echan ics - world radio history

BUILDING A 95m.m. CINE PROJECTORNEWNES

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November, 1936 NEWNES PRACTICAL MECHANICS 65

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This entirely new book provides a completepractical course of instruction in every importantbranch of engineering workshop methods,materials and equipment. It deals with the under-lying principals, craftsmanship, machines, tools,measuring processes and machining methods ofto -day, and it will prove indispensable to theengineer, draughtsman, mechanic, apprentice andengineering student. Its scope extends fromsimple hand tools and machines to the latestelaborate machines and methods employed formass -production purposes.

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SOME OF THE SUBJECTSFiles, Chisels, Scrapers, Shears, Punches, Burnishers,

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66 NEWNES PRACTICAL MECHANICS November, 1936

REEqiifIMPORTANT GUIDE

to SUCCESSFUL 0ENGINEERING CAREERSAfter months of intensive effort and research, we arepleased to announce that the 1937 edition of our Hand-book, " ENGINEERING OPPORTUNITIES," is nowout of the publishers' hands and ready for free distribution.Containing 268 pages of practical guidance, this book is,beyond argument, the finest and most complete hand-book on Successful Engineering Careers ever compiled.It is a book that should be on the bookshelf of everyperson interested in engineering, whatever his age,position or experience.

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PRACTICAL

MEECditeLM

Bind Your Copies of " Practical Mechanics "

THE binding case for Volume III, com-plete with title page and index, is now

ready and costs 3e. 6d. by post from thePublisher, George Newnes Ltd., 8-11Southampton Street, Strand, London,W.C.2. The index can be obtained separ-ately if desired for 7d. post free. Allreaders should have their copies of VolumeIII bound, and thus be able easily to referto the contents by means of the fully cross-referenced index.

Power from the Sun's RaysASTEAM engine run by the sun's rayswas recently demonstrated in Washing-

ton by Dr. C. G. Abbot. It was a crude -looking apparatus developing only halfhorse power, but its inventor says it is theforerunner of great revolutions in mechan-ics.

Pneumatic ShortsP OOR swimmers, claims a Viennese

inventor, V. Veldomon, may be sweptout to sea in safety if they are wearing hisnew " safety shorts." Victims of accidents,currents or cramp need only inflate thedouble front of the shorts. They can thenfloat on their backs until picked up.

£3,000,000 Power SchemeTHE £3,000,000 hydro -electric power

scheme in Galloway, which has beencarried out to provide electricity forSouthern Scotland and North-west Englandwill shortly be completed.

An Aeroplane which Folds its WingsLOCKED in a hangar at Villacoublay,

near Paris, is the most astonishingaeroplane ever built. When in the air,the pilot can wind the wings in, shorteningthe span, and the machine can then reacha speed of 280 m.p.h.

Flying into Spacer ROM New York comes the news that an

inventor has discovered how to build arocket 'plane that can be flown undercomplete control. Several flights havebeen made, some straight up through thestratosphere to heights of thirty miles.The inventor believes that rocket 'planescould achieve 1,000 m.p.h. or more in theupper stratosphere.

Into the DepthsSEVEN British scientists are leaving early

next year on an expedition to studyunder -water life at the bottom of Lake

VOL. IV. No. 38

NOVEMBER

1 9 3 6

NOTES, NEWS,AND VIEWS

Titicaca, which is on the boundary of Peruand Bolivia. The lake is 12,500 ft., nearlythree miles, above sea level.

Showing the attractiveappearance of the bound

volume of " Practical Mechanics."

So This Is LoveRUMANIA'S foremost neurologist, Prof.

George Marinesco, has invented an appar-atus for measuring the intensity of love.It consists of two lead plates, connectedto a series of electrical devices leading to a

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galvanometer. The two lead plates arefixed on the victim's arm, and the professorreads a list of names. As soon as thebeloved one is mentioned the needle of thegalvanometer begins to quiver, and themore intense the feeling the greater thedeviation.

A Chandelier OrganANEW type of organ has been con-structed in Berlin. It is electrically

operated, has 138 pipes, and has a mechan-ism concealed in a huge suspended chande-lier. Its quality is said to be normalwithin its range of tones.

Playing by EyeI T is stated that with the oscillographarrangement invented by Professor G.

Hannenman, of Chicago, a deaf person couldlearn to play a musical instrument, bywatching the visible records of the noteshe produces. It is said that it can evenpick out the instrument in an orchestraresponsible for a bad note.

A New BulletI T is claimed that a new type of bullet,recently patented, has, owing to its

unusual shape, about four times the acceler-ation of an ordinary -30 calibre projectile.The speed of the bullet is calculated atabout 3,600 m.p.h.

Largest Irrigation CanalWHAT will be the largest irrigation

canal in the United States is beingdug in Southern California. Forty-fourmiles of the canal have already beenexcavated and lined with clay, whileanother thirty-six remain to be done.

Invisible Laundry MarksI N Atlanta City, laundries have devisedan ingenious method of marking laundry.

Before the garment is laundered an in-delible invisible mark is stamped on it.When ready for sorting it is held before agiant mercury vapour lamp and its identityis revealed.

From U.S.A. to Europe by BalloonI T is learned that an attempt is to be madeby a Belgian and a Frenchman to cross the

Atlantic by balloon. They claim that thereare winds which should land them in Nor-way and they estimate that the crossingshould take about ninety hours.

A Magnetic ShipOF scientific interest is the decision of the

Admiralty to construct a non-magneticship for the purpose of compiling accuratemagnetic data at sea.



It Can be In uilt in aFew Hours at Very

Little Cost.

Fig. 1.-The finished Cine projector.

AFEATURE of theprojector shown inFig. 1, is that it

can be made without alathe and without theuse of toothed wheels ;also the mechan-ism has beenspecially worked

Fig. 2-Thetwo stops fixed

in position.

uildini) aProjector

Features of thisuilt withoutof Toothed

out so that the accurate posi-tioning of the film does notdepend upon the accuracyof machined parts. Any' per-son can therefore undertake

the construction ofthis projector if heis handy with adrill, file, and sol-dering iron, and isblessed with amoderate degree ofpatience.

The machinetakes Pathe BabyFilms, as these areseasonable in price,there is a goodselection to choosefrom, and also theya r e non -inflam-mable.

It is advisable tostudy the photo-graphic illustrationsto get a clear ideaof the working ofthe instrument before commencing necessary to turn the handle at threeconstruction. Fig. 1 is a compre- revolutions per second to operate thehensive photograph, showing the machine properly. This is quite a

ei 4x f Nx 4%G"

general arrangement of theparts.

How to OperateThe metal case containing

the film (every film is sup-plied in such a case) can beseen at the top of the pictureresting in a wooden cradleand held in position by arubber band. The filmpasses along a brass guidethrough the "gate" (i.e. thehole through which the lightshines), and out on to thetake -up -reel, which is con-spicuous at the bottom ofthe picture. On the rightof the picture is a woodendisc-turned by a handle-which carries four brasscams screwed on to its face.These cams operate themechanism which moves

the film ; each cam causes a picture tomove out of the gate and a new pictureto enter. Now the pictures have tobe changed at the rate of twelve asecond, so it will be seen, that it is

/0 :x4-k"x Ars

81x SCREWED OMFROM THE BACK

BRASSigriiIcK- - - -2 '?"6:

w000.2-4" HOLE IN BRASS.

54X 54-X3/4"I SCREWED oM.4;10 FROM BELOW.

;00L IN WOODHOLE IN BRASS,

Fig. 3.-The framework of the machine.



Home diney G6 1-- ome Mechanic "

Home Cinema Projector is that it Can bethe Aid of a Lathe and without the UseWheels.

convenient speed. While the pictureis moving across the gate, the light iscut off by one of four flat pieces ofmetal which project from the face ofthe cam -wheel, and act as shutters.These shutters uncover the lens im-mediately the picture comes to rest in

AS REQUIRED.

BRASS PLATEX XX.;

Fig. 5.-The'cam-wheel and spindle.

the gate, and allow the image to beprojected on to the sheet for its al-lotted period of a little less than one -twelfth of a second, when the nextchange becomes due.

The Mechanism for Imparting Inter-mittent Motion to the FilmThe mechanism which gives the

necessary intermittent motion to thefilm is shown in Fig. 4, which is a" close-up " view with the lens andgate removed to show the details

3%'2"x "x713 DIR BRASS ./16. SPLIT PIN

;(k "x %.4"2Vx.%"x

more clearly than in a photograph.Two " followers " will be seen

in the path of the cam which isassumed to be moving upward.The lower follower, pivoted nearthe top of the illustration, isjust coming into engagement withthe cam which moves it about116 in. towards the left ; on this fol-lower is pivoted a " bell -crank "lever, which is, of course, alsomoved bodily to the left, causingthe tongue of metal on the extreme leftto be pushed through one of the per-forations of the film (not shown inthe sketch). The cam as it moves up-wards then comes into contact withthe second follower-which has amovement of about in.-and push-ing this to the left, moves the film

&074"Lotto

aRAss }f6" THICK

Fig. 8.-(Right)Details of the

cam.

1-

F ig .7 .-(Lef t)T he up-and-down movementof the small tongue islimited by two stops,one of which is shown

here.

downward through the medium of thebell -crank lever. The movement ofthe tongue is limited by two adjust-

able stops, andwhen the cam haspassed, the tongueis withdrawn fromthe film, and themoving partsbrought back to

/ position ready forthe next cam byspiral springs intension.

Fig. 6.-The component parts for making the film -moving mechanism.

Details of the Con-struction of theMachineIn describing the

Fig. 4.-The mechan-ism which gives thenecessary intermittentmotion to the.61m.

construction of the machine onlyessential dimensions will be given, asit is intended that the parts should bemade and assembled in the ordergiven, each part being fitted to thosemade previously.

Commence by making the, frame-work shown in Fig. 3. This does notrequire much description, but all thepieces of wood should be planed andfitted truly square or complicationsmight arise during erection. Fig. 1shows the baseboard cut away toclear the take -up -reel, but this willnot be necessary if the dimensions onFig. 4 are followed.

The Cam -wheel and SpindleThese should be made next (see Fig.

5). The wood disc can be cut outwith a fret -saw ; the spindle is a 11in. by / in. B.S.F. bolt. A Whitworthbolt would do, though the finerthread is preferable, A washer is

SECT/ON TO SHOW$//OE FOR TOIYGUr

to

SLOT SOLDEREDro6ETHER

Fig. 9.-The details for ma!,ing the an guiZe



grAV4WASHERS

MilillinIMMIR111011-W-t116 Spur PIN\j'

WOODEN eoSs vIA. SPLIT PIN

DISCS .3-044frIETERSCREWED To BOSS.

Fig. 10.-The take-up reel.

soldered on each side of the head toform a small grooved pulley for thetake-up drive. Mount the wheel andspindle in its bearings, and fix a longscrew into the face of the disc as atemporary handle. If the wood discdoes not run true, the brass back platecan be taken off and refixed, and theface of the disc can be trued up bypacking the wood away from theback plate as required. The face ofthe disc should stand out about lig- in.beyond the tall upright of the frame.

The Film -moving MechanismThis is shown complete in Fig. 2.

All the separated parts are shown inFig. 6 together with a side view of thecomplete assembly. The dimen-sion marked in. from the centre ofthe tongue to the back of the baseplate is important, and should beadhered to. The protruding end ofthe tongue should be well rounded offto facilitate its entry into the filmperforations. The tongue itself shouldbe considerably narrower than theperforations, but its thickness shouldbe as great as possible consistent withfree movement into and out of thefilm. The angle between the tongueand the point of contact with the camon the other arm should be 120 de-grees, measured about the pivot ofcourse. This piece of mechanism isall built up from pieces of brasssoldered together, and is quite aninteresting part to make. It should,of course, work quite freely, and mustbe entirely without any tendency tosticking. When complete it shouldbe screwed on to the tall member ofthe frame with the edge flush with thewood, as in Fig. 4, the vertical posi-tion being such as to bring the twocam followers equally above andbelow the horizontal centre line of thecam -wheel. After fixing this part,screw a small flat piece of thin brasson the other face of the upright mem-ber to act as a stop for the membercarrying the lower cam follower ; theend of this stop can just be seen in

THIN BRASS STRIPSCREWED OM ATONE ENO ONLY.

Fig. 4. It engagesthe lower end of thevertical pivotedmember, where itworks in the guide,and prevents themember from com-ing out of the endof the guide.

The Two StopsThe up-and-down

movement of thelittle tongue is lim-ited by two stops,

as shown in Fig. 7. These are simplyflat pieces of brass, about 18 gauge,and are fixed as shown in Fig. 2. Theslotted holes allow for adjustment,the screws through the slots beinground -headed and fitted with washers.The two stops should be fixed in aposition to allow the tongue a move-ment of about i in. above and belowthe horizontal (about 4 in. in all)when the screws are in the centres of

SECTior+ TO SHOWFILM CLIP.

72

Fig.12.-Thekey for re-winding the

film.

Fig. 11 (Left) The lensshould be mounted in a tube,

as shown.

,3/4.014,WETER

10 FIT Fw_or spoolj

their slots. The exact adjustmentmust be left till later.

The two spiral springs may now befitted ; the longer cam operating thebell -crank should be of a " light andlively " type having a pull of betweenone and two ounces when fitted. Theother springs must be definitelystiffer and stonger, so as to ensure thetongue being withdrawn from thefilm before its upward movementbegins.

Now make four cams as shown inFig. 8. Fix one of these on to the faceof the cam -wheel as in Fig. 4 so thatthe cam projects 16 in. Turn thecam -wheel slowly and see that thelower follower is moved about in.by the cam ; if the movement ex-ceeds this amount appreciably, itshould be reduced by filing down thefollower a little, if less than 111-6 in., shiftthe cam out to give the requiredmovement. Next turn the wheeluntil the upper follower is fully lifted,and, leaving the wheel in this position,adjust the lower stop (Fig. 7), until itpresses quite firmly against the underside of its lever, but leave the adjust-

ment of the upper stop till later. The"other three cams may then be screwedin place, taking care that they all givethe correct movement to the lowerfollower. If everything has beendone properly the tongue should moveup and down too rapidly to be seenwhen the wheel is turned smartly byits temporary handle.

The Film GuidesBefore starting to make the film

guide shown in Fig. 9, the reader isstrongly advised to buy a film andmake sure that the parts fit the film ashe proceeds. Thirty foot films can beobtained new for 2s. 6d., or second-hand (from dealers who specialise infilm exchanges), for less. A second-hand one should do for the purpose offitting up, as it will probably becomescratched or torn before the instru-ment is finished. The construction ofthis part should be quite clear fromFig. 9. The copper foil should beslightly thicker than the film and thewidth between the two strips of foilshould be very little greater than thewidth of the film, only just enough toallow the film to slide freely. Thelittle bolts, 10 B.A. by in. can beobtained from a model engineerssupply store. The little spring shownlarger in the sectional view is to keepthe film over to one side of the guide,and to steady the film by introducinga little friction ; the blade that rubson 'the film should be rounded off toprevent scraping, and slotted holesfor the bolts allow the spring to bemoved to increase or reduce the pres-sure on the film. The blade of thespring should project far enough to bepushed aside by your finger when thefilm is being threaded down the guide.The slotted piece of brass at the bot-tom is a guide for the tongue, whichmoves the film ; it should fit thetongue closely, but not too tightly,and should be carefully centred beforebeing soldered on.

The hole forming the gate shouldbe left uncut for the present. Screwthe film guide on to its wooden sup-port (see Fig. 2) in such a position thatthe tongue works freely in its slot

(Continued on page 98)

PARALLEL. RAYS.

DIVERGENTRAYS)

ss/

CONVERGING RAYS,

LEns,

frovysEp x,4REFLECTOR

Fig. 13.-The arrangement of the condenser.



Fig. 1.-The latest type of " Direct Take -Off " autogiro. It is fitted with a two -bladed rotor, the blades of which are set to zero incidencewhile being speeded up before the take -off.

DEVELOPMENT OF THE AUTOGIROBy G. R. M. GARRATT, M.A.

In Spite of the Ridicule with which the first Autogiros were received, the InventorPersevered with the Machines until he succeeded. in producing the Machine as it is to -day.

THERE must be many readers ofPRACTICAL MECHANICS who re-member the amused and cynical

ridicule with which the first autogiros werereceived in this country barely ten yearsago. There were very few who took themseriously, and there were many wholaughed openly at the unconventionalmachines and at their courageous inventor,Senor Juan de la Cierva, of Spain. It iseasier, however, to make fun of some ratherstrange invention than it is to daunt or dis-courage a man of the calibre of Cierva, aman who is not only an extremely competentand practical engineer, but who is also abrilliant mathematician and whose know-ledge of the theory of aerodynamics issecond to none.

Plane Rebuilt from WreckageAn autogiro is so very different from the

conventional aeroplane that one may beexcused for wondering what led Cierva tohis invention. The story is not a long oneand has not often been told.

Cierva was barely fourteen years oldwhen he commenced to study aeronauticsfairly seriously, and with two companionshe constructed numerous models andgliders which were tried out on the hillsidesaround Madrid. The experience thusgained led to more ambitious experiments,

and when scarcely sixteen, Cierva and histwo companions purchased the wreckageof an early Sommer biplane and proceededto rebuild it entirely: Their efforts were

Fig. 2.-The rotor head of a type C19 autogiro. Thehinges which permit vertical and horizontal movementof the blades may be plainly seen, and also the frictiondampers and the driving mechanism for starting the

rotation.

successful, and " The Red Crap " as themachine was named on account of itsbrilliant scarlet colour, made numerousflights around Madrid before it finally fellto pieces from old age.

Cierva Designs a BomberWhile most of the rest of Europe was at

war between 1914 and 1918, Cierva spenthis time at the Civil Engineering School atMadrid, completing his mathematical andtechnical training and when, in 1918, theSpanish Government offered a prize of tenthousand dollars for the construction of alarge bombing plane, Cierva resolved tocompete. In due course the machine wascompleted, a large biplane with a wing spanof 80 ft. and equipped with three HispanioSuiza engines. The machine was anexcellent one and embodied many detailsof advanced design, but it crashed on itsvery first flight due to the inexperience ofthe pilot, who had never before flown solarge a machine and who attempted a turnnear the ground at too low a speed. Themachine stalled and was wrecked, thirty-two thousand dollars lost in a momentbecause an aeroplane cannot fly at a speedmuch lower than 45 or 50 m.p.h. !

This error of judgment was an expensiveone, but it served to set Cierva thinking ofways and means whereby an aeroplane



could be made to fly and to land at lowerspeeds. Some fundamental change hadgot to be made, for nothing had been doneor invented in sixteen years of mechanicalflight-and nothing has been done since,except the autogiro-to enable an aero-plane to fly at low speeds with safety.

Wing Speed EssentialCierva's theoretical knowledge of the

science of aeronautics told him that theessential factor in the " lift " of an aeroplanewing is speed. Without speed there is nolift above an aeroplane wing, and no supportbelow it, and to this bare principle there isno alternative. But could not some othermethod be found of providing and makinguse of the necessary speed without makingthe aeroplane itself travel fast ? Could notthe wings be made to travel fast while theaeroplane itself travels slowly ?

These questions led to several possi-bilities, a wing -flapping machine to imitatethe flight of a bird might have been devised,or a helicopter, a machine without wingsand depending for its support on a large

Fig. 1-One of the earlierproduction types of auto-giro. This type was fittedwith substantial wings andhad the usual ailerons, rud-der and elevator similarto an ordinary aeroplane.

airscrew on a vertical axis. Even before1919, a great deal of ingenuity and experi-ment had been devoted to these problemsof the ornithopter and the helocopter, andeven to -day they are still problems. Prob-ably they will never be solved since now,with the direct take -off autogiro a practicalreality, they are no longer necessary.

But though they were problems in 1919,they might not have been hopeless problemsand Cierva might have elected to develophis ideas on such lines. A helicopter didnot seem an impossibility, but to a mantrained in the mathematical theories offlight, a helicopter possesses many dis-advantages and even the lay mind canappreciate that a failure of engine povyermeans an almost inevitable crash.

An aeroplane derives its lift from itswings, and thereby escapes the difficultiesof the helicopter. The propeller merelydrags the wings through the air, but a wingof practical size must travel at a speed of45-50 m.p.h. to be of any use. Ciervawanted to make an aeroplane which wouldfly at only 10 or 20 m.p.h. He had, in fact,to find some way to make the wings travelfaster than the aeroplane, and he came tothe conclusion that the only way to do thiswas to make the wings travel in a circle.And so the autogiro was born !

Wings Free to RotateAt first sight, we are back again at the

helicopter,but wemust re-memberthat thehelicopterwas alwayssupposed to

have power -driven wings, whereas Cierva'sproposal was that the wings should be abso-lutely free to rotate of themselves. Thisis perhaps the fact most difficult for the laymind to appreciate, that the wings of an

autogiro revolve freelyon their own, entirelyunconnected with theengine except, in mod-ern machines, duringthe starting up andtake -off process.

Cierva's theory toldhim that his revolvingwing, built like a wind-mill, would behave likean ordinary wing whileallowing the machineto travel slowly anddescend almost verti-cally. But would thewings actually rotateas the machine wentthrough the air ? andwould they be strongenough and have liftenough to support themachine ? The only

Bevel Pinionilousings

,00,0Clubhiloitising

Frxe&ARlitng5e Pin

RotorBirrkeCable

RotorStorlingShall

Fig. 4.-A type C30a auto-giro, introduced about 1932.This was the first produc-tion type of " Direct Con-trol" machine and it willbe noted that it has neither

wings, ailerons orelevators.

way to find out was to build one and seeAnd it was to prove easier to develop thetheory than to make a practical machine,for the first two autogiros would not fly atall, and even the third was not capable ofsustained flight.

Two ProblemsThere were two major problems to be

encountered. One was the inevitable effectof gyroscopic action, for simple calculationshowed that the machine would be quiteunmanageable if nothing were done toeliminate the gyroscopic effect of the rota-ting wings. The second difficulty was thatthe blades on one side of the machine wouldbe travelling faster than those on the other-due to the forward speed of the machine-and the lift would thus not only be veryunequal but, which was even worse, theinequality would vary seriously with theforward speed of the machine.

To take care of these two troubles,Cierva proposed to have two sets of re-volving blades, one above the other, andhis first autogiro was actually constructed

4....CrownWheel

La eirtl Hinge PinBias.

Springs.,

4.4014zaiCeraictblawetozza

Ctrilm/CblzymaSwipe/ Jail)!

Calk to fore&A/177-imCbrzfrot

Fig. 5.-A drawing showing the principal mechanisms of the rotor head, thearticulation arrangements and the hinge pins which permit lateral and fore-

and-aft movement of the rotor axis.



with twin rotors. Unfortunately, the aircurrents from one rotor so upset the be-haviour of the other that the machinewould not fly.

The second autogiro had a single three -bladed rotor and attempted to overcome theinequality of lift by changing the angle ofincidence of the blades as they rotated.The blades moving forwards were given asmaller angle of incidence than thoseretreating on the other side. Unfortunatelya separate adjustment was necessary forevery different forward speed and, like itspredecessor, the machine refused to leavethe ground, falling over on one side at everyattempt.

Third Time LuckyThe number three is supposed to be a

lucky one, and it certainly proved to be soin the case of the autogiro, for the thirdmachine, which was partially controlled bya system of ailerons, actually left theground for a few moments, thus provingonce and for all the possibility of flight withrevolving wings. The gyroscopic action,however, made the machine almost uncon-trollable and if it had ever got properlyinto the air it would almost certainly havecrashed.

An almost accidental experiment gaveCierva the clue by means of which the gyro-scopic effect is avoided. The secret wasflexibility. The wings of his little modelwere made of flexible material, while therotor of his autogiro was a rigid constructionand while the model was free from anygyroscopic effects, the full scale machinewas uncontrollable.

It would have been a very difficult matterto construct full size wings of a flexiblenature, but the same result could be achievedby hinging the blades at their roots so thateach blade had complete freedom to moveup and down, and this was done in Cierva'sfourth autogiro.

An Articulated RotorWith an articulated rotor, as the hinged -

blade system is technically termed, theblades automatically take care of the greaterlift on one side. The forward -movingblades, which experience the greater lift,rise somewhat, and so automatically reducethe effective angle of incidence, thus losingsome of the lift ; the retreating blades falland thus equalise the lift on either side ofthe machine.

On January 9th, 1923, Cierva's fourthautogiro rose from the ground and flewsteadily under perfect control across thefield, and though the machine was primitivein many ways, the major difficulties weresolved and the future of the autogiroAssured. The essential principles wereestablished and every difficulty which re-mained was only a matter of improvementand perfection of mechanical design.

Many autogiros were constructed in the

Fig. 6.-A front view

years which followed 1923, improvementsbeing made in each, but there was onefundamental feature which was common toall. The rotors of all fulfilled the samefunction as the wings of an ordinaryaeroplane, and nothing more. True, theywere more effective at low speeds, but theywere " wings " pure and simple and took nopart in the control of the machine whichwas still fitted with ailerons, rudder andelevators. To Cierva, these controls werenecessary evils, but evils none the less, forthey added weight and complexity in orderto fulfill a purpose which, to Cierva, should

be capable of achievement by control ofthe rotor itself.

The Rotors PerfectedIt is useless to attempt to run before one

can walk, however, and the theory and con-struction of the rotors had to be completelyperfected before any attempt could bemade to control the machine itself bymanipulation of the rotor axis. Very manyrefinements had to be made, but only one

of the " flying bedstead."

will be mentioned here. I have alreadysaid that the blades are so hinged so thatthey are free to " flap " up and down as theyrotate. Not only are they free to movevertically, but they are also free to movelaterally through a small angle.

It was found that if the blades are rigidlaterally, unpleasant oscillations can be setup in certain circumstances. To overcomethis, the blades are hinged laterally, thepermissible movement being limited to a fewdegrees, and large friction dampers, whichmay be seen in the sketch, are fitted to damp


Fig. 7.-A side view of the " flying bedstead."



TRANSMITTINGSIGNALS OFCOMPASSBEARINGS

How Television aids

Navigation at Sea

UP to the present, interest in televisionhas been mainly centred around itsentertainment value. We are all

waiting to know exactly when the new pic-ture service is coming into operation, andhow much it will cost us to bring it into thehome.

Meanwhile, whilst these questions stillremain unanswered, the discovery of tele-vision is making itself felt in other directionsthan broadcasting. We have, for the firsttime in history, found out how to transmitinstantaneously a picture of events occur-ring at a point beyond the normal range ofvision, and it would be strange indeed ifthis new discovery did not find some usefulapplications outside the field of mereentertainment.

The whole subject is, of course, still in itsinfancy, but as a line of approach to someof the possible " outside " developments intelevision it will be helpful to see, in the

MOVING

FIXED FIX ED

OS C.

O

"PICTURE"

/vAMP

lit_MOD

Mt

D

/ \A

Fig. 1. Diagram of the apparatus used in a television " beacon station.

instruments on his dashboard. Finally,when he reaches his destination, short-waveradio beams help him to come safely toground, at the correct landing angle, evenwhen fog completely blots out all sight ofthe aerodrome.

Aiding Navigation in Foggy WeatherTelevision is already following closely in

the footsteps of directional wireless as ahelp to navigation in foggy weather. Ithas the definite advantage of giving a clearand unmistakable " picture " indication,which can be seen at a glance, so that thenavigator does not require either a know-ledge of the Morse code, or an ear sufficiently

sensitive to judgewhen the receivedsignals are at maxi-mum or minimumstrength in the midstof a confusion ofother noises.

For instance, in onewell-known methodof assisting marinersto find their locationduring fog, a rotatingbeam of wireless isradiated from a bea-con station, near thecoast, in much the

L same way as the rayof light from a light-house. In addition, acharacteristic call sig-nal-consisting of cer-

tain Morse letters which identify the station-is broadcast or transmitted in all direc-tions, together with the Morse letter N atthe precise moment when the beam is pass-ing through the North point of the compass.The wireless beam makes one completerevolution every 30 or 60 seconds, or more,according to the particular transmitterconcerned.

In order to find his bearings the navigatormust first be able to recognise the Morse callsign, so that he can identify the particulartransmitting beacon on his map. He nextlistens for the Morse letter N, which tellshim that the beam is passing through trueNorth on the compass, and immediately setsa stop -watch going. He then waits untilthe beam sweeps through his own position,where it produces a " maximum " signal inhis receiver. At this moment he stops hiswatch.

MOVING

Figs. 2 and 3.-The beam pictures as seen by thenavigator at sea, and which indicate the exact bearings.

first place, what has already happened inthe case of wireless. What can be donewith one, can, or will be done-where it isadvantageous-with the other.

Wireless first made its mark-long beforethe introduction of broadcasting-as ameans of keeping in touch with those cut offfrom all ordinary means of communication,so that ships at sea, and aeroplanes inflight, for the first time lost their peculiarsense of isolation.

