearly set,carefully scraped tern embedded in plaster of parts CL AY PATTERN spirit varnish which dr'es quickly.The cardboard box is now replaced on the plaster block so that it reaches high up above the surface (Fig. 4).The plasticine pattern is carefully replaced in the mould shape it has made and the whole remaining space is filled with fairly liquid plaster and allowed to set. Two Halves of the Mould Fig.5.-The double mould When hard, the surrounding cardboard November, 1939 NEWNES PRACTICAL MECHANICS 67 Chemistry for Beginners No. 8.-The Chemistry of Copper. Interesting and Simply -madeCopper Compounds which can be inexpensively The apparatus for pre- ProducedinanyHome Laboratory paringcopper powder by passing hydrogen gas NEXT to iron, copper is, perhaps, the over heated copper oxide. most valuablemetalwhich we possess. It has also the distinction of being one of the oldest metals known to mankind. As anelectricalconductor, copper is, next to silver, the most efficient of all metals.In order, however, that its conducting properties be not impaired, it is necessary for the copper used for electrical purposes to be of the highest .degree of purity. Fortunately,byelectrolytical methods of production, itis not difficult commercially toobtain metallic copper containing aslittleas 0.2 per cent.of impurity.Such " electrolytic copper," as it is termed, is nowadays employed for all electrical purposes. Hence, by using pieces of scrap copper wire for the experiments describedinthisarticle,theamateur chemistcanpreparesaltsandother derivatives of copper which are almost perfectly pure. An Interesting Metal crystallise satisfactorily. Itis, however,saturated with a strong solution of copper From the standpoint of the amateurquite a simple matter to evaporate thenitrate and then warmed by holding it in chemical worker, copper is an extremelycopper nitrate solution carefully to drynessfront of a fire, the paper will often ignite interesting metal, and many easily preparedand thus to obtain the saltin a non -spontaneouslyowingtotheoxidising compounds are to be obtained fromit.crystallised condition. powers of the nitrate.Similarly, if a few Many copper compounds, also, are Copper nitrate is a very interesting salt.pieces of copper nitrate be quickly wrapped extremelyusefulsubstances. CopperA 10 per cent.solution of itin waterup in tin -foil, the latter will rapidly become exceedingly hot and, often enough, will burstintoflame,thetin -foil becoming converted into white tin oxide. Practical Experiments for the From copper nitrate to copper oxide is a very simple step.The copper nitrate is merely heated, either in a porcelain crucible or in an old can or other suitable container. Home Worker When strongly heated in this manner, the copper nitrate will give off red oxides of sulphate,forinstance,isawell-knownprovides a blue light -filter used sometimesnitrogen-by the way, these fumes are fungicide, entering into the composition ofby microscopists and photographersforfairly poisonous and should not be breathed countless horticultural compounds.Otherpassing blue light only.Copper nitrate is,-and a black residue of copper oxide will copper compounds are employed in photog-also, a powerful oxidising agent.If,forremain. raphy. Others, again, are used as pigments,instance,apieceof blotting paper be whilst, through the agency of one copper Well-known Oxides compound, artificial silk becomes possible. There are two well-known oxides of In our preparation of a series of interest- copper, cupric oxide, CuO, which is black ing copper derivatives, let us. start with one and whichisprepared as above, and of the simplest of these compounds. Obtain cuprous oxide, Cu2O, a red powder, which is a few pieces of copper wire, cut it up into usually made by adding grape sugar to an short lengths and place the pieces in an alkalinesolution of a copper salt.On open -necked bottle. Add just sufficient heating, red cuprous oxide will be pre- water to cover the copper wire and then cipitated.The same red copper oxide can pour into the bottle a few drops of nitric also be made by gently heating a mixture acid. Immediately a chemical reaction will of sodium carbonate and cuprous chloride. take place.The copper and the nitric acid To return, however, to the more common will interact, giving rise to reddish fumes- black copper oxide.This is a most useful oxides of nitrogen-which will escape from substance to have, for, using it as a starting the bottle, and a brilliant blue solution of point, a number of pure copper compounds copper nitrate will be formed.When the can be prepared without difficulty. action ceases, add a further quantity of For instance,the well-known copper nitric acid and keep adding the acid little by sulphate is readily prepared in a state of little until all or nearly all the copper has high purity by dissolving black copper dissolved. oxide in warm dilute sulphuric acid and by Now pour the blue solution into a clean evaporating the resulting blue liquor down evaporating basin and heat it with a bunsen tocrystallisingpoint. Many amateurs burner or spirit lamp or by immersing the endeavour to make copper sulphate by basin in a pan containing boiling water until dissolving metallic copper in strong sul- a thick syrupy blue liquid remains.Then phuric acid.This, however, is not a good put the flask or basin aside to cool. method. For one thing, choking fumes of sulphur dioxide are given off, and, again, Copper Nitrate Crystals copper is only soluble in hot concentrated If you are lucky, long crystals of copper sulphuric acid, forming a mixture of copper nitrate will separate out after a time, but Canvas soaked in a solution ofcopper sulphate sulphate and copper sulphide, the latter of copper nitrate is a difficult substance to isrendered rot and mould proof. which is black and whose separation from 68 NEWNES PRACTICAL MECHANICS November, 1939 the hot concentrated acid -by filtration isthe well-known greenish mineral, malachite.otherwifie the black copper sulphide, CuS difficult. Artificial crystals of malachite can be made(cupric sulphide), will be formed. Crystallised copper sulphate, CuSO4.5H20by immersing a flat piece of limestone in a possesses a beautiful blue colour.If, how-moderately dilute solution of copper nitrateSchweitzer's Reagent ever, the crystallised copper sulphate isuntil the limestone is covered with a green One of the most interesting of all copper heated just above the boiling point of waterlayer and then by immersing it for a fewcompounds isthat whichis known as for some time, the salt loses four of itsdays in a solution of sodium carbonateSchweitzer's reagent. This consists of a solution of copper hydroxide, Cu(OH)2, in loosely attached water molecules and it(or common soda) of similar strength. . becomes converted into a pale bluish -white Coppercarbonateisalsoknown asammonia. It has the remarkable property of sulphate having the formula, CuSO4.H20.verdigris, and, it is very slowly formed on thedissolving paper or cellulose.It is most If crystallised copper sulphate is heatedsurface of metallic copper when the metalconveniently prepared by adding ammonia more strongly, say at a temperature ofis exposed for prolonged periods to moist airdrop by drop to a strong solution of copper 250 deg. C., it becomes converted into ancontaining considerable quantities of carbonsulphate contained in a flask. The character- hydrous (or water -free) copper sulphate,dioxide. istic pale -blueprecipitate ofcopper CuSO4, which is a perfectly white powder. hydroxidewillbeformed.Afterthe Soluble in Acids precipitation of the copper hydroxide ceases, Water Detector Copper carbonate and copper hydroxide,the addition of the ammonia is continued. Anhydrous copper sulphate is much usedas we have noted, are completely soluble inThe liquid will then acquire a rick dark- in chemistry for detecting the presence ofacids with the formation of salts.If, forblue coloration, due to the solution of the water. Exposed to the air,itquicklyinstance, we desire to make a quantity of.copper hydroxide in the excess ammonia. absorbs water and turns blue.Added tosay, copper tartrate, all we have to do is toAt this stage, the flask should be shaken liquids such as alcohol, benzene, petrol,pour some strong tartaric acid solution intocontinuously, the ammonia being added the anhydrous copper sulphate will indicate aflask and then tn_ add either copperdrop by drop.When thelastof the the presence of theslightesttraceofhydroxide or copper carbonate a little at aprecipitatedcopper hydroxidedissolves, contained water by undergoing its remark-time. The hydroxide or carbonate willadd a few drops more of ammonia and the able colour -change from white to blue. dissolve completely (in the latter instance.preparation of Schweitzer's reagentwill It is easily possible to obtain metallicwith much effervescence and evolution ofthen be complete.Cotton wool and good copper from a solution of copper sulphate.carbon dioxidegas) and abluish -greenquality filter or blotting paper will dissolve If, for instance, a steel blade br an iron nail be plunged into a solution of copper sulphate theblade ornailwill quickly become covered with a layer of red metallic copper which can generally he scraped away very readily. The solution can also be used for electro-plating.The article to be plated forms the negative electrode of the cell, and a bare piece of copper wire the positive electrode. Connect a flashlamp battery between the two electrodes and copper will immediately begin to be deposited on the article to be plated. Copper sulphate solution is a powerful anti -fungus and anti -rot compound. Soak wood, canvas or other fabric in moderately strong copper sulphate solution and then allow it to dry out.Such material will then have highrot -resisting andanti -mould properties imparted to it. If to a solution of copper sulphate or copper nitrate, or, in fact, to any soluble salt of copper a solution of sodium hydroxide (caustic soda) is added, a pale blue pre- cipitateof copper hydroxide,Cu(OH)2, will be formed. It will be advisable for the chemistry enthusiast to prepare a quantity ofthiscopper hydroxide,because, by dissolving it in organic acids, as, for example Preparing metallic copper in powder form by passing hydrogen gas over healedcopperoxide citric, tartaric or acetic acid, the copper salts of such acids can be prepared withoutsolution of copper tartrate will result. Thein the blue liquid and, on the addition of a trouble.When adding sodium hydroxidecopper hydroxide or carbonate is added todilute acid,will be re -precipitated in a solution to the solution of copper sulphatethe tartaric acid solution until all actiongelatinous form. Such a chemical reaction ornitrateinorder topreparecopperstops and until it ceases to be dissolved.forms the basis of one of the methods of hydroxide, only add theleastpossibleThe resulting solution of copper tartrate isartificial silk production. quantity of the sodium hydroxide solutionthen poured off and crystallised by evapora- The deep -blue colour of the above liquid toeffectcompleteprecipitationof thetion. Copper acetate and copper citrate areis due to the formation of copper ammonium copperhydroxide. Ifmoresodiummadeinthe same manner, employingsulphate.If methylated spirit is added to hydroxide solution is added, itwill con-solutions of acetic and citric acids respec-the deep -blue liquid and the latter allowed taminate the precipitated copper hydroxidetively. to stand for a few hours, deep violet -blue and will prove difficult to wash out com- If to a solution of any salt of copper wecrystals of copper ammonium sulphate will pletely when thecopperhydroxideisadd aquantity' of waterglass(sodiumbe formed. These can be filtered off, washed collected by filtration. silicate)solution,abeautifulgreenishwith water containing ammonia (not with fibrous precipitate of copper silicate will bepure water, for they would dissolve in this) Copper Carbonate obtained. Copper silicate is a most enduringand -then preserved in a hermetically -sealed When copper hydroxide,Cu(OH)2,is sdbstance.It occurs in mineral form astube.The crystals of copper ammonium boiled with water it turns black, becomingEmerald Copper and as Chrysocilla. sulphate cannot be preserved otherwise, for, converted into a compound havingthe In asimilar manner,if sulphurettedin contact with air, they slowly give off supposed composition, Cu(OH)9.2CuO. hydrogen gas or a solution of ammoniumtheir ammonia and change back again into If, instead of adding sodium hydroxidesulphide be added to a solution of a coppercopper sulphate. (caustic soda) solution to a soluble coppersalt, black copper sulphide, CuS, will be salt, a solution of sodium carbonate is addedprecipitated. This is insoluble in water, butMetallic Copper copper carbonate will be precipitated. Thisdissolves in mineral acids with the evolution Metalliccopper is notsatisfactorily isagreenish -blueinsolublecompoundof the evil -smelling sulphuretted hydrogensoluble in hydrochloric acid.Therefore, having,usually, when prepared inthisgas. copper chloride cannot be prepared- by manner, the composition, CuCO3.Cu(OH)2. Another form of copper sulphide havingdissolving the metal in the acid.Copper Like copper hydroxide, copper carbonatethe formula, CIO (cuprous sulphide),is oxide, hydroxide and carbonate are all very is completely soluble in acids, and, whenformed as a grey -looking mass when coppersoluble in dilute hydrochloric acid, a deep dissolving, it evolves carbon dioxide gas. filings are heated with sulphur. The coppergreensolutionof cupricchloridebeing A form of copper carbonate constitutesfilings must be in excess over the sulphur,produced. Copper (cupric) chloride has the November, 1939 NEWNES PRACTICAL MECHANICS 69 This is FIGHTING TALK Two vitally important matters demand your attention-one is your immediate future, the other your position when peace returns. Perhaps you have lost your job and have to turn to some diffc rent kind of work. Perhaps you are faced with new duties and requirements calling for specialised knowledge. Or perhaps you are realising at last that without trained efficiency a man is badly placed in thelife oto-day.

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NAME Age ADDRESS ICS 70 NEWNES PRACTICAL MECHANICS November, 1939 No. 1 Out To -day Iii The Popular Pocket Size (31) Of all newsagents and bookstalls TO -DAY "London Opinion" appears in the popular pocket size, full of new features, highly topical, convenient to haAlle and easy to pour co -4* men and womervmon active service. INTERESTING WORK "London OpiniL- was privileged toplay for WINTER EVENINGS itspartinthe fast war.Its leading car-- Build this splendid Working Scale Model of L.M.S. 2-6-0 toonist was Etym. " MOGUL type Locomotive from our wonderful new Thomas-"Arf parts. Even a beginner can buildthis Kaiser !"-and -once set of finished again,"London Opin- Gauge "0 Live Steamer in under 30 hours with them. ion" will keep the Illustrated descriptive Booklet supplied free with each set. flag of humour flying, ... E3 17 0 reflecting the cour- COMPLETE SET age and optimism of Separate Parts can be supplied if desired. those men and worn - Send for full details of the set, M.L.12 en now engaged in the NEW Catalogue A.B.I2 " Steam Locomotives, Stationary Engines and service of their coun- Everything for the Model Constructor." Over the counter 6d. try-onthehome Post Free 8d. front and abroad. G.R.12. Gauge - 0 " Railways. 3d. We invite old friends T.T.12. LatestDevelopmentsin theGauge 03-Twin Train- of the past and Railway. 2d. youngerfriendsof Sets of Parts forBuildingModel Ships-working or waterline :he future to get a miniatures-of all kinds are described in S.12, Model Ships Catalogue. copyofthis New Price 6d. "London Opinion" and tojudgefor Let MODEL MAKING be a REAL HOBBY THIS WINTER themselves whether it is worthy of their BASSETT-LOWKE Ltd. support. London :112 High NORTHAMPTON Manchester :28 KEEPS THE FLAG OF II UMOUR FLYING Holborn, W.C.I. Corporation Street A SHEET OF BLACK PAPER Be sure YOU have it! The famous All -British TILLEY LANTERN (Burns ordinary Paraffin) =7-Tair" Light of 300 c.p. for 6 hours for Id. Mechanics and owners of small work- A TUBE OF shops, lathe sheds, observatories, etc., willfinditinvaluable for work after dark, either in or outdoors.Holds enough oilfor10 hours' use on one filling.Can be placed anywhere with absolute safety. Easy to light. Wind and Steash?jC rainproof. Strongly made instout brass. No parts to rust, corrode or get out of order. For dependability you cannot do better than get the Tilley Storm Lantern, Price 36,-. old by all good Ironmongers and Stores. if any difficulty, write to:- NEM TILLEY LAMP CO. (Dept. P.M.), HENDON, N.W.4 ECONOMICAL ANTI -GLARE Does both jobs The IDEAL HOME ENTERTAINMENT The "Homray" Projector for LAMPSHADE FOR at once! Reliablity and Efficiency You willbefar more proud of your woodwork Hand VARNENE whenit has thatfine high gloss finish which Turned Varnene gives. Model stains and Varnene never becomes A. R. P. tackywhileworking. varnishes Itsstainsinks deeply 211 into the wood leaving the Ste -Fix is the neat, clean, in one varnishtoprovide a hard gloss which will not Mains speedy way to do a strong, readily chip or scratch. lasting job.Colourless, operation Motor From Handicraft Stores, Ironmongers, Oil- Driven odourless, needingno men. Grocers, and General Dealers.In Dark heat,itis a powtrful Oak. Walnut, Mahogany, Light Oak, Ebony Model adhesive and spreads Black and Clear (Colourless) Varnish. (Universal) straight from the tube. ad., 6d. and gd. the tube. THE £3.17.6 Made by the proprietors FINER ofStephen'sInks,57 VARNENE Obtainable front Darling Stores and Photographic Dealers Aldersgate St., London, OIL VARNISH STAIN Write direct _I or illustrated list, and name of 'teases! stockist E .C.1. Tins Bd.. D- anti 1/111. HOMRAY PROJECTOR COMPANY CHISWIC K PRODUCTS LTD., LONDON.W.4. (P.M. Dept.), 46 High Pavement, Nottingham VR11,57 November, 1939 NEWNES PRACTICAL MECHANICS 71 chemicalformula,CuC12. Itcanbewhereupon the cuprous chloride will be CuO + 2H = _Cu -I- H2O crystallised from water, the crystals havingprecipitated as a white powder. (Copper oxide)(Hydrogen) (Copper) (Water) thecomposition,CuC12.2H20. When Cuprous chlorideissoluble in hydro- It is best to seal off the copper powder in crystallisedcupricchlorideisstronglychloric acid, ammonia, sal -ammoniac andtubes if it is desired to preserve the material, heated,itgives off chlorine gas and iscommon salt solutions, but its solution infor the metal in this condition does not keep converted into cuprouschloride,Cu2C2, any of these liquids cannot be kept for long,very well. Indeed, on occasions, the powder which is another well-known chloride ofexcept in a hermetically -sealed tube. Fairlytakes fire or heats -up spontaneously when copper. rapidly, these solutions absorb oxygen fromshaken about in the air.This is due to its The terms cuprous and cupric are appliedthe air, first turning brown and ultimatelyrapid oxidation and its conversion into tocopper compounds todenotetheirdepositing a greenish precipitate of coppercopper oxide. chemical composition.Copper forms twooxychloride,CuC12.3Cu0.2H20. Finely divided metals which take fire in distinct series of compounds, to which the Copper Powder this manner are sometimes called " pyro- names cuprous and cupric are given. Thus, phonic metals." Lead, for instance,is as we have already seen, there is a cuprous A most interesting substance is copperanother metal which can be prepared by oxide and a cupric oxide, a cuprous chloridepowder.This can be made by placing achemical means in the pyrophoric con- and a cupric chloride, and so on. quantity of copper oxide in a glass tubedition.Iron, again, is another such metal

METALLIC COPPER (DEPOSITED) COPPER (METALLIC)L L IC) COPPER CARBONATE

NITRIC is*'<"' ACID 0 tr COPPER SALTS Ct. (E.G. - COPPER ACETATE, COPPER NITRATE COPPER HYDROXIDE COPPER SULPHIDE ec CAUSTIC COPPER TARTRATEetc) WO °GE% SODA (BLUE) D?' 111EAT IBOILED WITH WATER COPPER SULPHIDE Po COPPER OXIDE 0 COPPER CHLORIDE - pov Co o. COPPER HYDROXIDE (CUPRIC) (BLACK) IHYDROGEN COPPER AMMONIUM HYDROCHLORIC (SCHrVEITZERS ACID AND FINELY-DIV I DED-COPPER. yJ SULPHATE METALLIC 1 Ti REAGENT) COPPER COPPER HLORIDE COs ?PER SULPHATE /R (C UPROUS) ,ry COPPER SILICATE EIEcrR°Y.sis METALLIC COPPER AIR HEAT (DEP05/ TEO)

COPPER OXYCHLORIDE COPPERAMMONIUM CHLORIDE ANHYDROUS COPPER SULPHATE

Scheme showing the manner in which a number of interesting copper compounds can be made Cuprous chloride, Cu2C12, is a compound(such as a bulb -tube) and by gently warming Copper in its powder or finely divided which differs widely from cupric chloride,it, at the same time allowing a stream ofform does not differ in any way chemically CuC12.It is best prepared by dissolvinghydrogen gas (generated by the action offrom metallic copper as itis commonly crystals of cupric chloride in strong hydro-zinc on dilute sulphuric or hydrochloricknown. Perhaps, however, thefinely chloric acid and then by adding a quantityacid) to pass over it.Slowly, the blackdivided metal is rather more active.If, of clean copper wire cuttings to the liquid.copper oxide will turn to a brick -red shade,for instance, clean copper wire is placed in a The solution is now boiled until it becomesand then to an almost golden -red hue. Theflask and strong ammonia solution poured colourless or nearly so.During the boilingreddish material in the tube is no longeron to it, the liquid will, in time, become process, the hydrogen liberated as a resultcopper oxide, but is, in fact, metallic copperblue -coloured, owing to the action of the of the action between the hydrochloric acidof an exceedingly high degree of purity.ammonia on the copper.With ordinary and the copper converts the cupric chlorideInitspreparation,thehydrogenhasmetallic copper, the action of the ammonia into the cuprous state.After the decoloris-chemically combined with the oxygen of theis very slow, but, employing finely divided ation of the liquid, the contents of the flaskcopper oxide, forming water, and leaving thecopper, the production of the blue am moniacal are poured out into a basin of cold water,copper behind :- copper solution proceeds much more rapidly.

