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February, 1937 NEWNES PRACTICAL MECHANICS 249

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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 principles, 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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THE ILLUSTRATIONSThe book is lavishly illustrated so that the explanations

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250 NEWNES PRACTICAL MECHANICS

qiitIMPORTANT GUIDEto SUCCESSFUL

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February, 1937 NEWNES PRACTICAL MECHANICS 151

PRACTICAL t,MECHA\ I CS 4;1

A Cable RailwayA HALF -MILE long cable railway cros-rlsing the Seine from the first floor of theEiffel Tower is the latest idea for the amuse-ment park of the 1937 InternationalExhibition. Passengers will be carriedin aeroplane -shaped cars, the fare being,roughly, is.

Ever -greensGOLF greens that turn brown are now

being dyed a bright natural green in theUnited States. The dye costs 2s. 6d. agreen, lasts a fortnight, is not washed out byrain, and does not harm the grass.

The Photo -electric Cell Again

SOUTHENDpolice and fire brigade have

been experimenting with a local man'sinvention, which detects burglars and fires,and telephones for the proper authority.This is just one more use for the electric eye.

A New Motor -launchON the Thames recently appeared a novel

type of motor -launch. It is the fastestever built in England and is destined for theTigris and the Euphrates for river patrol-ling. Its estimated fuel consumption is agallon for every two miles.

An Underwater ExpeditionWE learn that Sir Hubert Wilkins, the

explorer, hopes to have a submarinespecially built for the purpose of makinganother scientific underwater expedition tothe Artic.

Linking the Baltic and Black SeasTHERE is a possibility that the Baltic

and Black Seas may be linked by a systemof canals. The canals would link theVistula and Dniester rivers. It is estimatedthat the cost of the work would be£10,000,000.

An Italian Motor -flyerASPEED of more than 100 miles anhour was reached by a new streamlined

motor -train, which recently ended its firsttrials between Turin and Venice. Thetrain consisted of three carriages locked to-gether to prevent unnecessary wind resist-ance, and to preserve the streamlining. Itwas driven by a motor of 1,100 h.p.

Only One Television System

THE Television Advisory Committee arenow contemplating standardising themethod of television transmission. Insteadof two different systems there will be one-simplifying matters for the B.B.C., the radiomanufacturers and the listeners. Atpresent each of the two systems is takenalternately and every looker -in has to ra-

EDITED BY F. J. CAMM

VOL. IV. No. 41

FEBRUARY

1 9 3 7

NOTES, NEWS,AND VIEWS

adjust his apparatus each Monday whilethe B.B.C. changes studios, transmittersand lighting at Alexandra Palace.

Showing the attractiveappearance of the bound

volume of " Practical Mechanics."

" Blind Landings "AT London's premier airport, landings,

when visibility is almost nil, are nowpossible with the aid of a new radio " blind -landing " system.

SUBSCRIPTION RATESInland and Abroad. 7s. 6d. per annumCanada - - 7s. per annum

Editorial and Advertisement Offices : " PracticalMechanics," George Newnes Ltd.

Tower House, Southampton Street, Strand, W.C.I.'Phone : Temple Bar 4363.

Telegrams : Newnes, Rand, London.Registered at the G.P.O. for transmission by

Canadian Magazine Post

Two-day Transatlantic Mail ServiceBRITAIN'S hope of starting a two-dayTransatlantic mail service this year lies

in a £25,000 'plane being completed for theAir Ministry behind locked doors at Hat-field, Herts.

A New Transmitting StationACCORDING to Mr. Guillon, the Resid-

ent -General, a 100 kw. station is con-templated for Tunis, and the cost of thetransmitter will be met by the FrenchGovernment.