With the help of the radio direction -finder, a navigator can now come safelyinto port under conditions where allordinary harbour lights and marks arecompletely blacked out. Similarly a coursecan be " marked out " in the air by over-lapping wireless beams, so that an aviatorcan fly blindly along a given route, knowingthat he will be automatically warned of anydeviation to port or starboard by the radio

The number of seconds between hearingthe " North " signal and the time the beamreaches him, then indicates his bearingrelative to the land beacon. For instance,if the beam takes 60 seconds for a fullrevolution, and his stop -watch reads 30seconds after hearing the North signal, heknows he must be lying due South of thetransmitter. It will be seen that all thiscalls for a considerable amount of skill, aswell as. a competent knowledge of Morse.

The Television " Beacon "By contrast it is possible to transmit

comparatively simple television signalswhich show his bearings pictorially to anavigator, no matter where he is situated.The apparatus used at the beacon station isillustrated in simple form in Fig. 1.

The directive aerial A which radiates aclear-cut beam of wireless energy is con-stantly rotated at a uniform rate by amotor M. On the driving -shaft is a drumor disc C which is marked along its edgeswith a divided scale representing the pointsof the compass. At one particular pointthere is a card AB carrying the identifica-tion letters of the station. This card doesnot rotate with the drum and aerial, butremains fixed.

Light from a source S is focused uponthe fixed card AB and upon the scale -markings of the disc C as the latter slowlyswings past. The reflected light passesthrough the usual rotating scanning disc D,and is thrown on to a photo -electric cell P,so that a television picture of the fixed cardAB and of the scale markings on the disc Dis fed first to the amplifier V, then to amodulator Ml (which is supplied with acarrier wave from 0), and finally backthrough brushes B to the aerial A, where itis radiated into space as part of the beam.

Simultaneously a second aerial (notshown) radiates synchronising signals, notas a beam, but in all directions, so as tokeep any television receiver within range instep with the scanning disc D.

All that the fog -bound mariner nowrequires to do is to watch his televisionscreen. As the beam sweeps past him, hewill see a picture similar to that shown inFig. 2, consisting of the stationary identifi-cation letters AB and a slowly movingimage of the compass scale, which indicateshis bearings relatively to the beaconstation. Every suitably equipped ship




FNGLIS

FEW landsmen realise the value andimportance of the modem lighthouse.There is an official map called the

" Wreck Chart " upon which everyspot where a shipwreck has occurred ismarked with a small black dot. In thechart these marks appear in thick clustersall round our shores, and there are severalnotorious danger areas which each havemore than a thousand wrecks. Imaginationstaggers at the thought of what this chartwould look like if we had not lighthouses !

An Ancient IdeaThe increasing size and speed of modem

ships, which makes for comfort (and safetyalso, in some ways), actually renders themmore vulnerable to the perils of sunkenreefs and hidden rocks than are smaller andslower vessels. When breakers are 'sightedthere is less time to change course, and afast steamer will rip her whole bottom openif she strikes a reef at speed.

The lighthouse is a very ancient idea,and one in the Troad was mentioned by aGreek poet as long ago as 660 B.c. Themost famous of all such structures inantiquity, was the famous tower on theisland of Pharos, near Alexandria, builtabout 270 B.C. It was built of whitemarble, and was six hundred feet high.At the top was a chamber in which a fireof wooden logs was kept burning, whichJosephus tells us was visible for fortymiles. Under the name of the Pharos, itwas one of the Seven Wonders of the ancientworld, and lasted for nearly sixteen centuries,when it was destroyed by an earthquake.

Pharos TowersThe Pharos has given its name to light-

houses in many languages, and it is inter-esting to mention that nearly two thousandyears elapsed before a better method ofilluminating lighthouses was discovered,than the fire of wooden logs used here.Log fires were liable to bum away tooquickly in a strong wind, and to be put outin heavy rain-just when they were mostneeded ; and the idea of carrying constantsupplies of fuel to the top of a six -hundred.foot tower makes one positively shudder.

The Romans built many Pharos towers

LIGHTHOUSESAND THEIR

STORYG. Long, F.R.G.S.

(Left) St. Catherine'sLighthouse, Isle ofWight. (Right) A closeup of the same light-house showing thescreens and guards tokeep sea -birds off the

glasses.

around the coasts of their Empire. Two ofthe most famous guarded the passage ofDover Straits. The tower on the Frenchcoast was built by order of the EmperorCaligula at Boulogne. It was 192 feet

The Value of the Light-house and the Important Part it Playsin Aiding Navigation

high, and lasted till the sixteenth century,when it collapsed owing the the rock uponwhich it stood having been undermined bythe waves.

But for this it would undoubtedly bestanding to -day, since its neighbour onDover cliffs is still in excellent repair. Itis an octagonal tower, forty feet high, withwalls ten feet thick. There are scantyremains of Roman lighthouses in half adozen places round our coasts. After thedeparture of the Legions, Britain went backto barbarism, and shipping almost vanishedfrom our coasts, so that many centurieselapsed before the friendly gleam of awarning light greeted the mariner acrossthe dark waters of the midnight sea.

It was the Mediaeval Church which tookup the work which the Romans hadabandoned.

There were men called hermits, who con-secrated their lives to prayer in solitaryplaces. Some of them were situated onislands, or lonely cliffs ; and were preparedduring their nights of vigil to tend a

beacon light to warn mariners. Some ofthese holy hermits erected little hill -topchapels, having a tower in which a beaconburned. The most picturesque and typicalstructure of this kind now in existence isSt. Katherine's Chapel at Abbotsbury(Dorset). The little chapel was used as apilgrimage church, and the open toppedtower held a beacon light visible far out tosea.

Church Towers UsedLantern Hill at Ilfracombe takes its

name from the beacon which formerlyblazed from the top of the little Chapel ofSt. Nicholas and guided ships into theharbour.

St. Michael's Chair, on the rocky summitof St. Michael's Mount (Cornwall), is anothervery ancient and charming tower for abeacon light.

Very often an ordinary church tower wasused in the same way. The glorious" Stump " at Boston-one of the mostbeautiful church towers in Europe-form-erly carried a beacon light to guide marinersinto the port of Boston ; it was visible farout in the North Sea. The hill -top churchsteeple at Rye, Sussex, carried another, anda second blazed on the top of the ancientYpres Tower, the two forming an admirablepair to guide shipping entering the narrowand difficult mouth of the Rother.

Modern LighthousesAnother was shown on the tower of

Arundel Church and served as a guidinglight to seamen entering Littlehamptonharbour, three miles away.

We now come to modern lighthouses,which are classified by seafaring men into



A Roman lighthouse at Dover.

three main, and two lesser groups :1. MAKING LIGHTS.2. WARNING LIGHTS.3. COASTING LIGHTS.

Making Lights are those first seen by anavigator as he " makes " the coast whenapproaching from far out in the ocean,such as the Lizard Light in Cornwall, andthe Bishop Light in the Scilly Isles.

Warning Lights are used to warn shipsof dangerous rocks or reefs in the fairway.The Eddystone and the Casquets are twoexceedingly well-known examples.

Coasting Lights are placed on convenientheadlands along the coast to lead themariner along. First he sees the MakingLight as a tiny point of flame in the far dis-tance, and as he nears the shore the coast-ing lights appear one beyond another-" Just like the lamps in the High Street,"as an old sea -captain put it to me. It is afascinating sight on a clear dark night tosteam up the Channel in a fast modernliner, and see light after light appear inmajestic succession. Each of them can bedistinguished by a skilled navigator bytheir differing beam or flash, and sometimesby a change of colour.

The other kinds of lights are found inharbours, and in the channels leadingthereto.

Leading Lights are placed at suitablepoints along a difficult channel to guide theseaman into harbour.

Port Lights are placed at the end ofpiers and jetties, and glow out in crimsonwarning, don't come too near." Themost famous and romantic of all Britishlighthouses is of course the Eddystone,because of the difficulty in building it on asmall rock surrounded by raging seas ; andalso on account of the tragic history of theearlier attempts. The first was sweptaway by a gale, and everybody in it wasdrowned, the second was burned down, andthe third became unstable because therock on which it stood was underminedby the force of the waves. But the epicstory of the Eddystone Light has been

told so many times beforethat it is unnecessary torepeat details of it in thisarticle.

St. Catherine'sOne of the most interesting

lighthouses around our coastis St. Catherine's, in the Isleof Wight. It was one of thevery first to be lighted byelectricity, and its beam hasthe stupendous power ofseven million candles. Sovivid is this searing ray thatany man who dared to standon the platform and gazeinto the incandescent blazewould be instantly struckblind, and those whosebusiness takes them near thelights are compelled to weardark glasses The lighthouseis shown to visitors and is oneof the most popular ex-cursions in the island. Theelectrical apparatus is induplicate, and an oil -firedsystem is kept as a final re-serve. The same powerwhich drives the dynamosworks the mighty doublesyren, whose roar can beheard far outto sea duringfoggy weather.The light hasbeen seen at

Cherbourg, seventy-two milesaway ; and glimpsed fromBournemouth - over thirtymiles distant - it resem-bles a searchlight, sweepingthe horizon. Another famouslighthouse is that at BeachyHead, which was built at thebase of the cliff in 1899. It is123 ft. high, and was erectedto replace the old Belle ToutLight which stands on the cliffabove, with a light nearlythree hundred feet above thewaves. Experience provedthat the summit of the cliffswas often shrouded in fogwhen the air was clear lowerdown, and so the light had tobe placed at a lower level.Beachy Head juts far out into

'the channel, and badly needs a warning light.The light of the lighthouse is a subject

on which a whole article could be writtenFor perhaps two thousand years, an openfire of wooden logs was the only method,but in the reign of our King Edward theThird pitch pots were tried. These failedbecause rain quickly extinguished them; coalwas the next idea, but was terribly smoky.

ReflectorsSpace will not permit a detailed descrip-

tion of the elaborate systems of reflectors bywhich the light is enormously increased inintensity. Since it is of the utmost im-portance that navigators should knowwhich lighthouse they can see, elaboratearrangements are made so that each lightshall be easily identified.

Lights can be roughly grouped as under:1. A steady continuous light.2. One showing a flashing light at regular

intervals.3. One showing a steady light, which at

intervals goes out entirely. (This effect isproduced by a revolving screen whichpasses in front of the light.)

4. Coloured lights.It will be realised that since various

permutations are possible, quite a numberof differing signals are practicable, and bymeans of this the identity of every light-house is known.

(Above)RyeChurch,Sussex, thetower onceused as alighthouse.(Left) St.K a therine'sChapel,A b botsbury,Dorset, alsoused as alighthouse



abiCRAMATEURS

GRINDING OPERATIONSBy W. H. DeIler

THE demands of certain classes of workare such that a high degree of accuracyplus good surface finish is called for.

Satisfactory work may be produced, pro-viding that a fair degree of skill is employed,by the use of ordinary turning methods.where the part or parts are subsequentlyheat treated, the care bestowed in obtainingaccuracy and finish, frequently results inwasted effort. While it is true that partsmade from mild steel may, with carefulhandling, be lightly case hardened andpolished without any appreciable deterioration in the surface condition (a point alsoapplying to direct -hardening steel, provid-ing that the hardening temperature is arelatively low one). The fact remains,however, that the distortion, even if onlyslight, resulting from heating and quench-ing is sufficient to render the part unservice-able. The nature of this distortion woulddepend upon the character of the part.Thus an object in the form of a bush mayshrink or become oval while one in thenature of a spindle of any length will tendto warp.

Grinding forms the most reliable andeffective method to employ as a finishingprocess for parts which need to be hardened.As may be gathered, these remarks areintended to apply mainly to cylindricalwork. Grinding of this nature is normallycarried out on a machine specially designedfor the purpose but really good work can beproduced by adapting a lathe to performthe operation.

A certain amount of additional equip-ment in the form of, a grinding attachmentwill be necessary, this aspect, by the way,having been dealt with previously. How-ever, in this direction two important pointsmust be stressed before good results canobtain, namely, the attachment must berigidly mounted on the lathe and the grind-ing wheel spindle needs to be a good fit inits bearings.

Grinding WheelsThe attachment apart, one of the most

important factors bearing on the quality of

Fig. 4.-A badly set wheel thatmay lead to breakage.

Fig. 1.-(Left) A grind -lead Bush ing wheel with a lead

bushed central bole.

3,)510N A

Fig. 2.-(Right) Themethod ofclamping the abovewheel on the spindlebetween two washers.

The importance of these requirements willbe more readily understood when it isrealised that grinding is actually a cutting

the work produced, is the question of propergrinding wheel selection. It is not suffici-ent merely to have a grinding wheel ofrequisite diameter, width and bore, to suitthe attachment, as the wheel must conformto requirements in other respects as well.

77/7/7/

Fig. 3.-Smallen-gine erswashersshouldnot be

used.

.011

Soft washers

Clampingcollars

Washertoo small

process in the same way that turning is, thematerial being removed in the form ofmicroscopic shavings.

A grinding wheel is composed of abrasiveparticles held together by a bond, theseparticles, sticking out from the face of thewheel, provide thousands of separate cut-

ting edges. Thus it will be seen that thesize of the particles will have a bearing onthe finish obtained.

Wheels are manufactured by one ofseveral processes namely, vitrified, silicate,rubber or elastic. The processes differ,chiefly as regards the method of bonding theabrasive particles together. Each type ofwheel has its particular sphere of usefulness.A greater number of wheels by far are madeby the first process than any other, andthose so made are readily distinguishable bytheir colour, which is a warm shade ofbrown. This type of wheel is most suitablefor the readers present requirements.

Grade and GrainThe term " hardness " as applied to

grinding wheels refers to the manner inwhich the abrasive particles are heldtogether. In use, the cutting particlesshould break away from the face of thewheel in contact with the work when theybecome too dull to cut and so expose, as itwere, a .fresh set of cutting edges.

Different classes of work and conditionsrequire wheels of different grades, so thatwhereas one that is too soft for a particularjob will wear away rapidly, one that is toohard will soon glaze up. The usual methodof designation of grade is by a letter of thealphabet. As already mentioned, the workin which the amateur will be interested is thatwhich is hardened and the most suitablegrade of wheels for such work will lie in thesoft range represented by letters I. J. K andL. The grain of the abrasive has a de-finite relation to the size of the particles,i.e. number 46 grain has been passedthrough a sieve with a mesh having thatnumber of holes per linear inch, thus thehigher the number, the finer the grain of thewheel. For hardened steel parts the grainof suitable wheels will lie between numbers46 and 60. Mention should have beenmade of the fact that elastic wheels areusually marked with a numeral to indicategrade, nos. 1, 14, 2 and 24 representing thesoft range. Such wheels are unsuited togeneral grinding, but a narrow wheel of thekind may be employed in cases where anordinary wheel would otherwise requiredressing extremely thin.

There is one other point, and that is inregard to the kind of the abrasive which hasa marked effect on the performance of thewheel. Aluminium oxide is probably thebest abrasive for the work under discussionand wheels so composed are sold under thetrade names of alumdum, aloxite, etc.

Conditions Affecting Grinding WheelsIt is impossible to advise regarding wheel

selection, unless the actual conditions inwhich the grinding is to be carried out areknown. The surface speed of theiwheel

Corner undercutUndercut

Fig. 5.-A method of undercutting where the face of ashoulder requires grinding.

Fig. 6.-A " huntingdvn" type of dresser.

Fig. 7.-Greater accuracy and bettergrinding will be obtained by working

on " dead centre."



and work must be taken into considerationand also the question of whether the con-tinuity of the grinding will be intermittentlyinterrupted by anything in the nature ofkeyways or splines. A Grinding Wheelshould be run at a speed in revolutions orfeet per minute very closely approximate tothat stated on the tag attached to the wheelwhen purchased. The effect of running

Emery wheel Free to revolve

Fig. 8.-A substitute for a diamond dresser.

under speed is the same as if the wheel wereof a softer grade than it actually is, and itmay therefore, wear away quickly in use.An excessive speed on the other hand hasthe reverse affect in regard to the grade, andis a practice that should never be indulgedin, having consideration for safety. Wherethe work is relieved by keyways, etc., it isadvisable to use a slightly harder wheelthan that used for similar plain job owingto the abrading action of the sharp corners.

Mounting Grinding WheelsGrinding wheels with the exception of

those intended for small internal work and-Olose of the " elastic " variety are suppliedwith a lead bushed central hole, Fig. 1,which fits the grinding spindle. The wheelshould be clamped on to the spindle be-tween large collars recessed away in thecentre (see Fig. 2). The inner collarnearest to the shoulder on the spindle ispreferably made a tight fit or better stillfitted over a small peg to act as a key. Athick paper washer (made from somethingin the nature of heavy blotting paper)should be interposed between each side ofthe wheel and the collars before tighteningthe nut. Most wheels are provided withsuitable paper washers but this point mustnot be neglected or the wheel may crackunder the strain of tightening. Washersmade from thin rubber insertion are moreeffective and will give considerably greaterservice. On no account must ordinarysmall engineers washers, Fig. 3, be used toclamp the wheel between as these will pro-vide insufficient drive and further will causethe wheel to move on the lead bush. Itmay happen that a grinding wheel (orwheels) can be picked up and which are suit-able except for the fact that the centre holeis too small for the spindle. When suchare to hand, care should be exercised inopening out the lead bush. This is bestaccomplished by setting up the wheel truein the lathe, and boring out with a boringtool. It is an easy matter to open out byhand, but not so as to ensure that the holeis at right angles to the side. This maylead to the result seen in Fig. 4, which, ifnot noticed, may lead to breakage.

Wheel TruingBefore any grinding can be attempted the

face of the grinding wheel needs to bedressed true and flat. A wheel surface goodenough for cylindrical grinding will not beobtained by the use of a " huntingdon "type of dresser, Fig. 6, or one of the typeshown in Fig. 8. These types are intendedfor hand use on tool or general grindingheads. An ideal tool to use is a diamonddresser, Fig.10. This may be used as a handdresser or mounted as afterwards described

for the present purpose. Such a dresser ora small diamond mounted in small shoul-dered stud will cost about 258. A substitutenot quite as effective in use is a " diam-carbo " dresser shown in Fig. 9. This con-sists of a steel tube filled with an abrasivemixture similar to Carborundum. Thiswears away in use and the tube acting as asupport is ground away at the same time.Possibly the best method of mounting thetruer is to make a substantial centred shafthaving a hole direct through the centre andfitted with a set screw to take the shank ofthe truer after the manner of a boring bar.This is fitted with a carrier and lockedbetween the centres, with the tail of thecarrier resting on the driving pin to stop theshaft from rotating. The point of thedresser is set towards the wheel and centralwith it, the truing being effected by drivingthe grinding wheel and bringing it in con-tact with the truer, traversing the wheelbackwards and forwards with the saddle.Where the face of a shoulder has also to beground the side of the wheel will need dress-ing appropriately. To accomplish this thedresser will need mounting on the catchplate in a manner similar to that described,or a flange to serve the same purpose fittedto the shaft, the dressing being carried outby feeding the wheel to the dresser by saddlemovement and working the cross slide.

Dead CentresPrior to grinding work between the

centres, see that the points of both centres

Steel tube containing dbrasive

Fig. 9.-This type of dresser is suitable for handuse only.

made in the corner, as seen in Fig. 5. Thisundercutting is essential where the diameterbeing ground must remain constant to apoint close up to the shoulder and also to pre-serve a sharp corner on the wheel. HardenedMild -Steel parts will need to be deeply case-hardened. Open hearth treatment willprove unsatisfactory as the depth of case soobtained will be removed by grinding.

As a general rule the following allowancesfor grinding will be ample providing thatthe finish of the turning is reasonablysmooth. Outside diameters plus .010 in.-015 in., faces of shoulders plus .002 in.-.004 in., and minus .005 in. - .008 in. ininternal diameters.

It is difficult to lay down any hard andfast rules as for work speed, etc., as manyfactors have to be taken into account. Awork speed of between 20 and 50 surfacefeet per minute will probably give bestresults. Too slow a speed may cause burn-ing of the work locally, while one that is toohigh is likely to cause chatter. Light cutsshould be taken and the wheel traversedfairly quickly, far in excess of the feedlikely to result from the sliding motion.On this account the saddle is best woundalong by hand as it can thus be bettercontrolled.

With the lathe running normally the-wheel, if in front of the work will need torun upwards. This should be avoided as thesparks will fly upwards and may be danger-ous to the eyes. Where a dead -centreattachment is made the direction of rota-tion of the work can be reversed by acrossed driving belt, otherwise unless thegrinding wheel can operate behind the worka crossed belt on to the cone pulley becomesimperative. For internal work this pointdoes not matter as the difference in directionof rotation can be obtained by grinding atthe side of the hole nearest to, or away from

Diamond

are in good condition and that the headstock centre runs truly when the spindle isrevolved. Greater accuracy and bettergrinding will be attained by working on" dead ' centres. This is accomplished bymaking a boss to screw on the nose of thelathe, on which a pulley secured by ascrewed ring runs (as in Fig. 7). A drivingpin is fitted to the face of the pulley anddrives the work via a carrier.Preparation of Work for Grinding

Work which is to be finished on centresneeds to be accurately centred with a com-bination centre drill as deeply as possibleto provide good bearings. Changes indiameter should, where the difference issubstantial, have, an undercut betweenthem and where the face of the shoulderrequires grinding, the undercut should be

Fig. 11 .-Details of a cupgrinding wheel.

Fig. 12.-Boring ahole in a broken wheelwith the tang of a file.

Fig. I0.-An ideal tool is the diamonddresser shown.

the operator to give the desired result.Small internal 'grinding wheelt can easily

be made from portions of broken wheelsabout }-in. thickness by boring a hole withthe tang of a file and rough grinding toshape, finishing to size on the outside withthe wheel truer (see Fig. 12).

Some surface grinding can be carried outby mounting the work on the face plate andusing a cup shaped grinding wheel. Forflat work to result the face or edge of thecut needs to lay parallel with the face plate.Where the width of the work will permit itwill not be, necessary to rotate the work,but owing to the power consumed and heatgenerated, the surface of the wheel mayrequire reducing in width by dressing awayas in Fig. 12.

Cutters and reamers can easily be sharp-ened between the centres or on a mandrel

providingthat a springtooth -restis fitted tosupport theteeth andpermit in-dexing as inFig. 13.

Tooth set belowCentre to g, ve

Clearance

Centre ofCutter & Wheel

Flat SpringrFingerDetails of thes,5ring tooth -rest.



An X-ray photograph oftwo coins and a hinge takenby the process described in

this article.

THE common gasmantle consists ofa " skeleton "

composed of 99 percent. of thorium oxideand 1 per cent. ofcerium oxide, thesmall proportion ofthe cerium oxide beingabsolutely essential tothe light -producing powers of the mantle.

Thorium, in common with uranium anda few other elements, is a radio -activeelement. Hence, all its compounds areradio -active, also. Thorium compounds,of course, have not a tithe of the intenseradio -activity of true radium preparations.Nevertheless, all such compounds andpreparations of thorium are definitelyslightly radio -active and, in many instances,this radio -activity can be applied to aninteresting purpose.

Gas -mantle PowderA readily available example of the radio-

activity of thorium compounds consistsin the making of simple " X-ray " picturesby means of waste gas mantles. Brokenand disused gas mantles should be storeduntil half a dozen or more of these articlesare obtained. Crush up the broken mantlesand pass the resulting powder through afine sieve in order to filter out the grosserparticles. The sieved material is thenstored in a dry bottle. It will not deterior-ate in any way, and it may be used overand over again for the photographicexperiments described in this article.

In order to make an " X-ray " picture,take a plate or cut -film of medium. speed,place it in an empty box provided witha light -tight lid and place on the emulsionside of the plate or film (which faces up-wards) a small flat metal article such as amodern key, one or two coins, a pen -nibor some similar object. Then scatter overthe surface of the plate or film a little ofthe sieved gas -mantle powder, taking carethat the plate surface is fairly well coveredwith the powder.

The whole of the above operations, ofcourse, must be conducted in a dark roomand in ruby light.

Using the PlateThe lid is placed on the plate -containing

X-RAY PHOTOGRAPHSAT HOME

How to Take Simple X -Ray Photographsby Means of Waste Gas -mantles

box and the latter is then gentlyplaced on a shelf and allowed toremain absolutely undisturbed for aperiod of between forty and fiftyhours. At the end of this time, theplate is again removed from the box(in the dark -room red light, ofcourse), the gas -mantle powdercarefully dusted off its surface and collectedfor further use, and finally the plate is de-veloped in any ordinary strong developer.The result will be that a silhouette image ofthe metal object will develop upon the plate.

If contrasting images are desired, thesecan best be obtained by " exposing " theplate for, about three and a half days(approximately sixty hours) and then by

A paper clip and washers.

(Centre)-A Yale key. (Below)-Pair of scissors. With the ob-scuring effect of brown paper.

developing it in the following hydro-quinone developer :Hydroquinone . 40 gr. - 2.5 gramsSodium sulphite

(tryst.) . . oz. or 15Caustic soda . 40 gr. 2.5Potassium bromide 5 gr... 0.3

The shadow images so obtained are nottrue X-ray images, for the rays from thethorium oxide in the gas -mantle powderpossess but very feeble penetrative powersand are incapable of passing through anyappreciable thickness of metal. Suchpictures, however, are exceedingly interest-ing as well as being very easy to obtain, andan instructive period of time can beexperienced by any amateur scientificworker who attempts their production.

Letters and DesignsBy cutting out letters or designs in silver

paper or tinfoil and by pasting down suchcharacters to the emulsion surface of theplate and by finally dusting the entire platesurface over with the gas -mantle powder,silhouetted or shadowgraph letters anddesigns can be obtained.

In most instances it is not advisable toprolong the " exposure " of the plate orfilm to the gas -mantle rays for an undueperiod. An exposure " of from forty tofifty hours is about right and it shouldnever exceed, say, sixty-five hours. If suchexposures are doubled, the image, instead ofbeing more clearly defined or more contrasty,will, on the contrary, be rendered flatterand less distinct owing to the general



fogging effect of the thorium rays on theemulsion of the plate or film.

Interesting effects can often be obtainedby mixing the gas -mantle powder withvarying proportions of some inert andfinely powdered material such as chalkpowder, the finest sand, fine metal filings,boric acid powder and many other similarmaterials. These have the effect of " dilut-ing " the active gas -mantle powder andspacing its constituent grains farther apart.Note, however, that gas -mantle powderthus " diluted " does not necessitate agreater exposure than the average beinggiven to the plate or film.

Ordinary Bromide PaperIf the individual experimenter has not

available a supply of plates or cut -filmswith which to make experiments on theabove lines, he should note that suchexperiments can be conducted with ordin-ary bromide paper in place of plates orfilms. In such instances, however, the

necessary exposure will have to be increasedvery considerably, according to the makeand speed of the bromide paper used.Even gaslight papers can be used for theabove purpose, but, in such instances, the'requisite exposures generally run into weeks.

The " gas -mantle radiograph " results onphotographic papers are never so good asthose which are made on plates or films.Moreover, such paper prints will be " nega-tives," that is to say the silhouetted imagewill be in white on a dark background.These paper " negatives " can only be" printed " by copying through the camera,using a piece of bromide paper for thereception of the copied image instead of theusual plate or film. In this way positiveimages can be obtained from the paper nega-tives of the gas -mantle radiographs.

It is advisable to use backed plates inorder to get the best results from the gas -mantle " exposures." The backing of theplates prevents the scattering of the plate -affecting rays from the thorium oxide in the

gas -mantle powder and thus assists in theproduction of a cleaner -cut image. If,however, backed plates are not available, afair substitute for them may be made bypasting a piece of black paper, or, betterstill, black cloth over the back of theplate. With films, no such precautions areusually necessary.

A WarningDo not on any account allow particles

of the gas -mantle powder to fall into a boxor envelope containing unused plates, filmsor papers, for if even a single grain of theradio -active gas -mantle powder obtainsaccess to such regions, it will play havocwith the light-sensitive material in itsvicinity. For this reason, the bottle con-taining the gas -mantle powder should bestored right away from all photographicmaterial and all manipulations with thepowder should be performed away fromsuch sensitive material except, of course,the film, plate or paper actually in use.

Radio Valves for Centimetre Waves

THE efficiency of the ordinary type ofwireless valve becomes very low at

ultra -high frequencies and only a few willoscillate at all at wavelengths as short as1 metre.

Now, however, a new standard valve hasbeen introduced by the Western ElectricCorporation of America which will oscillateat wavelengths as short as 40 cans. At

SCIENCE NOTESAND NEWS

40 or 50 centimetres as being ultra short,they are long compared with those nowbeing used by Dr. Potapenko and Dr. Mengof Caltech, U.S.A., who are using waves

Power and light are represented here as Boulder Dam, completed at last, and officially opened, starts turningwater of the Colorado River into electricity. This picture was taken as the electric circuit, closed by

President Roosevelt in the White House, opened wide the gates of the dam.

half a metre, it can generate an output of6 watts.