illustration shows a useful gadget which A Chimney -Sweeping Set can very easily be made from a hardwood caster and a piece of rubber. REALLY efficientchimney -sweeping2-i in. strips from it to suit your require- Cut out a strip of the caster so that the Aset can be made out of three-ply at aments. two halves form an oval when placed cost much below that of any marketed set. A 9 in. lap should be allowed, and I in.together.Next secure a strip of rubber Obtainapieceof fif in.three-ply,bolt holes should be drilled 1in. from thewith rubber solution inside each half, and 3 ft. 6 in. or 4 ft. long, and cut a number ofends of the strips, the two holes being 6 in.finally flute the outside of the caster with a apart. Keep the drilling standard in ordergrooving chisel: to facilitate assembly. A circular brush, such as may be purchased for 6d., is secured with wire to the Details of the end of one section, andin. bolts 1 in. long device - TYPE Or (under head) are used for, coupling the BOLT strips. USeD Removing Screw Caps from Bottles -FITTING screw caps on bottles Details of the TIGHTand jars are often the cause of much waste of time and sore fingers: in most construction cases the grip or milling on the cap is in- sufficient to obtain a really firm hold. The 72 NEWNES PRACTICAL MECHANICS November, 1939

MODEL would be connected to the boiler; the upper is the exhaust. Both of these are in straight lines with ports in the valve cover -plate, in the valve and in the block on the cylinder. Steam enters through the bottom port and does its work in driving the piston from one end of the cylinder to the other ;in the meantime the valve is moved by a small crank and this expanded or exhausted steam then passes out through the upper and somewhat larger pert tothe atmosphere. Single -Acting The simplicity of the engine lies in the fact that it is single -acting.Steam drives the piston in one direction only and the weight and momentum of the flywheel is depended upon to return it ready for another power impulse. Obviously, size for size, such an engine is Fig. I.-The completed engine showing the slide -valve mechanism not so powerful, but it is easier to make a larger single -acting cylinder and valve than NEARLY fifty years ago, when I waswill know that some engines have valves ofit is to make one of half the size which is an apprentice in the workshops ofsuch a type and design that the steamdouble-acting, closed at both ends, for such one of the old telephone companies,alwaysflowsinone direction throughclosing at the end towards the crankshaft I designed and made a model steam enginevalves and ports ; that is to say, steam whichinvolves a stuffing box to make a steam - of an unusual type. Actually there was nohas done its work of driving the piston istight joint around a piston rod, a crosshead prototype driven by steam from which toexhausted back through a different portand its guides between the piston rod and copy and my model was made to follow thefrom that through which it entered.Thethe connecting rod, and a closed steam lines of a Crossley Gas Engine; the old pat-object of this arrangement is to avoid thechest to contain the slide valve, which tern, of course, in which the gas admission valve was of the sliding form. Those were, I believe, the days before the introduction of poppet and mushroom valves. Anyway the engine, by which I was inspired and The Simplicity of this Engine Lies in the Fact that it is Single - which I had seen many times at work, had a flat valve. So I set to work, made my acting.Steam drives the piston in one Direction Only and drawings and from those the foundry pat- the Weight and Momentum of the Flywheel Returns it. terns for castings. First Serious Attempt This was my firstserious attempt at model -engine making andI have oftencooling of the live steam passages by thechest must have another stuffing box around wondered how the founder managed to castlower temperature of the expanded steam.a valve rod. my bedplate, since I made the pattern ofNow I do not anticipate for a moment that Turningtoactualconstructionand exactly the same shape as the casting wasI knew at the time what I was doing, but Idetailed dimensions, I do not think that required to be.Actually, I should havethink it likely that my little model mustmuch need be said regarding these, for I put a print on the cylinder end of thehave been one of the earliest to work on thehave endeavouredto make description pattern so that the hole, which was touniflow principle. unnecessary by completeness in the draw- receive the cylinder, could be cored out. An examination of the photographs willings, of which Fig. 3 is a side elevation, Fig. But I knew nothing about cores and core -show that there are two pipes leading to the4 a plan of the whole engine, and Fig. 5 a boxes, and I suppose the good-naturedslide valve ; one, the lower, is that whichdrawing, the main object of which is to founder, recognising thatIwas but a novice, and desiring to help me, stuck a long plug in the hole that I had bored in the wood and made a simple little round core to place in the mould. Most likely he explained to me what I should have done; I do not CA Le .7..t.,.° remember, but the result was satisfactory or VICHE> for my casting was as I wanted it. /3/4 One of the first thoughts which occurred to me, after I had tested its ability to work, was that its extreme simplicity made it an excellent subject for a beginner in model - making, so from my youthful effort I have made a fresh set of drawings for the use of the reader, and these are reproduced here. Before making references to the drawings, I think that the reader would like to know what the general appearance of the engine is, and so I have taken two photographs of it, which are reproduced here in Figs. 1 and 2.They both show the slide -valve side of the engine, but are taken from opposite angles. Uniflow Principle I do not know whether my reader is familiar with the term " uniflow " in con- 4y4' nection with steam cylinders.If he is he Fig. 3.-A side elevation November, 1939 NEWNES PRACTICAL MECHANICS 73

HORIZONTAL STEAM NG11NE give the reader exact measurements for all radii in setting out the spokes and other details of the flywheel when making the foundry pattern. The Bedplate Pattern When the bedplate pattern is taken in hand, do not forget that either the cylinder

By E. W Twining end should be left solid, to be drilled and bored out to take the tube of the cylinder when the casting is received, or a print put on the pattern of the correct diameter so that the foundry -man can make a core of the same size to drop into the mould in the impression left by your print. A core -box will not be needed ; he can make a cylindrical core without a box by ramming the core sand in a piece of tube. The flywheel should be cast in soft iron which is easy to machine, but the bedplate Fig. 2.-Another view of the slide -valve mechanism must be in gunmetal because the cylinderaway with paraffin in the same manner. The cylinder cover is soldered in at the is to be soldered in by sweating with a same time as the valve -face block.The bunsen flame. Hollow Piston little disc crank which serves as an eccentric The cylinder is made from a piece of As will be inferred from Figs. 3 and 4i ; knocked on to the shaft end and made thick seamless brass tube whia will dis-the piston is hollow, of the " trunk " type ; pense with the necessity for boring it out init can, being quite small, be turned from a the lathe ; indeed, were it not for the piston,piece ofin. diameter brass rod. It has one the cylinder cover and the turning of thegroove to be filled with soft flywheel, this model could be made without'cotton packing.The crank a lathe. It will be advisable to lap the insideshaft is of steel and is built up of the cylinder, after it is soldered in theas shown in Fig. 4. The joints in order to ensure that it is truecan,if it is so desired, be and smooth and a good fit around the pistonmade by brazing instead of which may also be lapped into the cylinderriveting and in fact this will, after it is turned. The preliminary lap canif facilities are available for be of wood, beech preferably, turned quitedoing it, make the better job, true and a nice sliding fit in the tube. Smearbutitinvolvesmakinga the lap with a little of the finest emerysplit big -end on the connect- powder in oil and work this backwards anding rod ; my own little cranks forwards with a circular or twisting motionwere not brazed, but the webs until you see the whole inner surface of thedrilled so that the shaft and tube bright, then wash the cylinder incrank pin were a good driving paraffin and, if possible, leave it, placedfit, and the ends -were just vertically in paraffin for a few days whilstlightlyrivetedover. The some other part of the engine is being made.flywheel also was a knock -on Lapping may then be completed by usingfit, the shaft being very slightly the piston itself, the abrasive being a finetapered with a dead smooth metal polish such as " Brasso." Wash thisfilein the lathe.

DIAMETGR 3%2*

SCALE Fig. 5.-Details of the flywheel cw INCHES fast by drilling and screwing in the pin which drives the valve rod. The Valve Block Details and measurements of the valve block or port face and cover plate will be .1 clear from the drawings, particularly from I Fig. 6, and I think it only necessary to 2 mention two things ; first that the nuts on two of the four studs may be placed on either diagonal and must be adjusted so t that the valve is pressed well up to both working faces but not too tightly; second, that the steam and exhaust pipes are soldered into the cover plate and the steam pipe will need a union between the engine 2 and the boiler, preferably close to the cover Fig. 4.-A plan view plate. 74 NEWNES PRACTICAL MECHANICS November, 1939 The Pulley portions as drawn in Fig. 8. The valve rod SLIDE - My own engine has no pulley uponalso of steel is rectangular in cross section ; VALVE the crank shaft but in the plan Fig. 4it can be filed up from a bit of strip and I have drawn the shaft long enough,curved as shown in the plan Fig. 4. There is beyond theflywheel, totake suchno need to fit brass ends to this. pulley, which the reader can add if he The base or block on which the engine thinks fit.Pulleys can be made byis mounted is a piece of hardwood, in my THICKtIESS casting from a pattern, or built up. Icase mahogany.To thisthebedplate .1%r --r- Yit VICK have shown the latter method becauseshould be secured with a stud and nut at / it will result in a lighter and neaterthe crank end and, immediately behind the job. The hub is turned from a piece ofcylinder, on the centre -line, by one counter- brass rod, the spokes are formed fromsunk wood screw. With regard to finish ; the rim of the fly- exhIAU,T a disc of brass plate, perforated and pint sweated with solder on the hub andwheel, pulley, crank shaft, cranks, connect- N the rim from a piece of lb -in. diametering and valve rods, should all be polished steel bicycle tubing also soldered. bright as also the gunmetal big -end and I have only dealt with STEAM NOE-. and drawnthemodel exactlyasI madeit, years ago, but I strongly recommendthereader % not to copy the diminu- wit CYLI/1DiR PORT FACE VALVE COVER PLATE tive size but to make his engine twice as large as Fig. 6.-The valve block and cover plate mine ; he will then have a model whichisnot The cycle of operations in one revolutiononly more imposing to look of the crank shaft, or as they are technicallyat but which will be useful for termed-the valve events-are set out indriving other models of machine the diagram Fig. 7, where at A the pistontools, etc.This he can., quite has nearly completed its exhaust or forwardeasily do by doubling every one stroke and the valve is just commencing toof thedimensionsgiven in open the steam ports. B shows the steamFigs. 3 to 6.But it will be port fully open with the piston nearly mid-very advisable to put -it little way in the power stroke whilst at C themore detail into one or two of stroke is almost completed and the portthe working parts.Thus the has just closed. connecting rodbig -end had In sketches D and E the exhaust port Ebetter be in two parts, made is shown, where at D the port is just aboutof gunmetal,bothseparate to open and at E has just closed. An inter-from the rod, and the main mediate sketch would, of course,havebearings be fitted with brasses. shown the crank in the position diametri- cally opposite to that at B and the exhaustChanges Recommended port fully open. Other reference letters in These alterationswillne- Fig. 7 are : V, the valve, P, the piston, MC,cessitate a little modification the main crank pin, and EC, the eccentricin the main crank measure- crank. The arrows, of course, everywhere,ments. Fig. 8showsthe indicate the direction of movement : of thewhole of the changes involved, steam, of the exhaust, of the valve and ofor recommended, in making .111 the crank shaft. /\y 5A6" -4-1' he larger model and it should 1-4- V

I;, / "

÷-716"" e '/ 't:113k's

Fig.7.-The cycle of operations in one revolution of the crank shaft brassbearings. Alltherestmay be enamelled in colours to suit individual taste. On my own model the base block, the fly- illSgr/U11111 wheel, the port face block and valve cover plate are black, the bedplate and cylinder a Q: bright blue-green ; as nearly as possible the Y colour which these parts of the Crossley Fig. 8.-Detailsgas engines are, or used to be, painted. of the connecting Sincecompletingthisarticleithas rod, crank, an.loccurred to me that a greater number of bearings young mechanics may be induced to build the engine if it were rendered possible for them to obtain the few necessary castings, already made and ready for filing up and machining; thus avoiding the necessity for be carefullynoted that inthismaking the foundry patterns. I will, if the drawing all figured dimensions applydemand warrants my doingso,make only to the double -size engine. arrangements with a supplier; providing, In both small and large models the con-of course, that the present critical war connecting rod is of steel.In the firstit isditions render it possible to get the foundry simply sweated into the brass blocks form-work done.Only the larger,or double - ing big and little ends, but in the larger thesize engine will be dealt with in this way. big end is shouldered and riveted into a All inquiries should be made through the steel plate which is bolted to the gunmetalEditor. November, 1939 NEWNES PRACTICAL MECHANICS 75 Undercarriages for Model Aircraft Although the present trend in Model Aeroplane Construction is for large models and increased speed, the drag of the landing gear has, in consequence, been considerably increased. Therefore, the undercart must be designed to overcome this drawback, and below we give a few types that have been used successfully.

TWO or three years ago, when thesome of the different types of landing gearmuch used phrase of models " settling to " slab -sided " model was universal,that have been used successfully.Firsta perfect three -pointer " no model, with the undercarriage was not consideredthere is the bamboo and wire type, which,an orthodox landing gear, ever makes a to add very much to the drag created byundoubtedly, from a point of mechanicalthree-pointlanding,but,ifproperly the rest of the machine. efficiency is one of the best ever devised.adjusted, hits the ground at its gliding ROLLED angle.Therefore, the undercart will be PAPER subjected to a backward and upward TUBE blow.There are two ways of absorbing the impact.Either by. mounting the landing gear rigidly, and thus allowing the shocks to be transmitted through the fuselage, or to use a sprung landing gear. In the case of the latter, the bamboo and wire undercart forms an excellent example. Another type of sprung undercart is shown in Fig. 2.This is a little better BAMBOO aerodynamically, than the previous type STRUT mentioned, but is usually a trifle heavier, since it has to be braced to the fuselage to prevent tearing out on extra hard landings. The type shown in Fig. 3 has good shock absorbing qualities, and generally looks Fig.1.-The bamboo and Fig. 2.-Another type of Fig. 4.-A rigid landing better than most other types, since it tends wiretypeofunder- sprung undercart gearfor lightweight to disguise that " lankiness " getrerally carriage models associatedwithdurationmodels. Its A conventional undercart on a modernIts aerodynamic efficiency, however, is, asaerodynamical faults lie, not so much in model,however,contributesamuchwill be seen from the sketch, rather poor.head resistance, as in its effect on direc- tional and lateral stability. The large side greater proportion than before, since with SHOCK the increased Wakefield weight rules, the RUBBERS area of the struts tend to draw the centre trend toward more powerful models, and of lateral area forward and downward in consequence, higher speeds, the 'drag of the centre of gravity, thus making a of the landing gear has been considerably large and higher fin necessary. increased,whilst the streamlining now Rigid Landing Gears PIVOTED TO generally employed has kept the drag of FUSELAGE For rigid landing gears, the type shown the rest of the machine comparatively low. HERE in Fig. 4 that has been' used for some The objects of an undercart are, of time on lightweight models is one of the course, to assist in the take -off and landing best. of an aircraft.Unfortunately its use in This is the ordinary single -leg bamboo these two functions is reduced to a hind- type, plugged into paper tubes.It has rance whilst the machine is_in flight. some distinct 'advantages, which account Recently,modelsemployingfolding for its popularity for contest models. It is airscrews have appeared, and so the only HARD/ light in weight, has a reasonably low drag, stage in which 'the undercarriage is an BALSA and in competition models, where dur- essential in this type is the take -off.The abilityisnot a governing factor,its ideal solution to this problem, of course, strengthisquitesufficient.Also, itfs would be to use an undercart placed simpletoconstruct,and beingeasily directly under the centre of gravity, which Fig. 3.-This type of gear has detachable,facilitatestransport. The would automatically release itself from the shock -absorbing qualities model when the latter was off the ground. struts should, of course, be a little weak, in Non -Streamlined Models order that they may break first in a very No Detachable Parts For light, non -streamlined models, thisbadknock, Unfortunately, we are prevented fromis, of course, an excellent type to use, sinceinstead of doing this by the rules laid down forit acts as a model undercart shotild; thatdamaging the various contests, which state quite clearly : fuselage. " no partof the model may becomeis, backward and upward. In spite of the Though detached during flight." And no wonder ! typical of Were it not for this rule, modellers would the types in be designing planes that not only would general use, SHOCK be releasing their undercarts, but, after "AN RUBBERnone of the power flight, throwing away their props, fourunder - rubber motors and everything not neces- carts men- sary !Plus a bit of fin area that would tioned are then not be needed !Our landing gear ideally suited therefore, has got to " stay put." We can, DURAL BALSA to a highly though, reduce the weight and drag to a TUBESY11 AIRINGstreamlined SECURED TAPERED minimum by using light materials, and TO FORMER model,and makingitwellstreamlined,oreven so we must retractable. devise one or BAMBOO However, we must not forget in this oinE two types to STRUT quest for low drag and weight that it has CORE meet our re- i Fig. 6.-An undercart to be strong enough to resist take -off and Fig. 5.-This type of undercart is suitable for quirements. which is light in weight landing forces, and so let us first examine almost any type of duration model In Fig. 5 and low in drag 76 NEWNES PRACTICAL MECHANICS November, 1939 an undercarriage which should be suit-7 a complete layout for a mechanicallyextendedposition(thismay easilybe able, not only to streamlined jobs, but forcontrolled undercart suitable for Wakefieldeffected by slipping a piece of wire through almost any type of duration model,istype models, which should not add muchwire D in place of guide C) and the model shown. It acts on the same principle as theweight, although, in fairness to the reader,made to rise off ground. With the aid of a landing gears in Figs. 1 and 3, and is con-it should be mentioned that we have not triedstop -watch, the time between the moment structed mainly from a single piece of steelout this particular mechanism in practice.of release, and when the model is in the wire (about 18 s.w.g. for Wakefield models).The Propeller Shaft correct altitude for retraction of the landing The exposed length of wire is encased Nevertheless, the design is quite simplegear, is then noted. in balsa, to prevent it from b'hnding and to ' preserve a good streamlined section.Ifand so no serious snags, are likely to beWeighted Tail the shock -rubber is made detachable atencountered. The propshaft thread should The only trouble likely to be experienced one end, it will be possible to fold the strutshave as fine a pitch as possible. A coarsehere is in the fact thatthe adjustments along the fuselage. Thia type of undercartpitch will necessitate a very long shaft,made with theundercarriage up are not has all the shock absorbing qualities of theespecially on models with a slew take -off.likely to have the same result when the bamboo and wire type, plus ,low drag andThe nut should be easy running on theundercarriage is down, since the centre of fairly light weight. shaft, and must be securely soldered to thegravity will be farther forward and the Another landing -gear which is light inwire guide C, which is of 2(1 s.w.g. steelcentre of drag lower. It should be advisable, weight and has low dragis shown inwire. The guide should be an easy slidingtherefore, to add a little weight to the tail Fig. 6.This type has been used on afit in the duralumin tube F, and in wiretemporarily, until the model assumes a good monocoque Wakefield machine with satis-loop D. glide again upon being hand launched. factory results, even though no form of Tube E is of dural or aluminium, andHaving found the approximate take -off springing (other than that of the bamboomust be braced firmly in all directions.Ittime of the model, the release mechanism is itself)isused. The bamboo struts are detachable and plug into tubes.These tubes are hollowed and shaped. from balsa blocks,whicharefirmlyboundand FOR.MER_ cemented to the bulkhead,thisbeing 1 NUT braced with a strip of hard balsa from the STOP apex of the tubes to the former in front. Wheels The wheels used on this undercart may be of interest to readers. They are made v'Sf fromfourlaminationsofjin.balsa,' grain crossing, and turned to an elliptical GUIDE "C" cross-section. One outer lamination is then