An Electronic " Nose "THE General Electric Company of

America recently announced that theyhad developed an electronic " nose " havinga sensitivity about one -fifth of the humannose. It was developed for detectingminute traces of mercury vapour in the air,and consists of a photo -electric cell andassociated apparatus.Telephones for Russian Villages

OUT of a total of 1,470 village Soviets inthe White Russian Soviet Socialist

Republic, 1,215 are equipped with tele-phones, and it is planned to instal tele-phones in the remaining villages this year.A sum of one million roubles was expendedin 1936 on the installation of telephones inthe rural districts of White Russia.New Power Plant in Donetz BasinTHE construction of a huge heat and

electric power station with a capacity of800,000 kw., to be operated on coal dustfrom the waste of the coal concentrationplants in the Donetz Basin, has been com-menced in the Stalino district of Donetz.In order to meet the tremendous waterrequirements of the station (about 200million litres per hour when working at fullcapacity) an artificial reservoir of a volumeof 52 million cubic metres will be built nearthe station.The Cup and the Grip

WHEN one holds a cup of tea it is notalways possible to obtain a firm and

comfortable grip. An American inventorhas designed a cup having at one side ofthe handle a thumb hole and a rectangularrib slightly greater in length than the hole.This device should prevent many a slip'twixt the cup and the lip.Corpatact Devices

THECorpatact Manufacturing Company

of Iver, Bucks, wish to advise all agentsand clients who are interested in Corpatactdevices, that these can now be obtaineddirect from the manufacturer and patenteewho is the owner of the registered trademark " Corpatact." All enquiries will haveimmediate attPntion.

252 NEWNES PKACTICAL MECHANICS

The Emitron Camera, or Electric Eye, in action at Alexandra Palace.

BEFORE describing the modernmethods of sending and receivingpictures by radio it is necessary to

examine the history of television, althoughit is obviously impossible to cover everyphase of its development in a short articleof this nature. Stated briefly, it may besaid that a picture is illuminated througha rotating perforated disc placed in frontof it, with the result that the perforationswill pass across the picture in a mannerdetermined by the arrangement of the per-forations. Some form of light sensitivedevice is then so placed that the lightreflected from the subject is picked up, andthence converted into electrical energywhich is sent out by a wireless transmitterin exactly the same way as the ordinarysound programmes with which we are all sofamiliar. In the first television systemsto be used in this country the disc wasperforated with thirty holes and thesetravelled across the picture from one sideto another, thereby dividing the pictureinto thirty separate lines, and hence wasknown as the thirty -line system. As eachhole travels up the picture it is seen thatat any one moment there would only beone small part illuminated, but owing towhat is known as the persistence of visionthe re-created picture at the receiver endappeared as a complete element and not aseries of dots. In order fully to understandthe improvement of the modem systems itmay be stated that the disc at the receiverend rotated at 650 revolutions per minuteand that the actual size of the picturewas about 21 in. by 11 in. and to enableit to be viewed in comfort a magnifyinglens was placed in front of the scanningdisc.

High -definition TelevisionIn the modern systems the scanning

disc is still retained on the transmittingside for many of the broadcasts, althougha new type of scanning device is employedfor certain direct transmission, as will bedescribed later. In order to providegreater detail there are many more holes inthe disc, and the disc is much larger.There are 240 holes, thus giving 240 lines,and there are 25 complete picture move-ments per second. This means that thedisc has to rotate at a tremendous speed,and to enable it to do this satisfactory it ishoused in a special chamber from which theair is evacuated. The bearings are watercooled, and to ensure safety against acci-dents the air pump and the water pump areinterlocked with the electrical supply, sothat in the event of failure the motor turn-ing the disc is stopped. The actual speedof the disc is 6,000 revolutions per minute,and in the Baird Spotlight transmitter usedat the Alexandra Palace two discs are used,one with the 244) holes arranged in fourspiral traces of 60 holes each near the outerrim, and the other with a spiral slit whichacts as a rotating shutter and thus onlypermits one hole to come into use at atime.