Bulbs of Pyrex GlassThe new valve is built into a heavy dome -

shaped bulb of Pyrex glass, about 2/ in. indiameter. The anode is about in. longand less than in. in diameter, but it iscapable of dissipating no less than 30 watts.

Studying Molecular StructureAlthough we think of wavelengths of

of only 1 centimetre to study molecularstructure. They use a three -electrode valvein which the anode is only one -fiftieth of aninch in length and diameter. The poweravailable is, of course, very small, butthey have discovered that the wavesgenerated will not penetrate a moisture -

laden atmosphere.

Atom SmashingALARGE equipment has just been in-stalled by the University of Rochester,

U.S.A., known as a Cyclotron for research

into the disintegration of atoms.The apparatus consists of an extremely

powerful electro-magnet which weighs about15 tons and which is excited by a currentof 400 amperes at 110 volts. Between thepoles of the magnet a metal vacuum cham-ber is placed in which the atoms can beaccelerated to an energy of 5,000,000 volts.When the magnet is energised, the powerfulmagnetic flux causes the atoms to travel in aspiral, and on reaching the outer extremityof the chamber it strikes an obstruction anddisintegrates.

Windows of SapphireWINDOWS of synthetic white sapphire

about f in. in diameter are being usedto provide transparent openings throughwhich the happenings inside the cylinderof a motor -car engine can be observed andstudied. Synthetic sapphire has been foundto be the best material for this purpose asit combines good mechanical strength withresistance to chemical action by the fueland lubricants and it transmits the visibleand invisible light rays with very little loss.

Microphotography in LibrariesNEW application of microphotography

Ais being widely developed in Americafor the recording of documents, drawings,newspapers and books in order to savestorage space. The pages of a large andthick volume, when photographed on tinefilm, weigh only a few ounces and occupyfar less space than the original volume.

In order to render the films readable,special reading machines are used. Theseare really a form of photographic enlargerand serve to magnify the film record torender the matter easily readable.

A Refrigerator Ship

THElatest advances in the science of

food preservation have been incorpor-ated in a 12,000 -ton refrigerating shiprecently launched on the Clyde. To pro-vide an even temperature in all climates,cooled sea brine will circulate throughmore than 1,000 miles of pipes laid through-out the ship and ozone will be used to keepthe cargoes of fruit and meat fresh. To dothis, over 300,000 cubic feet of sea air willbe passed through freezing chambers everyhour and discharged into the cargo space.

Thousands of cases of fruit are some-times tainted as the result of one case goingbad, but under the new conditions decaywill be prevented from spreading.


November, 1936 NEWNES PRACTICAL MECAANICS. 81

The famous railway track over Chat Moss as it appears to -day. It was originally laid down by Stephenson in 1839 in theface of great difficulties and against much opposition.

IN11AS1fEIRS or 1"41 ILCI CsNO. 15. THE STORY OF GEORGE STEPHENSON AND HIS ASTONISHING SUCCESS

WYLAM-ON-TYNE, so far as engin-eering, commerce and industry areconcerned, is one of England's most

historic villages. For there, even at thepresent day, stands the humble, stone -built cottage, in which, early on the sum-mer morning of June 9th, 1781, the eyes ofGeorge Stephenson, mechanical genius,inventor and, above all, the " Father of theRailway," were first opened.

Stephenson's genius is now universallyrecognised and, for the most part, is beyonddispute. Probably no single individualmanaged by a lifetime of endeavour tochange the face of the country more funda-mentally than did Stephenson. WhenStephenson was born the roads carried mostof the country's merchandise, although, toa large extent, the heavier classes of goodswere transported along the network ofcanals which had then been recently con-structed in many areas. Before he died,however, Stephenson witnessed an age inwhich the railway had begun to reignsupreme. Canal transport, towards theend of Stephenson's life, had been scrapped,road conveyances, for the most part, hadall been allowed to fall into disuse. Theentire kingdom had become railway -minded.

Surprising as it may seem, althoughStephenson, with the aid of his son, Robert,engineered the majority of the early rail-ways, he never put forward the railroad asa panacea for all industrial troubles. Fromthe beginning he opposed the mad specula-tion, the " railway mania," which quicklysprang up all over the country after hisinitial success in the construction of com-mercial railroads.

His Earlier LifeStephenson's earlier life was a much

impoverished one. His father, Robert

Stephenson, or " Old Bob," as he waslocally called, gained a precarious livingby acting as fireman for one of the collieryengines in the neighbourhood. On anincome which never exceeded twelveshillings a week, " Old Bob " found himselffaced with the necessity of maintaining awife and six children, the second of whichwas his famous son, George.

Gifted with inborn mechanical faculties,Steaenson managed to get himself takenon as an engine boy at his father'scolliery. That was at the age of fourteen,and the pay was a shilling a day. Gradu-ally, the boy worked himself up, devotingall his available spare time to the study ofengines and to making good the lost generaleducation of his early youth until at theage of nineteen he became appointed brakes -man at Black Collerton colliery at a wageof nearly a pound a week.

Busy as Stephenson was at this time, henevertheless found time to attend to onevery important business, namely that offalling in love. Fanny Henderson, a youngwoman employed at a neighbouring farm,had taken his fancy and before long shebecame Mrs. George Stephenson. Themarriage of George Stephenson was anintensely happy one. In 1803, Stephen -son's only son, Robert, was born, and inthe following year his young wife died. Theloss affected Stephenson deeply. Its ulti-mate result was to direct his activities intotwo directions, the education of his son,Robert, and the study of engineering and,in particular, of locomotive construction.

At KillingworthBeing promoted to the post of engineer

at Killingworth colliery, near Newcastle,one of Stephenson's first inventions was thatof a miner's safety lamp. For a consider-able time, this lamp was an active com-

petitor of the better-known lamp inventedby Sir Humphry Davy. Stephenson alsowent in for clock making and clock repair-ing and the small income which he drewfrom this occupation he devoted to, his ownbenefit and to the education of his son.

About 1814-15, Stephenson, with theaid of interested patrons, managed to con-struct his first successful locomotive. Theengine functioned well, but it was notcapable of continuous effort and Stephensonquickly grew dissatisfied with it.

Soon after this period came Stephenson'sgreat invention of the furnace blast bymeans of which the combustion rate of thefuel is automatically regulated by the workwhich the locomotive is doing. This inven-tion proved itself to be a fundamental onein the history of locomotive constructionand from it the success of the early railroadlocomotives may be dated.

In 1823, Stephenson, having by this timemade quite a degree of local fame for him-self, borrowed capital and set up for him-self as a, locomotive -maker in Newcastle.In his Newcastle factory he devised thetubular boiler and from this time, it is said,he never looked back.

Two years later-in 1825-the first rail-way in the country was engineered 'byStephenson. It extended from Stocktonto Darlington and it was opened on. Sep-tember 27th, 1825, the speed of the locosemployed on it being about that of a trottinghorse.

A Mistaken IdeaStephenson's success with his Stockton -

Darlington railway opened the eyes ofmany in the country. For a long time thenotion had gone about in influential circlesthat, under practical conditions, a loco-motive could never be got to run on rails, amistaken idea having prevailed that the


82 NEWNES PRACTICAL MECHANICS November, 1936.

The most amous of all historic locos. The original " Rocket," built by Stephenson in 1829.

plain wheels of a locomotive carriage wouldslip round without gripping the iron guid-ing rail. Indeed, some years previously,attempts had been made at working witha locomotive equipped with toothed carriagewheels which engaged in rack -cut rails.

Very quickly, Stephenson's early trialsconvinced interested parties that the weightof the locomotive was amply sufficient tokeep its wheels in firm contact with therails under practically any conditions.Money for the construction of railroads andimproved locomotives began to be forth-coming and quite a number of locomotivedesigns entered into competition with thoseof Stephenson's.

Perhaps the most spectacular and interest-ing chapter in Stephenson's life is that whichdeals with his conquest of Chat Moss and hisbuilding of The Rocket.

The county of Lancashire previouslyabounded in " mosses "-large flat areasof swampy, boggy land, the sites, mainly,of prehistoric forests and fit, usually, forlittle else than for cabbage and potatogrowing and for similar " coarse " agri-cultural purposes. The largest of theseboggy areas is Chat Moss which, in Stephen -son's day, was a veritable quagmire ofwatery, peaty pulp extending for miles onthe western side of Manchester. ChatMoss acted like an enormous sponge. Inwet weather, it soaked in water and ex-panded. In dry weather, the surface -water evaporated and the Moss contracted.Chat Moss, therefore, was almost continu-ally in a condition of upwards expansionor downwards contraction.

The Second RailwayWhen it was decided to build the second

railway in the kingdom, that betweenLiverpool and Manchester, Stephenson wasappointed as engineer and surveyor for thetask. It was impossible to drive a straightrailway from Liverpool to Manchesterwithout crossing Chat Moss. To go roundthe Moss, the railway would necessarilyhave to add many miles to its total length.Stephenson weighed up the matter anddecided to take his railway across the bogof Chat Moss.

Most of the interested parties wereaghast at Stephenson's revolutionary pro-posal. They called him mad and thedirectors of his company would have re-trenched themselves and called off the rail-

road project if they had been able to do so.However, they eventually expressed con-fidence in their appointed engineer andsurveyor and Stephenson went on his ownway with the " impossible " task of flinginga safe and durable railroad across thisrenowned morass of Lancashire.

The principles upon which Stephensondevised his plans were quite simple. Justas snow -shoes, by reason of their large sur-face, prevent a man from sinking into thesnow, so, he reasoned, could a railroad becarried across any bog if only it rested on asort of mattress or platform of sufficientsize.

Having surveyed out the projected rail-road track across Chat Moss, Stephenson'sfirst plan was to form a footpath of heatheracross the Moss. This was to provide aroute for workmen and it also served tocarry a light narrow-gauge railway for thecarriage of materials.

Across Chat MossGradually, from this beginning, Stephen-

son constructed a huge under -bed ormattress across the dreaded Chat Moss andupon this he laid his railroad. Thousandsof tons of dry moss, turf, bracken and other

raft -forming materials were used up in thetask. Whatever drainage was possiblewas performed and although, particularlynear the Manchester end of the Moss wherethe ground was very bad, progress wasexceedingly slow, the herculean task, aftermany difficulties and after the exercise ofalmost heroic optimism on the part ofStephenson, was accomplished.

The directors of the line, early in 1829,offered a prize of £500 for a locomotivecapable of fulfilling certain conditions.The announcement of the competitionaroused considerable interest amongpractical engineers up and down the countryand Stephenson himself, assisted by hisson, Robert, who was then in charge of theStephenson Locomotive Works at New-castle -on -Tyne, was soon busy with thedesigning and construction of a locomotivefor the new Liverpool -Manchester railwaywhich he had engineered.

The result of Stephenson's work in thisdirection is well known, for, eventually, itproduced The Rocket, Stephenson's famouswinning locomotive which, during its trialson the Liverpool -Manchester railwayattained an average speed of 15 miles perhour more than the minimum speed of10 m.p.h. laid down by the promoters of thecompetition.

Some ten locomotives were actuallydesigned for the Liverpool -Manchesterrailway trials, but, of these, only four actu-ally underwent the test, viz. The Rocket,Sans Pareil, Novelty and Perseverance,Stephenson's Rocket, as we have seen,winning easily.

321 Miles of RailroadAfter his astonishing success in the con-

struction of the Liverpool -Manchester rail-way and, also, in the design and making ofThe Rocket, George Stephenson, as well ashis son, Robert, became in demand every-where as railway surveyors and engineers.It is on record that in the course of two shortyears, no fewer than 321 miles of railroadwere constructed under the direct superin-tendence of George Stephenson at a cost of£11,000,000.

The close association and understandingwhich had always existed between the twoStephensons, father and son, now cul-minated in a sort of business partnership,the father attending to the actual layingout of the railways, whilst the son, Robert,devoted all his energies to the improving ofthe Stephenson loco designs.

The first railway station in the world I The Manchester terminal of Stephenson's original line.It is now used as a railway company's office.



A SUCCESSFUL 1-C.C. PETROL. ENGINEFULL CONSTRUCTIONAL DETAILS TO BE GIVEN IN THIS JOURNAL

The Model Maker's Ideal

WHEN an internal-combustion engineof 15 c.c. was produced it was re-garded as the ultimate in miniature

design for a prime mover of this class forthe propulsion of models. This,relatively speaking, was not solong ago, but during the interven-ing period, engines having capa-cities of 9, 6, and 3'5 c.c. havefollowed at fairly regular inter:vals. I am also aware of the factthat an engine of dimensions veryconsiderably smaller has also beenmade, and for which a very suc-cessful performance has beenclaimed, but constructional detailsof it have been withheld, nor haveI been afforded an opportunityof seeing it run.

In my possession is a petrolengine of 1.155 c.c. which I de-signed and built to provide powerfor model purposes. This engineperforms remarkably well, and itis really surprising that such asmall engine can develop the powerthat it does. I am entitled toclaim that it is the first workingpetrol engine in the world to bemade of such a small size.

In view of the keen interestcentreing round such productions,it is proposed to deal with theconstruction of this engine in futureissues. Blueprints will be sup-plied. As may be imagined, thework in all its stages must neces-sarily be carried out to closelimits. Such work calls for ahigh degree of skill, and thefull details will enablethose so equipped to pro-duce a similar workingmodel.

The particulars relatingto the engine are in brief :Bore, /78- in. diameter ;stroke fri in.; cycle, 2 -stroke ; total weight withplug a fraction over 2 oz.Carburation is effectedin a simple manner,the mixture being con-trolled by an adjustable The sparking plug is shown on the right. The other illustrations show the usual size of plugs for modelsneedle valve, the petrol 12 -mm. and t -in. respectively.

to which is fed directly to the jet tube fromthe tank. The inlet is taken into the bottomof the crankcase, the admission of the gasbeing governed by a mechanically -operatedpiston valve. This valve is operated by aface cam carried at the outer end of the

Here is a picture of the 1-c.c. engine compared with a standard sparking plug. Althoughonly 17-(5- -in. bore by -in. stroke, it starts easily and runs for long periods. It will

fly a model weighing 16 oz.

crankshaft, a lobe cam on the edge of whichserves also to operate the simple adjustablecontact breaker. No castings are required,the parts in the main being machined fromround bar material. All joints are screwed,only two screws are used in construction,

these being on the con-tact breaker. Due at-tention has been givenin the design to avoiddifficult machining op-erations, and for thisreason the cylinder headis made detachable.

One of the real diffi-culties with an engineso small lies in the pro-vision of a suitablesparking plug. An ideaof the size of the specialone used in this in-stance can be gaugedfrom the photographshowing it compared toa 12 -mm. and a 1 -in.sparking plug. A viewof the engine in com-parison with a standardsparking plug gives afair indication of itstiny overall dimensions.

The performance andpracticability of thisengine have been de-monstrated to thePress, and it wouldseem from the resultsobtained that there isno limit to the size to

which it is possible tobuild a petrol engine,except that one mustsoon reach that pointwhere internal fric-tion would exceed thepower developed, andwhere the weightof the associatedequipment-coil, con-denser, and tank-would be excessive.

The weight -per -horse -power is the im-portant factor. Theengine here describedwill fly a model weigh-ing 16 oz. W. H. D.

Two further views of the 1-c.c. engine, showing its almost microscopical size.



Two viewsof this novel two-seatershowing its attractive lines.

MOTORING has been brought withinthe reach of thousands more peopleby the introduction of the Lloyd car

which sells at the amazingly low price of80 guineas. Economy, of course, is thekeynote of the construction of this car yet,despite this, its specification is really quitecomplete.

Two-stroke EngineThe Lloyd car is powered by a Villiers

single -cylinder, two-stroke, water-cooledengine of 350 cc. capacity, mounted at therear. Both cylinder barrel and cylinderhead are detachable. The crankshaft ismounted on two large diameter ball bear-ings whilst the connecting rod big -end is ofthe roller -bearing type. Lubrication is byPetroil system, incorporating a mixingdevice in the petrol tank. A rear -mountedradiator and thermo-syphon system ensureefficient cooling. Coil ignition is used withautomatic advance and retard control.Starting is effected by a mechanical leveroperated from the driver's seat.

The chassis next commands attention :it is of the torsionless tubular -backbonetype with transverse members for bodymounting. Thecentral tube is 5in. diameter andthe cross membersare cantilevertype pressed steel.All four wheels areindependentlysprung. The frontsuspension is ar-ranged by bronze -bushed lever armsmounted on hard-ened steel pinsand employing atrans verse leafspring. A similarsystem is used atthe rear, but axletubes are em-ployed instead oflever arms. Therear axle itselfconsists of tworobust tubes eachterminating in abronze -bushedfork mounted onhardened steelpins and anchoredto two aluminiumbango housings.

AN INTERESTING350-c.c. CAR

A Novel Two-seater withRear -mounted Two-stroke Engine and Inde-

pendent WheelSuspension

Drive from the engine to the back axleis by means of a roller chain through athree -speed and reverse gearbox to thefinal -drive sprocket, and then through aHardy -Spicer universal joint to the near-side rear wheel. A multi -plate clutch isembodied in the gearbox. The gear -change lever is conveniently mounted onthe central chassis member. The gearratios are : top, 6.2 to 1 ; second, 10.5to 1 ; first, 16.1 to 1 and reverse, 21.5 to 1.

The brakes operate. on all four wheelsand are of the usual internal expandingtype, extremely powerful and smooth in

A rear view of the car.

action. They are operated by pedal,supplemented by a hand lever and ratchetfor parking purposes. There is a simpleindependent adjustment for equalising thebrakes and a master adjustment for takingup wear. The handbrake is adjustablefrom the driver's seat.

EquipmentThe general equipment, bearing in mind

the price of this car, is really very compre-hensive. A six -volt dynamo lighting setis used and there are two large headlampsfitted with parking bulbs. A dip switch isprovided. The chromium -plated switchpanel carrying the ammeter and switchwith locking device is placed centrally inthe instrument panel, which is in the middleof the dash. A cubby hole is thus providedeach side. An electric horn, windscreenwiper and driving mirror are, of course,provided. There is a full set of tools,including jack, wheel brace and tyre pump.The spare wheel is mounted in a horizontalposition under the " bonnet," above thedriver's legs. The hood and side curtainsare concealed behind the seat when not inuse. A three -gallon gravity -feed petroltank is mounted at the rear, above theengine. The overall dimensions of the cargive some idea of its size and roominess.Wheelbase is 5 ft. 9 in ; length, 9 ft. 3 in. ;width, 4 ft. 5 in. ; track (front) 3 ft. 8 in.,(rear) 3 ft. 5 in. ; ground clearance, 61 in. ;height to top of screen, 3 ft. 11 in. Theturning circle is 35 ft.

Maximum speed is said to be 50 m.p.h.,and, in second gear, 40 m.p.h. Cruisingspeed is 35-40 m.p.h. The manufacturersare Lloyd Cars Ltd., of Patrick Street East,Grimsby.

ORDER NEXT MONTH'SBig Xmas Number Now I



Fig. 1. - Theattractive appear-ance of thefinished calendar.

IHAVE read somewhere that laziness isthe mother of many inventions ; andwhen one comes to think of it, there is a

great measure of truth in the statement.For in practically every home and factoryto -day, work is being done by machineswhich was previously done laboriously byhand.

Take, for example, such a simple thing aschanging the daily calendar ; there is notmuch labour attached to it, but one feelsit a bother and moreover one will forget.Then, after a day or so, or a week or more,the date is required on a day, say, in Septem-ber. The calendar is consulted only todiscover that it has not been changed sincesomewhere in August. Off comes a handfulof leaves and again the calendar is broughtup to date.

To remedy this state of affairs and takethis work off my unwilling hands, I con-ceived the idea of a calendar that wouldchange automatically.

The older method of doing this by a trainof specially cut wheels did not appeal to me.Moreover, I had not the tools required todo such fine work. Then again, by suchmeans the size of letters and figures used isnecessarily small.

I wanted an automatic calendar withreal printed letters and figures of no lessa size than one inch high ; something Icould see if I happened to be at the oppositeend of the room.

Cost of MaterialsThe illustration shown of the completed

clock will help you to judge in what measureI have succeeded. Moreover, the total costwas not much over £1. The small eight -day clock which controls the calendar -changing mechanism was bought for 168.The other parts were made mostly fromodds and ends from my workshop ; whilethe clock -case was cut out of oak -facedplywood and French polished. The calen-dar and its changing mechanism aremounted on a wooden framework ofyellow pine. This has a brass drop handleon the back to enable it to be pushed into,or withdrawn from, the clock -case. Thesizes that are given are not arbitrary. Inmy own case they were dictated by theparts at my disposal. The clock could,therefore, be made smaller, or larger ifthat were considered desirable.

Each night on the stroke of mid-night the calendar turns and shows thedate of the day then begun.

AN AUTOMATICDAILY CALENDAR

Instructions for Making a UsefulCombined Time -piece and Calendar

are Given in This Article

Wheels RequiredWhen I bought the

clock I took it out ofits case, prised off thehands and lifted offthe face. Then onto the hollow spindleof the hour -wheel Ifitted tightly anotherwheel having twelveteeth (see Fig. 2, A).

This wheel I made to engage with anotherwheel having twenty-four teeth, which Ifitted on the left-hand side of the clock(see Fig. 2, B). It is obvious, then, that if the

wheel with twelve teeth turns with the hour -wheel once in twelve hours, the wheel withtwenty-four teeth will turn once in twenty-four hours.

On this wheel is fitted a small cam, asshown in Fig. 2. Now, this cam, as it turns,lifts lever D, which is pivoted through theclock -frame and then extends from the back

Fig.3.-Showing the year unit in position.

of the clock to trip pin E, on the calendarchanging mechanism (see Fig. 3).

The changing mechanism is simplicityitself. From a scrap merchant I pur-chased an old eight -day clock movement.From this I removed the time wheels, as allI wanted for my purpose was the train ofwheels that operated the striking of thehours. Then I took off the slotted discthat controls the number of hours beingstruck, and on its place I fitted a brass dischaving seven equidistant slots. When,therefore, the control pin F is lifted outof one of those slots, the brass disc is freeto move till the next slot is under control

Fig. 2.-The trip elementin the clock.

pin F. Into this slot the control pin falls,and so prevents further movement. Thismovement, which is, of course, equal to aseventh of its circumference, is transmittedby wheel H to a brass cylinder I, which asit turns moves the calendar a distance ofone day (see Fig. 4). Control pin F is fixedto trip pin E and is lifted out of a slot by

lever Don the clock acting on trip pin E.

The Hollow CylinderIt should be noted that the hollow brass

cylinder-an aluminium one would alsobe excellent-is driven by a clutch pinfixed to the driving spindle J (Fig. 4).A quarter turn on a knurled wheel Kwithdraws the clutch pin and allows thecylinder to run freely. This is necessarywhen turning back the calendar at thebeginning of a new year.

As mentioned before, the size of the fig-ures on the calendar is 1 in. and the spacebetween them is about a in. A simplecalculation will show that the length ofcalendar will be approximately 38 ft.

To make this, I bought a roll of goodwhite wallpaper, measured off a width of34 in., and cut it with a pair of scissors.



The NumbersOn this strip of paper I marked off, and

punched out, holes or perforations with a1 -in. leather punch ; the distance betweenthem being equal to the pitch of the sevenholes which were bored in the brass cylinder1 -in. distance from either end, and v

tapped to take -A-in. brass rod. Thesprockets were made from shortlengths of this rod ; these were thenscrewed and turned into the tappedholes in the cylinder, and the endsnicely rounded off. The cylinderitself measures 51- in. long by 2 in. indiameter, with a hole bored throughthe end flanges to takel-in. steel rod.

A local printer willingly gave meon loan a set of wooden type andsome printer's ink, black and red.With a little bit of patience and in-genuity I soon had the full yearfrom January to December, printed.

Two spools were then made andslots cut in their hollow spindles.These spools are 41- in. long with aflange of 21 in. diameter, and arefitted to run behind the cylinder.Into the slot of one of the spools oneend of the perforated calendar wasfixed, then passed round the cylin-der, the perforations falling nicelyon to the sprockets, and then intothe slot of the other spool.

Fitted to the ends of the spools, and alsothe cylinder rod or shaft, are small groovedpulleys. On these are placed s -in. roundelastic bands or belts. When, therefore,the cylinder is turned by the clockworkmechanism it draws the calendar from onespool and winds it on to the other.

Only the numbers of the days and thenames of the different months are printedon the perforated paper. The names ofthe days are printed on a separate band ofpaper and glued on to a thin metal sleevewhich fits over the left end of the cylinder.

7

SHU 10 sari

'11

A` X

Fig. 4.-Showing the disposition of the calendar mechanism.

This is spring -retained, and has sevennotches cut on its circumference, oneopposite each day, and into any one of thosenotches it can be placed as required.

Fitting in Leap YearThe reason for this is self-evident.

For if the days, the numbers, and the

months were printed together on the calen-dar it would only be correct for one year.For example, this present year began on aWednesday ; 1937 will begin-as this is aleap year-on a Friday.

So then, all that requires to be done whenchanging the calendar at the begin-ing of the year is a simple matter.The perforated calendar is woundback from one spool to the otheruntil January 1st appears, then thesleeve with the days is turned untilthe correct day is opposite, and thecalendar is set right for another year.

But, you will say, what about leapyear ? How does the calendar makeprovision for that extra day in everyfour years ? Easy enough. Februaryis printed with twenty-nine days,but the calendar is divided betweenthe 28th and the 29th. The twoends are provided with snap fas-teners and with these can be joinedtogether at either of two positions.February can then be made to havetwenty-eight or twenty-nine daysaccording to the pairs of fastenersthat are used. This adjustment ismade when the calendar is beingset at the beginning of a leap year.

The year unit is made separatefrom the calendar, and is held to

the baseboard by two wireless terminals.The figures 19 are a fixture ; but the twooutside figures are printed on separateendless bands ; that is from 0 to 9. Byturning them any number up to 99 canbe shown. In 1999 the 19 can be changedto 20 and the calendar would be good foranother thousand years !

F

fv-1 A PERPETUAL TABLE FOUNTAIN

Showing how the fountain is made.

TliIS little fountain is quite self-con-ained and does not need a constant

supply of running water. It is port-able, and can be used either indoors orin the garden. At first glance it looks asthough I had discovered the secret of per-petual motion. The water in the basin isforcing itself in a jet to a height of 10 in. ormore above its own surface ! Actually,however, the jet will cease when all thewater in the upper tank has been forcedout.

The fountain is made quitesimply. If you have a coupleof fold petrol cans of equal size,they will do dendidly for thetanks and will give about forty-flve minutes' working withoutattention. They should be fixedon their sides, one above theother, with a space of about 8in. between them. A simpleframe of wood or metal can beeasily rigged up to keep themin position. The lower tankmust have an air cock at thetop and a draw -off cock under-neath ; old gas fittings willcome in useful here. The topbasin can be made from anyhandy metal ; it rests on theupper tank and has a fillingplug, as shown.

Pipes A, B, and C are tubesof t in. or smaller diameter,preferably of brass. It is bestto solder all joints between pipesand tanks, as they must bequite watertight. To finish the

job, solder on the top of pipe C a thin brassdisc in which a pinhole has been drilled. Onthe size of this hole depends the volumeof the jet and the length of time the foun-tain will play.How the Fountain Works

To start the fountain, first put a plug inthe top of pipe A. Remove the plug fromthe bottom of the basin, fill the upper tankand basin with water and put back the plug.Now unstop pipe A and the fountain will

start to work.Magic ? Not at all. When you un-

plugged pipe A, the water ran down andcompressed the air in the lower tank. PipeB transmitted the pressure to the water inthe upper tank, which was forced up pipeC and so out through the pinhole, formingthe fountain jet. The flow will go on,because the. head of water in A is actingagainst a smaller head in C. No waterflows through B.

Of course, as the water rises in the lowertank, the " working head " of water isreduced and the jet weakened. The jetdoes not, however, become a mere dribble,but stops quite suddenly when the lowertank is full of water and the upper tank fullof air. The water level in the basin re-mains the same.

RestartingTo restart the fountain, plug pipe A, open

the air cock and empty the bottom tankthrough the draw -off cock. That tank willnow be refilled with air and the air cockshould, be closed again. Now refill thebasin as originally described, and thefountain is ready for another " run."

A painted casing, of either wood ormetal, will give the job a finished appear-ance. The fountain is silent except for thesound of falling spray.

ORDER NEXT MONTH'SBumper Xmas Number Now !