detached, and firmly glued and faired to TUBE " BALSA the end of the strut, so that the axle 4.Nogpt BRACES pierces the exact centre About a quarter of an inch of is in. birch dowel, drilled, TUBE "E" and lined with duralumin tube,is then WIRE AND TUBE zrz-1 slid on to the axle, and the end of the WIRE HINGE 1r:7 latter bent up or a small washer soldered TINPLATE STRIP on. The remaining three laminations are B SOLDERED TO then drilled so as to form a tight fit over BRASS TUBE & the dowel, the end of the hole being capped BOUND TO STRUT or filled -in with a small disc of balsa. The finished wheel is light in weight, yet quite strong, and the bearings will not wear loose, also it has a pleasing stream- BAMBOO STRIP lined appearance and adds little drag. -BETWEEN "A ft, -6 If a folding prop. is used, the weight and drag of this landing gear can be even further reduced, since it can then be placed Fig. 7.-A complete at a point farther from the nose and layout fora mechanically shorter strut used. controlled undercart THkEAD FROM suitableforWakefield The Retractable Undercarriage EACH STRUT type models A retractable chassis is no advantage TOWIRE "D" RECESS unless it c be made as 'ight as a fixed type, since the extra performance to be RETRACTING gained in reduced drag, will be lost in RUBBER added weight. Another point to remember is that the centre of drag (and centre of gravity in most types) is changed upon retraction. These two latter disadvantagesshould be of large enoughbore,whenthen adjusted to retract the chassis after do not have a serious effect, however, ifflattened to allow wire D to slip throughthe correct period. the landing gear can be made to retracteasily. .The operation is as follows.The With the adjustments found best during directly the model is off the ground, andnut is first wound right up to its stop. Then,the hand launched flights, and the under - before it has assumed a climbing angle. as the airscrew shaft rotates under thecart set to retract after the given time, the The only way of enstiring a correctlypower of the rubber motor, the nut movesmodel is then allowed to R. 0. G. timed retraction,itseems,isto use abackward and withdraws the wire guide It is now possible that the model will mechanically controlled releasing -gear offfrom tube F and finally from wire D. Thetake -off slightly quicker, thus making it the propshaft. From my experience, landingstruts are then released and will swing upnecessary to adjust the release gear to gears which are merely kept extended byinto their recesses under the pull of theoperate a little earlier (this is easily accomp- the weight of the machine against theretracting rubber. lished by slightly shortening the horizontal tension of a rubber band or spring are never The nut will now have reached or be nearportion of guide C). very satisfactory.Should the model beto the end of the shaft, and with the a Ili& In the construction, particular attention thrown momentarily off the ground (by aC will then commence to revolve. should be paid to the bamboo strut bearings. gust of wind or irregularity in the take off Test flying a model fitted with this typeMake sure that the hinge parts are firmly surface)beforeithas gainedsufficientof undercart, will call for a slightly differentbound and cemented in their respective speedto become air -borne,the under-procedure from that normally employedpositions, and that the brass tube is a smooth carriage will probably retract with disas-when testing a conventional model. Thebut not loose fit on the wire part.Also note trous results. machine should first be hand launched withthat the position of the bamboo strip be- Unfortunately, mechanisms for operatingthe landing gear retracted.All trimmingtween formers A and B allows the retracting a retractable gear, usually add considerableto get maximum climb and glide should berubber to have a straight pull. This ensures weight. However,forthose whofeelmade, and the various adjustments noted.that the struts will fit cleanly into their disposed to experiment, we show in Fig. The undercart should then be fixed in therecesses. November, 1939 NEWNES PRACTICAL MECHANICS

Fig. 1.-A vanishing la np showing how the body of the l ',II, collapses into the tray. The sha.le folds up like an umbrella.Fig. 11 (centre) Changing a care& to a handkerchief. The candle is hollow and fits closely into the metal case while the handkerchief is concealed insideit.Fig.l5.-(Right) A colour - changing candle.A metal shell representing a white candle is drawn down into the candlestick, revealing Conjuring with Lampsa red candle in its placeand Candles Interesting Secretsof Some Puzzling Featsof Magic MAKING a large lighted lamp sud-hinge and the entire lamp body collapses Finally, light for the lamp is provided in denly disappear is a performanceflat into the tray. the simplest manner possible by attaching a calculatedtosurprise any audi- Fastened to the top of this collapsiblepocket electric torch to the inside of the shade. ence. Fig. 1 shows one of the ways in whichlamp body is a square wire frame the same it can be done. size as the tray. The tray and this wireThe Cloth The lampispermanently fixedto aframe are covered with fabric of the same To perform the trick, take a large cloth square tray. The body of the lamp is con-pattern. It will thus be evident that whenof moderately opaque but not too heavy structed of hinged leaves of metal in muchthe lamp body is folded down into the traymaterial. Throw the cloth over the lamp. the same way as the folding lanterns sold forthe fabric -covered square completely hidesThe cloth should be translucent enough to Christmas decorations. In the lamp illus-it and the tray appears to be empty. permit the light of the torch to show trated the body is formed by two separate through, but not so thin as to permit the groups of metal leaves fixed one on top of the actual lamp body to be seen through it. other.When not supported these leaves R NormanHunter (TheWell-known Conjurer of " Maskelyne's 114jsteries") LOOSE SUPPORTING RESTING AGAINST Further Articles on the Secrets of ACROSS PIECE AT TP Conjuring will appear Regularly SHADE 1/ii

and Exclusively in this Journal 2 I

The Lamp Shade // This consists of a folding meat cover made on the same principle as an umbrella. The fabric is taken off the cover and replaced with bright coloured silk. A -deep fringe is added round the lower edge. The measurements of the tray are such that when the shade is opened it will fit neatly over the wire frame on top of the lamp body. The appearance of the complete lamp in this condition is shown in, Fig. 2. The lamp is held erect in its open position by a thin wooden rod attached to the inside of the lamp shade.This rod goes down inside the lamp body and props it up as shown in Fig. 3. It is only necessary to pick up the shade by the wooden knob on top to cause the rod to be pulled away and the metal body of the lamp to collapse and Fig. 3.-The wooden rod for holding the lamp in Fig. 2.-Details of the shade and tray remain hidden in the tray. an erect position 78 NEWNES PRACTICAL MECHANICS November, 1939 released the portion with the cut out spacethe handkerchief container to the front winds rapidly round thespringroller, (Fig. 8). drawing the solid part of the blind across The release of the lamp is made to coin- the tray, concealing the collapsed lamp. cide with the report of the pistol and the A small pocket lamp globe can be con-handkerchief appears to have been shot nected to a battery under the tray and astraight into the lamp. Again the dazzling switcharrangedsothatthelightis rays of the light prevent the container from extinguished as soon as the lamp starts tobeing seen, but the brightly coloured corner collapse.The vanish of the lamp is dis-of the handkerchief is quite visible. The guised by making a tipping movementhandkerchief is now drawn out of the backwards with the tray at the moment thatcontainer, coming apparently from inside the release lever is pressed. the lamp. Another sensational lamp trick consists This principle of using the dazzling light of shooting a silk handkerchief into thefrom a bare lamp to conceal an object can lamp globe.For this purpose a specialalso be employed for an effective production pistol is used, the details of which will betrick. In this case a shaded lamp is brought explained in a later article, which vanishesforward and the shade removed and shown SUPPORTING the handkerchief by winding it up on ato be empty. The shade is then replaced ROD TIED TO springinsidethe dummy barrel.The NSIDE OF and a large number of flags are produced SHADE appearance of the handkerchief, really afrom the top ofit with the lamp still duplicate, inside the electric globe is man -alight. Fig.9explains thesecret. A fairly SUPPORTING ARM large black container, open at the top, is IN HOLE THROUGH fixed behind the lamp.This container is TRAY packed with silk flags and the shade is put over lamp and load container. As long as 10411...-I the container is kept at the rear itwill throw no shadow on the shade that can be PIVOT ))seen by the audience. The shade may safely be removed, shown empty and replaced as 111 REALgSE long as the lamp, which should be a fairly Fig. 4.-The thin metal rod attached to the shade Fig. 5.-An enlarged detail of the base of the powerful one and of clear glass,is kept ..upporting rod alight. The rays of light dazzle the eyes Now, steadying the top of the lamp withaged as shown in Figs. 7 and 8.Fig. 7and completely mask the container. The one hand and with it grasping the knob ofshows a small metal container somethingshade is then replaced and the flags are the shade through the cloth, place the otherlike a pill box with a hole in the lid.Thisproduced from the container, through the hand under the cloth as though to pick up top of the shade. the lamp. Gently pull the shade upwards For the final lamp trick, here is a some- and as the lamp collapses, ease it down into what uncanny feat in which the performer the tray quietly. Move away carrying the -,..BLIND DRAWN ACROSS removes a lighted electric lamp from its cloth. The shade keeps it extended as if the WHEN RELEASED socket and it remains alight in his hands. lamp were still beneath it. Now with one He then causes the lamp, still alight, to hand switch off the light and with the other CUT OUT OPENING IN BLIND float about the stage. press the centre plug through the knob of The secret lies in the use of a specially the shade. The shade will collapse and is FREE ROLLER prepared lamp. The glass globe portion is tossed aside in the cloth.I have not given SPRING ROLLER carefully removed from a fairly large elec- details of the shade because these folding tric lamp of the pearl variety. A small square meat covers can be bought for a pocket torch battery lamp and case is then few pence almost anywhere. insertedinto the globe and fixed into A similar lamp which vanishes suddenly FURTHER LENGTH OF position with sealing wax or modelling wax without any covering is built, as far as the BLIND SOLID ON ROLLER or plastic wood. The switch of the torch body is concerned, in the same way. The should be fixed permanently in the " on shade consists of a large and small ring of Fig. 6.-The blind and roller built into the edge position and the cap at the base of the case wire with silk .sewn between. There is no of the tray may be loosened when the lamp is to be wire square on top of the lamp body, butcontainer is attached to the lamp standardextinguished. the lower ring of the shade is fastened to theby a length of wire terminating in a ring so This self-contained electric lamp is now top of the body instead. that the ordinary shade ring may be screwedput on a standard insiie a shade exactly as down over it to fix it The Base of the Lamp to the lamp holder. This lamp is supported by a thin metalThehandkerchiefis rod passing through the centre of the traytucked into the metal ;tnd up to a wire soldered across the top ringbox and agenerous of the shade as shown in Fig. 4.Fig. 5corner is left protrud- shows an enlarged detail of the base of theing. CONTAINER supporting rod. A strip of metal working At the beginning of on a pivot under the tray keeps the rod in.the trick the lamp is position. To make the lamp vanish the endalight and a shade is of the leverispressed aside by the handin position over the holding tray, the rod drops through theglobe.The container tray and the lamp collapses. is at the back of the Figs. 7 and 8.- (Left) Details In this version the collapsed lamp is hid-globe.The shade is TOP OF LAMP den by a spring blind the same colour as theremoved but owing to of the lamp trick STANDARD MAKES tray. The blind and its roller are built intothe dazzling effect of which consists of --A HALF TURN the edge of the tray. The roller on whichthe naked lamp the shooting a silk BRINGING CONTAINER the blind is wound is not a spring rollerspectators are unable handkerchief in- TO THE FRONT but simply runs free. On the opposite sidetosee the container to the lamp is a spring blind roller from which thebehind the globe. The bulb ratchet has been removed so that it willupperpartofthe revolve as soon as released. One end of thelamp standard works blind is fastened to each of these rollers.on a pivot actuated The blind is rather more than twice theby a spring. When a length of the tray and a piece almost therelease lever is pulled size of the tray is cut from the end nearestby means of a thread the spring roller.The result is shown inin the hands of an Fig. 6. The spring roller being at tension aassistant,theupper catch is arranged so that the descendingpart of the lamp makes lamp will release it. As soon as the blind isa half turn, bringing November, 1939 NEWNES PRACTICAL MECHANICS 79 if it were a genuine lamp and by tighteningThere is a white shell, made of thin metal the bap it may be lit when required.Ittube, fitting loosely over this red candle. SHADE CARRIER can of course be removed and passed fromThis shell is just the height of the candle- hand to hand while still alight. Note thatstick and when fully raised completely hides the lamp holder of the torch should bethe red candle but when allowed to drop removed and _the reflector inverted beforeinto the candlestiCk, falls right out of sight. being inserted into the electric globe, soA metal stud soldered near the bottom of the that the torch lamp projects beyond theshell slides in a slot cut the full length of the case.See Fig. 10B.Fig. 10A shows thecandlestick at the back. The change can complete self -lighting globe. thus be made from white to red or vice Causing the lamp to float about the stageversa by raising or lowering the shell while is simply a matter of a length of blackthe candle is hidden by draping a hand- cotton across the stage with an assistantkerchief over it. The shell is maintained in either side and a tiny hook on the base ofits uppermost position by giving it a slight the lamp to engage in the thread.Fullturn so that the stud rests on top of the details of this method of causing objects tocandlestick. float in the air apparently without support A neat trick of ad unusual nature is pos- will be found in a previous article of thissible with this apparatus. A small white series. silk handkerchief is laid over the red candle Fig. 11 illustrates a simple piece of appar-and the white shell raised to conceal both. atus for turning a candle into a handker-In front of the audience the candlestick is chief. The candle is a metal tube suitablyshown as containing a white candle. Over Fig. 9.-Pro- painted and plugged at one end with athis is draped a small red silk handkerchief. ducing a number piece of genuine candle.This tube fitsA dark cloth is draped over the candle for offlagsfrom snugly into another metal tube.Thisa moment and when itis removed the thetopof a second tube is polished and has a lid athandkerchief is seen to be white while the lighted lamp each end. One of these lids is shown on thecandle is red. table in the illustration.Each lidis a moderately tight fit. The candle having had a silk handker- up and down but is prevented, by a flange chief tucked inside, is put into a candlestick at the top of the candle, from coming out. and lit. To perform the change the candle is A weak spring under the little lamp keeps blown out and slid into the case, the wick it normally at the top of the tube where its end going in last. The lid is placed on and Hate is visible.A thread attached to the pressed home. When next the case is opened oil container and passing through the foot the other lid is removed, the handkerchief of the candlestick to an assistant permits taken out and the case shown empty. The the lamp, still alight, to he drawn down into hollow candle cannot be distinguished from the hollow candle, thusapparently the inside of the case. TORCH INSERTED extinguishing the candle.A fewsihall The trick can be made up in various INTO GLOBE OF holes must be drilled at the back of the forms. A cheaper method is to use a card- PEARL LAMP hollow candle near the top to allow air to board candle and a cardboard case. This is reach the flame, otherwise it will go out illustrated in Fig. 12. Note the rim at one when the lamp is drawn down. end of the case to prevent the hollow candle Another effective and very easy trick from falling out when the handkerchief is consists of lighting a whole row of candles withdrawn.Sometimes the metal candle by passing hand in front of them. TORCH WITH Apart from the candles all that is needed and case is constructed so that the candle REFLECTOR fits so closely into the case that it cannot be REV RSEQ is a fake consisting of a tiny metal tube withdrawn except by the use of a key that with a spirit soaked wick.The tube is screws like a plug into the open end of the clipped to the base of the second finger. shell (Fig. 13). The trick is usually perforMed by first Instead of changing the candle into a lighting all the candles and then blowing handkerchief thehandkerchief may be them out.After that the hand is passed vanished and found inside the candle. This Fig. 10.-Details of the self -lighting bulb along the line and the candles light again. is accomplished by using a prepared candle. The miniature wick in the fake is lit just This consists either of a genuine candle The trick is performed by drawing down.before the candles are first extinguished. It with a hole drilled down the centre tothe shell; thus biding the white candle andis then an easy matter to re -light the candles accommodate the handkerchief, or of a fakerevealing the red one. The red silk is takenby passing the open hand in front of them. candle made from two pieces of metal oraway with the covering cloth leaving theThe fact that they have only just been put cardboard tube with white paper pastedwhite one visible. out will cause them round, the two tubes joining end to end as A candle which lights itself and goes outto light again read- shown in Fig. 14.Notice that the joinagain on the command of the performer isily.If the candles is not a straight cut, but unequal. The hand-another amusing trick. The candle is againaretobelit by means of the fake kerchief having been concealed inside, thea metal tube painted white. Inside is a small RED candle is in due course broken across theoil container and wick which slides easilywithout any pre- CANDLE centre and the silk liminarylighting extracted. and extinguishing, Fig. 15 shows a candle- thecandlewicks stickforchanging the should be touched colour of a candle.The with petrol or WHITE candlestick is hollow and paraffin. SHELL

Fig. Fig.12.-The 16. - (Right)section HOLLOW shell candle and of thecandle- CANDLE- casewithtwo STICK stick for chang- (SECTION) lids the colour of the candle Figs. 13 and 14. a dummy red candle made - (Left) The of wood is attached to the key for ejecting base, passing up inside the metal candle. the hollow candlestick and (Right) The two projecting from the top the parts of the fake normal length of a candle. candle 80 NEWNES PRACTICAL MECHANICS November, 1939 WORKSHOP WRINKLES By " MECHANIC " Useful Hints that Save Time and Money clamped to the wire, or moved along it.etc., for two years, and the flex is only just A Neat Hydrometer The lamp is fed by a length of flex, and thebeginning to wear, but will last for another Drifi Stand slack in this flex which is produced by theyear yet. THE accompanying sketch illustrates amovement of the lamp is taken up by The lead weight can be cast by pushing rather novel hydrometer stand. A strip a broom -handle into clay for about 9 in. of mild steel constitutes the main support, depth and pouring molten lead in, while An easily made the lead is still liquid the end of the pulley and to this is soldered a brass clip made drip stand for a from a strip of ?-in. brass.The main T with the hole in it can be pushed in, and support is recessed into the base, and four hydrometer when the whole is cool, the pulley will be small rubber feet, screwed on as shown, SOLDERED found tq be firmly fixed in the lead. A prevent the stand from slipping. The small turnbUckle or wire -strainer is essential, as BRASS the piano wire must be kept very taut. jam jar is also recessed to the depth of CLIP three thicknesses of ply, and its fitment into the base in this manner should be tight, A Useful Bench Lamy, yetprovidingeaseofremoval when THE accompanying diagram shows a very required. HYDROMETER handy and inexpensive bench lamp. The stem consists of two lengths of j in. by 1 in. Keej5ing Soldering +wood, with one side slotted to take the flex, and both tops are slotted to receive the clip. Irons Tinned The base is three pieces of wood glued ELECTRIC soldering irons sometimes get together, with a in. by 1 in. hole in the a little too hot, and the solder on the centre. iron becomes covered with a coating of The clip A is folded round the lamp oxide.This nearly always happens when holder and fixed by means of a 6 B.A. held the iron is left for a short while, so to prevent this I kept the copper bit immersed How to in solder. How this was done is illustrated arrange a neat work- LEXT ANCHOREp in Fig. 1, and the tinned part of the bit is UNDERSIDE WO VIEW OF BASE shop light INSULATE) thus kept covered with the molten solder, STAPLES and remains well tinned. ell, Before I used an electric iron I heated 5 PLY my old bit with the point in the solder. ,cle BASE This was done by heating the crucible in RECESSED which the bit was resting. The crucible is TAR a simple system of pulleys and a weight A novel so that there is a constant tension on the method of flex which is just sufficient to take up the keeping slack. soldering STOUT OVE The sketch is self-explanatory, but one irons tinned WIRE or two points may be detailed. The flex while in must be of the round braided type ;if use CRUCIBLE FLEX F'PE CLAY ordinary twisted flex is used, the insulation 0; ROUND will wear off at the corners and give rise BRAIDED to trouble.There is,actually, very little TYPE RASS BLOCK wear on the round flex.I have had a emMOLID.IED ELECTRIC length in use with this system of pulleys, HOLE TO BE LARGE ENOUGH R:B MBTO BE JUST FULLED THROUGH

SOFT METAL OR DRAS5,63_,. FORMING LAMP HOLDER CUP - by two nuts on either side B. After Securing WAL the holder, with the flex wired in, run the CRUCIBLLE ALTERNATIVE flex down the slotted stem as shown. The METHOD FOR base of the stem is tightly fixed into the GAS IRON USERS base itself, thus holding the wire secure. Any switching arrangement may be used but the one shown is very simple. Fig.2 Fig. I The shade is made of 18 s.w.g., and the only point to remember is to leave the four wires protruding 1 in. Now cut two pieces a narrow one, to avoid wasting the heat. SWI)1.' of cardboard and cut a hole in the centre of The crucible is held in place by a pipe -clay each. One hole should fit the lamp holder triangle (Fig. 2). A piece of thick wire is exactly, and the other hole should be a i in. twisted round the iron support with the larger. Place the card with the larger hole loop for holding the handle of the iron. underneath the four wire ends and the other I heated the crucible with a blow lamp, card on top, and secure with wire or glue. but any convenient source of heat is suit- The cover for the shade can be made from a able.This method also keeps the iron piece of coloured paper. nicely tinned. The crucibles can be obtained from any chemist. -.4 METHODOF Of r; IIII0W RI rarT Details of A Workshoj5 Light the wooden -rHIS device consists of a piece of piano frameand I wire stretched between the walls of the wireshade shed, and this supports a metal fitting of the bench which carries a lamp in such a way that lamp the lamp may be raised or lowered, and by manipulation of a screwitcan be vs.- Noember, 1939 NEWNES PRACTICAL MECHANICS 81 "MOTILUS" PEEPS INTO THE MODEL WORLD Itis up to the Amateur Model Maker and Owner to Keep Interest Alive in this Vial Hobby-for it is one wh'ch mai be Badly Hit by Poor Trade. Our Model Fan with his Camera Finds News of Wartime Model Making.

dinghyondeck,ventilators,bollards, capstan, bridge with steering wheel and two starboard engine room telegraphs, two life - I ,uoys, port and starboard lights,etc. -- quite a collection !The cost of the model 1 he new lug boat -Mary at the moment of writing is 7s. 6d., but with the outbreak of hostilities there is almost WELL, fellowmodellers, nowisnew plastics and the detail, even in thecertain to be an advance on this.It can be the time when indoor modellingsmall life boat on deck is amazing, and justobtained from Messrs. Hamleys, Bassett- should be at its height.Let usgoes to demonstrate the possibilities of thisLowke's, Lucas of Liverpool, and at many hope this year it will be the same as ever,type of manufacture when large quantitiesof the leading toy shops in London and the for it is up to us all to carry on. This monthof a model can be placed in work.It isprovinces, and also a set of finished parts I bring you news from a model railway7 inches long by 2 inches wide and housesis available at 3s. 9d. the set. enthusiast in British Guiana, Mr. A. Smith,an efficientlittleclockwork mechanism. of Berbice, who sends this picture of hisThe hull isblack with white deck and" Cock of the North " scenic railway layout. " It is an enormousbrown deck houses. The funnel is red and I was in London last week and noticed attraction at our house," says Mr. Smith,black. Fittingsincludetheaforesaidthat Messrs. Bassett-Lowke have in their " and is besieged with visitors of all ages. Also it has made money as a side show at bazaars,etc.,with the operator of the distant contr 31s hidden behind a screen." As you have already guessed no doubt, the railway is a Twin Train Table Railway, with the scenery carefully painted to represent the natural colourings. This cannot be seen to best advantage in a photograph, but Mr. Smith has developed a technique of papier maths, coated with sand and saw- dust which gives a realistic representation The mo:Tel of bushes and grass in this scale. The roadsrailway are painted to represent tar macadam, the layout of rocks are real stones, and all the buildingsMr. Smith, are lit up. To prevent the whole being too of British sombre the arch facings and buildings are Guiana paintedinunnaturallybrightshades because " after all " (in the words of the owner) " the layout is a toy and not a model and this gives the happy finish." Person- ally I feel it has many 'model " points ! A New Tug Boat I wonder how many of you have seen the new tug boat placed on the market by Liras l'rnq P is construetrtd rf on- of the

shop a very fine unpainted model of the L.N.E.R. type of locomotive " Cock of the North,"inch scale, 2inch gauge. Those interested in high-class hand -made steam models should call in and see this_piece of work by expert craftsmen, as they may be able to get some ideas from it. Of recenttimes Bassett-Lowke have begun to cater more and more for the owner requiring a special Gauge " 0 " hand -made model in clockwork or electric, made up at a reasonable price using standard parts: Mr. Gilbert Thomas, the well-known writer and critic, who has now removed from London to Teignmouth, has just added to his line a G.W.R. 4-6-0 " Pendennis Castle." "I he G.W.R. "Peridcants Castle.' He told me that he is now well on with the 82 NEWNES PRACTICAL MECHANICS November, 1939 re -erecting of his gauge " 0 " railway, and that the price for the detail work of this special hand -made" Pendennis Castle " was 13 guineas all told, which appears to be very reasonable. He seemed to think so for he is ordering another G.W.R. locomotive, the " Llanfair Grange," No. 6,285, from the same firm.I am showing a picture of the " Pendennis Castle " model. Its prototype you will remember holds the remarkable record of making better times on a lower coal consumption than one of the 92 ton " Al " class Pacifies on the L.N.E.R., in the " exchange " trials of 1925. Incidentally the Castles are 80 ton expresses and they have been more extensively built than any other G.W.R. passenger type.They are responsiblefor many importantduties such as the 71.4 miles -an -hour " Chelten- ham Flyer " and the 67.6 miles -an -hour " Bristolian," the fastest trains on the line. Model Aeroplane Model aircraftis in the picture again, and in gorthampton I was lucky to see a batch of civil aeroplanes and flying boats At work on the Armstrong Whitworth Ensign G-ADSR model they were making for the Nen, Zealand exhibition, to show the progress of British commercial aircraft in recent years.Thepoints and piers of varying heights.I hadstraight track bases 141 in. long x 21 in. eight 'planes were made of African whitethe opportunity of examining a set of thesewide. The two tapered track bases carry mahogany wood, silver lacquered to givegradient parts. The sections and supportsthe track from zero to 1 inch and the piers a metal finish and were made over a perio Iare All made of African white mahoganylettered A to F continue the graduation of five weeks.The engines and nacellesfree from knots and shakes and finishedfrom that height to 3/ in. to the top of the were of metal and the machines modelledin a matt colour to represent moderntrack base, making a total length of 8 ft. 6in. were the D.H. 91 " Albatross " G-AFDI,concrete construction.If you want brickComplete set costs 15s. 6d., and parts are the D.H.95 " Flamingo " G-AFUE, Arm-piers, it is a simple matter to cover theseobtainable separately. strongWhitworth" Ensign "G-ADSRwith brick paper, which can be obtained in (shown in this picture), Short " G " classall types and colours as low as 3d. a sheet.Famous Motor Yacht flying boat, short" S.30 "classFlyingMy picture shows a typical under and over In these times of stress, it is pleasant to Boat (4-AFCI, Fairey " F.C.I.," Handleyroad, with a T.T.R. goo Is train above andremember the yacht racing synonymous Page " Hannibal " and the famous Mayothe new L.M.S. " Coronation Scot " passingwith the name T. 0. M. Sopwith.I have composite 'plane. on the under road. The standard " Lowko "recently come across this picture of an " Gradients " set as it is called consists of :2 tapered trackexcellent model of his famous motor yacht Each month Ilike to give you news ofbases, 6 piers of varying heights and 5Philante, modelled for the makers, Messrs. Camper and Nicholson of Southampton. Designed by C. E. Nicholson, M.Inst. N.A., the Philante was launched at Southampton on February11,1937, and underwent successful trials at the end of May of that year. Her principal dimensions are overall length 263 feet, extreme breadth 38 feet, tonnage (Thames measurement) 1,612 and cruising speed 14 knots.In my opinion this vessel is the ideal. of what a steam pleasure yacht should be. At the time of her trails she was the largest yacht built in the United Kingdom, while her M.A.N. Diesel machinery, which develops3,000total B.H.P. on normal fuel setting, gives her a very useful turn of speed.The model shown here is to a 'scale of 1 inch to one foot.

The new gauge "00" gradients for the T.T.R. railway some new gauge " 00 " development, and this time it is ".gradients." Some of you, I dare say, have visited Bassett-Lowke's at High Holborn and seen their working dis- play of the Twin Trains in the basement. This layout now includes gradients for high level tracks, and this novelty in gauge " 00 " is proving so popular that they have worked out a standard set which provides for a gradient of 1 in 30 in a length of 8 ft. 6 ins. At the top this gradient gives a 3 inch clearance.Fellow modellers will realise the big possibilities of this gradient set-the number of high and low level roads they can arrange by using these standard fitments, which consist of straight and curved sections, special sections for A in. to the ft. model of the motor yacht, -Phi/ante- November, 1939 NEWNES PRACTICAL MECHANICS 83 PRACTICAL MECHANICS " WIRELESS SUPPLEMENT - P.M. Short-wave Three A short-wave Receiver ofthe" Straight" type DesignedtoSatisfythe needs of those Enthusiasts who Require an Efficient yetSimple Installation

have been the requestsfor a superhet receiver designedfor Mbattery operation, and for short- wave reception. Quite a goodly number still favour a good straight receiver something along the lines of what is often affectionately called by theoldtimers- oldfaithful,"or,in other words, a circuit of the single H.F. type followed by an efficient detector, and one or two stages of L.F. amplification according to individual requirements. A circuit of this type has much to recom- mend it for every short-wave enthusiast's consideration; itis invariably reasonable as regards price, simple to construct and, onceitsoperatingcharacteristicshave A three-quarter front view of the receiver been rendered more or less perfect, quite The Circuit in this position, asitnot only gives a pleasant to operate, and reasonably con- greater output on a weak signal but it also sistent in performance. The theoretical diagram shown in Fig. 2allows a very efficient form of reaction to We are not overlooking the factthatdepicts a three -valve circuit. he obtained. in these days of station -swamped ether, The initial aerial circuit consists of an The output from the detector is fed into onehastofacetheever-increasingEddystone three-iwinding coil, one of whichthe first L.F. stage by means of a resistance - problem of selectivity and we fully realiseis used for aerial coupling, another for thecapacity coupling, and it will be noted that that the super -het, plus or minus a crystalgrid input circuit, and the other one for thea volume control has been fitted across the gate,goesa verylong way towardsreaction.It will be noted that no badgrid circuit of the first L.F. to enable the eliminating the hug -bear of interference.spreading, in the ordinary sense,is pro-ultimate output volume to be regulated so While givingalldue respecttothesevided. This was found to be unnecessarythat headphones or speaker can be used as items, it cannot be denied that such outfitsas the special type of mechanical drivedesired. are not within the range of every reader'susedintheslow-motiontuninggear, The coupling between thefirstL.F. pocket, and it would not be any exagger-providesanidenticaleffectwiththevalve and the output stage is provided by ation to say that the mass of short-waveadvantage of definite dial recordings. an L.F. transformer of the yarley Niclet listeners have to be content with something The gridcoil, which is tuned by antype, but, to prevent the primary receiving rathermoremodestthanareceiverEddystone .00016-mfd. variable condenser,an excessive current load, it is arranged in embodying all the refinements suggestedtype number 1131, feeds the detector viathe normal parallel -feed method which, above. It is, therefore, in an endeavour tothe usual leaky grid coupling col denser.incidentally, also provides a certain degree provide a good all-round receiver that thisAs sensitivity and gainareiml3rtantof decoupling. set has been designed. factors, it was decided to use an S.G. valve The output valve is a Cossor 220 H.P.T. pentode which is quite capable of providing 7 LIST OF COMPONENTS One Eddystone type No. 1131, 160 m.mfd. 3%B. var. condenser. One Eddystone type No. 969 six -pin coilholder. Two Eddystone type No. 949 four -pin valve - holders. One Eddystone type No. 950 five -pin valve - holder. 4,3'8DA Two J.B. .0001 mfd. var. condenser, type No. 2146. One Bulgin H.F. choke, type No. H.F.3. Fixed Condensers-Dubilier : Type 4601/S : One .0001mfd. ;one.01mfd.Type 4602/S : One .05 mfd. Type 4603/S : One 0.1mfd.Type 4608/S.: One 0.5 mfd. Type 4609/S : One 1mfd. Type 3016 : Two 2 mfd. One chassis (Peto-Scott), 14 x 9 x 3. One panel (Pero -Scott), 14 x 9. Fixed resistances-Erie.I Watt : Ore Imeg., one 0.25 meg.. one 10,000 ohm ; one 0.1 meg., one 50,000 ohm, one 20,000 ohm, 5% one 100,000 ohm, one 15,000 ohm, one 34DA 30,000 ohm. Potentiometers-Erie :One 0.25meg., one "sow Ow 50,000 ohm, with switch. L.F. transformer. One Varley Niclet D.P.21. L.S. panel (Clix). A1, A2, and E socket strip (Clix). Valves, Cossor 210 S.P.T., 210 H.L., and 220 H.P.T. 14 Coils-Eddystone : 22.47 metre, No. 959.6Y. Fig. 1.-Drilling diagram for the panel 84 NEWNES PRACTICAL MECHANICS November, 1939

the main tuning condenser, and the locating and fixing of the slow-motion drive. Don't .5,0000 try to rush this part of the work. Remember L4/FHONCS that the driveis dead central along a horizontal line of the panel, and that the distances of itsfixing, and that of the condenser bracket from the front panel, are I 5MFD. very important.

/ For satisfactory fixing of all parts bolts 0, TO. should be used, and, for a thorough job, use shakeproof washers under each nut. The Panel M. This can be purchased, the same as the chassis, from Messrs.Peto Scott ready drilled but, if you wish to do it yourself, 0 check alldrilling points before starting that operation. The large hole for the dial should be scribed on the metal, and then B. + cut out with a fretsaw, the edges being G.B. C.S. smoothed off with a small file. When handling this part of the assembly, Fig. 2.-Theoretical circuit diagram for the short-wave three see that the bench is free from all metal filings, and covered with two or three layers adequate output for all normal purposescertain components which will not onlyof stout paper, otherwise the fine polished and, providing the volume control is usedspoilthe appearance of the completedfinish of the panel will soon be marred. It in the manner intended, it will handle allassembly,butalsopossiblyaffecttheis attention to these little details which the input necessary for full output. efficiency.Particular care must be takenmakes all the difference in the appearance It will be seen from the above descriptionwhen setting up the bracket which supportsof the set when completed. that there is nothing fanciful about the circuit, and that no unnecessary components or gadgets have been embodied ; therefore, it should present no difficulties to any enthusiast as regards its construction; in fact, it is quite a safe proposition for a keen beginner to consider. Fig. 3.-Wiring diagram Layout of thereceiver The plan drawing of the chassis, Fig. 3, shows that a very clean and clear layout has been obtained, and it should also be to noticed that no attempt has been made to sacrifice space to make the overall dimensions smaller. 00016 MFD The main tuning condenser,together with its mechanical band -spreading drive, is located in as dead central position, which not only gives a pleasing appearance to the panel but also allows the controls to be placed at the most convenient operating 0 points. 16 ;5 17 As a steel chassis was used in the original model, it was decided to use the special low -loss baseboard -type valve holders pro- \ 04,/ 0001 ;Mn duced by Eddystone, and, as each valve- MFD 7 pin,socket on these holders is made in one piece, the possibility of contact noise] is considerably reduced. TOVACLAVPECF A2 Al By employing a chassis, the majority of As A, the components are housed out of sight and well protected, while the wiring is + 2 MFD. considerably simplified as is evident by the 30,00011 plan drawing of the underside of the chassis. MC is,000n. To avoid the use of plugs and jacks the Ig specialClixswitching outputpanelis employed and, for convenience' sake, it has 0 been fitted on the right-hand side of the 50300 chassis when it is viewed from the front. This simple device allows a most rapid 20,000 C-) change -over to be made from headphones to loudspeaker, and, when housing the 2 completed set in a cabinet, no difficulty MFD should be experienced in making a suitable aperture for access to this component. Assembly Before proceeding with any drilling, lay 9 out the components to be mounted on the OMFD top of the chassis on the actual metal GB -2 chassis and carefully mark off the exact Ls 0.6.-P positions for the holes to be drilled, after 00.000 making quite sure that all the components are in the positions indicated by the plan drawing.After drilling, clear all holes of G.B.-1 50,000 burrs, and then repeat the procedure for .25MCI M.0 those parts which have to be mounted inside the chassis.Don't attempt to fix anything down until all drilling is finished, 111111',4P10, otherwise damage might becausedto November, 1939 NEWNES PRACTICAL MECHANICS 85 PHOTO -ELECTRIC EXPERIMENTS

POLISHED METAL PLATE A Number of Simple and Easily APPROX 3' SQUARE PerformedPhotoelectricEx- periments which Demonstrate the Underlying Principlesof the Photoelectric Cell.