TRIXTWIN RAILWAY

Here comes the New " 00 " Gauge TRIX TWINRAILWAY; perfectly proportioned miniature models,electrically driven and sold at a price that all can afford.You'll be wildly excited when you see how the twoTWIN trains travel on the same lines at different speeds,in the same or opposite direction, backward or forward,fast or very slow. The TRIX TWIN RAILWAY hasautomatic couplings; couples up its own vans and coachesin the simplest possible manner; all you have to do ismanoeuvre the engine into position.

The patent rails are beautifully mounted on BakeliteMouldings, making them strong and rigid and impossibleto bend. They are fixed and unfixed in an instant.

With :the TRIX TWIN RAILWAY you can have themost elaborate railway system in a quarter of the spaceusually needed. You can't do better than suggest a TRIXTWIN RAILWAY for a present this Xmas. There's aTRIX dealer in your district anxious to demonstrate.

This illustration shows the MotorHouse of a Gantry Crane you canmake yourself. Think what excite-ment it will give! The Motor Houseand Jib revolve realistically and cantravel on the Gantry Bridge from oneend to the other. The Crane itselfcan lift a load and turn sideways atthe same time! You can place thecrane in one part of the room andcontrol all these fascinating move-ments at some distance from themodel.

Read how inexpensive TRIXConstructional Sets really are.

AS MODERN AS THE FLYING SCOTSMAN

TRIXCONSTRUCTIONAL SETSNo extra parts to buy; no expensive

accessoriesYou can have hours of fun and delight-

ful entertainment with the latest TRIXConstructional Sets. From the simplestmodel to an elaborate crane, you canmake them all, and, what's more, you canmake them work! Start if you wishwith a No. I TRIX at 6d.-it has 51pieces. Every now and then you canadd to this, or even buy a larger set.

There are Gear Sets, which make thewheels go round, and for half a crownonly, " TRICY TRIX," the electricTRIX which works from an ordinarypocket battery.

" MOTO-TRIX " with the famous" Trix Motor " gives you even greaterpower, whilst the very last word inmagnificence and completeness are the" TRIX MAJOR " and " SUPER TRIX,"two lovely sets, each in its handsomecase. There are lots of others besides,all at most reasonable prices. Youought to see them.

Trains and Sets obtainable from Toy Shops and Storeseverywhere.If any difficulty, write to TRIX Ltd., St. John'sHouse, 45/47 Clerkenwell Road, London, E.C.I.



PERFECT SCALE MODELSOF FAMOUS SHIPSEach of these true scale shipkits makes a fine exhibitionmodel . . . every kit is sentout on a money -back guaranteeof satisfaction. You may re-turn the kit within 3 days-asit was received - and yourmoney will be refunded with-out question.

BUILD THE"QUEEN MARY"SHAPED HULL. LENGTH 18".A real bargain kit containing many finished details, such as metal lifeboats, davits,anchors, ventilators, etc. Fully shaped hull. Masts, spars, rigging, printed balsaparts, winches, funnels, cements, and coloured dopes, etc., and clear full-sized plan.

Complete kit, carriage paid 7/6" Queen Mary," 10" Model. Without carvedhull and finer details.

Complete kit, carriage paid

CLIPPER SHIP

"FLYING CLOUD"This kit makes a fine model of a record -breaking Clipper. Kit includes balsa blockfor hull, printed balsa sheets, masts, spars,rigging, coloured dopes, etc., etc. Length12 inches.

Complete kit, carriage paid

Send penny stamp for illustrated list show-ing many models of famous ships.

SEND YOUR P.O. NOW TO

P. M. SWEETEN LTD.BANK HEY STREET - BLACKPOOL

Balsa Model AeroplanesREAL FLYERS

We are offering the finest American Kits of parts ever puton the market for the Model Aeroplane Builder. All Kits arecomplete, including all Balsa wood, Japanese tissue, wheels,pins, wire, elastic and full-size Drawing with instructions.

PRICESKits for 26" wing span flying model of the Fokker D8, Nieuport, CurtissRobin, Puss Moth, Sopwith Camel, Douglas, Fairchild 22, Monocoupe.

Price per Kit 2/6, postage 4d.Super Kits for building up 24" wing span models which can be fully con-trolled from the cockpit; everything wanted is included in these Kits tomake a Stinson Reliant, Curtiss Swift, Albatross D -5A, Spad, Hell Diver,Douglas 0-38. Price per Kit 7/6, postage 6d.If you are starting to look for Christmas presents, send for Bond'sGeneral 198 Page Catalogue, price 6d.; this contains everythingwanted for the Model Aeroplane maker, Model Railway builderfrom Gauge " 0 " Scale, or the Model Ship Builder; also all

Tools and Materials required.

BOND'S O'EUSTON ROAD LTD.254, Euston Road, London, N.W.1

'Phone : Museum 7137 Est. 1887

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SIMPLE ELECTRICAL APPARATUSACCUMULATORS

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MODEL BOAT BUILDING25 SIMPLE WORKING MODELS

THE HOME WOODWORKERTHE HANDYMAN'S ENQUIRE WITHIN

HOUSE DECORATION & PAINTINGPOWER DRIVEN MODEL AIRCRAFT

And these are just a few of the attractivetitles included (all fully illustrated).

From Booksellers Everywhere or 112 post free from

GEORGE NEWNES, Limited,8-11 Southampton St., Strand, London, W.C.2

ES1IVALUE KITS" Value Kits " because we do not offer huge parasols at ridiculousprices but because of sound design and construction.

READ THIS AMAZING REPORT from the "Romford Recorder" (Sept. 4th).REMARKABLE FLIGHT OF CADET MAJOR.

" Climbing in circles, it quickly reached an altitude of about 50Q feet. At the end of 12 mins. themodel was so high up as to be nearly invisible. The timekeeper, no longer being able to see themachine, stopped his watch. Time, 18 mi.. 20 sees. out of sight I The machine landed unharmedin a field at Dagenham. It is impossible to say how long It remained in the air, but it i s estimated tobe several hours. The distance flown is also hard to compute, as the machine was circling all thetime, but as the crow flies it must have been at least seven miles."

ELASTIC DRIVEN. 18 mins. 20 secs. out of Sight!THE CADET MAJOR SCORES AGAIN !CADET MAJOR KIT (Elastic Endurance Model).Identical with the above, 9/- Complete, post free.

Sole British Agents for Cadets and all Bunch Models. Scientific Hi -flyer Kits.Gwin Aero Petrol Motors. Tornado Motors and all Imp Supplies.

MODEL SUPPLY STORES iSend 2d. for 18 -page I

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Our NEW ENGINEERING GUIDE explains clearly howall the best lobs are secured. It shows how to obtainsuch money -making qualifications as A. M.I. C. E.,A.M.I.Mech.E., A.M .I.W .T., A.F.R.Ae.S., etc. Howto secure permanent, progressive and pensionable postsIn the Government and Municipal Service, and describesnumerous " Higher -pay Courses" in CIVIL,ELECTRICAL, MECHANICAL, AUTO andAERO-ENGINEERING ; TELEVISION, TALKIE -PICTURE WORK, etc.

SUCCESS-OR NO FEEWe definitely guarantee success. If you fall yourexamination, or if you are not satisfied in every way withour service, then your full tuition fee will be returnedwithout question.Write to -day for this remarkable publication and detailsof our employment service, etc.

NATIONAL INSTITUTE OF ENGINEERING( Dept. 29), Staple Inn Bldgs., High Holborn, London, W.C.1



(Left) Making sparklers. Wooden splints being coated with the sparkler composition contained in a test tube. (Right) Incorporating pellets of special composition ina firework " candle" in order to produce the " silver star " and " basket of flowers" effect.

Makin (S)

(EP Fireworks at HomeTHE making of fireworks dates back a

considerable number of years, andalthough in modern times the com-

mercial manufacture of pyrotechnical pieceshas reached a supreme degree of excellencewhich cannot be imitated on a small scale,there is no reason why any amateur whois interested in chemistry and its alliedsciences should not try his hand successfullyat the making of a number of safe and simplefirework articles for home display purposes.

Spectacular DisplaysThe various firework " mixes " described

in this article are all easy to make and, usedintelligently, they are capable of givingspectacular displays. Moreover, providedthat the most elementary and commonsenseprecautions are taken during the manufac-ture of the various firework pieces, noaccident can possibly occur. Do not,therefore, compound the firework in-gredients near to a fire or in the vicinity ofan open flame. Always treat potassiumchlorate with great respect. This fireworkingredient is normally perfectly safe tohandle, but if, for any reason, it is requiredto be mixed with sulphur and /or charcoal,the potassium chlorate MUST NOT be groundup with these materials, otherwise it will beliable to explode spontaneously. Always,when mixing potassium chlorate with anyother material whatsoever, employ no othermethod for this purpose other than a verygentle stirring of the ingredients together.Potassium chlorate, of course, can be pow-dered up alone with impunity ; it is onlywhen it is powdered or ground up withother materials-particularly sulphur-that it becomes dangerous.

Coloured FiresHaving now sounded a necessary warning

to all home experimenters who propose toengage in the truly interesting task of small-scale firework making, let us now proceed tothe actual details of simple pyrotechnicmanufacture.

The very easiest firework pieces to makeare the coloured fires, of which many differ-ent varieties are possible.

Below are given several tested formulaefor the preparation of coloured fires. Theyare all fairly slow -burning, but, if required,the rate of burning can be speeded up byadding to each " mix " a small proportionof saltpetre and/or powdered sulphur.

The coloured fire ingredients should beintimately mixed together and, if required,the various " mixes " may be damped witha little methylated spirits. The colouredfire powders are best put up in little pill-boxes (procurable cheaply from any drug-gist) or, if more convenient, similar boxesmay easily be made at home by gluing card-board strips together. Having filled theboxes with the coloured fire powder, providefor each pill -box a fuse. See that the fuse

This simplefirework piece,the making ofwhich is des-cribed in thisarticle, givesthree brilliantflashes of lightin quick suc-

cession.

]Fireworks at F omedips below the level of the powder in thebox and passes through a hole in the lid.Such fuses are made from ordinary tow orstring and a description of their preparationwill be given later.

White FireSaltpetre .Sulphur .

Charcoal .Shellac .

Green FireBarium nitrate.Potassium chlorate .

Saltpetre .Charcoal .Shellac .

. 25 parts

. 81

3 parts41

1 ,,



Red FirePotassium chlorate . . 30 partsStrontium carbonate (or nitrate) 6Charcoal .Shellac .

Blue FirePotassium chlorate .

Copper sulphate .

Shellac .

Charcoal .

4

. 30 parts

" Fountains " and " Coloured Candles ""Fountains," "Coloured Streamers," and

" Many -coloured Candles " can be made byutilising the properties of the above col-oured fire " mixes." Make up a number ofcylindrical cardboard containers, each abouthalf an inch in diameter, or even smaller, andfour or five inches long. Fill a container aquarter full with a coloured fire mixture.In this instance it is best to have the mix-ture slightly damped with methylatedspirits and to compress it within the con-tainer by tamping it down with a pencil' end.On top of this coloured fire layer, tampdown another layer of a different burningcolour, and so on until you have three orfour layers of different coloured fire mix-tures within the one container. Place thefuse in position and then seal up the upperend of the container by means of a plug oftissue paper which has been soaked in salt-petre solution and dried.

Fireworks so fashioned will burn first inone colour and then in another, the colourschanging according to the type of " mixes "which they contain. For the best effect,the colour changes should be placed in thisorder : white, red, green, blue, white. Donot let green follow either red or white, orelse a good deal of the spectacular effectwill be destroyed.

An Interesting " Candle"A still more interesting " candle " can be

prepared on the above lines by making uplittle pellets (about the size of a pea) of thefollowing mixture :

Barium nitrateFine iron filingsAluminium powderSaltpetre .Methylated spirit

6 parts1

. 1

. Sufficient to dampthe mixture.

In the middle of the firework candle pre-pared as above (and such can be either ofthe single or multi -coloured variety) placetwo or three of the above pellets, surround-ing them with a mixture of powderedsulphur and potassium chlorate (equalparts).

A firework so prepared will, when theburning layer has reached the pellets, throwout a number of silver stars, the potassiumchlorate -sulphur mixture igniting thepellet composition and driving out themetallic part of the latter with an exceed-ingly spectacular effect.

Fuses for fireworks are readily made.Simple touch -paper may be prepared bytaking ordinary tissue paper and soaking itin a strong solution of saltpetre, afterwardsallowing it to dry. Such paper will burnslowly, as also will string and tow whichhas had the same treatment. If to the salt-petre solution a little potassium chloratesolution is added, the burning of the touch-paper will be speeded up.

Quick -burning FusesA quick -burning fuse may be prepared by

making into a paste with a little dextrine

or gum solution a quantity of the followingmixture :

Saltpetre. . 15 partsSulphur . . 2Charcoal. . 2

String, tow, hemp, flax or other fibrousmaterial is smeared over with the above -mentioned paste and allowed to dry.

Sparkler manufacture is an interestingfirework preparation which can be carriedon at home. The sparkler mixture con-tains the following ingredients :

Saltpetre. 5 partsIron filings (fine) 1Aluminium powder . . 2Potassium chlorate .

This is made into a thin glue -like mixturewith a methylated spirit solution of shellac,and wooden splints are coated with it andleft overnight to dry. In actual home

fuse -blobs together with string or towimpregnated with either quick- or slow -burning fuse mixtures and provide, also, asimilar fuse -tow to the first " blob " inorder to start the firework. A light appliedto this latter fuse -tow will travel up the towand, reaching the first " blob," will igniteit, the result being a brilliant flash of light.The other " blobs " will similarly ignite inquick succession, thus giving rise to asuccession of flashes.

For its most effective display, such apyrotechnic piece should be nailed up to awall or to the end of a long pole.

Gunpowder, as is well known, consists ofa mixture of sulphur, saltpetre and charcoalin varying proportions. Not much interestis attached to its making, however, for it ismessy and dirty stuff to handle, and itsmode of burning is not spectacular. More-over, when burned in a confined space,gunpowder, in any but small quantities,may exhibit dangerous properties.

Coloured fires in the foreground and" candles" in the rear.

practice, it is best to make the sparklercomposition up in a test-tube and to dip thewooden splints into this. The splints arethus coated efficiently and wastage of themixture is prevented. If preferred, ofcourse, the sparkler " mix " can be coatedupon wire instead of upon wooden splints.Such sparklers, when ignited, burn with abrilliant shower of sparks, the colour ofwhich can be modified a little by incorporat-ing with the sparkler " mix " a small quan-tity of any coloured fire mixture.

A Firework PieceQuite an interesting firework piece can be

made from any of the above sparkler com-position which may be left over. Placetwo, three or more " blobs " of this com-position upon a cardboard or wooden stripand in contact with each " blob " attach alittle of the quick -burning fuse compositionpreviously mentioned. Connect all these

PinwheelsIf, however, gunpowder

" mixes " are rolled up intolittle cardboard tubes ofabout * in. diameter andthe latter coiled around acentral disc, the familiarpin -wheels will result.Similarly, such tubes whenfolded concertina fashionand bound securely in thatposition will constitute thewell - known " rip - rap "fireworks.

Detonating mixtures ofsulphur and potassiumchlorate and/or gunpowder

not safe to handle,let alone to make. Conse-quently, details of theirpreparation are not givenhere. The reader, however,may be assured that in thefirework preparations de-scribed in this article hewill find ample opportunityfor making numerous ex-periments in the directionsin which his own fancy maydictate. Many variationsin the composition of themixtures given in thisarticle are permissible, butthe mixture -compositionsgiven above are the oneswhich, under normal con-ditions, are calculated toproduce the best results.

Powdered CharcoalIt should be noted in all cases that

powdered charcoal cannot be very success-fully substituted by soot or lampblack.Any attempt to do so may result in poorresults, or even in complete failure, sincesoot has the effect of " blocking " the burn-ing of a firework.

Finally, remember the warning uttered atthe commencement of this article. Do NOTgrind or otherwise powder together sulphurand potassium chlorate, and no NOT makeor store firework mixtures in the neighbour-hood of an open fire or naked flame. Tak-ing those simple precautions, no harm cancome of home firework making on the linesdescribed above.

All the various chemicals mentioned inthis article are to be obtained from anyordinary chemist or druggist or, morecheaply, from one of the suppliers oflaboratory and chemical equipment who areto be found in every large town.



TAKEN as a whole, the human raceis a lazy one and it generally hailswith enthusiasm the advent of any

device or mechanism which can save thecarrying out of some monotonous process.I suppose that it is this natural lazinesswhich has contributed so largely to thepopularity of the automatic gramophone.In spite of the fact that these automaticmechanisms are by no means cheap, morethan two thousand are sold in Englandevery week, and if it were not for the com-paratively high price which one must payfor such complicated luxuries, the numbersold would undoubtedly be considerablyhigher.

Important FeaturesA complete description of even one of

the many delightful mechanisms now avail-able would be far too long for these pages,but a brief outline of the more importantfeatures and some of the mechanical" dodges " may be of interest. In theoperation of a gramophone, there are anumber of separate operations to be carried

Row--

Automatic Record ChangersWorkBeing a:Brief Explanation

of Some of the

Mechanismsnow Available

Fig. 1.-The latest model introduced by the Garrard Company. The records are supported partly by the bracket seen on the left and partly by a special notchedspindle which, of course, does not rotate.

out. For example, there is the placingof the record on the turntable, the lifting ofthe tone -arm or pick-up, the movement ofthe pick-up over the edge of the record, the

71/R0/TABLE...570/LADLE

P/Cle--- L40%/F7 -/LAG CAM

cannot be a very simple affair. In fact,the various devices which control the se-quence of operations are among the mostingenious of modern mechanisms.

CLUTCH LEVER

7,4,/,,4,9A1

L//v/r

Prcr ao ARM

P/nr- L/,0 Taen.,:eseC,444Fig. 2.-Simplified diagram of the H.M.V.unit showing clutch mechanism, gearing, and pick-up cams.

Fig. 3.-The H.M.V. Automatic Record Changer. The recordsare supported by the blades of the two pillars, which may be set

for either 10 in. or 12 in. records.

dropping of the pick-up on tothe edge of the record and thefeeding -in to the playing grooves-to name only the few motionsconcerned with the start of arecord, and when one considersalso the various operations at theend of a record, the changing orrepeating mechanism, and thenecessary provision for differentsizes of records, it will be realisedthat an automatic gramophone

Although the various operations to becarried out are complicated, they followeach other in a definite sequence. Thisfact enables the actions to be controlledby various types of cam gearing and thecam arrangements really constitute the" brains " of the whole mechanism.

Four CamsThere are too many individual actions

which operate simultaneously for one camto be able to control all, and the majority



L

Fig. 4.-Showing the cams, links, and guide -plates of the record -dropping mechanism.

of automatic mechanisms contain no lessthan four. In the H.M.V. mechanism,which is perhaps one of the best known,two of the cams control the jaws whichsupport the records and drop them, oneat a time, on to the turntable ; anothercam controls the lifting of the pick-up arm,and a fourth controls the lateral movementof the arm. The contours of the respectivecams are so designed that each motiontakes place in its proper sequence, butsince the automatic sequence only comesinto action at the start or end of a record,the cam gear must be declutched and out ofaction during the actual playing period.

The following brief description of theH.M.V. mechanism will serve to give ageneral idea of the operations which haveto be carried out by an automatic gramo-phone, and although the constructionaldetails are very different in the variousmakes, the changing sequence is similarin all.

At the end of a record, or at the beginningof a fresh series, the changing mechanismrequires to be brought into action in orderto place the next record on the turntableand bring the pick-up on to the disc. Inthe H.M.V., the cam gear is brought intooperation by means of a " trip " mechanismwhich is shown in Fig. 2.

The Trip ArmIt will be seen that the turntable spindle

carries a small wheel which rotates with theturntable and which has a single square -shaped tooth. When the mechanism istripped, either by pressing the startingbutton or automaticallyby the pick-up reachingthe spiral finishing grooveat the end of a record, thetrip arm releases the pointof the clutch lever and thesquare tooth on the turn-table spindle engages witha similar tooth on theclutch lever and carries thewhole clutch assemblyround with it. The clutchwheel is geared through anidler wheel with the set of

Fig. 5.-(Below) A sideview of the H.M.V.

mechanism.

cam gears and hence, as soon as the mechan-ism is tripped, either by depression of thestarting button or by the pick-up reachingthe end of a record, the cam gear com-mences to make a single rotation and thechanging cycle is carried out.

"r4

record, and they remain stationary untilthe mechanism is tripped, when they com-mence to rotate quite slowly in a clockwisedirection.

The Pick-up Traverse CamThe top cam, shown black in Fig. 2, is

called the " pick-up traverse cam " andengages with a small roller on the end oflever A. This lever is pivoted near itscentre and at the other end it engages withthe lower part of the pick-up pillar. It thuscontrols the lateral traverse of the pick-up.

As the cam ro-tates, the roller endof lever A isgathered in by theedges of the camand by the time ithas completed halfa turn, the roller isat the point of mini-mum radius, B, andthe pick-up is thenright outside theperiphery of therecord.

During the timewhen the pick-uphas been moved out-side the record, ithas also been raised

ZftvA-

Fig. 6.-Diagrain of pick-up lifting

Since the cam gear comprises four inde-pendent cams, it will be clear that four separ-ate sequences occur together, two of which-those connected with the raising andtraversing of the pick-up-en be followedin Fig. 2. The cams areshown in the positionswhich they occupy duringthe actual playing of a

Fig. 7.-The Garrard Automatic Record Changer. The records atecarried by the three pillars, a quick angular movement of which

rm,w the bottom record to fall on to the turntable.

mechanism.

above the recordsurface by means ofthe second camshown dotted in

Fig. 2. This cam engages with a rolleron the end of the link C which is connectedto the bottom of the pick-up lifting leveras shown in Fig. 3.

While the pick-up is raised and rightoutside the periphery of the recordas described above, the next record,which has hitherto been resting onthe rest plates D (Fig. 4), is



allowed to drop on to the turntable bythe withdrawal of the rest plates underthe action of the links E, the slidingguide plate F and the heart -shaped camG.

Further rotation of the cams brings thepick-up again over the edge of the record,and at this point, the increasing radiusof the dotted cam in Fig. 2 causes thepick-up to be lowered on to the recordand fed into the playing grooves. Therest plates have now returned to theirnormal position, and the separator plates,which have been isolating the bottomrecord of the pile from the others above,withdraw and deposit the pile of recordson the bottom rest plates.

The Mechanical SequenceThe cam assembly has only

made one rotation during thechanging cycle, which is nowcomplete, and the clutch gear isthrown out of action. The play-ing of the record proceeds andthe changing cycle is notrepeated until the mechanismis again tripped by the pick-up

X/101/Z DER OF ..20/7voLE OveR1,14N/CH THE PECO/20 FALLS OrNENAICKE0 gYt9RACKET 0 / Y ZEFT

e

Fig. 8.-Diagram showing the principle of operation of the latest Garrard mechanism.The little pegs on the arms of the bracket shown on the left cause the bottom record to

be shifted slightly to the right, thus passing over the shoulder of the spindle.

reaching the end of a record or by thepressing of the rejector button.

This very brief account of the changingcycle has only covered the main featuresand there are innumerable details which,however, belong more properly to aninstructional manual than to the pages ofPRACTICAL MECHANICS. Sufficient has beensaid, however, to give an indication of themethods by which mechanical sequencescan be achieved.

Prominent among other automaticmechanisms which can now be purchasedby home constructors of radio -gramophonesare two made by the Garrard EngineeringCompany. The first is shown in Fig. 6,and it will be seen that the records arecarried on three standards, the top of eachof which is fitted with a special knife -edgedblade known as the separator blade, the

Fig. I0.-The mechanism of theCollaro automatic gramophone.This mechanism is designed toplay single records which are loadedand played by pushing them gently

Fig. 1I-TheAutotrope, anautomaticrecord - changerde lure whichis capableof playing aseries of 33records whichmay be of anysizes and in anyorder.Thismech-anism has theunique featurethat it playsboth sides of therecords without

attention.

.6ga61,-2

. N

function of whichis to isolate thebottom record ofthe pile duringthe droppingmotion. Thethree standardsare connectedtogether by alink arrangementunderneath t h emotor board andare controlled bya special form ofcam. At thecorrect instant,

into the slot of thecase. The mech-

anism draws the record in,places it on the turntable

and after playing, the record is

pushed partially out of the slotagain.

Fig. 9-The newCollaro f automaticmechanism which canplay either 9 in., 10in., or 12 in. recordsin any order without

special setting. Therecords are supportedby pressure springsand a notched spindlesomewhat similar to

that of Fig. 8.

the standards make a quick angular move -ment, the knife edges separate the bottomrecord from the rest of the pile, thebottom record is dropped on to the turn-table, and the standards return to theirnormal position.

This mechanism is controlled by a veryingenious cam, which, unfortunately, defiesdescription in brief and simple language.It is unusual, however, in that it combinesall the essential movements in a single camby means of employing both a traversingand a radial contour to the cam face.

The Garrard MechanismThe second mechanism made by the

Garrard Company is delightfully simple inoperation and is shown in Fig. 1. Therecords are supported, partly by an in-genious bent spindle which fits into a slotin the centre of the turntable, but whichdoes not rotate, and partly by a bracketseen on the left. The arms of this bracketare fitted with two little pegs, and in orderto drop a record the bracket is caused to




The giant German flying -boat " Zephyr" is shown leaving the catapult aboard the steamer Schwabenland, on a test hop. The " Zephyr with its sister -ship" Aeolus" are being used on tests over a proposed Trans -atlantic commercial air route, with the Schwabenland acting as a floating, mid -ocean airport. The

above illustration gives an excellent example of the advances in transportation with the huge flying -boat leaving the stern of the steamship.

IN THE WORLD OF

SCIENCE AND INVENTIONTesting Metal Castings

ANEW method of testing metal castingsand machined parts whereby cracks and

similar defects can be detected dependsupon the use of supersonic sound waves.The material under test is covered with afilm of oil on the surface opposite to thatupon which the sound waves fall. Thesound waves pass through the material andproduce visible oscillations in the oil film.The waves are unable to permeate throughany defective portion, and thus a defect,such as a crack is shown up by static ornon -vibrating patches in the oil film.

Cosmic Rays

NO one can yet say with certainty whatcosmic rays really are or how they

originate. So much research is being done,however, that their nature cannot remaina mystery for ever. Cosmic rays can becounted, their direction and intensitymeasured-but what are they ?

An Automatic Radio TransmitterTHEY are found to be more numerous at

high altitudes, and a balloon equippedwith recording gear and an automatic radiotransmitter has been developed by theFranklin Institute to provide data of cosmicrays at extreme heights. The radio trans-mitter sends out a series of dots, theinterval between which indicate the heightof the balloon, and the arrival of cosmicrays also causes the transmitter to sendout special signals which are received andinterpreted by special oscillographs on theground.

Cosmic rays research at present seems tolead nowhere, but the energy of the rays isso enormous that it is not inconceivable thatpractical applications will be discovered. .

Glass ErasersGLASS has many strange applications,

and a new one is a rival to the familiar" india-rubber." Thin fibres of glass aresecured in a holder like the bristles of abrush and the numerous tiny points are sosharp that they will erase indian ink, type-writing, or even paint. The " brush " issaid to be soft and less liable to wear ahole through the paper than ordinaryrubber.

The Nation's Petrol ResourcesAVALUABLE discovery which wouldrender England independent of im-

ported motor spirit has been made recentlyin Edinburgh. Experiments have shownthat considerable quantities of motor spiritcan be distilled from cannel coal, a poorform of coal which was once mined inconsiderable quantities in Scotland but isnow regarded as a waste material and leftunworked whenever possible.

Cannel CoalIt is claimed that if the gas industry

were to use cannel coal for gas production,it would be possible to produce 700 milliongallons of petrol yearly-three-quarters ofthe nation's requirements.

It has been shown that cannel tar can behydrogenated by the low -temperature pro-cess, one ton of cannel producing 26,500cubic feet of gas, 57 gallons of motor spiritand 28 lb. of wax. The coke which isproduced in the process has been foundsuitable for domestic use in boilers andopen grates.

A " Death Ray " for InsectsONE of the most serious troubles of

wheat storage is the damage caused byweevils, a tiny form of beetle which multi-

plies exceedingly rapidly, and the cost ofpreventative treatment and the fumigationof storehouses is a very serious item.

A method has been developed by Mr.C. G. Lemon by which all grain could beeffectively treated and all insect life;whether in the form of eggs, larvae or matureweevils, exterminated by passing the grainthrough a special machine as it is stored inthe warehouse.

The MachineThe experimental machine consists of a

chute down which the grain is fed and itthen passes on to an oscillating metalplate above which are a series of gas -tubes..These tubes are electrically energised by avery powerful induction coil and a miniaturelightning display takes place between thetubes and the metal plate beneath. Anyinsect life is immediately killed by electro-cution.