the plate, otherwise the H.T. battery cir- -EBONITE cuit would be completed and the galyano- "E-SCREWHEADS meter probably ruined. Note now the galvanometer reading.It will be seen that no current flows.Now take a few inches of magnesium ribbon and Fig. 1.-A simple apparatus burn it in front of the metal gauze and at a for demonstrating the photo- distance of about 6 in. away from it.The electric effect burning magnesium will flood the metal plate with ultra -violetrays. Instantly the galvanometer needle will be deflected showing that a current is passing. Moreover' IT is known by all television amateurs that LIGHT-SENSITIVE CELL the modern photo -electric cell owes its (COPPER PLATES IN origin to the discovery made in 1888 COPPER SULPHATE CLOSED CARDBOARD BOX by Hallwachs, a German physicist, that SOLUTION areas of certain metals, when strongly CONTAINED IN illuminated by violet, or, better still, by JAM JAR) ultra -violet rays, lose almost immediately a charge of negative electricity" which has been previously imparted to them.This APERTURE OR effect is usually known as the' "Hallwachs "WINDOW" effect." In addition to the above, however, it was discovered also that an uncharged insulated metal plate is able to acquire a positive JcHT SOURCE charge when ultra -violet rays fall upon it. COPPER PLATES Such phenomena were studied by a number of scientists, and, eventually, they gave rise to a device of supreme practical importance -the photo -electric cell. OUTPUT TO- It is possible for the amateur to make a AMPLIFIER number of interesting experiments based '''RUBBER 'PHONES OR upon the early observations of Hallwachs BANDS MiLuAMMETER and others.Such experiments are easy to carry out and they are of value in view of the fact that they illustrate in a very Figs. 2 and 3.-(Left) Details of the light-sensitive definite and striking manner the funda- copper cell construction, and (Right) Showing an mental principles of the photo -electric cell. experiment with liquid light-sensitive cells In the first of these experiments con- EBONITE SHEET struct the apparatus shown in Fig. 1.It consists of two small wooden bases, approxi-of a galvanometer or other current -indicat-as the burning magnesium ribbon is moved mately 4 by 2i in. in area. Each base hasing instrument, the more sensitivetheup to the wire gauze the galvanometer an ebonite upright.To one of these up-better. deflectionwillincrease,whilstifthe rights is secured a piece of coarse wire Next connect another wire to the metalmagnesium ribbon is withdrawn from the gauze. To the other upright is fixed aplate and the other end of this wire to thegauze the galvanometer needle will show a metal plate, the plate being fastened bynegative terminal of a radio high-tensiondecreased deflection, thus proving that the means of a lump of plasticine or a dab ofbattery which should possess an E.M.F. ofcurrent -generating property of the ultra- sealing -wax placed at the back. The metalthe order of 100 or 120 volts. The positiveviolet light is proportional to its intensity at plate should be about 3 or 3i in. square,terminal of the H.T. battery is connectedthe metal surface-a law which governs the area of wire gauze being about the sameto the galvanometer, thus completing arigorously the functioningofalllight- dimensions also. circuit from metal plate to metal gauze.sensitive devices. Before making these connections be sure Preparing the Plates that all the apparatus (H.T. battery andThe Effect on the Plates A number of plates of different metalsgalvanometer excepted)isperfectly dry. Repeat the above experiment with the should be provided, such as plates ofIf you have any doubts upon the matter itvarious metal plates. It will be found that copper,zinc,sheetiron,tinnediron,is best to place the wooden stands supportinga zinc plate gives the best results.After aluminium and brass. Itis absolutelythe metal plate and gauze for half anzinc comes aluminium.Copper, brass and essential that these plates should be broughthour in a warm oven in order to drive offtinnedironshow a veryconsiderably to a high polish on one side. A mirror-liketraces of moisture which would very prob-decreased effect and sometimes, if they are surfaceisnot essential, but the platesably ruin the experiments. not highly polished, they do not show it at should be rubbed over first with coarse and Having fixed up the apparatus as shownall. then with fine sandpaper (with- the excep-at Fig. 1 and described above, move the What is the expination of the above tion of the tinned iron) in order to exposewire gauze assembly up to the metal plateeffect ? It is not difficult to grasp. The metal a fresh and untarnished surface to the lightso that the gauze faces squarely up to theplate, being connected up to the negative action. plate and is separated from it by a space ofpole of the H.T. battery,isnegatively Connect a wire to the gauze and connectaboutor 4 in. (not more). On no account,charged.When the plate is acted upon up the other end of the wire to one terminalhowever, must the gauze actually touchbl ultra -violet rays it loses a portion of its 86 NEWNES PRACTICAL MECHANICS November, 1939 charge. Thus theequilibriumof thewill be present on the surface of the plates,clicks being generated by pulses of current battery circuitis disturbed and a smallthis thin film being light-sensitive. from the light-sensitive cell. current flows. Now obtain a cardboard box sufficient- A cardboard disc provided with radial It will probably be found that any givenly large to contain thecell. Make anslots will, when revolved in the path of the metal platewill only show the photo-aperture in the side of the box so that lightlight rays, give rise to a humming noise in electriceffectin this manner a certainpassing through this " window " may fallthe phones of speaker.Also, if by any number of times-say, half a dozen times.upon one of the copperplates of the cell, thechance a miniature arc -light can be obtained, After thisitwill undergo aspecies ofother being unillumined. Connect leadsit will be possible to listen -in to the irregular "photo -electric fatigue." This is due tofrom the copper platestoapairofpulsations of current passing through the the slight tarnishing or surface oxidationheadphones or to the input terminals ofarc. undergone by the plate.If the plate isa radio amplifier equipped with a loud- Needless to say, all these effects may be rubbed over thoroughly with fine sand-speaker. studied by substituting a sensitive micro- paper so as to expose a fresh surface, it will On holding a bright light -source near tometer in the external circuit of the cell in be found to show the photo -electric effectthe " window " of the box and interruptingplace of the phones or radio amplifier. as well as ever. the light more or less rapidly by jerking aMicro -ammeters, that is to say, instruments The underlyingcauseof thephoto-sheet of cardboard up and down in the pathwhich read down to a few millionths of an electric effect is readily grasped. When aof the light rays, a series of clicks will beampere, are costly articles, however, and light ray of a certain vibration-frequency-heard in the 'phones or loudspeaker, thesenot many experimenters possess them. a ray of ultra -violet light, in the above case-falls upon a polished metal surface, it knocks away from one of the surface atoms one or more electrons, the electrons being shot off from the metal surface in a AROUND THE TRADE manner similar to that in which they are Model Maker's Box Spannerand the 6 -volt bulb is a double pole, dual emitted from a heated valvefilament, BONDS 0' EUSTONfilament which gives an even diffused light. although less copiously. The H.T. battery ROAD, LTD., have justIt is worked from a 6 -volt " Dagenite " simply supplies a "driving potential," the marketed a model maker'sunspillable accumulator and the terminals electrons being caught by the gauze screen, box spanner which has beenof the battery are insulated and cannot the circuit thus being completed. specially made to fit the M.E.short circuit.The lamp will give a con- The photo -electric effect is best shown by tinuous brightlight of 12 -watt candle- thealkalimetals,potassium,sodium, power for 9 hours or a continuous dim rubidium andcaesium. Suchmetals, light of 3 watt candle -power for 20 hours. although they enter into photo -electric cell Using an intermittent lightitwill give construction, cannot be employed in the 250 hours' service. The lamp costs £3 19s. 6d. above experiments because, in contact with The " Compact " Patent Ladder air, the surfaces instantly become covered A model maker's with a layer of oxide. In photo -electric cells THE Southern Ladder & StepCo., such metals remain bright indefinitely on box spanner have recently produced an ingenious account of the absence of air in the vaccum type of ladder which actually shuts up. cells. Itdiffers from the ordinary folding or Besides metal plates certain crystals aresize Whitworth nuts and hexagon bolts, light-sensitive and can be made use of inwhich as readers know are smaller across the above experiments.If, for instance,the flats than the standard Whitworth sizes. The"Compact- instead of a polished zinc or aluminium Spanners can be supplied for A -in.,patent ladder plate we employ a crystal of galena, theA -in., *-in. and A -in. M.E. sizes of nuts. well-known wireless rectifying crystal ofThe price per box spanneris9d., plus former days or, better still, a piece of molyb-postage. denite,the same effectwill usually be obtained with the apparatus described.A.R.P. Handlamp Not allgalena crystals are sensitivein this manner. Their 'sensitivity dependsCASCO ELECTRICAL S)RVICE have upon some unknown factor.Hence, the recently marketed aportable hand - experimenter who has a quantity of galenalamp which has a number of uses.It is crystals available will have to play theconstructed of 18 S.W.G. metal, has a game of trial and error with them until heswivel handle and a hinged lid fastener. hits upon a crystal which displays strongly The inside of the box is painted with the photo -electric effect. anti -sulphuric paint, whilst the outside of Other crystals which are similarly photo-the case is black crinkle.The photograph electric are chalcopyrite and iron pyrites,shows the neat and novel appearance of the both of which were formerly well-knownlamp.The light is fixed on top of the lid as radio rectifiers. Liquid Light -Sensitive Cells Thesecellsprovide alargefieldfor amateur experimentation. One of the simplest cells of this type is seen at Fig. 3. It comprises two copper sheets, approximately 2 x 1in., which are cut with an attached lug, to which a connection may be made. The copper sheets should be well cleaned by rubbing them over with strong soda solution, then by rubbing them with coarse and, finally with fine sandpaper. A suitably -sizedpieceofebonitesheet separatesthecopperplates which are attached toit by means of two rubber collapsible types and has been designed for bands. easy carrying and convenient storage.As Make up a 1 per cent. solution of copper will be seen from the sketch, it takes up the sulphate (about 5 grains of copper sulphate minimum of space when closed and when in an ounce of water is the right proportion) open is held rigid by means of a metal bar and stand the copper pates in a vessel con- and a wing nut.The uprights are made taining this solution.Preferably, a three from selected well seasoned timber and the or four days' immersion should be allowed rungs are made from oak.When closed and the immersion should be carried out the rungs fit into special grooves cut into in the dark. each side of the uprights.The ladder is After a few days thecellwill have 8 ft. high (open) and costs 25s.A 10 ft. " formed." A fine coating of copper oxide A portable hand lamp suitable for A.R.P. worker ladder can be obtained for 5s. extra. November, 1939 NEWNES PRACTICAL MECHANICS 87

" That's an odd way to work," remarked Blewitt, Areyousure, dear old boy, you won't rue it ?" Practical Handbooks Said Brown," That's all right, See! I'm using FLUXITE. for the So you see, on my head I can do it ! " Modern Handyman See that FLUXITE is always by you - in the house garage-workshop - wherever speedy soldering is needed. Used for30yearsin Government works and by leading engineers and

manufacturers.Of Ironmongers -in tins, 4d.,8d.,1 4 and 2 8. Ask tolsee the FLUXITE SMALL -SPACE SOLDER- ING SET --complete but substantialcomplete with full instructions 7 6.Write for Free Book on the ART OF " SOFT " SOLDERING and ask for Leaflet on THE CASE -HARDENING STEEL and TEMPERING TOOLS with FLUXITE HOME TO CYCLISTS !Your wheels will NOT keep round and true unless the spokes are tied with fine wire at the crossings and SOLDERED.This makes a much stronger wheel.It's simple --with FLIJXITE -but IMPORTANT. MECHANIC THE FLUXITE GUN is always ready to put Fluxite on the soldering job instantly. A little pressure placesthe right quantity on theright SERIES spot and one charging lasts for Price 1/6, or filled 2,6. ages. Thisseriesofpracticalhandbooks is ALL MECHANICS WILLHAVE designed specificallytohelptheamateur mechanic or craftsman. Eachvolumeis simply written by anexpertandprofusely FLUXITE illustrated with photographsand diagrams. IT SIMPLIFIES ALL SOLDERING FLUXITE Ltd., Dept. P.M., Dragon Works, Bermondsey St., S.E.I OnlyILEach CURE FOR 'BLACK -OUT' BOREDOM Build a Model Aeroplane, which can easily The HomeElectrician ". be constructed without any special tools Megow The Handyman'sEnquireWithin Balsa Flying Kits The HomeWoodworker Kitsfor24in.wing spanFlying Models of the STINSON RELIANT, Power -drivenModelAircraft WACO CUSTOM, MONOCOUPE, CONSOLIDATED P/30,FAIRCHILD, Model AeroplanesandAirships HAWKER FIGHTER, CURTISS HAWK, RICHMAN AND Accumulators MERRILL'S VULTEE. PRICE 216. Postage 4d. Twenty-five SimpleWorkingModels Large range of smaller kits to make up 12" Flying Models. Simple Electrical Apparatus and PRICE lld. Postage 3d. Experiments Or start a Model Railway, and commence by laying the track with Bond's "00" or "0" GaugeTrack Parts PracticalLeatherWorkandAllied PRICES. Gauge "00" Parts Steel Chairs ...... per 100 I4 Steel Rail, sheradised finish Fishplates ...per doz. 3d. Crafts per yd.I fd., 1/3 doz. yds. Sleepers, Wooden ... per 100 Bd. Brass Rail per yd. 3d., 2/3 doz. yds. Electric Raised Chairs...per doz. Bd. Toy MakingforAmateurs Cast Chairs ... per 100 1/4 Pins 3d. packet PRICES. Standard Gauge "0" Parts Steel Rail, sheradised,per yd. 2d. I'S doz. yds Lathe WorkforAmateurs Brass Rail ...... per yd. 40. 4'3 doz. yds. Cast Chairs, slide -on fit...... per 100 1/2 Electric Raised Chairs ...... per 100 2' - House DecorationandPainting Fishplates ... ..per doz. 3d. Sleepers, stained correct colour ...per 100 2.3 Battens, Fn. x i-in. section per yd., 21d., 2/3 doz. yds. Pins, approx. 1,000 ... 6d. packet Track Gauge, special, with elec. chair -jig Available at allBooksellers,I !-net,or by 9d. each All Track prices plus 10%. Plus Postage. postI f2 from the Publisher SEND FOR BOND'S 1940 GENERAL CATALOGUE, PRICE 6d.; THIS WILL INTEREST YOU AS ITS 208 PAGES ARE FULL OF PARTS REQUIRED BY George Newnes, Ltd. (Book Dept.), THE MODEL MAKER INCLUDING TOOLS AND MATERIALS. BOND'S 0' EUSTON ROAD LTD. Tower House, Southampton Street, Strand, 357, EUSTON ROAD, N.W.I W.C.2. 'Phone EUSton 5441-2 Established 1887 88 NEWNES PRACTICAL MECHANICS November,1939

The War Office, Air Force, Admiralty, G.P.O., Metropolitan Police, L.C.C., and Municipal Authorities everywhere, have universally adopted Rawlplug Fixing Devices-they are using them for securing A.R.P. shutters, swing shutters, black -out curtains, partitions, electric light fittings, clothes racks, brackets for fire equipment, seats,ventilation, and air filtration appliances, etc.

DARKENING OF WINDOWS : The Government has stated that plans are being made on the assumption that war may last for 3 years, owners of premises are, therefore, taking immediate steps to replace their temporary A.R.P. fittings with more permanent ones, which can be conveniently operated. There is a Rawlplug of a size and type for every class of work, from the fixing of curtains and FIXING OF blinds to the holding down of heavy machinery and other fixtures where a strain of over zo DETACHABLE SHUTTERS tons may have to be contended with.

RAWL 4j-1- Write for copy of our IRAIAII latest "Fixing Devices" book and special A.R.P. Blast, Splinters and Flying Glass:The best way to obtain protection against blast, splinters and shattered glass is to fit metal or wooden folder. shutters over the windows: At nights, shutters serve the dual purpose of protecting against blast and obscuring the light, thus obviating the need for B.240 blinds or curtains. Rawlbolts or Rawlplugs ensure that these shutters are fixed quickly and absolutely securely without damage to walls or decorations. The Raw;p!ug Co.,Ltd., Rawlo!ug House, Cromwell had, London, S.W.1

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November, 1939 NEWNES PRACTICAL MECHANICS 89 urusyInventors speech, depends upon notes, to which he Ink Detective By " Dynamo " makes frequent reference. inquisitive person-vulgarly To help the latter type of spokesman, an THEknown as " Nosey Parker "-will have invention has recently been submitted to his or her curiosity baulked by a newdefinite warning to the driver that one ofthe British Patent Office.It happens to be steam -sensitive ink.When printed on thethe tyres on the trailer has declined from itsthe conception of a subject of the German flap' of an envelope, this ink, under thenormal rotundity.The clacker is mountedReich, and is an apparatus for facilitating influence of steam, changes colour.Con-on the rim, touching the tyre.As the tyrereference to a manuscript by a speaker. sequently, a printer's inkling is given thatis deflated, it presses against the clackerLecturers generally use manuscripts which the envelope has been tampered with byand, with each revolution of the wheel, noare either horizontal or upwardly inclined some Paul Pry or his feminine equivalent. uncertain sound informs the driver thaton their desks.From time to time, the something untoward has happened. lecturer glances at his manuscript.In so doing, his gaze is diverted from his audience. Nonslip Bowl for Pets Brow Mop This means some loss of power over his I N taking its food from a vessel placed on hearers, as the eyes of an orator have a THE primal curse upon theground,magnetic influence upon the rapt hearers the floor, an animal is apt to push it making it necessary for man to earn hiswhom he addresses. about and spill the contents. A new non -bread by the sweat of his brow, was a And his voice is less spill combination food and drink bowl for audible when he is looking down at his blessing in disguise.And the beads ofmanuscript, because the sound direction dogs and cats has been contrived.Thishonest sweat which bedew the forehead of the vessel will not slip nor tip on the smoothest naturally changes. village blacksmith are intrinsically of greater These difficulties,itis maintained, are waxed linoleum. A patented rubber basevalue than the jewels that gem the -crown of prevents it from skidding.The bowl has overcome by the new appliance. The a monarch.But this sweat, which ourmethod consists in the manuscript being two compartments, each holding a quart.refinedVictorianforbearstermedper- And this receptacle being made of Bakelite, reflected into the direction of gaze of the spiration,is at times inconvenient.Forspeaker.It appears between the speaker there is no fear that Bonzo will have chipsinstance, tennis players and other folks with his fish. and the audience in a reflector which neither engaged in vigorous sport, not to mentionhides him from the latter nor hinders him the horny -handed sons of toil, find the tinyin any way.As a result, the manuscript Antidrip Gadget rivulets which meander across the featurescan be read in the reflector without the are apt to blur the vision.To dam theselecturer having to turn his direction of gaze WHEN the umbrella has been on dutystreams, a sweat pad has been devised and in apeltingshower, it has a bad habit of or speech from the audience during the patentedintheUnitedStates. Thiswhole speech. treating the floor of a room as an umbrellaabsorptive mop for the brow will prevent stand.Therefore, an anti -drip catchingperspirationfromcascadingdownthe attachment, which has been patented in thecountenance. Eloquent Reflections United States, will be acceptable.It con- AT this point the intelligent reader will sistsof ahollow,resilient,cylindrical The following information is specially supplied to naturallyobjectthatareflected arrangement affixable to the umbrella in the "Practical Mechanics" by Messrs. Hughes & Young manuscript would appear in reverse. He is neighbourhood of the ferrule. (Eat. 1829), Patent Agents, of 9 Warwick Court, High quite correct : Holborn, London, W.C.1, who will be pleased to send the words would run like, readers mentioning this paper, free of charge, a copy the writing Alice saw looking -glass. Paper Bibs of their handbook, "How to Patent an Invention." So, if there were only a single reflector, the manuscript would have to be written or THEHE bib has for many a long day shielded typed like Hebrew, the lines of which read dress of the babe from waywardDi used Airwaid from right toleft,in the manner that diet.A patent for a newly -devised paper printers set up type.To obviate this, the bib has been granted by the United States inventor suggests that, as an alternative to Patent Office.The bib has extensionsWarnings the manuscript being a la mirror -writing, arranged to encircle the neck of the juvenile,I T is contended that the effective range ofan auxiliary, reversingreflector may be and glued on it are straight narrow strips of air-raid warnings, even when powerful,interposed. reinforcing paper. The youngster would beare limited.Less strident and more numer- And so with this apparatus the speaker intrigued vire this dress protector decoratedous alarms are said to be preferable. Actingcan administer tothepublicpowerful withpie esof JackHorner,Littleupon this belief, an application has beenreflections. Red Riding Hood and other charactersmade to the British Patent Office to protect dear to the natives of the nursery. an idea embodying the principle in question. It is pointed out that, when air raids areFountaimPen Seal expected, normal lighting is extinguished.I T has been said that a bad workman Medicine Musket The lighting fittings are then available for quarrels with his tools.But an efficient THE giving of medicine to children andaudiblealarms,and devicesforthesetool is a necessary factor in first-class work. animals requires a blend of coaxing andalarms may be adapted to be readily sub-For example, Robinson Crusoe, with crude coercion.As regards the horse, the veter-stituted for lamps. The alarm device is pro-implements, could not produce the finished inary surgeon used to employ a bottle or avided with a cap to co-operate with the lampwork of the well-equipped craftsman.This horn, which he inserted in the side of thesocket in a street -lighting fitting. And it isis certainly true of the pen.Take care of horse's mouth.The contents of this con-so constructed that it can be worked by thethe pens and the writing will take care of tainer were sometimes evenly distributedsupply of electricity to which the socket isitself, is a slogan which, if original, I present between the internal economy of the sickconnected.One cannot predict that theto " His Nibs " the pen manufacturer. quadruped and the sleeve of the operator. arrangement will be generally adopted, but An improved self -filling fountain pen of But the modern horse doctor can availan important company has sponsored thisthe piston type has recently been patented. himself of a veterinary dose gun, which hasalarming invention. It is characterised by a piston adapted to been patented in the United States.This slide in the barrel of the pen with a close comprises a tubular nozzle and a piston, and and easy fit.Fluid tightness of the piston the medicine is fired, so to speak, into theFor the Modern Cicero is secured by means of a groove containing throat of the four -legged patient.In using PPUBLIC speakers are of two sorts.Theremercury. With such a seal, it is stated that this medicine musket, the " vet " adminis- is the born orator, whose eyes are nota much greater suction is obtained witha ters what may be termed a gun -powder. glued to a manuscript.He prepares hisshorter stroke than is the case with a piston thoughts but relies upon the inspiration ofhaving the ordinary packing. the moment for the language with which he And so that tiny tubular pocket inkpot Puncture Alarm clothes them.Like an artesian well whichhappily named the fountain pen, will not WHEN a tyre on a motor trailer goesbubbles up scintillating in the sun, hisonly resemble the shape of the column of the flat, it is not at once apparent to thefountain of sparkling words rises to thethermometer, but will also contain that driver of the preceding vehicle. To summondelectation of the enraptured audience.sprightly metal commonly called quick- attention to this defect, there has beenBut he is the exception.The averagesilver. devised a metal clacker which gives aspeaker, if he does not actually read his (Continued on page 92) 90 NEWNES PRACTICAL MECHANICS November, 1939 A STEAM -DRIVEN SPEEDBOAT

ANY ship,boat,ormodel moving will always be much faster than the ordinary through water has constantly to be Fig. 1 . -A boat of the same power, even allowing for displacing a certain mass of water photograph of the power expended on dynamic support. of the same weight as the model itself, and the finished the water has to fill in the subsequent void. modelofthe Obtaining the Maximum Speed from a Boat To do this with the least expenditure of steam -driven (1) The boat must be long in proportion energy, it must do it as gently as possible. speedboat to its breadth. If it is not done gently, a wave is formed (2) It must be as light as possible, i.e. on either side, indicating that energy is displacement must be at a minimum. being wasted in raising the water above its (3) Itsshapemustofferminimum normallevel.These 'wavescannotbetwenty-fourtotwenty-seventimesitsresistance, i.e. it must have a sharp cutting eliminated entirely, but itis the businessbreadth. Water offers very little resistanceedge and a tapering form of stern to fill up of the naval architect lip reduce them toto bodies moving slowly through it, butthe void without turbidity. a minimum. thisresistance of inertiaincreases very (4) Its centre of gravity must be as low In addition to this displacement resistancerapidly with the speed; at high speeds aspossible. thereisthe resistance due to whatis (above16 knots)itbehaves more like What type of boat bestfulfilsthese known as skin friction per square foot ofa solid than a liquid. conditions ?In all probability (with the ex - wettedsurface,andthisresistanceis proportionaltothe amount of wetted surface.It varies with the nature of theMany Interesting Experiments can be carried out skin, i.e the substance of which it is made or with which it is coated. This resistancewith this novel Speedboat, which incorporates a in the case of destroyers has been found to be: number of ingenious features in Design At 12 knots 80 per Cent.

At 16 70

At 20 The advantage of the hydroplane overeeption of No. 4) an eight -oared racing boat.

At 30 boatisgreatlyincreased This type of boat has, of course, a high .. t) theordinary These figures are taken from a standardspeed. In the boat, the power is employedcentre of gravity, and is balanced by the work on marine engineering. inwave making and overcoming skinlong oars of the rowers, but there is an easy friction. The hydroplane, when travellingmethod by which this can be overcome. An Experiment with a Rotating Disc atspeed, may haveits wetted surface A gyroscopic disc (with a certain stringreduced by as much as two-thirds, leavingThe Three Models pull) was rotated for the and half minutesonly one-third to produce skin friction- Three types of boat are dealt with in in air. With the same pull in water it spunthe displacement resistance having lessenedthis article. The ,smallest one is 3 ft. long for ten seconds only. The disc was thenin the same proportion.Thus, providedand has a maximum width of 4 in.; a coated with a film of paraffin wax ; it thenit registers sufficient speed, the hydroplanecylindrical boiler, 12 in. long and 14 in. in diameter; a special vapour lamp (to be described indetail later); and a Stuart li" 21" --->1< 14" - - Turner " Meteor " engine.It is carefully " lagged " to prevent steam condensation. The torpedo -shaped body beneath is the keel, and all three models have such keels. WWI STERN The long, narrow model is 5 ft. long and 3in.maximum width.Theplan,or PLAN horizontal section, is that of a racing eight. 48° The third model has a maximum width - - of 54 in. and is 4 ft. long.It has a boiler, ELEVATION 1 ft. long and 2 in. in diameter; a Whitney engine, 4 in. bore and ft in. stroke double- acting; and also a Stuart Turner lubricator Fig. 2.-A plan and elevation of the sheer ofthe speedboat shown above and steam tap. rotated for twenty seconds.This experiment shows in a very striking manner how great this resistance can be, and how it can be lessened. Hydroplanes Why are hydroplanes so much faster than ordinary boats? A hydroplane, or skimmer, is so constructed that it lifts itself out of the water when running, and actually displaces very much less water and has far less wetted surface than when at rest. To enable the boat to lift from the water, it must have a speed of about 16 kr ots, and unless this is the case this type of broad, flat-bottomed boat is not nearly so army to drive through the water as the long and narrow type- say, the racing eight--vhose length is from Fig. 3.-A close-up view of the engine of the steam -driven model November, 1939 NEWNES PRACTICAL MECHANICS 91 The long, narrow model is electrically prow and stern. Screws through the holes a., driven by means of two 4 -volt accumulators described above fix them to the tubing. and an 8 -pole motor geared down about --NEARLY 374. ----- In the case of the electrically -driven 1 to 6. model the tube was 4 in. in diameter, total The idea underlying the design of these length 9 in., distance from bottom of boat keels is to lower the centre of gravity the 64 in., and weightlb. necessary amount-on the principle of the In the smaller steam -driven model the lever-with the minimum of weight, a 1 -lb. FRONT tube was 84 in. long and 4 in. in diameter; weight 4 in.below boat bottom being HOLDER. distance below boat 84 in., length .7in., equivalent to 4 lb.1in. below it.Their weight 4 lb. torpedo shapes offer minimum resistance. For the larger model the tube diameter Results is I in., total length 7 in., distance below boat 7 in. and the weight, 1lb.From Let us take the electrically driven model a minimum resistance -point of view the - first. Various motors were tried and various 9°. first has the best proportions. dry cells. Finally the plant described above was installed. Unfortunately this was very The Power Plant and Lamp heavy-each accumulator weighed 1 lb. After considerable experimenting, two and the motor 14 lb. -34 lb. in all.The lamps of different design were constructed, balancing -keel weight was lb., and had both of which gave very good results. The to be placed 64 in. below the boat. The REAR. first lamp, however, did not give quite so hull weighed 4 lb., and the result was that HOLDER low a centre of gravity for the boiler, was the boat was too deeply immersed for good not so easy to start, but had the advantage results. Nevertheless, with freshly charged of simplicity. A vertical section of the lamp accumulators, using 8 volts, and favourable 4 . - conditions, a speed of between 6 and 7 milesFig. is shown in Fig. 6, and its construction is per hour was obtained. Detailsof the quite simple. The smaller of the steam -driven models,two side plates Obtain a piece of thin tin, 114 in. by of theboiler 24 in., and bend a piece of thin sheet at a steam pressure of 80 to 100 lb., was copper to the shape and dimensions shown capable of a speed of 8 to 9 miles an hour. in Fig. 6. Solder the two edges of the latter This model, although not so deeply im- to the edges of the strip of tin (note the mersed as the long electric one, obviously central rectangular portion must not quite suffered from an insufficientfloatational touch the tin) and solder two rectangular capacity.The larger steam -driven modelround the inside edges and V-shaped piecesstrips of tin, one at each end, to the central was capable of practically the same speedat the prow and stern to make themrectangular portions of the copper, Make as the smaller, at a pressure from 60 tothoroughly watertight. the joints fluid -tight, and then solder a 80 lb. per square inch. The hull of the long electrical model hadpiece of thicker copper over each end, Its general behaviour was, moreover, fara backbone or keel of wood, 5 ft. long withhaving previously drilled two small holes, taperingends, 4in. G broad and 4 in.deep.one at each end in the bottom of the 4". copper. When spiritis poured into the To thiswas fastenedcentral trough itwill run through and ribscutfrom4 in.partly fill the entire chamber. A number three-ply, and the shellof small holes are drilled from end to end was of three-ply,ifin. thick. A piece of 4 -in.on the upper outside edge of the trough, three-ply, in.deep,and when the spirit in the trough is ignited was fitted to the top, onthe copper, a good conductor, is soon heated. each side, from end toSpirit vapour is thus formed, and, issuing R end. V-shaped piecesfrom the holes, at once ignites. This lamp O 0 0 0 0 0 0 0 o 0 0 0 is to be preferred to any form of wick lamp were placed at prow andand gives a far more intense heat. Owing 0 0 0 0 0 0 0 0 0 o o 10 o stern.Ineverycase V-shaped pieces of tinto the narrowness and depth of the trough, 1 capped the bowandthe spirit is troublesome to ignite (especially 33/4 in cold weather) unless it is poured in hot. stern to give a knife-edge.It is heated by standing the container in 0 0 0 0 0 0 o o oio o Boats constructedasboiling or very hot water. O 0 0 0 0 0 O o 0 o o above are much stronger The second lamp is shown pictorially in lc than would be supposed.Fig. 6.It contains three distinct parts: an The Torpkdo Keel ordinaryspirit lamp with wick, E ;a Having decided on thechamber, F, in which spirit is boiled and MOLE FOR SAFETY VALVE1 M weight to be used,aevaporated, and from which a pipe leads 5i piece of thin brass tubingto a piece of brass or copper tubing of CUT-OUT PORTION FOR STEAM OWE I should be cut and filledrectangular 4 -in. section, closed at both ends. STEAM PIPE 6 PIPE TO PRESSURE GAUGE I1 with molten lead (ex-This tubing rests on the bottom of the boat, 1 .1 cepting in. at eitherthereby giving the lowest possible centre end). Three small holesof gravity for the boiler. In the top of this F -4 Fig. 5.-Constructicnal details of the casing of the boiler M are drilled very near thetube isdrilled a large number of holes two ends of the tube,(fifty to sixty in number), using a 69- to superior to the smaller one. So far as ishaving equal circumferential differences, and75 -twist drill.They commence at A and known, these speeds are in excess of any-into these are fitted suitable turned or shapedcontinue to B, as shown. This lamp gives thing hitherto reached with a similar typepieces of wood to give the tapering forms ata steadier flame than the previous one, and of plant and size of boat. A SECOND LAMP Constructional Details of the Hulls AIR -TIGHT RiNG CAP FILLER In the case of the steam -driven models the bottom is a piece of ordinary 4 -in. VAPOURCHAMBER three-ply, cut to the shape shown in Fig. 2. VAPOUR TUBE The sides are h -in. three-ply, glued and fastened to the bottom with small gimp pins.At the bow and stern, V-shaped FINE HOLES FOR pieces of wood are fitted, to which the FULL LENGTH OF LAMP bottom and sides are glued and pinned. WICK TUBE Round the top of the sides, from end to end, a strip of 4 -in. three-ply, 4 in. broad, is fastened. The hull is further strengthened AIR VEN117,-- by one or two transverse pieces of L-shaped N tin fastened to the sides. The hulls were SECT ION OF than given three coats of varnish and two of FIRST LAMP aluminium paint.Paraffin wax was run' Fig. 6.-The construction of the two types of vapour lamp 92 NEWNES PRACTICAL MECHANICS November, 1939 can also be regulated by the flame of theThe Boiler essential to line the sides with thin sheet heating lamp. It has only one disadvantage, This must be brazed. Obtain a piece ofasbestos inside. A similar sheet of asbestos however, for if the heating lamp wick iscopper or brass tubing of about 18 gaugeis placed on the top of the boiler-slightly blown out it very quickly ceases to function.and of asuitablelength.Blanks arecurved and with the necessary holes for With this lamp, when once started, 6 oz.required for the ends, a heavier gaugethesafetyvalve,etc.Any additional of cold water has been raised to a steamshould be used for these, say 16, or even 14.corner or end pieces of tin that may be pressure of 60 lb. in ninety seconds.It To provide the dry steam you must havenecessary to thoroughly shut in the flame generates steam sufficiently fast to keep upa steam dome and a safety valve. Theymust be fastened on with very small nuts the pressure for the " Meteor " engine andcan be bought from 3d. up to 5s. 6d. and itand bolts ; soldering is useless. for the larger f in. bore and stroke, theis certainly advisable to use a good one. The safety valve (if spring is external) pressurefalling very slowly with bothThe same hole into which this screws is,must be protected from the flame or its engines going all out, and using a 2 -in.of course, used to fill the boiler, which shouldtemper may be spoilt. Asbestos -lined caps propeller in both cases. The tins used forbe filled not more than two-thirds full.should be fitted over the ends of the boiler the lamps were made out of lower parts ofA 2 -in. boiler, 12 in. long, holds 16 oz. ofto prevent radiation. old fruit tins, and only soft soldering waswater. A pressure gauge is essential and To obtain the best results, careful lagging used throughout. if using a vertical engine it is essential toof the pipe conveying steam from the boiler The dimensions of the various parts areuse a lubricator. to the engine and of the engine itself is as follows : For the larger model (see Fig. 6), To mount the boiler cut two pieces ofessential.To dothis,placepiecesof the container, E, is 3 in. in diameter, 1 in.thin tin to the dimensions shown in Fig. 4,asbestos in a saucepan containing a small deep ; container, F, 3 in. in diameter, If in.and bend as shown. The 2 -in. hole can beamount of water and boil, at the same deep, and for the smaller model, E, 2 in.cut with an ordinary 2 -in.centrebit.time pounding the asbestos to a pulp. by ftin.,F,24in.by1l4in. They are then placed one at each end of theNow squeeze it in a cloth and apply round The actual amount of spirit to put inboiler, allowing about in. to protrude.the pipe, etc., afterwards binding with tape. each is best found out by a few experiments,They should be a good fit, their upturnedThe slide valve and cylinder of the engine but E needs but little, and should not goportions being screwed to the bottom ofshould be siniilarly treated. on heating F after all the spirit is evaporated.the boat. The boiler and container F, especially There is very little actual pressure and no the bottom, soon become coated with a safety valve is needed ; soft soldering aloneThe Casing or Cover deposit of carbon-a powerful non-conduc- will answer-but silver soldering makes the This is of thin tin cut to the dimensionstorof heat ;thereforetheymust be best job. shown in Fig. 5 and bent to shape.It isfrequently cleaned.

OUR BUSY INVENTORS A Watch "Put (Continued from page 89) and Take" Accommodating Legowear A Wooden Hat THE materials required for making this A SWISS citizen has applied for a patent present year is the centenary of the simple device are a cheap watch, a sheet rl in this country for an invention relat- THEdeath of William Murdoch, the inventorof thin notepaper, and some water colours. ing to trousers. The specification describingof gas for illuminating purposes.AfterRemove the back of the watch and care- his device states quaintly that it is meantarriving in England from Scotland, wherefully remove the escapement (see Fig. 1). for " sports people," i.e. cyclists, mountainhe was born, he altered the spelling of hisThis will allow the hands to spin round climbers,gymnasts,walkers,etc.,whoname from Murdoch to Murdock on accountwhen the watch is wound up. Next remove possess both long and short trousers.Itof the inability of Englishmen to give it thethe front of the watch, take off the hands, adds that there are " sports people " who,true guttural pronunciation.In his earlyand remove the dial. A circle should then for financial reasons, can acquire only onedays Murdoch, in the course of an interviewbe cut from the notepaper (the size of this of these two kinds of trousers. The inventorwith a prospective employer, owing to ner-circle being effected in accordance with the provides trousers which will play the role ofvousness, dropped his hat upon the floor.size of the original dial, and ruled off into both the abbreviated and the elongatedThe peculiar sound made by the fall excitedeight sections as shown.These sections variety of nether garments.The legs arethe curiosity of the gentleman he was inter-should then he coloured and the printing divided, and can, consequently, be used asviewing.Murdoch then revealed the fact shorts. But, if desired, an additional lengththat the hat was made of wood. He had may be affixed. The connecting means mayturned it on a lathe of his own making. But, be slide fasteners or hooks and eyes. although his hat was made of wood, his head was not composed of that material, Station Indicator for his ingenuity conceived many valuable inventions. COME time agoIstressedinthese * * * * J columns the desirability of an indicator in railway coaches to inform the traveller at what point the train had arrived.There Tilley Products has now been patented in the United States a that restrictions have been placed station indicator comprising a movableNOWon electricity andcoal,the Tilley web having thereon the names of theparaffin radiator will prove ideal for warm- stations in the order in which they appear.ing small rooms and is especially useful An electric motor causes this indicator towhere heat is only temporarily required. function.It should relieve the oft -puzzledAsitisportable and independent of passenger from the necessity of picking outconnections, it can readily be moved from A novel game made from an old watch the name of his destination amid the crowdroom to room, and being a radiant heater, its effect is felt immediately. It will give sixdone in accordance with the illustration. of advertisements which surround it. hours' heat for one penny per burner, andP represents the word " put " and T the container holds sufficient paraffin for" take."Res. means " re -spin " and T. All Streamlined Turkeys ten burning hours. The radiator is 17 in.being" takeall."Itisadvisableto CHRISTMAS is coming.The season ishigh, has a 124 -in.reflector and weighspaint the sections up to the dotted line as festive but, from the point of view of34 lb.It costs 37s. 6d.If you require ain Fig. 2, the reason being apparent on the turkey, it is tragic.It seems that thelarger size of heater, there is the Tilleyreferring to Fig. 3. Now stick the paper full-sized bird is too huge for many smalltwo -burner radiator costing 72s. 6d. disc on the front of the watch (after making ovens. To overcome this difficulty, I learn This firm also have a large range ofa small hole for the hand " drive "), replace from an American source, that, instead ofparaffin lamps, an interesting line being thethe minute hand only, and finally the casing. seeking an expanding oven to suit the vary-storm lantern at 36s.It is strongly made Should the watch have an unbreakable ing dimensions of the turkey, it is the aim ofwith no parts to rust or corrode. burnscelluloid cover (not glass), this will be an certain breeders to produce a bird of lesssteadily, and isunaffected by weatherasset, since by slight pressure of the thumb ample proportions.The object is to caterhowever severe.The burner hood has(to prevent the hand turning), a good wind for families which are not so large as thata small reflector which prevents rain fallingcan be affected and consequently a good of the lady whose residence was a shoe. on the globe. spin attained on removing the thumb. November, 1939 NEWNES PRACTICAL MECHANICS 93