Safer SubmarinesWHEN a submarine is on the surface

it is propelled by a Diesel engine, butwhen submerged it has to rely on electricpower derived from large accumulatorsbecause the Diesel engine would rapidlyuse up all the air. The accumulators,however, are a serious potential danger,because they give off poisonous 'gases ifthey come into contact with sea water.

A New Power UnitA new power unit has been evolved in

Germany which can be operated by com-pressed hydrogen and oxygen when sub-merged and the cumbersome and dangerouselectrical equipment will no longer benecessary.

This development will facilitate thebuilding of very small but highly efficientsubmarines.



FAIR COMMENTcgily Crhe Editor

Time, Tide, and PrintersTHE three things which never

return are the past life, thespoken word, and the neglected

opportunity, and there are threethings which wait for no man-time,tide, and printers. I hope the printerswill excuse me for designating them asinanimate " things " instead of theextremely virile, animate and activebeings they have to be and are.

They have been called lots of names,but never before, I believe, things.They, too, are blamed for many thingswith which they have had nothing todo. It is very convenient for someEditors to lay the blame for a piece ofremissness at the door of the printerby labelling it as a printer's error.Sometimes the journalist will inserta paragraph under the egregious titleof " errata et corrigenda," thus ob-scuring the fact that he is acknowledg-ing a list of his own mistakes.

What I merely started out to saywas that printing presses have vora-cious appetites ; they run to a clock -like schedule, and when the printerrings me up to say that he must havethe last bit of copy by such and such atime, who am I to say him nay? Thusit was that I was unable to deal in thelast issue with the Model EngineerExhibition sponsored, engineered, andfostered by my old friend PercivalMarshall. I visited this Exhibitionseveral times, and as one who is notunacquainted with the work involvedin building models, I was amazed atthe ingenuity and the thousands ofman-hours of toil which this exhi-bition epitomises. It must havebeen a source of extreme satis-faction to Mr. Marshall to see hislarge family of model -makers gatherround each year at this large familygathering of modellers. This Exhibi-tion is a national institution and I wishit a long -continued existence.

" What shall I be ? "MANY years ago the hoardingsI I were adorned with a posterwhich asked the pertinent question," The Boy-What Will He Become ? "It drew a parallel between the futureof a boy who digested the contents of acertain Educator and he who did not.The poster was not far wrong, forknoidedge is always power, scientiaest potentia. It is even more neces-

Random Remarks onDiverse Topics

sary to -day, when competition is keenand education has advanced, forevery individual to fortify himselfwith sound knowledge as a back-ground to experience in the particularfield which he will make his metier inlife. Indeed, competition is now so keenthat in a few years a man will have tobe a master of arts in order to get ajob as a road sweeper. You may be askilled artisan but without theoreticalknowledge your progress will belimited. You will never progressbeyond the stage of becoming a fore-man or a charge hand. That littlemore, how much it is ; that extraeffort to lift yourself from the rut, togain that extra knowledge which willplace you ahead of your fellows re-quires effort and abnegation. Eachyear our heritage of knowledge isricher, and it is there for all to tapin the nation's storehouse of know-ledge-its technical books. I visitthe homes of many readers in thecourse of a year, and I am able toassess the mental plane of each by aninspection of the books which reposeon the shelves. There are those whoregard books as ornaments to fill abookcase. Some have never beenhandled more than two or three times,others bear the marks of frequent con-sultation, they are well worn, containmarginal notes, press cuttings ampli-fying a particular point in the book ;those possessing such volumes go far.

I am often consulted by parents asto what they shall do with their boyswhen they attain school -leaving age.The only information provided for myguidance is the headmaster's report,and perhaps the fact that the boy hasmatriculated. That does not help me,

for the power to get on is not providedby some well-known formula. Thedriving force must exist within theindividual himself, and given thatforce, plus the knowledge, there areno limits. Influence means nothing,except to provide perhaps an earlyopportunity. Knowledge alone is use-less. It is a key, but it does not un-lock the doors to self -advancement ofits own accord. Those who have notthe advantage of a sound educationcan remedy this defect by purchasingtechnical books on subjects in whichthey feel they could do well. Theyshould also take advantage of themany splendid Correspondence Cour-ses now available at modest terms-even on hire-purchase terms-andplanned by those who have them-selves been through the mill. If youare on the threshold of your career,you must remember that you cannotkeep a good man down, for good wineneeds no bush.

WHICH brings me to another pointconcerning queries. PRACTICAL

MECHANICS is a magazine which isreferred to long after the issue ceasesto be current, and hence many readerspreserve their copies. This is a danger-ous practice, for loose issues becomelost, or mislaid. We supply eachyear a binding case and an annualindex at the inclusive price of 38. 6d.,and I recommend readers to have theirvolumes bound, and thus preserve inpermanent form with the contentsindexed and readily consultable, thetwelve issues which make a volume.Even though you do not have thembound you should certainly purchasean index, which costs 7d.



Fascinating to Build?THEY CERTAINLY ARE !There is real pleasure in working with balsawood, and our special quick -drying cementis a joy. Once start and you will be fas-cinated. Send your order now !

PUSS MOTHThe ideal kit for the beginner.Wingspan s6 ins., length 12ins. It is an excellent flyer.Complete kit with shapedflying prop., carriage ripaid, for .. z

HAWKER FURYWingspan 19 ins.,length 17 ins. Exact

in. scale. A verysturdy model,whichis a strong and fastflyer. Complete kitwith all balsaneeded, quick -dry-ing cement, shapedflying prop., etc.,carriagepaid, for .. 6/6

Send two penny stamps for illustrated catalogue showingthe largest range of scale model flyers in England.

If you live in a country district state your nearest railwaystation (carriage extra abroad).

GLOSTER GAUNTLETAn exact in. scale model.Wingspan 21 ins., length ifitins. The plan has a greatdeal of fine detail. The modelis sturdy and a good flyer.The kit is splendid value andhas everything needed. Thereare special transfers for thedelicate R.A.F. rudder num-bers. The fuselage is built onComet's special feature, theAuto -line-up method. Clearfull-size plan with special in-structions. Completekit, carriage paid, for 6/6

BRISTOL BULLDOGWingspan IS ins., length 122 ins.A most attractive kit, whichmakes a model of great beautyand detail. Everything requiredis included with a clear plan.Built on Comet's exclusive Auto -line -up principle. Complete kit,carriage paid, for .. 3f6

WESTLAND WALLACEWingspan 18 ins., length 13 ins.A very detailed model, whichbuilds an exact replica of the realplane. Complete kit, /carriage paid, for .. . 01 VP

P. M. SWEETEN LTD.Send your Order NOWto: Bank Hey Street, BLACKPOOL

FLYING MODEL AEROPLANES"BURD" MODELS

A "BURD " ALWAYS FLIES

25 -inch Waco MILITARY " D "

These kits are the famous " BUR!) " Kits of America. They containeverything required to build a " FLYER " ; even the 1/3 kit contains ashaped saw -cut propeller.

10 -inch span 1/3 post free. Six models: Mr. Mulligan, Fokker D.7,1936 Stinson Reliant, Curtiss Hawk, Ryan St., and Curtiss Robin.

25 -inch span 2/3 post free. Six models, including : Consolidated P3o,Waco Military " D," Monocoupe, etc.

30 -inch span 3/3 post free. Mr. Mulligan, Boeing P26A, and DouglasObservation.

80 -INCH WING -SPAN FAIRCHILD 24, only 9/8 POST FREE. WHATA KIT! Two Ether models. These kits include a 12 -inch PROPELLER,READY CUT-OUT RIBS and SHAPED COWL where needed. 80 -inch" KING BURD " Gas Model £1.1.0 post free.

SELLEY-TEX KITS LigBhter thanalsa"

The simple Method of Construction. Super Detailed Kits, Flying Models.12 Models from 5/- to 23/- post free.r6 -inch span Rearwin Sports 5/-. Monocoupe 8/-. so -inch span, Waco

Military 23/-, 24 -inch span.The De Luxe Models have included an "ADJUSTABLE PITCH

ALUMINIUM PROPELLER." What is SELLEY-TEX ? Read all aboutthese practically INDESTRUCTIBLE Models in our Catalogue. EVERYmodel illustrated. Full list of accessories, " LATA " balsa. AdjustablePitch Props, etc. Price 3d.

ELITE MODEL AIRPLANE SUPPLIESDept. 3,

45 Tamworth Av., PRESTWICH, Manchester

BRITISH RECORDS held by models built withOUR MATERIALS

FUSELAGE MACHINESRising off Ground . 9 mins. 50 secs.Rising off Water .. 1 min. 46 secs.Hand Launched .. 23 mins. 10 secs.

Our petrol engine model, "COMET," during 1935entered 3 Competitions, won these awards :

First Prize : B.M.A.S. Power Competition.First Prize : " Hallum " Power Com petition.Second Prize : S.M.A.E. Sir John Shelley Competition.

Yon can build this model, or the " Sky Rocket " which made the flight of 1985(Cranborne to Isle of Wight: 85 miles I), from drawings or kits obtained from us.

The "COMET" 18-c.c. 2 -stroke petrol engine is the finest onthe market, its only fault being that it runs so well that a timeswitch is necessary if you don't want to lose your model

Send 2d. stamp for lists, and become a satisfied customer of

MODEL AIRCRAFT STORES133 Richmond Park Road, BOURNEMOUTH

THE WONDERFUL"BABY CYCLONE"

ENGINEOf outstanding Superiority. BriefSpecification :1/6 h.p. Rotary Valve2 -cycle ; Bore r, Stroke 13/16'.Runs upright or inverted. VariableSpeed from 500 to 5000 r.p.m. with13" propeller. Fitted 11 oz. capacitylight weight petrol tank -constantfeed in steep climbs. Exhaust man-ifold permits perfect cowling ofengine. Special A.C. plug. Weightcomplete with Tank, Coil and Con-denser l04- ozs. Dimensions, 31-long ly wide (without exhaustmanifold) x 41" high. Send forfull specification.

£4 19s. 6d. £2 15s. 6d.NORTHERN MODEL AIRCRAFT COMPANY

3 7 a FOUNTAIN STREET, MANCHESTERModel Aeronautical Specialists for 27 years.

CYCLONE "MODEL AEROPLANE

KIT FOR ABOVE(Home Constructor's Kit).



MO E L

pro Pay g.

A 3 5-c.c. Petrol Engine

M ESSRS. E. GRAY & SON, LTD., of18/20 Clerkenwell Road, London,

E.C.1, have sent me details of their new3.5-c.c. two-stroke petrol engine. Readerswill observe that the march towards the idealmidget petrol engine goes on, and I have nodoubt that within a year there will beseveral engines of 1 c.c. on the market. Thespecification of the Grayson " Gnome " isas follows : i-in. bore by -in. stroke, 3.5 c.c. ;light alloy cylinder and crankcase cast inone with shrunk in cast-iron liner ; mainbearings phosphor bronze ; very firm andsimple mounting which allows the engine tobe detached from the plane in a few seconds ;connecting rod of duralumin working directon steel crankshaft ; special alloy pistonwith one ring ; cylinder head detachable;fin. plug ; carburettor of the single jet typewith adjustable air sleeve and needle valve ;petrol is drawn by engine suction from thetank ; lubrication on the petroil system ;car type contact breaker, adjustable andensuring trouble -free ignition. The engineis of the four -port type, two-stroke, and thesize of prop. recommended is 8 to 9 in.diameter.

This engine reduces the model power -driven aeroplane to a convenient size, as theengine is suitable for biplanes as small as3 -ft. wingspan.

ICS

A Free -Wheel Device

MR. R. GINN of Luton, Beds, has sentme a description of his device for a free-

wheel airscrew. I have illustrated it onthis page. As I have mentioned in anotherissue the motor runs for but a fraction of thetotal duration of flight, and the airscrew,it is thought, offers considerable resistanceduring the glide. In the device shown theratchet is for a clockwise propeller (viewedfrom the front of the machine) and operatesas follows:

The arm A, which is the portion bent atright angles to the shaft, is bent over at thetop and a brass washer C soldered in posi-tion. Another piece of wire is bent to shapeof B, placed on the shank of A, and anotherbrass washer Cl soldered on. Thus the armB is free to swing in the direction of thearrow Q, but locks up against A in the otherdirection. Thus during winding and flight,the arm B is locked hard against the left-hand side of the propeller, until the driveceases when the rubber is unwound, whenthe propeller, which being bushed rotatesloosely on the shaft, swings round due to themotion of the machine and brushes the armB aside, thus allowing it to rotate freely.

Automatic Rudder Control

APROPOS my recent remarks concerningdevices for predetermining the flight

course of the model, especially power drivenmodels, Mr. A. E. Mulholland, M.A., hasdevised an ingenious method of operatingthe rudder. This is illustrated on thefollowing page.

ER

The method utilises the tensionof the rubber skein when fullywound, and the loss of tension whenrun out.

The rear -hook H, instead ofbeing anchored to the rudder -postX is fixed to spring A, which issecured at the lower end but freeto move up and down by slot Sengaging with pin C (Figs. 3 and 4).Thus, when the rear -hook is movedbackwards and forwards accordingto the tension of the motor thespring moves up and down in the Fig.slot S.

To the end of the spring is attachedthread T which is fixed to the horn H on theport side of the movable rudder hinged tothe fin. The horn H, on the starboard side,is connected to the right fuselage by meansof elastic E.

Fig. 2. -Mr. R. Ginn's idea

fora free -wheel airscrew.

SOLDERED.

C SOLDEREDTO 'A HERE

A

Fully wound, the tension of the motordraws forward the spring A and it movesdown the slot S. As power runs out thetension of elastic E moves the rudder in theopposite direction and so controls the pathof flight. As thread T slackens so the pullof elastic E increases.

Experiment alone will decide the strength

1. -The Grayson " Gnome'. 3.5-c.c. two-stroke.

of the spring, and the length of thread T willdepend upon the shape of the flight -pathdesired. Thus by varying the position ofrudder by the length of the thread differentflight -paths may be arranged previous to theflight.

When normal flight is desired the deviceis at once put out of gear by removingelastic and thread.

One disadvantage is the grouping of extraweight round the rear of the machine andthis suggests that the system would berather heavy for balsa duration models,whereas negative incidence on the elevatorscould be employed in a heavier -weightmachine.

The rudder control is simple and easilyadjustable, and a similar system could beemployed for the actuation of other mov-able control surfaces, particularly theelevators, for it cuts out a complicatedarrangement of threads and pulleys whichmight interfere with the motor as it woundout.

Note. -The arrangement of the controlwill, of course, depend on the directionaltorque, and hence on the direction of re-volution of the airscrew.

Biplane CompetitionFROM results of various competitions it

seems that the enthusiasm for model air-craft is keenest in and around London, theBristol Club being the next most enthusi-astic. There were fourteen entries for thedecentralised biplane competition in spiteof the weather.

RESULT

Order Name Club 1st 2nd 3rd Aver -age

1st S. R. Crow Blackheath 91.2 50.4 78 73.22nd F. Almond North Kent 27.4 54 50 42.853rd C. Edwards North Kent 42.8 49 35 42.264th R. T. Howse Bristol 51.7 37.7 104 33.265th G. Thompson Mid Kent 46.2 6 37.2 29.86th C. Gibson North Kent 37.6 10 41.4 29.667th H. W. Conn Bristol 51 7.6 28.2 28.938th H. Jones North Kent 18.8 224 44.1 28.439th L. C. Darling Mid Kent 33 37.8 7 25.93

10th C. W. Needham Bristol 12 10.5 44.5 22.3311th R. Brown Blackheath 11.4 7.25 26.15 14.912th P. Montgomery Blackheath 5.1 13.85 11.3 10.08313th R. W. M. Mackenzie Blackheath 5.25 8.65 6.7 6.86314th L. B. Mawby , Unattached 6 Smashed 2.00



The Park Model Aircraft League (Mitchamand Tooting) Mr. Mulholland'sNovember 4th, at Streatham Hall, Hints idea for automatic

and Tips, led by H. W. King. rudder control.

December 1st, Photographic Competitioncloses.

December 9th, at the Bedford Hotel,Bedford Hill, Balham (near BalhamStation). Second Annual Dinner, Prize -giving, and Social Evening. Tickets 3s. 6d.each from Officers. At 7.45 p.m. for 8 p.m.

January 27th, at the Farnan Hall, asabove, Third Annual Dance, Exhibition, andSocial Evening. Tickets 2s. each fromOfficers. 7 p.m. till 12.

February 3rd, at Streatham Hall, SixthAnnual General Meeting and Election ofOfficers.

March 3rd, at the Streatham Hall,General Debate. Motion : " That fromthe point of view of model aircraftsmanshipheavyweights are superior to lightweights."Mover, G. S. Broadway ; opposer, R. T. S.Gillett.

Fig. 1.-A near side elevation. The elevators andelevator fin are omitted for clearness.

Fig. 2.-A plan view.

BUILDING A HOME CINE PROJECTOR(Continued from page 70)

within the limits of the large holesopposite. Then adjust the top stop(Fig. 7), so that the tongue hasexactly the required movement tobring it directly opposite to a perfora-tion in the film. It should withdrawfrom one hole when at the bottomstop and come directly opposite thenext hole when at the top. Theposition for the gate should then bemarked out, so that when the tongueis in a perforation at the top of itsmovement there is one picture be-tween the tongue and the bottom ofthe gate.

The LensThis should now be fitted. An

ordinary magnifying glass of about12 in. focus will give a fairly goodresult, though, of course, a better lenswill give a sharper picture. Theglass should then be mounted in atube as shown in Fig. 11, this tube be-ing a sliding fit (for focusing purposes)in another tube which is soldered onto the film guide centrally over thegate.

The ShuttersThey are simply thin brass in. by

11- in. bent at right angles and clippedunder the cams. Position them sothat they come opposite the lens whilethe film is being moved, but leave thelens uncovered when the film is at astandstill. A permanent handle canthen be fitted tight behind one of theshutters (Fig. 1).

The take-up reel, Fig. 10, is simple,the centre is part of a cotton reel andthe cheeks of aluminium ; the hole inthe outer cheek is to allow the film tobe pushed into its clip by one'sfinger. The pulley is the remainderof the same cotton reel fixed by aradial wood screw, and a rubber bandserves for a driving belt. The take-up reel is loose on the spindle anddriven only by the pressure of thevery light spiral spring, so that it canslip readily without putting appreci-able tension on the film.

The Film CradleThe cradle for carrying the film can

be made of three-ply wood, as shownin Figs. 1 and 2. No spindle is re-quired as this is embodied in themetal case. For rewinding the filmafter a show a key like Fig. 12 shouldbe made. It can be " twirled "between the fingers, this being aquicker method of rewinding than atiny handle.

The LampA lamp of the type illustrated in

Fig. 1, but provided with a " bull's-eye " condenser, will give a goodpicture about 12 in. wide. A condenseris an absolute necessity and should bearranged to make the light convergeright into the lens, as illustrated inFig. 13. The more powerful the light,the larger the picture. A motor -carheadlight could be arranged to giveexcellent results.

T4

C;

HORN ONRUDDEP

Figs. 3 and 4.-A near side section.

A NEW BOOK!THE MODEL AIRCRAFT BOOK

By F. J. CAMMPacked with Illustrations and Instructionsfor Building Power Driven and RubberDriven Models, and Including a Chapteron Building a Primary Glider. 3s. 6d., or4s. by post, from Geo. Newnes, Ltd.,8-11 Southampton Street, Strand, W.C.2.

TRADE NEWSEllison Plastic CompoundELLISON Plastic Compound has almost

innumerable uses. It will insulate elec-trical apparatus, protect metal from corro-sion by acid, and seal a leak in a motor -carradiator. It is proof against petrol, oil,water, most chemicals and acids, and is notattacked by vermin. There are two gradesof plastic. Grade A, for electrical work, is astiff plastic compound at normal tempera-tures. It does not shrink in a dry atmos-phere, and does not run or drip when warm.The plastic is applied by first warming tomake it easily workable, and then pressingon to the part to be covered. It can beshaped with the fingers to the thicknessrequired.

Grade D is softer than grade A at normaltemperatures, and consequently takeslonger to harden. It is intended for usewhere heating is impossible. Grade A costs3s. 9d. per 2 lb. tin and grade D 3d. a lb.extra. It is produced by Ellisons Insula-tions Ltd., Perry Barr, Birmingham, 20.

Lionel TrainsTHE latest catalogue issued by the

London agents for Lionel Trains, 35-6,Aldermanbury, London, E.C.2, reveals awide range of stock. Complete electrictrains for seniors range in price from 508.to £14 148. Accessories of every descrip-tion are also included, as well as completetrains for juniors ranging in price from32s. to 38s. 6d. Readers should apply forthis 24 -page well -illustrated cataloguewithout delay.

Index and Binding Cases for Vol. 3 ofPRACTICAL MECHANICS are now ready.Indexes cost 7d. by post, and bindingcases complete with title page and indexcosts 3s. 6d. from Geo. Newnes, Ltd.,8/11 Southampton St., Strand, W.C.2.



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The Pilot, U.650 which is reviewed on this page. It isa powerful 6 -valve Super -het, giving world-widereception during day and night. The tuning beaconsimplifies accurate and silent tuning of stations withvolume control at minimum. The 5} in. calibratedCompass Dial gives selective illumination for eachof the four wave bands covered. It costs 16 guineas.

AS may be seen from the illustrationon this page, this new Pilot receiverrepresents the last word in modern

receiver design. Apart from the largefull -vision, four -band tuning dial which isfitted, the front of the cabinet also containsa unique tuning device, known as the" Tuning Beacon." This may be seen situ-ated in the centre of the loudspeaker grille.Four controls are provided, two of thesebeing in the form of dual controls. On theleft is the volume control and on the rightthe wave -band selector, whilst the twocentral knobs control tuning (the upperknob) and a combined on/off and tonecontrol. The tuning knob in addition to arotary movement also incorporates a push-pull movement, and this operates the gearreduction used for turning the condenser.When pulled out a very high gear is em-ployed, a reduction of 95 to 1 being obtained.When pushed in a more rapid movementis provided, the reduction gear being12-} to 1.

An interesting feature of the tuning dialis the provision of separate sections behindthe transparent dial, and each division isprovided with its own illuminating device.Thus the scale is divided into two circles,one inside the other, and a horizontal linedivides both circles. The lower waverange (from 16 to 52 metres) occupies theouter lower half of the scale, and the nextshort-wave range (from 48 to 150 metres)occupies the inner lower half. The mediumbroadcast band (from 176 to 550 metres)occupies the outer top half of the scale andthe remaining central portion is taken upby the long waveband from 750 to 2,000metres. A double -ended pointer traversesthe scale, and when the wave -band selectorswitch is turned to the requisite setting theappropriate lamp is illuminated, and onlythat portion of the dial is illuminated (withthe exception that on the medium waves theentire dial is illuminated).

The CircuitThe circuit which is employed in this

A PILOT ALL -WAVESUPERHET

A Review of the Model U.650 A.C. Mains Receiver

receiver consists of a more or less standardsuperhet, with a pentagrid converterfollowing a signal H.F. stage. A vari-able -mu pentode I.F. amplifier followsthis stage and feeds a double -diode -triode2nd detector which in turn feeds the out -pentode. A comprehensive system ofA.V.C. is employed and from this partof the circuit the cathode-ray tuning in-dicator (the " Tuning Beacon ") is fed.Variations of signal strength affect theradiation from the cathode of this deviceand a green light which illuminates theouter portion of the mounting of the in-dicator varies. Tuning is, carried out forthe maximum green area (or if foundsimpler to follow, for the smallestdark space). The speaker which is fitted inthe receiver is of the mains energised type,and the field coil is used as a smooth-

ing choke on the H.T. side of the mainssupply. A plug is provided so that anexternal loudspeaker may be employed

operation

had to be set almost to minimum to avoidoverloading. Full sensitivity on the shortwaves was experienced and all of the well-known stations could be easily tuned in.

The station -calibrated dial was found ofgreat utility in this particular section, andthe majority of the names marked on thedial could be received during our test.No doubt when tested on a domesticaerial clear of the interference which isexperienced at this particular point, all ofthese stations would be heard with con-sistent strength. We were particularlyimpressed by the ease with which the Ameri-can stations could be heard, and the tuningbeacon gave a substantial indication of thetuning of these stations, which meant thatthey could be located, when once thecorrect tuning point was found, by firstsetting the volume control to the mostsilent point and then tuning by the beacon.In addition to Caracas, Melbourne, Tokio,Ecuador, and one or two other stations

named on the dial,numerous experimentalstations were heard, andthe amateur band alonewould provide anylistener with an even-ing's entertainment.Similarly on the longwaves 'the sensitivitywas adequate for allnormal requirements.

The Pilot, U.355. A 3 -bandsuperheterodyne receiver of advanced design for

on long, medium and shortwave bands. It costs 12 guineas.

when desired, and a jack is provided for theconnection of a gramophone pick-up.

Test ResultsThe receiver was tested out without an

outside aerial. The short aerial lead whichis provided in the receiver was connected toa short length of wire slung across a room,and full volume was obtained on a largenumber of stations. With the local B.B.C.stations, of course,T the volume control

The A.V.C. CircuitThe A.V.C. action was

found to be perfectlysatisfactory, and heldthose stations whichnormally faded badly ata good constant volume.The tone control wasfound to provide a verycomplete range of tone,from maximum bass to

highest treble, and this was, in fact, found tobe of extreme value when removing some ofthe atmospheric noises which were obtainedon very weak stations. The controls allfunctioned in a smooth manner and nobacklash was experienced.

The maximum output, when the last valveis fully loaded, is 3 watts, which is, of course,ample for all normal domestic requirements.

The receiver may be thoroughly recom-mended and will be found very good value at16 guineas.

SPECIFICATIONReceiver : All-Wave'Superhet.Circuit : Signal H.F. stage, pentagrid frequency changer, H.F. pentode I.F.

stage, double -diode -triode second detector and A.V.C. stage, and pentode outputstage. Nine tuned circuits, with visual tuning indicator, and resistance -capacityL.F. coupling. Energised loudspeaker, and provision for gramophone pick-up andexternal loudspeaker.

Tuning covers four wavebands : 16 to 52, 48 to 150, 175 to 550 and 750 to 2,100metres.

Controls : Four ; volume control, wave -band selector, combined on/off switchand tone control, and tuning control. The latter has a two -position setting pro-viding two separate gear ratios -14 to 1 and 95 to 1.

Price : 16 guineas, for A.C. mains.Makers : Pilot:Radio Ltd., 87 Park Royal Road, London, N.W.10.



SUPER -DUMOTO 11\ FO

AIRCRAFTD. A.

CYLINDER OF .1-8BALSA OR -15.2

TH REE PLY.

RATION RUMODEL

ussell, A.I.Mech.E.

SINCE duration of flight is the mainconsideration in the majority of modelaircraft competitions, the following

description of an arrangement for a " super -duration " rubber motor may be of interest,particularly since the idea has been triedout experimentally with very promisingresults.

Essentially the arrangement of the rubbermotor is such that approximately 2+ timesthe usual length of rubber may be accommo-dated in the aircraft.

Fig. 1 is a diagrammatic layout of thearrangement, from which it will be seenthat only one length of rubber extends fromthe nose to the tail of the fuselage in theusual manner.

At the tail, instead of a fixed hook toreceive the rubber, there is a twin gear,consisting of two Fin. diameter spur gearwheels running in constant mesh ; thesecarry the drive back to a point at, or near,the leading edge of the main wing, where isfixed a bevel gear, which transmits thedrive out to each wing tip.

A High -wing MonoplaneIt will, of course, be appreciated that

this arrangement calls for a wing with littleor no dihedral angle, and also for a " solid "method of anchoring it to the fuselage ; butas the machine would definitely be built forcompetition work, no particular attemptwould be made to " beautify " it, and a" high -wing " monoplane, of the type inwhich the wing is made in one piece and isanchored to the flat top of the fuselage,would be the obvious choice. By havinga fairly long landing chassis, the centre ofgravity would be kept well down so that,despite the lack of dihedral angle, goodlateral stability could still be obtained.

The bevel gear box would be built intothe centre of the wing, the under -surfaceof which would be cut away to allow theloop of rubber from the twin gear box to be

LOWER LOOPOF RUBBERPASSING FROM

NOSE TOTAIL

B) ER

Fig. 3.-The apparatus onwhich the experiments were

carried out.

Fig. 1-Showing howthe bevel gears link up

the elastic.

brought up to the hook on one of the bevelwheels. The axis of the other bevel, beingof course at right angles, would lie acrossthe span of the wing, and the loops of rubberrunning out to each wing tip would beenclosed in tubes made from sheet balsaor 3 -ply birch, in. thick. These tubeswould, in effect, constitute the main" spars " of the wing.

Fig. 2 is a sketch which indicates thevarious features mentioned above, whilstFig. 3 is an illustration of the equipmentwhich was built to enable tests to be carriedout to ascertain the kind of results whichmight be obtained from such an arrange-ment.