certainly experience no difficulty in getting the gas to explode. 11QUERIEScvia Colouring Concrete I HAVE some pure white cement which 1 wish to tint blue and grey. Can you tell me of a non -fading blue or grey pigment to ENQUIRIES use?-E. H. (Bucks.) l YOU do not mention the exact purpose for which you wishto use the coloured stampedaddressedenve.ope, hreepenny oncrete.Hence, we cannot advise you ->U\ ;tamps, and the query coupon trom the current upon the precisedetailsofitsmixing. ANL/ issue, which appears on page iii of cover, must be However, an average mixing of dry Portland enclosed with every letter containing a query. Every query and drawing which is sent must bear cement and fine sand (approximately equal the name and address of the sender.Send your proportions of each) may be coloured by A Special Enamel queries to ..he Editor, PRACTICAL MECHANICS. Geo. Newnes, Ltd., Tower House, South mpton incorporating with it a suitable insoluble is possible to make an enamel capable StreetStr:nd, London. W C.2 pigment in amount proportionalto the Iof resisting the action of sulphuric acid, depth of colour required. and wouldthisneed any specialunder- For black or grey colourations, ordinary coat if used on wood?-N. J. (Essex). not get the gas to ignite.i am using theiampblackmixedwith a littlefinely. UNFORTUNATELY, you do notsay hot -tube principlefor ignition and the gaspowdered pyrolusite or manganese dioxide to what strength ofsulphuric acid isat atmospheric pressure.I am certainwill give the effect' required, this pigment youwishyour enamccoatingstobe that once I can get an explosion, the valvebeing absolutely permanent. The most permanent blue pigment which resisting.Itisimpossibleto obtain an I have designedforcontrollingignition enamel whichwillresisttheaction orand inlet gas will work. you can employ is Cobalt blue, which ha. a concentratedsulphuricacidover,ong Could you suggest any reason why therather greenish shade and which is expen- periods, but with sulphuric acids of ,owergas does not explode, or any other means 01sive. Ultramarine is a good blue, but is not strengths (say up to thirty per cent. orignition? --G. G. (Hull). resistantagainst water, containing traces of acids.Lime blueis a cheap pigment even more) any enamel containing bitumen lailureolthe gas to explode In willbesufficientlyresisting.You canTHE and may suit your needs. None of these prepare such enamel by making up a your pump must be due to one (orblues, of course, possesses the same degree both)of two reasons:viz.-the gas -airof permanence to light and other influences strong solution of bitumen in turps and bymixture may not be of the correct propor- adding it to any ready -prepared enamel in as common lampblack, and for use as a tions and the ignition tube which you areconcrete pigment in an exposed position such quantity that it does not thin downginploying may not be hot enough. the latter too drastically.The woodwork we should say that an absolutely permanent For an effective coal -gas explosion youblue does not exist. should be given three or tour coats of thisrequire a mixture containing about twelve enamel, each coat being allowed to dryparts of air to' one part of coat gas.if the thoroughly before applying the next. mixture " Carblyst' Anti -sulphuric enamel istoo richincoal gas or too of this typedeficient init.itwill not fire.Also, the I UNDERSTAND that a " catalyst " is a is a commercial commodity and may beignition tube must be heated to a bright metal that has the power of assisting Obtained fromthe leadingphotographiccherry -red heat.Preferably,it should beother chemicals to interact, merely by their supply houses,as,fOrinstance,Messrs. made of nickel alloy,or,betterstill,ofpresence, without entering into the reaction Jonathan Fallowfield, Ltd., 61-62, Newmanplatinum, which enormously facilitates thethemselves. Is this correct ? Street, London, W.I. or from Messrs. Mayready ignition of the mixture. Assuming that the above is right, could and Baker. Ltd.. Battersea. Without being acquainted with the designyou give me alist of metals that have The enamel prepared as above will notof your engine, it is practically impossible" catalytic " properties ? need any special under -coating, althoughfor us to offer detailed suggestions concern- Could you give me an address or addresses a preliminary thin coat of priming painting it, but we incline to the opinion thatwhere I could obtain such metals ?-F. M. will do the woodwork no harm. (Hants). We would warn you not to expect tooyou would have more success .withit,if much of these anti -acid enamels. They are,you could discard the hot -tube method of ACATALYST " is'asubstance,no, ignition and rely upon electrical ignition necessarily,but usually, a metalin of course,quitesatisfactoryfordiluteby means of a spark derived from an" finely -divided " or powder form, which acids, but strong mineral acids quicklyinduction coil or a high-tension magneto.initiates or accelerates a chemical reactiot, attack them. Possibly; though.you may have verybut, so far as we can tell, does not its.') special reasons for sticking to the hot -tubeactually take place in the reaction. Yost, Zinc Oxide Adhesive Plaster method of ignition. definition of " catalyst " (whieh, incident is the recipe for the zinc oxide In general, however, provided tat yourally, is itselfa pretty meaningless word) c. WHATadhesive plaster used on surgical tape?gaseous charges have an approximatelycorrect. -K. A. (Middlesex). correctcompositionand,also,provided As a typical example of a catalyst, let us that your ignition tube is maintained at a infinely -dividedform. YOU can make zinc oxideplasterfor takeplatinum, spreading on tape in two ways :- ufficiently high temperature, you shouldWhen oxygen and sulphur dioxide are (a) Make up a mixture of olive oil and heated, they do not combine. When. hom. zinc oxide, employing somewhat more olive ever, these gases are passed over heated platinum. initfinely -divided form, they oilthan zinc oxide.Allow itto stand IMPORTANT NOTICE overnight and then heat it on a water combine almost completely, forming sulphur bath for two hours. On cooling, it will set Owing tothe restriction of paper trioxide. which can afterwards be combined to a white adhesive mass. with water to form sulphuric acid.This is supplies in war time,readers may avery important example of catalytic (b)Dissolve 1 oz. of powdered Castle finditimpossible to get " Practical action and forms the basis of the present- soap in 20 ounces of water and add this Mechanics " each month unless they day " contact process " for the manufacture to a moderately strong solution on zinc give their newsagent a regular order of sulphuric acid. Note, however, that iron sulphate. A white precipitate, consisting for their favourite magazine, now. oxide has a similar catalytic effect and hence mainly of zinc oleate will be formed. This Wastage of surplus copies in the that a catalyst deed not necessarily be a should be filteredoff, washed with cold shops must be avoided, and readers metal. water and allowed to dry. It can be spread can be of the very greatest help if they The metals which are most used on on tape and will retain its adhesive condi- will fill up the Order Form given on account of their catalytic properties are tion indefinitely. page 88 and deliver it to their usual platinum, palladium, tungsten, mercury, Remember, when spreading the plaster newsagent or bookstall. An order of iron,nickel, vanadium. All these are material on the tape, that only the thinnest thissortensuresregulardelivery employed in " finely -divided " form. Well- possible layer of it is required. during War time,and theEditor known non-metallic catalysts are iron oxide, asks every reader to help in this way. nickel oxide,- ammonium vanadate, man- A Direct Explosion Pump PLEASE ORDER " PRACTICAL ganese oxide, manganese sulphate. I HAVE designed and built a direct explosion MECHANICS " NOW AND USE You can obtain any of the above materials pump to work on coal gas, but so far I THE ORDER FORM ON PAGE 88 (to order) from your local branch of Boots have not met with any success as I could the Chemists or from a chemical supply firm 94 NEWNES PRACTICAL MECHANICS November, 1939 such as Messrs. Harrington Bros., Ltd., ELECTRADIX City Road, London, E.C. In WORKSHOP and HOME At a time like this we are only advertisingimmediatelyuseful keep warm with a PORTABLE THE WARitems. Previous adverts. detailed D.C. Motors on A.C. a wide range of goods. Where stock is limited preference is now given to National Service users. IS it possible to run a 200 volt, 0.5 amp, ELECTRIC SUPPLY.An Independent Emergency or J continuous current motor on a 240 volt Stand-by set may be of great value to you.Can be alternating current circuit? TILLEY RADIATOR transported on any car that can carry 3 cwt. All these I understand that A.C. can be used to The unpleasant conditions of winter sets that we are offering are in first-class order anddrive ordinary D.C. motors so long as they aresoonforgottenamidstthe straight from reserve Govt. Stores, kept unused as comforts of the home. The Tilley stand-by.Being a pre -crisis release they are an oppor- are not very large. My attempt to do so Radiator being PORTABLE, pro- tunity for a low price purchase that might not otherwise with a motor of the specification given above vides warmth in workshop, sitting - have occurred and certainly cannot be repeated. Thehas, however, proved unsuccessful.It may room, bedroom, bathroom,etc., Half Kilowatt Set is worth £50, but our price is only tit, as required. Burns ordinary and with engine and dynamo carry the full Electradix be that the motor itself is faulty. -H. W. paraffin at the low cost of Id. guarantee. (Bethnal Green). for 6 hours. Requires no con- A.R.P. PETROL ELECTRIC GENERATING SETS for nections or fixing. Absolutely safe. Lighting and Charging. Half h.p. DIRECT WHETHER a directcurrent motor No wicktoadjustand causes COUPLED 150 watts D.C., 1,800 r.p.m., will run on alternating current depends neither smoke, smellnormess. 2 -stroke water-cooled 1-cyl. upon the type of winding. A series -wound British throughout. Price 37.6. Engine, magneto ignition.On bedplate with 30 volts 5 amps commutator -type direct current motor will Soldbyallgood Ironmongers and Dynamo, 112. operate on A.C. fairly well, but will not Stores.If any difficulty, write to:- 80 larger size t kW. S.T. Petrol develop the same amount of power, and the Electric Sets, 500 watts, 2 -stroke TILLEY LAMP CO. (Dept. P.M.), HENDON, N.W.4 water-cooled 1 h.p. 1-cyl. engine speed characteristic will be much steeper, on bedplate direct coupled to 50170 volts 10 amps. D.C. that is the speed will fall off more rapidly Dynamo, magneto Ignition, fuel and oil tank, tie. with increase of load than when used on STORAGE. You may have charging facilities and want D.C.Also itis essential that both fields to install high capacity steel accumulators which will hold their charge almost indefinitely. and armature should be laminated, other- CHEMISTRY EXPERIMENTS A.R.P. EDISON HIGH CAPACITY STEEL CELLS at wiseconsiderableoverheatingislikely. half price for stand-by lighting, 120 A.H. to 300 A. H. at With a shunt wound D.C. motor, however, FOR BLACK -OUT EVENINGS 20/- to 25/-. Makers' price is £5. Ask for leaflet. FULL the case is different.Since the armature Post Free OFFER PARTICULARS gladly given as far as we are able to OF SAMPLE PARCEL A.R.P. ENQUIRIES. and the field circuits are independent of containing many YOU MUST KEEP YOUR BATTERY PREPARED !!! one another and the self induction of the usefulpiecesof Battery Charging on A.C. Mains. The A.G. NITN-DAY field winding far greater than that of the will keep your battery fit without attention.Model CHEMICAL N/A0, 100/250 volts A.C. and D.C. 6/8 volts t amp., armature, the lag in magnetisation of the 15/, Model 11 / BO, 100/250 volts to D.C. 6/8 volts I amp., fields is so considerable that armature and APPARATUS 25/,Model N/CO3 100[250 volts to D.C., 6/8 volts 2 field currents do not arrive at their maxi- amp., 35/-.Model N/011, 100/250 volts to 12 volts I mum value at the same time, one being amp., 32/..Ditto, 12 volts 2 amps., with 6 -volt tap, 2/9 55/-. 5 amp., 114/101-. near zero value while the other is at maxi- Fuggy Dugouts or Ill -ventilated shelters must be kept mum, consequently thereislittle or no Write also for PRICE LIST fresh. torque. A.R.P. SHELTER Ventilation and AirCondffroning. of other Sets. Compact unit, drive off A.C. or D.C. mains, 80 watts; 25/- is a (Scientific Dept. A), 60, High St., 9 in. Blower, 20 cub. ft. fresh air per min. Wind Motor for Fountain BECKStokeNewington, London, N.16. bargain pricq. Rpokiet, "Experiments in Chemistry," 6d. P.O. WET WEATHER ELECTRIC PUMPS, for A.C. or D.0 I intend to erect a wind pump for the 12 v. to 230 v. Centrifugal all -bronze pump, throws 120. purpose of pumping water up intoa gals. per hour, 72/8. Type R pumps. Twin piston type tank of 28 gallons capacity and 9 ft.in for draining shelters, dug -outs, etc., 318/17/11. height. RADIO SIGNAL PHONES. Complete sets with 5 line or 20 line exchanges. Portable army wardens' phones, etc. The wheelconsistsoftwelvevanes, INSTRUMENT Willa State wants. each having an area of 15 square in. andBARGAIN OFFERAt Half Ordinary Prime POCKET HEADPHONES. W.D. all leather being included to the plane of motion at Price per lb. for Double Cotton Covered , headband strap and cords, 2/6 pair.Wireless 25 SWG 1/8 28 SWG 2/2 30 SWG 2/10 an angle of 35 degrees. The total diameter 32 SWG 3/4 34 SWG 3/IS 36 SWG 4/9 type with aluminium headbands, 2/9.4,000 Price per lb. for Double Silk Covered ohms., Ct.LISTENING MIKES, steel -clad of the wheel is 30 in. and it will be 9 ft. high. Electradix, indestructible; are ears outside The water from the tank will be used to work 26 SWG 2/8 28 SWG 2/10 30 SWG 3/2 32 SWG 3/8 34 SWG 4/8 40 SWG 9/ - your dug -out. a small fountain.Could you let me know Postage 6d.Reels and Winding 6d. per reel CABLE.Lightweight twin field cable, unbreakable SPLIT PHASE A1 -4C2.5 MOTORS mile. Heavier types, the following :- Army steel reinforced,66/- 1. What size pump (single acting) this mill All voltages. 65/- and 70/-. Idealforworkshop and FIRE CONTROL SIGNALS. Emergency day Lucas and would work ? industrial uses. Heavy duty Aldis Hooded Army Signal Lamps, telescopic sights, 2. Whether this size pump will keep the rating.No radio interfer- hand or tripod. For Fire Brigades and Police, 60/-. tank supplied with water? -H.G. (Don- ence and silent.I h.p. 55/-; AID RAID SIGNAL BELLS -FIRE ALARM BELLS. t h.p. 65/,Other motors Waterproof mains, Battery or Hand magneto Buzzers; caster). from 16/6.Universal, Cap- Morse Practice Sets.Morse Keys.Recorder gear, as ITisalwaysdifficultto estimatethe acitor,Repulsion,at low previous adverts. prices. Low voltage Trans- CRYSTAL SETS. Model B, Pol. Mahog. case, 9 in. by power available from windmills of the pfoinrgmsemj4ecoon=ta6/pi. 10 in., 2 tuning condensers, plug-in coils, Permanent type shown in your drawing, not only Leaflets Detector, 7/6. 4,000 ohms. 'Phones, 4/6. because of the variable nature of the wind Post 6d. CRYSTALS, RECEIVING. Super Detector, glass cover, velocity but also on account of the suita-LL. WILKINSON, 204 LOWER ADDISCOMBE ROAD, CROYDON fine adjustment, 10/-.Enclosed 2 -crystal permanent Detector, 2/-.Carborundum Marconi Army Detector, bility of the site chosen and presence of 2/6. Galena point Detector, mounted, 1/8. Galena andany deflecting obstructions.One cannot Neutron Crystals, 4d., 6d., and Perikon, 1'-. arborun- expect very much from a wind vane 30 dum mounted, 8d. CHARGE YOUR L.T. CRYSTAL OR BATTERY SET BUILDERS. Fitted inches in diameter on a tower only 9 ft. Table Cabinets, polished oak, 131 in. by 7i in. by 6 in., high, but the nearest estimate that can be AT HOME Battery ..1311ex"Charger oval aluminium black panel fitted geared, .0005-mfd.,given as to the pumping capacity assuming Justplug-in,fit spades,switchon,that'sall! sunk dial, 3 -way coil switch and a single plate vernier Prices :2v., 1 amp, 12/6; 2 amps, 18/6; 6v., 1 amp, condenser, and 10 terminal Strip, new stock, 15/, a moderate wind velocity of 20 miles per15/,Car BatteryModels :6v.,2amps,25/-; MORSE PRACTICE SETS, No. 3, with key buzzer and hour with a pump of 2 in. bore and 4 -in. 12v.,30/, CommercialChargerfor1-14, 2v. lamp for sound and visual, line plug, etc., 7/-. Sound stroke would be approximately 60 gallons cells, 0-3 ammeter, Low, Medium, High taps, 50/-. Type, 1A type key and buzzer, 3/-.Visual Type 2A, Larger Models, 75/-, 90/-. All have Metal Rectifiers per hour. Whether this would keep your and strong steel cases. Send 3d. for REAL PHOTO key and lamp, 2/-.Buzzers from 1/- each. 28 -gallontankfullysupplieddepends and FREE TRIAL terms. KEYS. Govt.surplus table Morse Keys. Type entirely upon the discharge rate from the BRIGHTON RADIO SERVICE, RBSL.Polished wood 34 Middle Street, Brighton. base, massive brass fountainjet,amatterforexperiment pivot bar, tungsten alone. According spring-mountedeontacts to" Molesworth,"a for quiet working andcircular vane -type mill of 12 ft. diameter base lamplor light.A working in a wind velocity of 15 miles per Easily made from our first-class Key for opera- hour would only develop castings 12/6 per set. tors. h.p., and on Complete Engines 6'. EMERGENCY PARCELS ofuseful the assumption that the power developed readytorunfrom stand-by electrical and radio repair material is approximately proportional to the square NM. and apparatus, 10 lbs. for 5/-.Post Free.\I of the respective diameters of the wheels HALLAM & SON Don't forget to send now for our Bargain List P. the ratio would be 144 to 6.25, indicating Ilwiteglamr Upton, Poole, thatthe maximum output from your ,Imo' Dorset ELECTRADIX RADIOS itlIASH Vat. rasscut. ENGINES . . . for 30 -inch mill would only amount to a trifle Aet °planes and Speed Boats. 1 to 15 c.o. 218, UPPER THAMES STREET, LONDON, E.C.4 Send 3d. for particulars Telephone Central 4611 over one hundredth horsepower. November, 1939 NEWNES PRACTICAL MECHANICS 95 GREAT NEW TECHNICAL PARTWORK FIRST PARTS. Now on WEEKLY Sale AEROPLANE PARTS MAINTENANUEOPEATIN Every young man beginning a career in aeronautics or changing over from motor engineering should be certain TOBECOMPLETEDIN ABOUT 40 WEEKLY PARTS to buy it to -day ! CE PART THIS authoritative new part work is compiled under the supervision of technical experts in close touch Jr AEROPLANE with the very latest aviation practice in England and America.Itisabsolutely comprehensive and of invaluable assistance to GROUND ENGINEERS, MAINTENANCE&OPERATION INSTRUCTORS, AIRCRAFT MECHANICS, A COMPREHENSIVE WORK INTENDEDFOR ALL AIRCRAFT ELECTRICIANS,andallwhose INTERESTED INCIVIL OR MILITARY AIRCRAFT livelihood is wrapped -up in aeronautics. Every detail of repair and overhaul, dismantling, inspection and reassembling iscovered.Whether DEALING WITH the subject on which you require technical and SERVICING, trustworthy information deals with boost control, MAINTENANCE, hydromaticairscrews,ignitionscreening,latest and REPAIR of de-icingequipment,operationandservicingof LEADING BRITISH accessories and instruments, you willfinditin AND AMERICAN AEROPLANE MAINTENANCE & OPERATION AIRCRAFT and A Brief Outline of the Important Contents: AERO ENGINE AERO ENGINE CARBURETTORS. COMPONENTS Principles of Carburation. Automatic Boost Control. The Hobson AVT9.5. MB Carburettor.The Hobson AV70-M Carburettor.S.U. Carbu- GIVEN IN THIS PART rettors.Rolls-Royce Carburettors. Zenith Aero Engine Carburettor-. etc. DATA SHEET All the above will be dealt with from the point of view of operation. maintenance. tuning, adjustments and repair GIPSY XII ENGINE ENGINE STARTING EQUIPMENT. AERO ENGINE MAGNETOS.. AIRCRAFT ELECTRICAL EQUIPMENT. Electrical Equipmentfor opirating Wag Flaps and Undercarriages Electrical Speed Indicators.Electrically, Driven Fuel Pumps and Vacuum Pumps.Rotax Weston Engine Indicating Equipment.Electric Genera- tors.Electrical Fuel Contents Gauge Navigation and Cabin Lamps Ignition Screening for arm e -eines AERO ENGINE DATA SHEETS. It is hoped in this series to cover most of the Engines given in the list be ow Readers will, however, appreciate that this list may be subject to modification, should official requirements necessitate this. GEORGE NEWNES Gipsy XII, Gipsy VI, Series I and II, Gipsy Major, Series 1, Gipsy Minor, Hercules, Taurus, Perseus, Kestrel, Dagger, Cheetah Genet. Lynx, Leonides, Pelides, Rapier, Cirrus. Mikron Peregrine. Aeronca Tiger. VARIABLE PITCH AIRSCREWS. UNDERCARRIAGES AND TAIL UNITS. FREE Eachpart throughout the work will conta n Landing Legs.Lockheed Airdrauiic.Vickers Oleo Pneumatic. Turner With Oleo Pneumatic.Dowty Oleo Pneumatic and Hydraulic. Aeroplane an Engine Maintenance Data Chart. Wheels and Brakes-Dunlop-Palmer. Dowty Hydraulic Brake Cont.ol. ParttaData Sheet is presenteddealingwith the famous PneumaticBrakeControls.Undercarriages.DowryandLockheed Retractable Systems. Turner Olaer System.Tail Wheel Units Nut Gipsy XII Engine. cracker Retractable Struts.Bendix Pneudraulic Shock Atsorber AIRCRAFT 'CONTROLS. Over 1,000 specially approved -action" ControlsforWing Flaps andUndercarriages.Lockheed Hydraulic Control System.Dowty Hydraulic Control System. " Messier " photographs of operations and drawings, Hydraulic Control System.Dowty Hydraulic Accumulator-Rudder Bar also invaluable tables and data. etc. Differential Control System Sperry Gvropilot-P.B. Deviator-Smith Automatic Pilot. * INSTRUMENTS AND ACCESSORY EQUIPMENT. AEROPLANE WIRELESS EQUIPMENT DE-ICING EQUIPMENT. GET YOUR COPIES TO -DAY THE LINK INSTRUMENT AND RADIO PILOT Of all Newsagents and Bookstalls. TRAINER, etc.