In this apparatus, ball thrust bearingswere fitted behind the airscrew to bothshafts in the spur gear box and behind thebevel wheel to which is attached the upperrubber motor in the fuselage ; thus frictionwas reduced to a minimum.

-

This Ingenious Rubber Motor willAdd Considerably to the Durationof the Flight of A Model Aeroplane

To allow for ease of assembly and adjust-ment, ordinary gear wheels and spindleswere used ; but in an actual flying modelmuch lighter parts would, of course, befitted, enabling the twin gears and thebevel gear box to be constructed for a totalweight of not more than I ounce.

The Rubber Motor

The first series of tests waswith the apparatus as it is shown in Fig. 3,and on reference to the sketch Fig. 2 itwill be seen that the total length of therubber motor is 65 in., made up as to (a)30 in. from nose to rear of fuselage, (b)20 in. up to the bevel gearbox, and (c)15 in. out to each wing tip (these twoloops of rubber of course being in " par-allel," and therefore each containingonly half the number of strands of the .twoloops in the fuselage.)

The curve " A," Fig. 4, shows resultsobtained from using 54 ft. of 11',3- x -in.flat rubber, arranged in loops of 10 strandsbetween the hooks in the fuselage, and aloop of 5 strands in each half of the wing,i.e. in (a) 10 strands each of 30 in. = 25 ft.,in (b) 10 strands each of 20 in. = 16 ft.6 in., and in (c) 2 groups of 5 strands eachof 15 in. = 12 ft. 6 in., making a total of54 ft., which weighs 2 oz.

Langley's Formula

Using Langley's formula R

to calculate the maximum number ofturns available and remembering that1-41.5 = L x VL).

---

t

I I

I I

I I

1

1-c-----15''-----",-....).--.4,2)..- 5 x 65 X ArtB.........- Thsn R ---- - - - -

1 out of the motor. 1" 412

II

I

I

1 I Fig. 2 .-A dia-

The two loos inI 1 20 the fuselage arsoile

1grammatic lay- _ 5 x 65 x 8VE

I

I

I

III tual model the of tests was of 18 -in. diameter, and 24 -in.I ness. In the ac- The airscrew used for this first seriesI by side for clear- maximum to which to work.I here shown side of this figure giving 1,665 as the normalI .1 = 1,850 turns, 90 per cent.

....I 1....... shorter loop pitch, with an efficiency of 75 per cent.... --.... is placed at the relatively slow speed at which it.....

_ .....,) above the was driven.--- ....-- longer loop. Referring to Fig. 4, it will be seen that

51,"



the initial speed is about 450 r.p.m., fallingto about 350 r.p.m. during the first minute.After this the rate of fall slows up consider-ably, and a relatively steady power outputis maintained until about the end of thefourth minute, after which the power fallsoff rapidly.

The performance of this combination ofrubber motor and airscrew may be calcu-lated as follows :

Between the end of the first minute andthe end of the fourth minute the averageairscrew speed is approximately 300 r.p.m.,and with a pitch of 24 in. and an efficiencyof 75 per cent. the rate of forward travelcan be calculated by multiplying the revolu-

tions per second Ik 60 /" \ by pitch (24 in.)

and dividing by the efficiency (75 per cent.).= 7'5 feet per second, which would besufficient to fly a model of which the wingloading did not exceed 2 oz. per sq.ft., whilst the initially higher r.p.m. in thefirst minute would provide that extra powerrequired for " taking off " and a goodclimb.

However, since the rubber motor andgear boxes would weigh 2f oz. a modelwith a wing area of 2+ sq. ft. lifting surfaceand a weight not exceeding 2f oz.would be required to keep to this lowloading ; rather an exacting requirement,unless the machine were a freak of balsaand tissue, with a safety factor of 1 !

Airscrew SpeedOf course, by putting up the speed of the

airscrew, a larger wing loading could besustained, but this would only be obtainedat the expense of cutting down the lengthof flight, thus defeating the purpose ofthe whole idea.

It appears, therefore, that to obtain thegreatest benefit from this arrangement, not

too small a machine should be built ; andafter a further series of tests had beencarried out, the following specification fora model was developed, of which the par-ticulars given of the performance of therubber motor and airscrew may be reliedupon-should a machine be built-sincethey were obtained from the apparatusalready described, which was alteredto conform to the revised measurementsgiven in the specification, which is asfollows :Weight of model aircraft (less gears and

rubber), 3+ oz.R.P.M.

600-

500

400

300

200

100

OO

CURVE %.

CURI/E. "A#

CUFtVE*

Au 10 STRANDS 1B I DIA: A1RSCREWB" 16" - -

PITCH OF BOTH AlRSCREWS 24"RUBBER X," X )''

i I

1 2 3MINUTES

Fig. 4.-The graph shows the result obtained with the motor.

2 gear boxes, f az.68 feet raa- x h -in. rubber, 2+ oz.Wing area = 364 sq. in. = 2+ sq. ft.Size of wing, 52 x 7 in. = Wing loading

2'6 oz. per sq. ft.Minimum flying speed, 11 ft. per second.Length of fuselage, 37 in.The rubber motor was arranged as to(a) 10 strands 35 -in. long = 29 ft. 4 in.(b) 10 strands 23 in. long = 19 ft. 4 in., and

4

(c) 2 groups, each of 5 strands 23 in. long= 19 ft. 4 in., so making a total of

68 ft. of A x -in. rubber.The total length of the motor was

therefore 81 inches, and by calcula-tion as before, the maximum numberof turns available is found to be 2,300(5 x 81 x Vgi)

V2'5 , working number of turns

(90 per cent. of full) = 2,070.

Tests MadeIn this series of tests, an airscrew of

slightly smaller dia-meter (16 in.) but withthe same pitch of 24 in.was used, the resultsbeing as shown in Fig.4, Curve " B."

After the initial " falloff " during the firstminute, the averagespeed for the next 2minutes is just over400 r.p.m., which givesa calculated forwardspeed of a little under12 ft. per second. Theextra power available

6 during the first minutewould ensure a quicktake off and a goodrate of climb, and thus

in the following 2 minutes very little, ifany, height would be lost. It will benoted that the power continues to be sus-tained at a very useful figure until afterthe fifth minute, which should ensure avery slow rate of descent and an overalltime of flight duration of anything up to 6or 7 minutes, depending on how highthe aircraft can climb in the firstminute.

A NEW HEIGHT RECORD'r HE Air Ministry recently announcedI that the Royal Air Force experimental

high altitude aircraft, the Bristol138 " with a special " Pegasus " engine,piloted by Squadron -Leader F. R. D. Swainof the Royal Aircraft Establishment, Farn-borough, Hants, reached an altitude of49,967 ft. (15,230 metres), thus breaking thepresent world altitude record of 48,698 ft.(14,843 metres) by 1,269 feet (387 metres).

This result is particularly gratifying,especially as it is the first occasion on whichthe Royal Air Force has attempted to beatthe altitude record, and the development othe aircraft and the special equipment hasbeen undertaken during a period when thefirst preoccupation of the Air Ministry andof the constructors was necessarily theexpansion of the Royal Air Force.

High praise is due to the pilot for hismeritorious flight, and to the constructorsof the aircraft, engine and special equip-ment-all of which are of British design andmanufacture for their share in the achieve-ment.

Total Flying TimeThe aircraft took off from the aerodrome

at Farnborough, Hants, at 7.30 a.m. andlanded at Netheravon, Wilts, at 10.50 a.m.,the total flying time being 3 hours 20 min-utes. During the ascent visibility was good

but there was a cold north-easterly wind ofconsiderable strength at lower levels and ofhurricane force in the upper air. The per-formance of the aircraft and engine wasentirely satisfactory and the sealed pressuresuit enabled the pilot to remain at very highaltitudes for nearly two hours while heendeavoured to attain the maximum heightpossible.

The attempt was observed by an officialrepresentative of the Royal Aero Club, andthe height attained has been officially com-municated to the Ministry by the Club ; itwas arrived at from an examination by theNational Physical Laboratory of the sealedbarothermographs which were carried inthe wing of the aeroplane. The figures aresubject to the usual confirmation, andacceptance by the Federation AeronautiqueInternationale to which it is necessary tomake application for homo-logation of the record.

Essential ResearchesThe minimum pressure

measured during the flightwas 92.0 millimetres of mer-cury, and the lowest temper-ature was -49.8° centigrade;both those measurementswere at the highest pointattained.

Squadron -Leader F. R.D. Swain, R.A.F., inthe cockpit of the specialBristol "Pegasus"

Monoplane.



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Why ? With so many fine loco-motives and accessories availablethis season, every boy canachieve his heart's desire-agood layout at a reasonablecost.4-4-0 Locomotive No. 601 (Class 2P), clockwork 42!-; electric

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#t 6 I F. 30 4/

Fig. 21.-A design for a tunnel front.

Adapting the Twin -Train `fable RailwayIN my last article I gave some designs

for terminal station buildings and inthis I propose to make some suggestions

for engineering works, following the samearchitectural style ; that is to say, a stylewhich is quite modern and so up-to-datethat the reader may not be able to find any-thing approaching the modernity of thedesign in the tunnels, bridges, etc., on ourmain line railways. On the Tubes, how-ever, around London where the structuresare carried out in concrete similar severelyplain formation has recently been followed.It is, therefore, quite appropriate that weshould carry the style of buttress as wasintroduced into the stations through to theengineering works for the Twin TrainRailway. These for our model will bewholly carried out in wood, and this materialfor the walls can everywhere be plywood.I am proposing to deal with tunnel fronts,a single arch bridge, and a viaduct only,because Mr. Beal in his series of articles hasalready given a large number of otheraccessories, in fact he has catered prettyfully for the model railway enthusiast.

Tunnel FrontsI have already referred to the matter of

single and double tracks, that is to say,up and down roads, and explained thereason why, with double track, the railshave to be so widely separated that the

By E. W. Twining(Concluded from page600, July 1936 issue)

centre rails, or 3rd rails, are 90 mm. apart.Now if we were to attempt to make onetunnel embrace both roads, the shape of theopening would have to be a horizontalellipse or a portion of the same. Thiswould look bad because tunnels are nevermade this shape and therefore it will bevery advisable to follow what is quite usualfull-size practice under certain conditions,and make a separate tunnel for each road.In the tunnel fronts, therefore, there will betwo openings, side by side, as shown inFig. 21. The reader can quite imaginefrom this drawing how bad it would lookif one flattened arch were made to coverboth sets of rails. Tunnels are alwaysbored with the major axis to the ellipse in avertical direction, because this is the bestform which the arch can assume to carrythe weight of the soil or other materialforming the hill through which the tunnelis cut.

I venture to think the reader will agreethat the architectural style which I haveshown is eminently suitable for severely

practical engineering work. Each tunnelfront, I am assuming, of course, that therewill be two faces to our tunnel, will be madeof three thicknesses of 5 mm. plywood,arranged as shown in the cross sectionthrough one of the arches on the right-handside of the drawing. The innermost ply-wood will be rebated back about 116- in.,that is to say, the elliptical opening willbe made that amount larger than themiddle ply. This is to provide for a sheetof stout cardboard which, bent to theshape of the ellipse and glued and pinnedto the innermost plywood, will form thelining of the tunnel, that is to say, the partwhich in a full-size tunnel would be ofbrickwork. It will be obvious that thesheet of cardboard should be large enoughto extend from one end to the other of thetunnel. If the tunnel is required to belonger than any cardboard obtainable, athird piece of plywood will have to be cutto go somewhere between the tunnel frontsto provide a means for securing the card-board.

In the event of the tunnel requiring to belaid on curved track, the cardboard canonly extend for a short distance in fromeach tunnel front, since it will not be pos-sible to bend the cardboard in twodirections.

To form the surface of the hill for thetunnel a second sheet of cardboard can be

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In Fig. 24 I give a diagram by means ofwhich the reader will be able to set outgeometrically the correct form for thetunnel arch. Here it will be seen that thecurve on each side of the centre -line isstruck from three 'centres with a compass,I have given the measurements of eachradius in millimeters, and the heights abovethe table level at which the curves stop.

A BridgeThe type of bridge selected is the very

usual one which carries the railway over awide road or river ; it will have a span of

42-k7m.

Fig. 24.-The geometrical setting out of the tunnel opening.

Fig. 23.-A design for a u aduct.

247 mm., which represents in a full-sizebridge approximately 62 feet. It will havea rise from the springing to the soffit ofthe arch of 74 mm. The springing is thehorizontal line on the pier or abuttmentwhere the curve of the arch commences.The crown is the highest point of the arch ;the span is, of course, the horizontaldistance between the springing points.The soffit is the underside of the curve ofan arch, and the rise, the vertical heightfrom the springing to the crown.

ButtressesIn this bridge, which is shown in Fig. 22,

the buttresses are again of the same designas was introduced into the stations andalso into the tunnel, but the proportionsare somewhat heavier. I do not thinkthat the details shown in the drawing

call for further comment, the con-struction will be exactly the sameas that of the tunnel. The widthof the bridge between the para-pets will depend upon whethersingle or double track is to be laidover the bridge. In any case thecentre rail will be 28 ram. from the

inner face of the parapet, thewidth of the bridge measuredoutside will, for single track,have to be 70 mm. and fordouble track 160 mm. Themethod of setting out thesemi -ellipse of the arch isgiven in the drawing and thereader should have no diffi-culty in copying the curvesby means of his compass onto the plywood from whichthe arch is to be cut.

A ViaductHere again as I have drawn it in Fig. 23,

the design is very similar to the otherstructure, except for slight differences inthe form of the buttresses. These aremerely introduced to give the reader alittle variety from which he can make aselection. He can adopt just which evershape he prefers and use the same form inall the works, or perhaps what would bebetter would be to let the differences remainjust as I have drawn them.

The span of each of the arches I havemade 200 mm. This measurement is, Iconsider, about as small as one couldreasonably adopt, for if the arches werereduced in size below this the viaductwould not have that imposing' appearanceof importance which it should have, forobviously in actual practice it would not bethere at all, but embankment would takeits place.

As will be seen, I have not drawn bothends of the viaduct because the number ofarches of which it consists will depend uponthe space which the reader has on his rail-way for such a structure. If room is limitedit can be given say, three arches, with onlytwo piers reaching to the lower groundlevel. The width over the outside wallswill of course be the same as the bridgeshown in the last figure. On the inside ofthe piers I have drawn thin buttresseswhich are merely decorative ; they canbe omitted if the reader prefers to dowithout them. On both the bridge, theviaduct, and in fact on the whole of thetrack, assuming it is permanently laid, Istrongly recommend that a fine gravelshall be laid up to the level of thesleepers.

FROM the earliest days of civil aviation,when the first experiments were beingmade with wireless telephony between

aeroplanes in flight and ground stations,wireless has played a vital part in theoperation of commercial air services.

From pioneer stations operating on theContinental routes, the wireless network hasgrown till it now stretches link by link fromEngland to Egypt, Africa, and India, andon thousands of miles eastward to China andAustralia.

As a part of the improved ground orgRni-sation for the big new Empire air schemewhich comes into operation next year-andby which first-class letter -mails are to be flownin bulk, without aerial surcharge, betweenEngland and distant parts of the Empire-many developments and improvements aretaking place in wireless communication.

Throughout the Empire air -lines approxi-mately twenty new wireless stations arebeing established ; while both on the groundand in the air the equipment will embody thelatest devices evolved by scientists andtechnicians. ,

WIRELESS AND THE NEWEMPIRE AIR SCHEME

Most Up-to-date EquipmentThe wireless installations now being fitted

in the new Empire flying -boats are, it isclaimed, the most modern and efficient everconstructed for use in commercial aircraft.One feature of these improved installationsis that a direction -finding apparatus isembodied in the main set, and is not aseparate piece of equipment, as has beenthe case hitherto. By the use of thisdirection -finding equipment the wirelessoperator will be able to tune in to any groundstation that may be operating within range,and plot out th air -liner's position at anytime during a flight.

In addition to the new apparatus that isbeing installed in aircraft, and at groundstations, the amplified air scheme is natur-ally calling for increases in the highly -skilled wireless personnel. In addition to

pilots entering the service of Imperial Air-ways, and whose studies at the Company'sinstructional school include the obtaining ofofficial certificates in wireless, specially -chosen operators are being drafted from themarine service into that of the air, and arebeing given the additional and specialisedcoaching necessary to enable them to passtheir examinations for obtaining, as air-liner wireless men, the aviation equivalentof the official certificate which has to beheld by ocean -liner operators.

TuitionPupils at the airway wireless " school "

have fascinating equipment with whichthey work, in addition to their tuition intheoretical matters. The latest types ofaircraft gear are provided for the making ofpractical tests. Installations are arrangedso that pupils can originate and receivemessages just as they would if they were inan air -liner in flight. They are also able tolisten to the exchange of messages actuallytaking place between the airport and ma-chines in flight on the Continental routes.



Clocks of the PIT would appear that clocks moved by

wheels and weights in contradistinctionto water clocks, which were of a much

earlier date, were first used in the monas-teries in Europe about the eleventh century.It is recorded that the Sultan of Egypt in1232 sent a " horologium " to the EmperorFrederick II.

Horologia signified dials as well as clocksso that too much credence must not beplaced on the " horologium " of 1232.

The first author who refers to " horolo-gic " that struck the hour, and consequentlycould not have referred to a dial, is Dante,born in 1265 and died 1321.

The Earliest ClockThe earliest clock in England is stated to

have been set up at Westminster Hall in1288 and paid for out of a fine imposed onthe Chief Justice of the King's Bench,Ralph de Hengham. However, as this fineis first recorded in the Year Book duringthe reign of Richard III (1452-1485) it is notat all proved that a clock was actuallyinstalled in 1288, it is more probable that atower in Palace Yard, Westminster, wasbuilt out of the fine and a clock installed ata later date. It is clear however, thatJudge John Southcote, who became aJudge in 1563, referred to the tradition thatthe clock existing at that time had beenpaid for out of the Chief Justice's fine.During the reign of Henry VI (1422-1461)the clock at Westminster was considered tobe of such consequence that William Warby,dean of St. Stephens, was paid sixpence perday for the keeping of it according toStowe's Account of Westminster.

There is a record showing a sum of £30being paid in 1292 for a clock at Canter-bury.

A Famous ClockFroissart records that in 1332, Philip the

Hardy, Duke of Burgundy, removed fromCourtrai to his capital at Dijon a famousclock which struck the hours.

In 1368, Edward III granted letters ofprotection to three clock makers of Delftso that clock -making was apparently a well-known art on the Continent at this date,and in 1370 or 1379 the great clock at Pariswas installed, being the work of a German-Charles de Wic (? Henry de Wyck). -

According to Cathedrals of England, byR. J. King, published by John Murray1861, the clock which occupies the northside of the transept of Exeter Cathedral iscelebrated, and is probably the one thatexisted there in 1317. This clock is attri-buted to Peter Lightfoot.The " All -by -One "

John Ireland, the celebrated antiquary,records that in the fourteenth centuryRichard of Wallingford constructed a clockwhich he called ' ALBIoN " (all -by -one).Richard of Wallingford, born circa 1292, wasreputed (by the Hon. Dairies Barrington)to be the son of a smith, and lived in thetown of Saint Albans, ultimately becomingAbbot of St. Albans, and died in 1336.The clock was an astronomical clock ,butthe date of manufacture appears uncertainprobably about 1326. (Barrington isobviously wrong in stating it was made inthe reign of Richard II and E. B. Dennisonin referring to the inventor as RobertWallingford.)

by A. MillwardClocks with a History,some of which areStill Working To -dayPeter Lightfoot who was a monk of

Glastonbury besides being the reputedmaker of the Exeter Cathedral clock, theclocks in the Church of Ottery St. Mary,and Wimborne Minster is better known asthe maker of the original clock of WellsCathedral, also known as the Glastonburyclock. This clock was presented to theAbbey of Glastonbury by Adam de God -

stshows the age of the moon and position ofthe planets. Above the dial plate aremounted four " Knights " on horsebackwho at the hour, ride circularly round inopposite directions. The hour is precededby a chime struck by the heels of a sittingfigure some distance from the dial, and thehour is struck by the arms of the samefigure on different bells. According to Mr.J. B. Planche, a student of heraldy andcostume, the " knights " are probably notthose of the original clock, since two appearto be Jesters and another is a civilian of thereign of James I or Charles I.

Probably the only part of the originalclock now at Wells is the dial plate and thepresent clock was reconstructed in 1835.

The Dover Castle Clock which is still in working order at the Science Museum, South Kensington.

bury and afterwards came into the posses-sion of Wells Cathedral. The date ofmanufacture is probably about 1325. Itis thought to be the first recorded exampleof a clock striking the hours automaticallywith a count wheel. It is also noteworthyas employing lantern pinions and a crownwheel or recoil escapement, which is thesame balance adopted by de Wyck in theParis clock.

According to William of Worcester, thisclock was originally in the south transeptof Glastonbury Abbey but was removed toWells Cathedral at the time of the dis-solution of the Abbey by Henry VIII, whenthe Abbot was executed, in 1539.

The present clock at Wells is in the northtransept of the cathedral and has a 6 ft. 6 in.dial marked with twenty-four hours, and

The original works were for some years inthe crypt of the cathedral and were removedto the Patent Museum, now the ScienceMuseum, at South Kensington, in 1871.The original verge escapement has, however,been replaced with an anchor escapement.

The Dover CastleIn the same museum is another ancient ,

clock that was originally in Dover Castleand dated 1348. It was removed fromDover Castle in 1872 and is probably ofSwiss origin.

According to Derham in his ArtificialClock -maker, published in 1714, the oldestclock in England which was going well atthat time was the well-known astronomicalclock at Hampton Court Palace made in1540.



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I 10 NEWNES PRACTICAL MECHANICS November, 1936

Valuable New Part Work For Builders and Architects

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THIS great new Part Publication provides an up-to-date, comprehensivework of reference for the busy Architect and Builder, and also for the

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George Newnes, Ltd


November, 1936 NEWNES PRACTICAL MECHANICS III

Are PerpLampsProbing the

An ancient brass lamp, one of the type supposed tohave powers of perpetual burning conferred on them

by the ancients.

THE notion of the perpetual lamp isbasically an offshoot from the idea ofperpetual motion. Just as inventors

throughout the ages have devoted enormousamounts of time and ingenuity to endeav-ours to bring about a perpetual motionmachine, so, also, there have not been want-ing individuals who have attempted toinvent lamps which would go on burningfor ever.

Perpetual lamps should not be confusedwith the many undying flames which weread about in ancient history. The latterwere admittedly fed by continual additionsof oil or other fuel. A true perpetual lamp,however, is one which either burns an un-consumable fuel (if such a thing werepossible) or else it is a lamp which, in theact of burning, automatically replenishesits fuel supply.

An Impossibility.On the face of it, therefore, a perpetual

lamp seems to be an obvious impossibility.Yet there have not been wanting credibleinventors who appear to have implicitlybelieved in the subject of perpetual lamps.John Baptist Porta, the Neapolitan physic-ian, originator of the magic lantern andmany other optical and mechanical devices,took a lively interest in the matter of thesesupposed ever -burning lamps, but althoughhe devoted much time and thought to theelucidation of their mystery, he confessedhimself, in the end, beaten by the problemswhich they presented.

History contains many supposedly auth-entic relations of perpetual lamps. Suchstories date back to Roman times and theyare particularly prevalent after the medievalperiod. To take a single example vouchedfor by the British historian and topographer,Camden, a vault attached to a little chapel

etualPossible?

Secrets of an Age.01c1Mystery

at York was broken into and therein anignited lamp which had apparently beenburning for ages was discovered. Before,however, it could be picked up and examinedit went out.

Such is a typical narration of a perpetuallamp discovery. Apparently these wonderlamps, which take the form of the ordinaryilluminating devices used in ancient days, arealways discovered in tombs, vaults, or inother closed chambers, in which apartmentstheir ever -burning flames were, one sup-poses, designed for the purpose of dispellingthe perpetual gloom. Frequently thesepulchres and other subterranean passagesin which these lamps are supposed to havebeen found have contained the remains offormer burials and, naturally enough, theundying lamps have been considered tohave been placed there by people possessedof their secret for the purpose of lightingthe body of the dead person until such timeas the soul re-enters it.

A Fault.The great trouble :with all these perpetual

lamps is that invariably they becomeextinguished immediately they are dis-covered and, on account of that considera-tion alone, all such perpetual lamp storieshave nowadays come to be discounted.

A little reflection upon the subject, how-ever, may convince us that although trueperpetual lamps are in themselves an utterimpossibility, there may be certain elementsof truth in all the old yarns concerning thediscovery of burning lamps in undergroundchambers.

COMBUST/ONCHRPISER

HYDROGENFLAME

DROPS OFCONDENSED

WATER

HYDROGENFROMNEGRY/VEELECTRODE

OXYGENLIBERATEDAT POSIT/VEELECTRODE

THERMO-COUPLE

PARTITIONS

An ingenious scheme for obtaining an ever -burningflame. It is, of course, a fallacious one, as explained

in this article.

The old philosophers, if they agreed withthe possibility of perpetual lamps at all,explained the principles of the latter simplyby asserting that the lamps burned anunconsumable oil of unknown composition.Bishop John Wilkins, a learned prelate ofChester and an early mechanician who,towards the end of the seventeenth century,prophesied flying machines and trips to themoon, very naively suggested that this" unconsumable oil " might be a substanceextracted from asbestos, since such materialcould be used for the making of the uncon-sumable wicks.

More recent explanations of perpetuallamp yarns have sought to establish asecret connection between such lamps anda natural supply of petroleum or petroleumgas in the immediate vicinity. Suchexplanations obviously fail, since, in themajority of instances, perpetual lamps aresupposed to have been found burning inregions which are far removed from oil-bearing localities.

Other Explanations.Two other explanations of these supposed

perpetual lamps are worthy of our notice.The first of these supposes that the ancientsknew how to prepare " pyrophoric metals ";that is to say, metals in so fine a powderform that they take fire immediately theycome into contact with air or oxygen. Thelamps were originally filled with thesemetals, together with a quantity of oil orother combustible material.

It is easy to see that if, on the discoveryof the hidden burial chamber, the lampwere in any way broken, the pyrophoricmetal powder, coming into contact with thefresh air admitted into the tomb, wouldinstantly glow brightly and might possiblyserve to ignite whatever combustiblematerial remained in the lamp after thepassage of time. The lamp, therefore,would burn for a few moments and after-wards would become extinguished.

Phosphuretted Hydrogen.The other theory concerning these semi -

mythical lamps assumes that the well-knowngas, phosphuretted hydrogen, is responsiblefor the observed phenomena. Phosphuret-ted hydrogen is an evil -smelling gas whichmay be generated in damp earth fromdecomposing bones and other matter.There is one variety of this gas which isspontaneously inflammable ; that is to say,it takes fire instantly it comes into contactwith air or oxygen.

Now suppose that, during the ages, atomb had gradually accumulated a quantityof this spontaneously inflammable phos-phuretted hydrogen. When such a vaultwas broken into, it is possible that thegas might inflame for a moment or two,filling the chamber with a mysterious green-ish light, the source of which might, in theexcitement of the moment, be credited to



any ancient lamp which was subsequentlynoticed.

It is pretty safe to assert that all storiesconcerning perpetual lamps found burningin closed tombs and other undergroundchambers must be based upon some decep-tion or other, since even if it were possible toproduce an ever -burning flame, such aflame would at least require a continuoussupply of oxygen to feed it and such anoxygen supply would obviously not beforthcoming in an hermetically sealedapartment.

During the last hundred years a fewinventive minds have, from time to time,toyed with the old idea of the perpetuallamp not so much with the intention ofexplaining away the discoveries of supposedperpetual lamps in ancient tombs andelsewhere, but more directly with the aimof actually constructing a lamp whichwould burn continuously for ever, or atleast for a very prolonged period.

An Idea.

One such notion comprised a plan forelectrolysing slightly acidified water in aglass vessel. The oxygen and the hydrogenwere to be separately collected and thehydrogen was to be burnt at a little jetplaced in a glass chamber, to which theoxygen was to be admitted. The hydrogenflame was to heat a thermocouple and thisdevice was to supply the necessary currentfor the electrolysis of the water. Thehydrogen in the act of burning combinedwith the oxygen to form water, and thislatter liquid dropped downwards from theflame through a funnel-like device into theelectrolysing chamber.

In the above manner a continuous actionwas to be brought about and, once started,it was to go on for ever. Unfortunately,the propounders of such a proposition failedto consider the fact that the heat of thehydrogen flame would not be sufficient toprovide enough current, via the thermo-couple, for the electrolysis of the water.

If, by any chance, it were ever foundpossible to devise a thermocouple whichwould give up a relatively enormous currentfor a small initial heating, then the abovescheme -would probably work.

Alas, however, such a notion will nevermaterialise, for it goes directly against theuniversal law of the Conservation of Energy,which tells us that we cannot make self-operating machines and that we cannot getmore energy out of a machine or a systemthan we put into it.

For such reasons perpetual lamps, inthe true sense of the term, are and ever willbe impossible, just as perpetual motion andall schemes based upon that principle arenot possible.

Nature, throughout her universal realm,has conspired against us to see that neverunder any circumstances shall we obtainfrom her, in the words of the Lancashireman, " owt for nowt." Perpetual lamps,like perpetual motion, would elicit from oldMother Nature something for nothing andit is for this reason that all such playthingsare for ever denied to us.

2

LATHE WORK FORAMATEURSBy F. J. CAMM

96 Pages

1 /- or 1 /2 by post from Geo. NewnesLtd., 8/1 I Southampton Street, W.C.2

WOODWORKING HINTS

IN using any kind of saw the chief pointto watch is that the first finger should not

be used to grip the handle, but shouldpoint down toward the tip of the bladewhere it gives a steadying effect.

Different kinds of saws have their teethcut to different angles, according to thepurpose for which they are intended, andin sharpening care should be taken toretain the exact angle.

All saws are sharpened by holding themin a special kind of wooden vice, withclamping bolts, which is gripped in theordinary bench vice.

A saw file (triangular in section) is usedand is kept at an angle of about 60 degreesto the line of the blade. Alternativeteeth are sharpened by turning the filethrough 60 degrees each time.

The easy and correct working of a saw isgoverned very largely by the " set " ofthe teeth. Alternate teeth are bent out-

wards slightly, in opposite directions ; theamount of set is dependent upon the typeof saw, and is greater for larger teeth-the exact amount can only properly bedetermined by trial and from experience.There are different ways of setting a saw,one of which is to lay the blade of thetool on a flat hardwood board and toslightly bend over alternate teeth bymeans of a pin punch and hammer.This method demands a fair amount ofskill, and should not be tried on a goodsaw until some experience has beengained on an old one. An easier' andmore usual way is to use a saw setand grip the teeth in the appropriatelysized notch, and then to bend them over ;this is done whilst holding the saw in thesharpening vice referred to above. Thesimplest way of all, especially for thenovice, is to use a special saw set which israther similar in appearance to a pair ofpliers. Such a tool is supplied by severaltool makers, and can be adjusted to giveany required amount of set. Very littleexperience is required to use it success-fully.

Why do they soundso MUCH better?

Cabinet Models37SC (Senior)37 IC (junior)37 CC (Cadet)37 BC (Baby)

37 S37)37 B37 M

Chassis Models. . . .

The larger models are availableon Hire Purchase through yourdealer. Terms from 7/6 down.

CELII"" 911;11:01Ceyji t fixed

" 4 vlaw.lou. ni°°col% Pre

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1937

3 7 s

To the eye there is little apparentdifference between one year'sspeaker and another. It is natural,therefore, that when his ear noticesthe newest Stentorian's marked im-provement in performance, thelistener should ask " How ? Why ?"Complete answers would occupyseveral books; for eight enthusiasticdesigners cannot report on a wholeyear's work in a few words. Here,however, are two important points:Further improvement in magnetic materialAn alteration in the magnetic alloy has brought about15°;, increased flux. He nce the greater volume and range.(Note : The material is exclusive to 1937 Stentorians.)

New Seamless ConeW.B. Engineers have evolved the first seamless coneto offer advantages over the special " seamed " typeused before. This new cone is manufactured in theW.B. factory from an exclusive and carefully preparedpulp. It reduces resonances enormously.These two points provide a partialanswer only- for every part of thenew design has been studied, experi-mented with, and improved. Theextra results as seen in the abovecurves taken from 1936 and 1937Stentorian Senior Speakers aredefinite and substantial.This new reproduction is availableto you. Ask your dealer.

1937 STENTORIANPermanent Magnet Moving -Coil Speakers

WHITELEY ELECTRICAL RADIO CO., LTD. (Technical Dept.) MANSFIELD, NOTTS.www.americanradiohistory.com


The attractive appearance of the dial of the Enfieldclock.

A New Type of Electric FireTHE principle of the reflector fire is so

familiar that it is unnecessary to enlargeupon it here. It has been employed for aconsiderable while with a fair measure ofsuccess, but the outstanding disadvantageis that the angle of reflection has beenstrictly limited. Consequently the heathas been emitted in a concentrated beamwhich unfortunately allows a considerablearea in front of the fire to remain coldthrough being out of beam. With a newtype of electric fire, however, recentlyintroduced by the Limit Engineering Co.,Ltd., 15-29 Windsor Street, Essex Road,Islington, ,the heat is distributed evenlyover an angle of 120 degrees fromthe centre of the heating element in thehorizontal plane.-- Thus, assuming the firestands in the fireplace in the centre of thewall, only the fireplace wall will be im-mune from direct radiant heat rays. Thisresult is obtained through the patenteddesign of the parabolic reflector and themathematical precision with which thesefires are made.

On this page we show the " Windsor "Radiant Radial Reflector which is of ultra-modern design and is available in oxidisedsilver on oxidised copper finish. It is28 in. wide, 151 in. high, and the pro-jection of the stool is 13 in. Double -pole kick switches are fitted as stan-dard and revery fire is supplied with6 ft. of 3 -core flex. The price for the1 -bar, 1I kW fire is £4 12s., andfor the 2 -bar 2f kW, £4 19s. 6d.

New Wilco Dynamo Sets

WILCOdyna-

mo sets forthe 1937season,made by L.Wilkinson,204, LowerAddis-combeRoad,Croy-don, are ofattractivedesign.Several setsare madeat 2 1 s . ,

AROUND theTRADE

A Review of Items which have recentlybeen placed on the Market.

the Torpedo de luxe, with its all -chromiumheadlamp, dynamo, and rear light, has twobulbs controlled by a rotary switch on thelamp, which will operate either bulb fromthe dynamo or stand-by battery.

The Torpedo lightweight, which costs138. 9d., is an outfit including a headlampwith a 3k -in. chromium -plated front and ablack body. The chromium -plated dynamohas automatic voltage regulation and canbe switched on or off with the foot.

The Radiant Radial Reflector fire described on thipage:

The Enfield Construction ClockWE recently tried out one of the Enfield

Clock Construction outfits, a productof the Enfield Clock Co. (London), Ltd.,Edmonton, London, N.18. The outfit,which sells at the moderate price of 108. 6cl.,comprises all the parts necessary for mak-ing a novel and really serviceable clock.We found it quite a simple matter to con-struct the clock from the instruction booksupplied, and found it to be an efficient time-keeper. The front of the clock is made toresemble the front of a locomotive, ascan be seen from the illustration on thispage. The outfit is packed in an attractivered and blue box, together with instruc-

tion book, assemblingblock, tweezers, oil, etc.

(Top) The Torpedo set. (Bottom) The headlamp ofthe Torpedo lightweight. The dynamo is the same as

in the other set.

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in the pages of which you will read thestory of Pelmanism, and, more fascinat-ing than fiction, the stories told byPelmanists themselves of how their liveshave been changed beyond their fondesthopes by Pelmanism, stories of promo-tion, increased incomes, of greater en-joyment of life.

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PELMAN (OVERSEAS) INSTITUTES: PARIS, 80Boulevard Haussmann. NEW YORK, 271 North Avenue,New Rochelle. MELBOURNE, 396 Flinders Lane.JOHANNESBURG, P.O. Box 4928. DURBAN, NatalBank Chambers (P.O. Box 1489). DELHI, 10 AliporeRoad. CALCUTTA, 102 Clive Street. AMSTERDAM,

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DEVELOPMENT OF THEAUTOGIRO

(Continued from page 73)

out any undesirable oscillations.By such gradual developments, the rotor

was perfected until, in 1932, the first"direct -control" type of autogiro was intro-duced. This machine had no stub wings orailerons as had been used hitherto, and atfirst it had no tail unit either, the entirecontrol of the machine being accomplishedby tilting the rotor axis. The modernmachines are all of the direct -control type,and in certain types even the rudder hasbeen suppressed.

The axis of the rotor is carried in a com-plicated assembly which can rock backwardsand forwards and also sideways in responseto the movements of the control column bythe pilot. Instead of the control column,or joystick, standing up from the floor ofthe cockpit, as in the case of an ordinaryaeroplane, it hangs downwards from therotor head into the cockpit. By movingthis "upside-down" control column, thepilot can tilt the rotor either sideways,backwards or forwards and so cause themachine to bank, turn, climb or dive at will.

The " Jumping " AutogiroThe various developments which I have

briefly outlined above have all been im-portant and necessary, in the developmentof the autogiro. But though essential,they dwindle almost into insignificence, atany rate in the popular view, in comparisonwith the very recent development of the" Direct Take -Off " or "jumping" auto-giro, a machine which requires no forwardrun whatever, and which is capable oftaking off from a very confined area. Thisdevelopment must be classed as one of themost important advances in the practice ofaeronautics yet made, and it will certainlydo more than any other to populariseaviation since there is no longer any neces-sity for a large aerodrome.

It has been usual for a number of yearsto set the rotor in initial motion by meansof the engine in order to reduce the lengthof take -off run required. When the rotornearly reaches its flying speed, the machineis permitted to run forward and the take -offgenerally requires only a short rim. Thetake -off run could not be abolished alto-gether, however, for if the rotor was speededright up to flying speed, the machine itselfwould momentarily leave the ground, and,the reaction between the machine and theground having vanished, the relative torquebetween the rotor and the fuselage wouldturn the machine in the air and it would atonce fall back to the ground. In order toachieve a direct take -off, some means hadto be found for keeping the machine on theground while the rotor was speeded up wellabove the normal flying speed, and then,simultaneously with the release of themachine from the ground, the drivingtorque to the rotor had got to be cut off.This would not appear a very difficultproblem, but it is one which has taken along time to solve.

Instead of securing the machine to theground by some mechanical arrangement,it is prevented from rising by reducing thepitch angle of the rotor blades to zero duringthe process of starting up the rotor. The gen-eration of lift is thus prevented and the dragtorque diminished considerably. Both factsallow the rotor to reach an initial speed verymuch in excess of the one corresponding tonormal flight, and, if, simultaneously with

the declutching of the mechanical drive tothe rotor, the pitch angle of the blades issuddenly increased to the normal value, liftis instanteously generated and the machinewill leave the ground in an almost verticaltrajectory.

As the rotor speed decreases, the machinewill hover for a moment, but if the pull ofthe airscrew during the upward motion hasimparted to the machine at least the mini-mum horizontal speed at which it canmaintain level flight, the machine will notfall back to the ground but will continuethe flight initiated by the jump.

In this way, a direct take -off, without anyforward run whatever may now be accom-plished, thus giving to the autogiro the onequality which has hitherto 'appeared tobelong only to the helicopter.

The development of direct take -off willenormously amplify the field of applicationand the gradual attainment of higher speedswill make it competitive for very manypurposes with the ordinary aeroplane.Doubt has sometimes been expressed as tothe ability of the autogiro to attain speeds ofthe order of 200 m.p.h. without losing con-siderably at the slow end of the scale.There is, however, no fear on this accountas the standard rotor at present in use onthe C. 30 type of machine could be usedappropriately on a machine of similar weight,but having an engine capable of developingsufficient power to attain 175 m.p.h., andonly slight modification is required to extendthis range. Tests have shown that theefficiency of the rotor is practically constantover a very wide range of speeds.

TRANSMITTING " PICTURE "SIGNALS OF COMPASS BEARINGS


within range will pick up a correspondingpicture of its own bearings, since therotating beam carries on its back, so tospeak, a visible record of each point of thecompass through which it is moving.

The Picture SignalAlthough the system provides a picture

signal which can be easily understood bya navigator ignorant of the Morse code, it isopen to the objection that the scale markingsare slightly " on the move " during thecritical moment of observation. For thisreason there may be some difficulty intaking an exact reading during the shortperiod of time available.

In order to remove this uncertainty theprocedure at the beacon station may bevaried, by radiating the picture signals on abroadcast wave, which travels outwards inall directions, instead of putting them onthe back of the rotating beam. The latteris, instead, used to transmit a tone signalwhich has the effect of producing at thereceiver a " black bar " or distinguishingmark under the exact scale -reading whichrepresents the ship's bearing at any giventime.

In this case, the picture seen by thenavigator would be as shown in Fig. 3,where C again represents the compass scale,and AB the stationary identification lettersof the beacon station. As before, the lettersAB remain " still " on the received picture,together with a special pointer P and anaperture marked L, whilst the compassscale C continues slowly to move round.But at the precise moment when the rotat-ing beam sweeps past his ship, a black barM appears in the aperture L, and thenavigator knows that the pointer P thenmarks his exact bearing.


November, 1936 NEWNES PRACTICAL MECHANICS 1 I 5

A DEVICE FOR CASEMENT WINDOWS" I HAVE thought of a device for preventing

the entry of rain at the top of casementwindows. I enclose drawings of my ideaand would like your advice on same, also ifyou think it would be a paying proposition."(R. M., Surrey.)THE improved device for preventing

entry of rain at the top of casementwindows, is thought to be novel and formsfit subject matter for protecting by LettersPatent.

The invention is ingenious and wouldundoubtedly be efficacious in practice, andprovided the invention be novel should havea good chance of proving a commercialsuccess.

The only certain way to ascertain thenovelty of the invention is to search amongstprior patent specifications dealing with thematter which, in view of the large numberof patents allocated to the class coveringsuch devices, would be a somewhat expen-sive matter.

You are advised to apply for a Patentwith a Provisional Specification, which willgive you about twelve months' protection.A PLUMB RULE AND LEVEL" HAVE devised, after considerable ex -I

periment, a plumb line and rule, andwould like your advice as to its novelty."(R. B., Ayrshire.),THE improved plumb rule and level is

thought to be novel from personal know-ledge and forms fit subject -matter for pro-tection by patent. Advise to file anApplication for Patent with a ProvisionalSpecification, which will give you protectionfor about twelve months in the least ex-pensive way.

After the application for patent has beenaccepted by the Patent Office, you will haveabout twelve months in which to try andinterest firms likely to take up the inventionbefore having to incur any great expense.By approaching firms in the trade, you willalso probably be advised as to the noveltyof the invention.

The inventor is advised to have profes-sional assistance in applying for his patent.THREE INVENTIONS" I WOULD like your opinion on three in-

ventions of mine, details of which Ienclose herewith.

" Models are not too difficult to make, andthe descriptions for the patent forms caneasily be explained.

" As I only wish to patent one at a time, Iwould like your opinion as to which one tochoose.

" I have numbered each description sothat there is no need to return them. Re-ference to the numbers will do." (J. S.,Durham.)INVENTION NO. 1 is thought to be novel,and forms fit subject -matter for protection

by patent. It would probably meet with a

Advice by our Patents Expert

certain measure of success if properlymarketed. It is possible that fountain -penmanufacturers would be interested in theinvention as a novelty, for which reason it isthought that this invention is more likelyto be readily taken up commercially thanthe others.

Invention No. 2 is also probably novel,but it would be advisable to search amongstthe prior patent specifications dealing withvalved containers. It is possible thatsomething similar has been previouslyemployed in connection with oil -cans. Theinvention, if novel, is capable of beingpatented, and if it can be inexpensivelyproduced, should be commercially suc-cessful.

Invention No. 3 is the least meritoriousone. In view of known arrangementsemploying a roller of felt or like absorbentmaterial for a similar purpose, it is notthought to form fit subject -matter forprotection by patent. The mere substitu-tion of one material for another analogousmaterial, unless invention is reqnired toadapt the new material to its puipose, isnot patentable.

MINER'S SAFETY LAMP" WOULD like your advice as to theI

novelty of a safety lamp for use inmines, which is ideal for demonstrators andmining students." (W. C., Monmouth.)

THE mines safety lamp model for the useof demonstrators and mining students

is probably novel and forms fit subject-

matter for protection by Letters Patent,which is the only effective way in which theinvention can be protected. Although wethink the invention novel, the only cer-tain way of ascertaining the novelty is tosearch amongst prior patent specificationsdealing with the subject.

Unfortunately for you, this ingenious andpracticable invention can only appeal to arelatively small and restricted class ofpersons, so that we do not think it wouldhave any great commercial value, for whichreason it is problematical if it would beworth the cost of patenting the invention.

COLOUR IN CINEMATOGRAPHY" HAVING conceived an idea, probably

quite different from any other scheme inconnection with the rendering of colour incinematography films, I am submitting it toyou for consideration." (G. L., Notts.)

THE improved method of taking andprojecting cinema films in colour is in-

genious, but the novelty of the inventionis doubtful. The inventor is advised tosearch prior patent specifications dealingwith the subject before going further.

The original " 'Cinema colour," whichonly employed two colours, owed its wantof lasting commercial success largely tothe fact that the film had to be run throughthe projector at twice the normal speed forordinary film.

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LOGUE No. 3, 6d. post free.

STUART TURNER LTD.HENLEY- ON - THAMES



If a postal reply is desired, a stamped addressed envelope must be enclosed. Every query and drawing which issent must bear the name and address of the sender and be accompanied by the coupon appearing on page 126.Send your queries to the Editor, PRACTICAL MECHANICS, Geo. Newnes Ltd., 8-11 Southampton Street,

Strand, London, W.C.2.

MAKING BOOT POLISH" I am about to start manufacturing boot

polish for sale, and I need a dye that willblacken a mixture of beeswax and turpen-tine. I have heard of nigrocine (spiritsoluble), but I think it is too dear to use.Is there any cheaper alternative, and wherecould I obtain it ?

" I also need a brown dye to make thepolish brown. Could you give me the nameof a chemical that will do this for me ? Thedyes should not take any of the shiningproperties from the polish." (J. 0' C., Lim-erick City.)THE dyes most suited to your needs are

" Oil Black 500," and " Oil Brown 501."Both of these are obtainable from Messrs.Boak, Roberts & Co., Ltd., Stratford,London, E.15, their cost being 48. and7s. 6d. per lb. respectively.

The above colours are completely solublein turpentine, spirits, naphtha, white spirit,and similar solvents, and they will notinterfere with any of the properties of yourproposed boot polish.BATH SALTS

"COULD you please describe a method

of making bath salts in either powderform or crystals ? " (R. H., Devon.)

ORDINARY bath salts are nothing morenor less than carbonate of soda which has

been recrystallised, and had incorporatedwith it a trace of a dye and a perfume. Ifthe salts are required in powder form, theyare gently heated for a period until theyfall to powder.

Dissolve carbonate of soda in boilingwater until no more will dissolve. Filteraway the liquid, add to it a trace of a dye(as, for instance, methyl violet) and also aperfume, and allow the liquid to cool. Itwill deposit crystals. These are removed,dried, and packed. On further concentra-tion the liquid will deposit another crop ofcrystals.NEON TUBES, RADIUM, ETC." WOULD you please inform me on the

following :" (1) What are the names of the non-

metallic elements ?" (2) Is A.C. or D.C. current used for neon -

tube lights and mercury -vapour lights ?" (3) Can any inert gas, such as nitrogen,

be used in place of neon in a neon -tubelight ?

" (4) Is radium deposited from any othersubstance, and what are the changes it passesthrough before it becomes lead ?

" (5) Of what thickness must an infra -redray filter be ? " (A. V. P., Middlesex.)

(1) M ON -METALLIC elements are the`a following : Argon, Boron, Bromine,

Carbon, Chlorine, Fluorine, Helium, Hydro-gen, Iodine, Krypton, Neon, Niton, Nitro-gen, Oxygen, Phosphorus, Selenium, Silicon,

Sulphur and Xenon. Arsenic and Tellur-ium are half metallic and half non-metallic.

(2) A.C. current is best for neon andmercury -vapour tubes.

(3) If, in place of neon, another inert gas isemployed in an electric discharge tube, anillumination will be produced, but it willnot consist of the orange -red glow which ischaracteristic of neon. Moreover, highervoltages will, usually, be required.

(4) Radium is formed by the slow break-down or disintegration of uranium, anelement of higher atomic weight. Duringits very slow disintegration into lead,radium is converted into the followingelements in sequence : Radium emanation(or Niton), Radium A, Radium B, RadiumC, Radium D, Radium E, Polonium, Lead.The " life " of some of the radium modifica-tions is only a matter of minutes.

(5) An ebonite infra -red filter need not bemore than a12- in. in thickness.

PLASTER CASTS" I READ recently of gelatine being used to

make flexible moulds for plaster casting.I melted some gelatine, which when setagain was just as brittle and useless formoulding as before. Can you tell me whatto add to the gelatine to make it into a jelly-like mass, capable of being bent to allowextracting a plaster cast ? I heard also ofplastic rubber being used for the same pur-pose. Where could I obtain plastic rubberand how should it be worked ? " (J. D.,Sheffield 3.)

(1)GELATINE dissolved in a small

quantity of water and allowed to setshould not form a brittle medium. If itdoes, re -melt the gelatine and add morewater. The proportion of water necessarywill have to be determined by experiment,since different classes of gelatines vary agreat deal in their setting properties. Ifyou wish, you can incorporate a little pureglycerine and/or a few drops of castor oilwith your gelatine mixture, but we are ofthe opinion that a well -prepared gelatinemixture should set in a flexible conditionwithout the addition of such plasticisers.

(2) We doubt whether you will be able toobtain true rubber in a plastic condition forthe purpose you require. However, youmight write to Messrs. May & Baker, Ltd.,Battersea, London, S.W.1, who are manu-facturers of plastic materials of variouskinds. Also, an enquiry sent to the Insti-tution of the Rubber Industry, FaradayHouse, 10 Charing Cross Road, London,W.C.2, would bring you the latest particu-lars on the subject of your requirements.

COMPOSITION OF BAKELITE"(1) WHAT are the substances employed

in the composition of bakelite ?" (2) Is it pressed, moulded, or machined

into shape ?

" (3) Is it a patented process, or can it bemade by anyone ? " (S. B., Barnsley.)(1)THE exact composition of bakelite is

I unknown. It is made by heatingcarbolic acid and formalin under certainconditions. A complex chemical reactionsets in between these two compounds and,ultimately, a brown powder results. This,when subjected to pressure and heat, againchanges its composition and becomestransformed into the now familiar material-bakelite.

(2) Bakelite and similar materials arepress -moulded, powerful hydraulic pressesbeing employed for the purpose.

(3) Bakelite and all similar compoundshave been covered by letters -patent, butsome of these patents have now lapsed, andit is open to anyone having the necessaryskill and experience to manufacture thematerial formerly covered by patents.Note, however, that the descriptive tradenames are, in nearly all instances, legallyregistered and therefore cannot be used byunauthorised persons.

ANODISING SMALL ARTICLES

"I SHOULD be glad if you could give me alittle more information with reference to

your pages on Aluminium and Its Alloys.'" Could I anodise articles with a small

plant I have for plating and what voltagewould I require ? Also I have been underthe impression that the bath was of chromicacid, not sulphuric. Would you kindlyclear up this point for me and tell me thestrength of the bath ? " (K. D., Herts.)

YOU do not describe the design of yourplating plant and hence we are not able

to state definitely whether you could con-vert it successfully to anodising uses. Twotypes of anodising baths may be used, onecontaining sulphuric acid, the other con-taining chromic acid. In the sulphuricacid bath, the moderately concentratedacid has passed through it a voltage ofbetween 10 and 20 volts for a period of30 minutes. The anode consists of thearticle to be " anodised," the cathode com-prising a strip of lead.

The chromic acid anodising bath is morecomplicated to operate, but, in the opinionof many, it produces better and finerresults. A 3 per cent. chromic acid solutionis employed. The cathode consists of alead or iron strip, the anode again compris-ing the article or articles under treatment.In this bath the voltage is applied as follows :

During the first 15 minutes the voltage isslowly raised to 40 and, afterwards, it iskept at this point for a further 35 minutes.During the next 5 minutes the voltageof the bath is raised to 50 and it is main-tained at this figure for a further 5 minutes,after which time the current is turned off.The bath should be maintained at a tem-perature of 40-45° C.

L. W. (Dalston).-We are sorry that wecannot give you a full list of the poisongases used during the Great War. You donot mention the make of the microphone soit is difficult to advise you. We recommendyou to try increasing the voltage and to usewet cells. The secondary of the trans-former should be joined between the gridand grid -bias battery at the correct voltagefor the valves in use.

HAVE YOUR COPIES OF"PRACTICAL MECHANICS"

BOUNDSee the announcement on page 67!



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HAVE YOU A RED NOSE?Send a stamp to pay postage, and you willlearn how to rid yourself of such a terrible

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P. TEMPLE, Specialist"Palace House," 128 Shaftesbury Avenue, W.I

(Est. 30 peers.)

DON'T BE BULLIEDLearn to fear no man. TheBEST self - defence ever In-vented, namely. 7 IN I T S U.Easy to learn. Send 2 panto,stamps for SPLENDID =USTRATED LESSONS, PhotoA RTI OL E, Testimonials andpartionlars, or P.O 1/. forFIRST PA RI of my sour. Youwill be more than delighted.A Japanese Secret, Kill FearPure, Fees to pupils.Dept. P., Blenheim House, Bed-tont Lane, Feltham.

All Clix components are designedand built so that the public can relyupon them for perfect contact, pluslong and faithful service.

The 1936-7 range of Clix Valveholders includesthe well-known Standard type and the newFloating type with frequentite base. Both arefor chassis mounting and can be used withequal efficiency for metal chassis or woodbaseboards. Then there is the baseboardtype for Ultra -Short-wave work and thespecial Clix chassis type for use with HivacMidget valves.

The illustration shows the new Floating type.

All types employ Clix patent resilient, helicallyslotted sockets, which give perfect contactwith any type of valve -pin.

You can rely upon Clix ,for long' and faithfulservice. Send for Folders " P.M."

LECTRO LINX LIMITED

For the fraction of the cost of a newset you can, by replacing ' tired'valves with their modern equiva-lents, not only restore the originalquality of your set, but actually giveit a higher sensitivity and greaterpower output than it originallypossessed.Investigations prove that ' tiredvalves' are responsible for thegeneral deterioration of otherwiseperfectly good sets. Your dealerwill confirm this if you let him testyour old valves.HIVAC have produced a specialvalve Replacement Chart whichshows the correct HIVAC type toreplace those worn out. HIVACvalves, as used in the latest receivers,are highly efficient, give long serviceand cost less.The sure and economical way toget the best from your set is toreplace all 'tired ' valves withHIVAC.

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For Work after DarkMechanics and owners of small workshops,lathe sheds, observatories, etc., should get the

TILLEY LANTERN(Burns ordinary Paraffin)

Light of 300 c.p.f or 6 hours for Id.Its magnificent light enables work tocontinue after dark, either in or outof doors. Can be placed anywhere.Made in stout brass, and there are noparts which can rust, corrode, or getout of order. Burns steadily any-where, unaffected by weather, how-ever severe. Get rid of all antiquateddevices and use this marvellouslyefficient All -British Tilley StormLantern. Price 36/-.

Remit 361- or can be sent C.O.D.Post and Charges Paid.

TILLEY LAMP CO. (Dept. P.M.), HENDON, N.W.4

TROUSERS MADETO MEASUREAny Waist fitted, 28 in. to 68 in.

or larger.Inside Leg, 26 in. to 36 in. or longer.We cut and make from tested cloth

of Blue, Grey, or Brown.Please state waist, inside leg, side seam

and width of bottom required.

511 i. 616 816Post 6d. or C.O.D.

Satisfaction guaranteed or money instantly returned.Send for FREE Patterns.

C. HAROLD NURSE,108 BORDESLEY GREEN, BIRMINGHAM 9.

There are101 uses for

H A R B U T T'SPlasticin ein the work -shop

Plasticine, in 16 colours, Is. per lb.

Write for illustrated price lists to :-Harbutt's Plasticine Ltd., 241 Bathampton,

Bath.

PRACTICAL HINTS ONPATENTS

Ssnt frss on application

THE IMPERIAL PATENT SERVICEFirst Avenue House, High Holborn, W.C.1.

Preliminary Consultation Free.

INVENTORS.VALUABLE GUIDE

General Advice Free. POST FREE 6d.

CHATWIN & CO. Est. 1880Regd., Patent, Design and Trade Mark Agents for

all countries.263 (D) Gray's Inn Road, London, W.C.1

ADVERTISERS WILL BEPLEASED TO LEARN THAT

YOU SAW THEIRADVERTISEMENT IN

" PRACTICAL MECHANICS"

HOW AUTOMATIC RECORDCHANGERS WORK


kick inwards, with the result that thebottom record is moved very slightly to theright. The bent spindle in the centre isnot a plain one, as might be imagined fromthe photograph, but is notched as shown inFig. 8. When the bottom record is givena slight kick to the right, its central holepasses over the shoulder of the spindle andthe record falls downwards on to theturntable.