George Newnes, Ltd. 96 NEWNES PRACTICAL MECHANICS November, 1939 AUTHORITATIVEBUY, EXCHANGEorSELL TRAINING TOOLS-Continued 120 Combined Engineers & Woodworkers Vices, a FREE SERVICE most useful tool in any workshop, 6" Jaws, opens 4r. Clearance price,4/9 each;honestly worth double. in Wartime -Below. 500 Woolworker:Vices,4" Jaws, clear 2/9 each.- Below. In peace -time the T.I.G.B. home -study courses 85 Machine Vices for Drilling or Milling Machine. For FOR READERS Robust design, Width of Jaws Of", opens ilf"very provided first-class technical education. cheap to clear, 3/3 each, below. severalyearspastthepasspercentageof 2/9 any lot.Eight lots St -Below T.I.G.B. Students at Professional Engineering Toolholderwith four H.S. Tools. Examinations such as A.M.Inst.C.E., I" Adj. Boring Tool with H.S. Tool. A.M.I.Mech.E.,A.M.I.E.E., A.F.R.Ae.S., i" Drill Chuck, taper or straight shank. C. and G., etc., has not once been lower than -i" to " Silver Steel, 1:1 pieces, 13" long. 96%-and no fewer than 22 FIRST PLACES READERSrequiringin- f" to f" SilverSteel,4 Ili., 2" to 4" long. have been gained.In War -time the advantages 500 Ass. Brass and Steel Screws. etc. formationconcerning 100SteelHex. Bolts and Nuts, i" to i". of T.I.G.B. Training-free from black -out and 16 H.S. Drills, 1 3.2" to 5/32". travel difficulties-are most marked.To -day, Slitting Saws, Ike 1'32" to A" thick, 1" hole. The T.I.G.B. courses are the ideal method ofgoods or services advertised in Two dozen Fine and Odd Thread Taps, to I". qualifying quickly for thegreatrange of posts Three dozen Tungsten Hack -Saws, to 12". being offered by Industry and the Govern-PRACTICAL MECHANICS 18 Grinding Wheels, 1" to 1" diam. ment to technically trained engineers, the Three H.S. Tap Fluting Cutters, 11" diam. should give names of Adver- One dozen Ass. Fees, 4" to 12". need for whom needs no over -stressing.Write Dozen Toolmaker's Needle Files, indispensable. TO -DAY for"TheEngineer'sGuideto Best Carborundum Wheel, 7" by j" by f" hole. Success," containing the world's widest choicetisers from whom particulars 200 Springs I, al Trox. 6" long. of engineering courses covering all branches and Four Ass. Carborundum Wheals, to 31" diam., f" hole. recognised qualifications.Mention branch, post are desired. Any number of Doz. Emery Wheels, -111-to f" thick. r hole. orqualificationthatinterestsyou. The 0" to 1" Adjustable Tap Wrench.Burke.-Below. names may be included and 12 Sets Stocks and Dies, eta, {uSplit Dies, cutting 3/32". T.I.G.B.guarantees At", 5/32", 136", 7/32", 1, -ea', Whit. or B.S.F. or 0, 1, 2, training until success- 3, 4, 5, 6.B.A. Completewith Taper Taps, Adjust- ful for the one fee. we will obtain for you cata- able Tap Wrench and Die -Stock, Seven Dies and Taps,usualprice of these sets is 12/6, clear while logues, lists, and any other stocks lasts at 6/6per set, extrasets of Taps, Seconds The Technological or Plugs, 1/9set ofseven.-Burke. Small Taps, 7, 8, 9, 10, 12 B.A.; -11," Whit. 6d. each. Instituteof information you may be want- No dies these sizes.-Burke. Great Britain 1" Round Dieu, Screwing .1" 156"; II": 4"; I" Whit., ing. THERE IS NO CHARGE B.S.F.; or Brass. 26 'Threads;or American Fine 218 Temple Bar House S.A.E. for Yankee Cars, Set of Five Dies 2/9 ; Four London - - E.C.4 FOR THIS SERVICE. Sets 10/- ;Best Quality 1" Die -Stocks, all Steel unbreakable with Hardened adjusting Screws, 1/9 each (Founded 1917) -Below. 20,007 Successes 4,000 Taps, Taper, 2nd or Plug, same sizes and threads as Dies, 2;9 set, flair sets 10/ -.-Below. Yea Blocks and Clamps,Starretpattern. accurate, Readers desiring particulars from a first-class finish, 4/- pair.-Below. £1 orders carriage paid, except abroad. number of Advertisers will, by thisJ. BURKE, 30 TRIPPET LANE, SHEFFIELD, 1. An Absorbing Hobbymethod,savetime and postage.If any 3UILDING A STUART MODEL IS Advertiser stipulates that stamps or postal orders arenecessarybefore 31 in.WINFIELD AN ENGROSSING PASTIME, AND i OR VALUE AND RELIABILITY THE RESULT A CONTINUOUS samples or catalogue are sent, please PLEASURE enclose the necessary amount with your instructions.You are cordially We illus;rate. invited to make fulluseof this Service. STUART NO. 10. High Speed ADVERT. SERVICE DEPT., As illustratedE110 - 10 - 0 Steam Engine. PRACTICAL MECHANICS, or by 0 monthly payments of 18'4 3 in. B.G.S.C. Lathes fromE4 - 10 - 0 Bore 1". The Winfield Mfg. Co.`12NeGSEA7aiks Stroke r. TOWER HOUSE, SOUTHAMPTON Each set is qu.te STREET, STRAND, W.C.2 complete- drawings and Please obtain and send to me par-BLUS instruct:ons are included. to all sufferers, particulars of a ticulars from theAdvertisersinFREEprovedhometreatmentthat quickly removes all embarrassment, and per- Ifyou have alathe- your November issue whose namesmanently cures blushing and flushing of the face The rough castings - 8/6 and neck.Enclose stamp to pay postage to I give on list attached. Mr. M. Temple (Specialist), " Commerce House," If not- 72 Oxford Street, W.I.(Est.38years.) Fully machined set- 18/6 Ditto, withallholes drilldd Advertiser I Page No.I Information Required and tapped - - - - 25' - GRINDING AND POLISHING UNIT This and many other Stuart engines are I/10thH.P., A.C.-D.C., 100 fullydescribedinthe72 -page CATA- Attach sheet of paper, with par- or 250Volts,5,000r.p.m. Fittedwith4in.Mop. 3in. LOGUE No. 3, 6d. post free. Grinding Wheel, Guard ticulars, and your name and address andTool Rest. Built-in STUART TURNER LTD. Switch and 4 feet of (written in BLOCK letters), with Flexible Cable. PriceE3//6 HENLEY - ON -THAMES 18 P.M., Brixton 111.11.1:i,Lundr,,S.W.9 date, to this announcement. EASCO BUY, EXCHANGE OR SELL Advertisements are accepted for these columns at 3d. per word (minimum 12 words at 3s.-advertisements of less than 12 words ara charged at the minimum rate of 3s.) subject to a discount of 24% for 6 consecutive monthly insertions or 5% for 12 consecutive monthly insertions. TERMS :-Cash with order. Cheques, Postal Orders, etc., should be made payable to George Newnes, Ltd. The Proprietors reserve the right to refuse or withdraw advertisements at their discretion. All advertisements must be received on or before the 5th of the month preceding date of publication and should be addressed to the Advertisement Manager, " Practical Mechanics," George Newnes Ltd.. Tower House, Southampton Street, Strand, W.C.2. BATTERY CHARGING PLANT MODEL AIRCRAFT SITUATIONS VACANT-Cont. NO INCREASE IN PRICES while stocks last; see PETROL ENGINES complete, £2 15s. 6d. or ready DRAUGHTSMEN. Numerous vacancies available Displayed Advertisement. Brighton Radio Service, 34 machined assembly kit, 39s. 6d.Timers, propellers, inElectrical,Mechanical,Aeronautical and other Middle Street, Brighton. gas and rubber kits.List 11/21:I.-Lowe, 10 Lindbergh Branches of Engineering.Buildirg, G.P.O., etc., for Road, Bournemouth. men age 17-40. Exp. unnecessary if willing to learn. Details of openings, salaries, prospects, etc., FREE CANOES from N.I.E. (Dept. 372), Staple Inn Buildings, W.C.1. MODELS BOAT AND CANOE. Kits irons 27/6.Also com- pletedcraft. Lists stamp.Winter reductions.- FOR TRIX RAILWAYS :special 4-4-0 Tank WATCHMAKING Metacraft (P), Christchurch, Hants. Locomotives and Coaches.List 1 1/2d.- Below. WATCH & CLOCK REPAIRERS. Send 3d. for PERFECT USED MODEL TRAIN BARGAINS. complete list of material and tools.-Blakiston & Co., Popular makes. Send 4Vgd. for our catalogue and save Ainsdale, Southport. CINEMATOGRAPHY money.-Georges', 11, Friars Street, Ipswich. ART CINE FILMS.Exclusive 9.5 and 16 mm. MISCELLANEOUS Cine Bargains, all makes. State wants.-P. M. Dane, MUSICAL INSTRUMENTS 64 Stanley Street, Liverpool 1. BE TALLER I ! Extra inches count !! Details BAND GUIDE. Hints on the Bugle, Drum, Flute, 6d. stamp.-Malcolm Ross, Height Specialist, Scar- StaffParade formation,etc. Free,post paid.- borough. Potter's (Manufacturers), West Street, London, W.C.2 TELESCOPES, MICROSCOPES, Scientific ELECTRICAL Instruments, etc. Send for lists. Sale or Exchange.- AC/DC MOTORS, 1/12th to 1/8 h.p., from 10/.. C. V. Bolton, F.S.M.C., 49a Leigh Road, Leigh, Lancs. Stamp particulars.-Brookes, Banners Street, Cradley, CASTING MOULDS for Lead Soldiers, Indians, Staffs. PATENTS AND INVENTIONS Animals, etc. Sample mould, 2/9. Catalogue stamp.- HAVE YOU a sound, practical invention for sale, Industries 2, Waldegrave Park, Twickenham. patented or unpatented? Ifso,write Chartered Institute of American Inventors, Dept. 18-C, Washing- ENGINEERING ton, D.C., U.S.A. WIRELESS METAL FOR THE MODEL ENGINEER Sheet, Tube and Sections in Aluminium, Copper, Brass, CRYSTAL SETS KITS, complete, 4/6, post free. etc.No quantity too small.Stamp for lists.The -W. J.Buckle, 63 Avenue Approach, Bury St. UniversalProductions.RigbyLane,Bromsgroye, PHOTOGRAPHY Edmunds. Worcs. £500 worth, good, cheap Photo Materials, Films, Plates,Cards,Papers,Chemicals.Catalogue and TOOLS 4 Samplesfree.-Hackett'sWorks,JulyRoad, Liverpool, 8. BRAND NEW POWER TOOLSofquality. METAL WORK DON'T TAKE RISKS. Good developers mean10 -inch bandsaws, 54/-; Jigsaws, 22/6; Bench Drills, good results. Our reliable stock developers keep twelve 11/-; Circular Saws from 25/-; 3 -inch S.C. Toolroom MAKE METAL TOYS.Easy, profitable with "Success" Moulds.List free.Complete trial mould months after mixing. Satisfaction certain to amateursLathes, from £4 5s.New 1 -inch chromium plated 1/6.-Lee's, 1 Birkin Avenue, Nottingham. and professionals.Best developers ever put on the Micrometers, 12/6; Electric Drills, 37/6; Grinders.- market. Make two pints strong developer.6d. each John P. Steel, Bingley. 6 for 2/3, 12 for 4/-.Post free.- Hackett's Works, GRAYSON'S Glass -boringOutfitsandTube. July Road, Liverpool, 6. Cutters avoid risk.-Below. MICROSCOPY PHOTOGRAPHIC MATERIALS. Plates, films, Taps, Dies, Files, Chisels and Punches. "THE MICROSCOPE AND ENTOMOLO- mounts, chemicals.Interesting money -savinglists Best quality at keenest prices.-Grayson & Company, GICAL MONTHLY."-The premier journal for allfree.-" Kimber's," 105 Queens Road, Brighton. 300 Campo Lane, Sheffield. students of nature.1/-, from newsagents, or 1/1 from Microscope, 20/21 Took's Court, London, E.C.4. WORM DRIVE SITUATIONS VACANT JUBILEEHOSE CLIPS G.P.O. ENGINEERING DEPT. (no experience MONEY -MAKING required). Commencing £3113/0 per week. Age 18-23, The long -life clip with OPPORTUNITIES Excellent prospects.Free details of Entrance Exam. from B.I.E.T.(Dept.579),17-19 Stratford Place, the ever -tight grip. SALES REPRESENTATIVE wanted, spare time;London, W.I. 35s. weekly easily made.-Richfords, Ltd., 8a, Snow The Best Known Hill, London. For Radiator Joints, PLEASANT EVENINGS Mr, Oil, and Water Hose Joints. 1111 AT THE PIANO II SP Think of the intense pleasure to your- We guarantee a self and friends in being able to play Tight during long evenings and dull Sun. Joint. days.LET ME teach YOU to play really well so that you shall make Stocked by all Garages the piano sing-andreadmusic and Accessory Dealers readily at sight l BY POST, from I;alterCR 600 ordinary Music, no freakish methods. You shall quickly play Songs. Dances. L. ROBINSON & CO., sat 54 Hymns, and Gems from the Great Mas- 25London Chambers, ters so that your friends will want you always. I have taught over 51.000 adult GILLINGHAM, KENT. pupils during 35 years, they were of all "Easily the Best Soldering tto stages from Absolute beginners, who The *ADEPT Fluid Obtainable." This started without knowing a note, to quite LATHE statement by a regular user Advanced Players.I taught them and I f In. centres, tin. Se. of "BAKER'S" expresses the CAN TEACH YOU. Send P.C. for free tween centres. general opinion of the Motor book and advice. Say if Ad - With compoundslide - and Engineering Trades. Moderate, Elemen- rest 22/-, or with hand. tory, or Beginner. rest °MY. 13/6. Sold in bd., If- and 1/6 tins. H. BECKER Screw TailStork, 5'6 also in bulk. British by Ili and extra Poet 1 Descent) -ADEPT' 21 in. INDEPENDENT4 -JAW CHUCK, SIeWM.BURNETTICO.( cot micial)LIMITED (Dept. 1 5131, 6 9 ,Hoot St., London, E.C.4 Price 13,-; Post gd. THE SUPER ADEPT,' 33', GREAT WEST 50551SttWerito,1DIVIM F. VV . PO RTA SS,VflRRt7ii' CUT THIS OUT- OUR ADVICE BUREAU Practical Pen Coupon Value 3d. MAKE MORE MONEY Send five of these coupons with only 3/- (and 2d. stamp) £3 to £6 weekly can be earned at home in a wonder- direct to theFleet Pen Co., 119, Fleet Street, E.C.4. ful business of your own.No matter where you COUPON By return you will receive a handsome lever self -tilling live you can commence to make money In your This coupon is available until November 30th,1939, FLEET S.F. PENwith solid gold nib (tine, medium, or spare or whole time. No risk, canvassing or exper- and must be attached to allletters containing broad), usually 10/8. Fleet price4/3,or with 5 coupons` ience required. A wonderful opportunity for anyone queries, togethrt with 3 penny stamps. A stamped only3/-.De Luxe Model,FLEET SELF -FILLER. wishing to add pounds to their income. Particulars, addressed envelope niust also bee closed. 2/- estra. stamp. PRACTICAL MECHANICS, NOV., I BALLARD. York House, 12 Hambrook Road. LONDON.S.E.r..

All application* respecting Advertising in this Publication should be addressed to the AD VERTISEMENT MANAGER, GEORGE NEWNES LTD. Tower House, Southampton Street, Strand, London, W.C.2.Telephone Temple liar 436:

. . Send for copies of GamagesTool BargainLeaflets for Metalworkers GAMAGES and Woodworkers

ELECTRIC FURNACES MAINS An indispensable appliance where hardening,tempering,annealing, TRANSFORMERS brazing, soldering, or the melting of BRITISH MADE small quantities of metal is carried THROUGHOUT at a Remarkably Low Price out,. The finest materials only are used in Exceptionallyrobustconstruction its construction and there is nothing First Quality Heavyweight Operate on any 200-240 volt A.C. liable to get out of order.Specifi- main, transformingto6 volts,3 cation : Size, 7 in. long by 51 in. wide 3in. SCREWCUTTING, BACK GEARED, amps.Ideal for machine tool light- byet in.high;weight,71 lb.; ing, driving models, garage inspec- Chamber Capacity, 1 in. diameter by GAP BED LATHES (Sliding, Milling, Surfacing) tion lamps, and as a component for battery chargers, eine pro- :1in.long; Consumption, An opportunity to secure a high-grade lathe at a remarkably jector work, etc.Brand 200 watts;Temperature, low price.Be advised and order now while ample stocks are 850 deg. C.-1560 deg. F. new and guaranteed. available. Post 6d. Carriage 1/- England or Wales. SPECIFICATION:- Exceptionallystrong headstock with adjustable bearings. Heavy,solidbed ensures accurate work.Machine cut change wheels for allEnglish threads. Saddle and slide have large bearing surfaces, and the tailstockis of rigid design.Swing, over saddle 41 in.,over bed 6 in., over gap 8 in.Diameter of mandrel 2in., mandrel nose 1 in. OR DELIVERED ON x12 threads.Mandrel and tailstock bored 1 in.clear. FIRST OF SIX Centres No. 1 Morse taper, leadscrewin. x 8 T.P.1.Cone MONTHLY pulleys 31 in., 31 in., 21 in. x t in. Back gear ratio 30 to 20, PAYMENTS distance between centres 12 in., overall length 27 in., weight OF 52 lb.Complete with face plate and ten change wheels. Carriage (outside our extensive delivery area) 316 extra England or Wales

ELECTRIC SAWBENCH voltsFor2 2A.G. 0 2 4 0 6 in. combination teeth saw, rise and fall only table. Adjustablefence, adjustable Please confirm mitre guide.Ball -bearing spindle and voltage. .. dust -proof housings.Motor is h.p. totally enclosed; dust -proof bearings (do SWIVEL BASE VICE not requirelubricatingfor2years). DELCO-REMY Windingsheavilyimpregnatedwith with two Sets of Jaws insulating varnish and tested to with- ELECTRIC MOTORS A strongly madevice,especially stand 2,000 volts. 2,800 r.p.m. Internal at a Substantial Reduction suitable for borne garages, workshops centrifugalstartingswitch. Sizeof Designed for heavy continuous use, etc. Steel -lined jaws and special table top 12 in. by 10 in.Saw will cut theyareequallysatisfactoryfor jaws to take pipes and rods.Width 11 in. by 51 in. Weight repeated intermittent work such as of jaws,4 ins.. 54 lb.Complete With in refrigeration.No special switch opening to maxi- 2 yards cab tyre flex.£9.7.8 is needed for starting, and the motor mum of 5in-. Weight complete. IOR37/6DEPOSIT, BALANCE epg /.1 can be operated by means of an 25 lb. in 8 MONTHLY PAYMENTS of I ordinary tumblerelectric light Carriage, 1/- Eng- switch.All brand 166 Carriage (outside our extensive delivery area) 3/- England or Wales. new. land or Wales. 1/5h.p.A.C. Cap- acitor start. 200/ 6in. ENCLOSED eh p. ELECTRIC 250volts. 50 cycles. HEAVY DUTY Originally listed at DOUBLE GRINDERS 4/, AIR COMPRESSORS Heavily constructed, they are ideal for the workshop Also D.C. motors as above. On, wheregrindingjobsconstantlyarise. Totally Assorted voltages 100 to 250, asv Single-phase motor. 3,000 Please state voltage whenordering. A first-class compressor at a enclosed. Ball bearings, Carriage a mostcompetitiveprice. r.p.m.Complete with Wheel Guards, Ii in. Grinding (outside our extensive Wheels.Weight 52 lb.For delivery area) 116 England or 1tiales. I in.bore,11 in.stroke. 200/220 and 230/260volts, Splash lubricated, sealed A.C. 50 cycles. L-5.19.6 Heavy Duty Block Type crankcase.Diameter of fly- 24/6 DEPOSIT, BALANCEin 6 I wheel 9 in.Weight 34 lb. IORMONTHLY PAYMENTS of 17/6 CONDENSERS Carriage (outside our extenove detztery area) zit, Engtana or Is ities. 1 M.F.D. Capacity. Suitablefor Carriage voltages up to 1,000 A.C. or 2,000 ,/6Eng- 63' D.C.Tested to ian d or Alsolarger 4,000 volts D.C. t Pales and more Make Money with one of these Dimensions powerful approximately model 41in. wide,9 with 2 in. ELECTRIC ENGRAVERS in. overall bore, 2 in. An efficient,reliable outfit which will mark height, /- in. stroke. thick,Bakel t e £4.17.6 write,etchor engrave on any hard, ease.200 to be orEl hardened, or soft metal.Enables you clearedatan Deposit, tomake money by engraving enormous Balance reduction. in Six identity discs, etc.Most use- Monthly ful for marking all tfilet P a y- your small tools. men ts 216 Works off any 6 - Post free. of 14'3 volt accumulator. 396 Post 6d. GAMAGES. HOLBORN, LONDON, E.C.1 Phone war order: liOLborn R4R4 Oily Branch. 107Cheapside, Street, St and, London, W.C.2., and Printed I ublished about the 30th of each month by GEORGE NEWNES, LIMITED, Tower House, Southampton Sole ,k,,nts in England by THE SUN ENGRAVING CO., LTD., London and Watford, Hens.Sole Agents for Australia and New Zealand-Gordon & Gotch, Ltd. r 'south Africa-Central News Agency, Ltd. Subscription Rates: Inland andAbroad, 7s. 6d. per annum. Canada, 7s. per annum.Register.;fi at the G.P.O. fcs transmission by Canadian Magazine Post.