Another mechanism which depends upona somewhat similar " notched spindle " isthat recently introduced by Messrs. CollaroLtd. This is shown in Fig. 9, and, unlikethe mechanism already described, it will beobserved that it is capable of playing abatch of records of mixed sizes. The recordsmay be mixed in any order and the pick-upis automatically dropped into the correctposition and biased into the first grooveaccording to the size of the record justdropped.

The Collaro MechanismAnother mechanism made by Messrs.

Collaro Ltd. is not strictly similar to thosealready described, since it is not intendedfor the automatic playing of a pile of recordsbut it deserves mention on account of itsunique features. It is an automatic gramo-phone, but it plays single records only.To play a record, it is only necessary topush the record gently into a slot. Themechanism then draws the record right in,plays it automatically, and then pushes itpartly out of the slot again. The mechanismwhich is shown in Fig. 9 is entirely auto-matic and it plays either 9 -in., 10 -in. or12 -in. records in any order without anypre-setting or manipulation. The construc-tion is such that the records are treatedeven more gently than is possible by hand-which is certainly not true of some ofthe changing mechanisms.

Before drawing this survey to a close,a very brief account must be given of theAutotrope, an automatic record changerinvented by John Hopwood. This isperhaps the most remarkable mechanism ofits type yet produced, for it is not onlycapable of playing a series of no less thanthirty-three records which may be of mixedsizes in any order, but, unlike any otherautomatic mechanism, it can play bothsides of a record.

Separate Motors EmployedThe mechanism is, of course, very com-

plicated, and separate motors are employedfor record playing and record changing,but the construction is such that the recordsare treated very gently and they are neverin sliding contact with any part of themechanism.

The records are taken from a magazineto the turntable by a traverse arm whichengages with the central hole of the record,whilst the turning over of a record is per-formed by a pair of levers which hold therecord gently by the edges. After playing,the record is delivered on its edge on torubber buffers in the rejection chamber andit is then pushed on one side by delicatefingers.

As may well be imagined, such a compre-hensive mechanism can only be sold at aluxury price. But there are always thosewho will pay a high price for the best, andif capacity and capability are the standardsof comparison, then the Autotrope is cer-tainly the doyen of automatic gramophones.

BECKS CHEMISTRY

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STOKE NEWINGTON, LONDON, N.16

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PRICES FROM:

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Be a MAN thatWomen ADMIRE

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REFUND YOUR MONEY IN FULL. Thousandsof testimonials, seen by leading Editors. The one com-plete all-round MAN -MAKING System. CompleteCourse 5/iiip or send 2/6 now and 2/9 when satisfied. Sentprivately under plain coven-Lionel Stabbing, StebbinsInstitute, 28 (MP -6), Dean Road, London, N.W.2.

WEBLEY AIR PISTOLSMarvellouslyaccurate fortarget practice.No license required to purchase.

Senior 45/-, Mark 1 30/..Junior 20/-, Webley Air Rifle 80/.Write for List. WIMILLY & SCOTT LTD.,I06 WEIMAR STRIRT, BIRMINGHAM, ENG.

PAM82 - 17 -

Machuavia la,.

The 'ADEPT' Bench Hand ShaperLength of stroke of ram, 3I ins.; Length ofcross travel of slide, 3 ins. ; Size of Table,41 ins. a 4 ins. ; Rise and fall of Table, 2 ins. ;

Vertical feed of tool slide, 14 ins. ; Maxi-mum distance between tool and table, 3 ins.;Weight, 18 lb. Also the ' Adept' No. 2 B.H.Shaper,6I-in. stroke. Price 65 - 17 - 6.

Manufactured byP. W. PORTASS

83a Sellers Street, SHEFFIELD.

THE "00" & " HO" GAUGE SPECIALISTAll interested in ModelRailways should send twolid. stamps for my latest list of specialities. Myall -brass scale model permanent way is guaranteed,

and the price is reasonable.Latest addition-Fully equalised Coach Bogies,

3/6 per pair.GEORGE E. MELLOR

ALLANSON ROAD, RHOS -ON -SEA. N. WALES

FOYLESBooksellers to the World

New and second-hand books on all technical sub-jects. Catalogues free on mentioning interests.

119-125 CHARING CROSS RD., LONDON, W.C.2Telephone: Garrard 6660 (12 Ems).

IF you are tired of yourpresent position and feel thatyou are worthy of somethingbetter send for our bookletand learn how to quicklyqualify for a higher positionand better pay. Expert

postal tuition In Book-keeping, Business Training, SecretarYshiP,Hotel Book-keeping, Salesmanship, Journalism, etc., from 2/- perlesson. Prospectus and testimonials free.

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ARE YOUTIRED OFYOUR JOB ?



BUY, EXCHANGE OR SELLAdvertisements are accepted for these columns at 2d. per word (minimum 12 words at 2s.-advertisements ofless than 12 words are charged at the minimum rate of 2s.), subject to a discount of 22% for 6 consecutivemonthly insertions or 5% for 12 consecutive monthly insertions. TERMS :-Cash with order. Cheques, PostalOrders, etc., should be made payable to George Newnes Ltd. The Proprietors reserve the right to refuse orwithdraw advertisements at their discretion. All advertisements must be received on or before the 5th of the monthpreceding date of publication and should be addressed to the Advertisement Manager, " Practical Mechanics,"

George Newnes Ltd., 8-11 Southampton Street, Strand, W.C.2.

CINEMATOGRAPHY

ARTISTIC CINE FILMS. Exclusive 9.5 -mm.and 16 -mm. productions. List Free. Projectors, CindCameras.-P.M. Dane, 64 Stanley Street, Liverpool, 1.

CINEMATOGRAPH FILMS. Standard size from6d. 100 feet. Machines, Accessories. Sample Films1/- and 2/6 post free. Catalogues free.-" Filmeries,"57 Lancaster Road, Leytonstone, E.11.

WANTED for prompt cash. Home Cind-Cameras,projectors, films, accessories, microscopes, telescopes,binoculars, optical and mechanical goods. Mathe-matical and precision instruments. Small lathes.Modern cameras. Enlargers.-Frank, 67 Saltmarket,Glasgow.

MOVIES AT HOME. How to make your ownCinema Projector. Particulars free.-Moviescope ( N),Pear Tree Green, Doddinghurst, Essex.

FILMS, 35 mm. of every description, from 5s.-Baers, 176 Wardour Street, W.I. Est. 1907.

CHEMISTRY

CHEMICALS and apparatus. Elementary andadvanced. Bargain prices-GRAY, 40 Grange Road,Lewes.

CLOCK MOVEMENTSCLOCK MOVEMENTS of every description ready

for cases. Lists and hints on case making post free.-Needham, 25 Stratton Road, Manchester, 16.

ELECTRICALELECTRIC MOTORS, 1/10th and H.P. A.C. and

D.C. 200/240 volts. New and second-hand from 35/-.-EASCO, 18 Brixton Road, S.W.9.

ELECTRIC MOTORS, large stock, guaranteed ;cheap.-Electrique, 47 Pitt Street, Glasgow, C.2.

SURPLUS ELECTRICAL and EngineeringMaterials, low prices.-The London Electric Firm,Croydon.

ELECTRIC LIGHTING, 5/- a point ; progressivewiring diagrams and instructions, 6d., materials, whole-sale prices ; lists free.-P. Symax & Co., 263 Lichfield,Road, Birmingham, 6.

SUPER A.C. MOTORS. New 1/10 h.p., 28/-;h.p., 36/6, 46/- and 50/-; h.p., 70/-, and larger sizes.

-John P. Steel, Bingley.

ENGINESENGINES. Build Butler's Practical Model Petrol

Engine, 4-h.p., castings, 9/9. Interesting Catalogue 3d.Charging Dynamos, Boat Propellers, Sterntubes,Shafting Blocks.-Write Butler's Profit-sharing Works,Wade Street, Littleover, Derby.

FORMULASFORMULAS, RECIPES, SECRET PRO-

CESSES, from shilling upwards. Lists, interestingliterature, 4d. stamps. Make Money from old drainedmotor oil, instructions, 1/-.--" Technocraft," 41Longford Place, Manchester, 14.

PLEASE GIVE

GENEROUSLY

NOV.11REMEMBRANCE

DAY

ASTOUNDING BARGAIN

CHESTS OFITTED

F GUARANTEED£6.6.0 TOOLS

1 Hand Saw, 24" Blade.1 Tenon Saw, 10" Bla..e.1 Keyhole and Pad Saw.1 Claw Hammer.1 Pin Hammer.2 Files (Handled).1 Rule.1 Gouge (Handled).3 Chisels (Handled).2 Brad Awls.2 Gimlets.1 pair Pipe Grips.1 pair Construction Pliers

and flat grip.1 Oil Can.2 Pencils.1 Soldering Iron.1 Tool Chest.1 Smoothing Plane.1 Brace.

47 Strongly MadeStandard Size ToolsFOE

50!-EVERY TOOL

FULLYGUARANTEEDOffer cannot berepeated afterpresent stockcleared.

3 Centre Bits.1 set of 3 Gimlet Bits.1 Square.1 Axe.1 Oilstone.1 Pair Pincers.1 Small Screwdriver.1 Large Screwdriver.1 Glass Cutter.1 Spokeshave.1 Punch.1 Level.1 Marking Gauge.1 Cork Rubber.2 Sheets Sand Paper.1 Rawlplug Outfit.1 Instruction Book.1 Croid Glue.1 Tin Fluxite.

FREE To every purchaser of the " Zyto "Guaranteed Tool Chest, a hand-

some 7/6 cloth .bound copy of " HomeRepairs and Renovations."DON'T DELAY-ORDER NOW.

List of special offers in wood and metal workers'tools free. Post 2d. Please state which you require.

S. TYZACK & SON LTD.TOOL SPECIALISTS,

341, 343, 345 OLD STREET,LONDON, E.1.

YOU CAN USE YOUR SPARE TIMEto start a Mail Order Business that quickly bringsyou a full-time income. Follow the lead of others'who are averaging £12 per week net profits. Get awayfrom a drudgery routine job-join the big -moneyclass. No previous experience necessary. Few poundscapital only needed. No samples or outfits to buy ;no rent, rates or canvassing. New method makessuccess certain. Write to -day for FREE BOOKLET toBusiness Service Institute (Dept. 880c), 6 CarmeliteStreet, London, E.C.4.

HYPNOTISM & MAGIC25 LONG LESSONS IN " HYPNOTISM," 2/6.

"Ventriloquism," 1/-. " Parlor -Magic," 100 tricks, illus-trated, 1/-. " Magic Mind -reading Slips," 1/-.(Get these and be the lion of the party at Xmas.)Professional " Mental -Telepathy " act for sale £1.-Professor Devine, 41 Longford Place, Victoria Park,Manchester.

LITERATUREJUST IMPORTED. Latest American, Science,

Mechanics, Inventions, Magazines. 6 different, 3/3.Lists free. Books, magazines, bought, exchanged.-P.M. Final, 15 Nashleigh Hill, Chesham, Bucks.

MAIL ORDER" MAIL-ORDER Ideas " and " Directory " where

to buy (both for 3/-).-" Technocraft," 41 LongfordPlace, Manchester, 14.

METALS

MAKE METAL TOYS. Easy, profitable with" Success "moulds. Lists free. Complete trial mould,1/6.-LEE'S, Bentinck Road, Nottingham.

MISCELLANEOUS" HOME TOYMAKING " just published with 180

designs and illustrations of practical fascinating toys.Posted, 1/2.-Industries (below).

ALUMINIUM MOULDS for casting lead soldiers,cowboys, etc., at home. Catalogue stamp.-Industries,13 Gordon Avenue, Twickenham.

MODELS, tools, motors. Send for list.-QueensEngineering, 60 Queens Road, Battersea, S.W.8.

WATCH, CLOCK AND JEWELLERY RE-PAIRS a speciality. Materials, Tools, Invar Steel andwheel -cutting. Catalogue 6d. Shockproof Watchesfrom 213 (overseas excluded). List 10.-Young & Son,Material Dealers. Chippenham.

MODELS

STEEL TUBING, Seamless, v}" to 41-", sig" to i"thick. Please say lengths you cut to.-Cotes, ChurchWalk, Brentford, Middlesex.

EVERYTHING FOR electrical rewinds and re-pairs. Screws, nuts, and washers for model engineers,Lists free.-Lumen Electric Co., Litherland, Liverpool,21.

PERFECT SECOND-HAND TOYS ANDMODELS ; bargain catalogue 41d. Models purchased.-Model Exchange. 11 Friars Street, Ipswich.

MONEY -MAKINGEXCELLENT MONEY -MAKING OPPOR-

TUNITIES constantly occurring, strongly recom-mended. Send stamped addressed envelope for freeparticulars.-Messrs. Green, 17 Church Lane, Hull.

MUSICAL INSTRUMENTSBAND GUIDE. Hints on the Bugle, Drum, Flute,

Staff Parade formation, etc. Free, post paid.-Potter's (Manufacturers), West Street, London, W.C.2.



BUY, EXCHANGE OR SELLPATENTS

REGINALD W. BARKER & CO. (Established1886), 56 Ludgate Hill, London, E.C.4.-Patent andTrade Mark Booklets Gratis.

PHOTOGRAPHY" PANTOGRAPHS" make large accurate draw-

ings from small photographs, printed drawings, etc.,easily, 1/-, post free.-Cooke, 33 Hawthorn Road,Levenshulme, Manchester.

E5on worth good, cheap Photo Materials, Films,`Jr Plates, Cards, Papers, Chemicals, Catalogue

and 4 Samples Free.-Hackett's Works, July Road,Liverpool 6.

DON'T TAKE RISKS. Good developers meangood results. Our reliable stock developers keep twel' emonths after mixing. Satisfact ion certain to amateursand professionals. Best developer ever put on themarket. Makes two pints strong developer. 6d. each,6 for 2/3, 12 for 41-. Post tree.-Hackett's Works,July Road, Liverpool O.

BRITISH MADE' UNIQUE SLIDE RULES

5/- 3/6 6/6

ACCURACY GUARANTEED.Ten -inch Slide Rule in Polished Mahogany, celluloid facedwith log -log scale in addition to Scales, A. B. C. and D.Flexible back. Aluminium framed, view free unbreakablecursor. Size of rule 1171 ins. x 14 ins. Serviceable as21/- model. Supplied with case and full instructions,including conversion Tables for Money Calculations.Price 5/- each (post 3d., 3 post free). 5 -in. model 3/6(postage 2d.). a o -in. Universal rule with additionalTrig and Reciprocal Scales 6/6 (postage 3d. extra).

THE TECHNICAL SUPPLY CO. (P.M.).Norfolk House, Carden Avenue, Brighton 6:

SITUATIONS VACANTPOST OFFICE ENGINEERING. Good positions

open to youths and men, age 17 to 30. Start £2 13s.weekly at age 17. FREE details of vacancies fromN.T.O. (Dept. 307), 335 High Holborn, W.C.1.

MODEL ENGINEERS, AMATEUR MECHAN-ICS and others experienced in fine metal work. Inthese days of mass production and semi -skilled work-men, you represent the only remaining body of crafts-men in hand -finished metal work. Your hobbydemands skill, accuracy and attention to detail.Such experience is rare to -day, and is worth severalpounds a week to you. Let us show you how you mayapply this experience to a spare -time occupation forwhich only you are qualified. This is the mostgenuine and straightforward spare -time occupationever evolved. No repetition work. It is an adaptionof your own hobby, but more fascinating than yourhobby has ever been. Send lid. stamp for particularsto : Artcraft Electrical Products, Nasec Buildings,Manchester Street, Oldham.

RADIO MEN WANTED.Messrs. Marconis anticipate requiring 200 Marine

Wireless Operators in the next few months.TRAINING PERIOD 8/12 MONTHS.

APPOINTMENTS GUARANTEED.TRAINING FEE CAN BE PAID AFTER

SECURING AN APPOINTMENT IF DESIRED.BRITAIN'S LEADING WIRELESS TRAINING

CENTRE.COLLEGE ON SEA FRONT. BOARDERS

ACCEPTED.WRITE FOR FULL PARTICULARS:WIRELESS COLLEGE,

COLWYN BAY.Or London Representative, 4 WINTON AVENUE,

N.11.

STAMPS

FREE ! I Twenty Unused Colonials. " Neurope,"1)d. Fifty for 9d.-G. H. Barnett, Limington, Somerset.

TOOLSGRAYSON'S Glass -boring Outfits and Tube

Cutters avoid risk.-Below.

DRILLS, Taps, Dies, Files, Chisels and Punches.Best quality at keenest prices.-Grayson & Company,300 Campo Lane, Sheffield.

THE MYFORD 3 -in. LATHE. Have you seenour new superior model with additional refinements.Standard model still in production. Economical in firstcost. Generous in design. Proclaimed best value onthe market. Write for illustrated list and instructionbooklet, or ask your local Tool merchant.-MyfordEngineerineCo., Neville Works, Beeston, Notts.

BE TALLYour Height increasedin 14 days or moneyback. The amaz.ngStebbing System soonbrings 3-5 inches

increase and new energy. The first, original andthe one GENUINE GUARANTEED Height IncreaseSystem. Reco-emended by Health and Efficiency. Corn-plete Course 5/, or Booklet free, privatelySTEBEING SYSTEM, Dept. M.P., 28, Dean Rd., Loudon, W.1

DEFERRED TERMS ARRANGED

"IDEAL -LATHES"34 in. S.C.B.G. from £7/18'6. LISTS, Stamp please.J. WILLIMOTT & SON, Neville's Factory, Chilwell, Notts.

NERVOUSNESSEvery nerve sufferer should send for my Interestingbook, which describes a simple, inexpensive home treat-ment for Self-consciousness, Blushing, Depression,Worry, Insomnia, Weak Nerves, Morbid Fears, andsimilar nervous disorders. This wonderful book willbe sent In a plain sealed envelope to any suffererwithout charge or obligation. Write NOW and learnhow to conquer your nervousness before It conquers you!

HENRY J. RIVERS(rj.t..3) 40 tabiHri,ConduitiS t. ,

MAKE MORE MONEY/3 to £6 weekly can be earned at home in a wonderfulbusiness of your own. No matter where you live youcan commence to make money in your spare or wholetime. No risk, canvassing or experience required. Awonderful opportunity for anyone wishing to addpound to their income. Particulars, stamp.BALLARD, York House, 12 Hambrook Rd.,

LONDON, S.E.25

FREE ADVICE BUREAUCOUPON

This coupon Is available until Nov. 30th, 1936,and must be attached to all letters containing

queries.PRACTICAL MECHANICS, NOV., 1936

TOOLS (continued)NEW POWER TOOLS. 10 -in. Bandsaws, 50/-;

Jig Saws, 21/-; Bench Drills, 22/6 ; Circular Saws,Electric Drills, Grinders, Spray Plants, Guns, AirCompressors, etc.-John P. Steel, Bingley.

A.J.W. Gas blowpipes. Invaluable for soldering,brazing. Sample 3;-, approval.-WRIGHT, 10Mitchell Street, E.C.1,

3 Tons Bright Steel Wood Screws, 4' to 3' long,a special quick clearance offer, 3 lb. assorted 2s. 6d. ;very good value.-Below.

Genuine " Crown " Lathe Chucks, self centring,precision quality guaranteed accurate. Two setshardened and ground steel jaws, 3", 26/6 ; 4', 29/6 ;5', 36/- ; 6', 42/- ; 74", 50/- ; 9", 65/- ; 104', 80/- ;12', 105/-. Carriage paid.-Below.

160 Large End Mills, f" to 1k' diameter, clearingat 3 for 4s. 6d. ; Nos. 2 and 3 Morse Taper Shank.-Below.

120 Bundles Silver Steel, 1/16' to I", diameter,16 assorted pieces, 13" long, 4s. bundle.-Below.

Independent Chucks, four reversible steel jaws,best quality, heavy engineers' pattern, 6', 45s. ; 8",57s. 6d. ; 10", 72s. 6d. ; 12", 90s. ; 14', 105s. ; 16',125e.-Below.

Independent Chucks, amateur, light pattern,suitable for small Lathes, Four Reversible Jaws,Hardened and Ground. Fully guaranteed, completewith Key and Face Plate Bolts, 3', 18s. 43d. ; 4", 248. ;6", 32s. 6d. each.-Below.

20 Only 1' Micrometers, decimal equivalentsmarked on frame, usual price, 27s. 6d. each, an oppor-tunity, 16s. 6d. each, all complete in plush -lined case.-Below.

1' to r Micrometers, 23s. 6d. ; 2' to 3', 308.;3' to 4', 36s. ; special quotation for full set High ClassMicrometers, 0" to 6', complete on polished woodstand.-Below.

Drilling and Milling Machine Vices, a quantityfor disposal at extremely low prices. Send for illus-trated lists.-Below.

500 Lathe Tool Holders, f" Square Shank, suitablefor Lathes up to 4'. Fitted with Super High-speedTool, ls. 9d. each, worth double.-Below.

300 Boring Bar Tool Holders, 4' Square Shank,.1" Round Adjustable Bar, 3s. 9d. each.-Below.

150 Genuine Norton GrInding Wheels, saucershape, suitable for small tool and twist drill grinding,44' dia., r thick, f' hole, ls. 6d. each, 15s. doz.;also 6" dia., 4" thick, 4" hole, 2s. 3d. each.-Below.

30 Bundles Bright Mild Steel, round, I', 4', 4',I' dia. in 5' to 6' lengths, 10s. per bundle.-Below.

600 High-speed Centre Drills, three' assortedsizes, small to medium, suitable for model makers,ls. for three.-Below.

3 Tons Best Sheffield Files, Flats, Half Rounds,Square, Rounds, in rough and second cut sizes, 6", 8',10', 12". This Is a very special bargain offer, wonderfulvalue, three dozen assorted, 105. ; also large tiles, 14',16', 18', dozen assorted 8s. 6d., carr. forward.-Below.

250 Bundles Bright Drawn Mild Steel, approx.5' length each piece, sizes 4', 5/32', 3/16', 7/32', 4',0/32', 5/16', 7/16", 4' round, 5s. 6d. per bundle of50' ; also Square Bright Steel, sizes 4', 3/16', 1',5/16", f", 7/16", 4", 5" lengths. 6s. bundle.-Below.

5,000 Small Slitting Saws, f' dla., 1/32' thick,clear at 2s. per doz.-Below.

2,000 Slitting Saws, 24' dla., 1' hole, 1/64' to4' thick, six assorted, 3s. 6d.-Below

1,300 Sets Hexagon Die -Nuts, Sheffield made,Whitworth, B.S.F., also American thread, U.S.S. andS.A.E. suitable for Ford and other American cars4", 5/16", I", 7/18', 4', worth 7s. set, our clearingprice, 2s. 9d. set ; all the above four sets, 10s. lot.-Below.

300 Drill Chucks, takes to 4', three jaws. No. 1Morse taper shank or 4' straight shank, Is. Id. each.-Below.

500 Gross Tungsten Steel Hacksaw Blades,8', 9', 10', 12', is. 3d. per doz. ; 12s. per gross ; alsoMachine Blades, 12' x 1", 2s. doz.; 20s. gross;14' x 1", 3s. doz.-Below.

1,200 Best Quality Straight Shank End Mills,standard sizes, 4". ls. 3d. ; 5/16", is. 4d. ; 4', ls. 6d. ;7,16", ls. 9d. ; 4', Is. each. All right-hand, suitablefor use in lathe.-Below.

800 Sets l' Circular Dies. Screwing 4', 6/16',f', 7/16', 4', Whitworth and B.S.F. Clearing at25. Id. per set. Both sets 5s. Die stocks to suitls. 9d. each.-Below,


BUY, EXCHANGE OR SELLTOOLS (continued)

5,000 Small Grinding Wheels, suitable forFlexible Shaft use, etc., r to 1' diameter, assortedthicknesses, etc., brand new, unused, 2s. per dozen.-Below.

60 Only, Genuine Norton Grinding Wheels,suitable for general shop use, 9' dia., r wide, r hole,4s. 9d. each, also few 1r wide, 5s. 9d. each.-Below.

1,000 Fine Emery Wheels, 2" to r dia., hole,r to I" thick, slightly used, but quite serviceable,ls. M. per doz.-Below.

10s. Orders Carriage Paid except where statedotherwise, steel bars and files carriage extra. --.T.Burke, 80 Tr'poet Lane. Sheffield.

WATCH MAKINGWATCH AND CLOCK REPAIRS. Everything

for the watch, clock and model maker. Large stockof watches, clocks, and clock movements, etc. Wholesale prices. List 3d.-BLAKISTON R CO., Ainsdale,Southport.

CATALOGUE, 7th edition, post 3d. Book onWatch or Clock Cleaning and Repairing, ls.13d., post 3d.Guaranteed Watch, Clock, Optical and Jewellery Repairs,Wheels and Pinions cut. Clock and Watch dials restoredUnbreakable glasses fitted. Per Return Service forTools, Materials and small jobs,-D. Coburn, 47 RedLion Street, Clerkenwell, London, E.C.1.

JOHN MORRIS, Clerkenwell, Ltd., Expertwatch and clock makers, complicated work and newparts to all Watches and Clocks. Jewellery repairs.Estimates free.

JOHN MORRIS. Best house for all Tools andMaterials. Wheel and Pinion cutting. Stamp forlist, 04 Clerkenwell Road, E.C.1.

WOODWORKCABINET HARDWOODS, Oak, Mahogany, Ash,

Whitewood, Ply -woods, etc. Lowest Prices. SendCutting lists. Planing free. Speciality Prime JapOak, all thicknesses.-Wilfred Parr dc Co., MarchWorks, Lancaster Road, Leytonstone, E.11.

FREE SERVICEFOR READERS

READERS requiring informationconcerning goods or services

advertised in PRACTICALMECHANICS should givenames of Advertisers from whomparticulars are desired. Anynumber of names may be includedand we will obtain for you cata-logues, lists and any other infor-mation you may be wanting.THERE IS NO CHARGE FORTHIS SERVICE.Readers desiring particulars from a number ofAdvertisers will, by this method, save time andpostage. Halfpenny stamp only is required if yourenvelope is left unsealed. If any Advertiser stipu-lates that stamps or postal orders are necessarybefore samples or catalogues are sent, pleaseenclose the necessary amount with your instruc-tions. You are cordially invited to make full useof this service.Post this toADVERT. SERVICE DEPT.,

PRACTICAL MECHANICS,8-11 SOUTHAMPTON ST., STRAND, W.C.2

Please obtain and send to me particularsfrom the Advertisers in your November issuewhose names I give on list attached.

Advertiser' Page No. I Information Required

Attach sheet of paper, with particulars, andyour name and address (written in BLOCKletters) with date, to this announcement.

JOHANNESBURG

AIR RACEby

CHARLES

W. A.

SCOTT

Read the thrilling Personal Story of thegreat Air Race which was won by C. W. A.Scott and Giles Guthrie, flying a PercivalVega -Gull -6,450 miles in 52 hours 57

minutes-in THE NOVEMBER

POPuLAR

LYINGTHE NATIONAL AVIATION MAGAZINEAt all Newsagents or Bookstalls, or by post71d. from the Publisher, C. Arthur PearsonLtd., 18 Henrietta Street, London, W.C.2.

611).

NOVEMBER

C. Arthur Pearson, LW.

All applications respecting Advertising in this Publication should be addressed to the ADVERTISEMENT MANAGER, GEORGE NEWNES5-11 Southampton Street, Strand, London, W .C.2. Telephone: Temple Bar 4303. -

ii i

LTD.,


"In PROVE hronly 7 DaysI that I Can MakeYOUaNew Man!"

No other PhysicalInstructor in theWorld has everDARED makesuch an offer!

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MI NM NM WM UM IICHARLES ATLAS, Dept. 10-L

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1 want the proof 'that your system of Dynamic=Teristonwill make a New Man of me-give me a healthy, huskybody and big muscle development. Send me your book." Everlasting Health and Strength." FREE,

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1I

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as he is to -day

48 -Page Book FREEIt tells you all about my DYNAMIC -TENSION method,and what it has done to make big -muscled men out ofrun-down specimens. What my system did for me andthese hundreds of others it can do for you, too. Don'tkeep on being only half of the man you CAN be! Findout what I can do for you. There is no cost or obligationof any kind-and no one will call on you. Whew shall I

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Published about the 30th of each month by GEORGE NEWNE'S, LiDdilif:D, 8-11 Southampton Street, Strand, London, W.C.2. and. Printedin Great Britain by H.V.El.r.W ATFON It Crne y. LTI).. London and Aylesbury. Sole Agents for Australia and New Zealand --Gordon It Got h Ltd. Sole Agents for South .Afilea-Central News Ageney

Ltd. Subscription, Sate!;: Inland and Alitioail. 7s. lid. per annum Ciiniels,. 7s. per annum.


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