A similar piece of apparatus is alsoemployed by the Baird Company in con-junction with ordinary cinema films, andthese pass through a machine very similarto an ordinary cinema projector, but in-stead of passing tough in jumps as in theordinary film it plsses through at a steadyspeed. The artists in the studio are photo-graphed by an ordinary cinema camera(using a 17.5 mm. film) and the film passesthrough a tank divided into six compart-

February, 1937

A Detailed ExplanoLanguage, of the

Transmissionments, where it is developed, washed, fixed,washed, passed before the scanning discsand so transmitted. There is a lapse ofonly thirty seconds from the taking of thepicture to its radiation from the aerial inthe form of electrical energy, and this systemis known as the Intermediate Film Process.

TelecineTo add to the entertainment which may

be provided in the studio ordinary cinemafilms may be scanned and broadcast in amanner similar to that outlined above,except, of course, that the developing andother processing tanks are not required.This system of television is now generallyused by manufacturers for research pur-poses, as it avoids the necessity of a studioand living performers, and enables a sceneor event to be repeated over and over again,which is ideal for comparative purposes.

The Electric EyeAlternating with the above apparatus is

that supplied by the Marconi-E.M.I. Com-pany, and this is generally referred to as the

Electric Eye." Its technical name is theEmitron Camera, and it is to all outwardappearances a cinema camera. It ismounted on a travelling carriage with anoperator behind it, and it may be swung invarious directions just as in the case of astandard cinema camera. It is provided

This illustration shows the internal arrangement of theModel T.5 Baird Televisor. The large tube which is

employed may clearly be seen.

February, 1937 NEWNES PRACTICAL MECHANICS

011 TIIENISIONation, in NonotechnicalModern Systems of Televisionand Reception.with a lens, and it " takes in " the scene inexactly the same way as a cinema camera,but it converts the scene into electricalenergy without the intervention of the film.It is one of the most wonderful pieces ofapparatus which can be imagined and en-ables outdoor events to be televised and,owing to its mobility, it may be run alongthe ground so that a tour of inspection of alarge stationary object may be transmittedor any similar arrangement carried out.The Marconi-E.M.I. apparatus also includesa tele-film unit similar to that alreadydescribed, but in all of the transmissionsemploying the Marconi-E.M.I. systems aslightly different arrangement of thepicture is given. Instead of a 240 -linepicture repeated 25 times per second, eachpicture consists of 405 lines, and each altern-ate picture is interlaced with the previousone. In this way we obtain the equivalentof a frequency of 50 pictures per second,each picture consisting of 202.5 lines, andthe line frequency being 10,125 lines persecond. So much for the brief details ofthe transmitting systems, and now wemust examine the problem of reception.

The Cathode-ray TubeAs the definition is now so high, we can

take advantage of more elaborate methodsof reproducing the picture, and moderntelevision utilises what is known as thecathode-ray tube. This may be considered

A time -base unit with cathode-ray tube inposition, which shows the size of the tube

compared with ordinary valves.

as a giant wirelessvalve, as it incorpor-ates filament, cath-ode, grid and anodes,and an electronicstream from the cath-ode is employed ex-actly as in a radiovalve. In the cathode-ray tube, however,the electron stream ispassed between twosets of plates arrangedat right angles to oneanother, and by ap-plying various volt -

The G.E.C. televisionreceiver removed fromits cabinet. The doubletime -base is in the fore-

ground.

LOU SPEUIR

CATHODE RAY TUBE

SOUND It VISION AMPLIFIER

DOLIfitt !ME RASE

ages to these plates it is possible to move theelectron stream. At the end of the cathode-ray tube the glass is brought out' to a largesurface, and this is coated on its inside witha special chemical which glows under theinfluence of the electron stream. Conse-quently, if the stream is drawn steadilyfrom one side to the other it will trace a lineof light upon the screen, and the fourdeflecting plates, as they are called, areconnected to a special electrical circuitknown as a time base, with the result thatthe voltages applied to the plates changein a regular order. This causes the spotof light on the end of the tube to travel notonly across the screen but slowly down-wards, and so a large rectangular lightpatch appears to the eye. In the modernreceiver this is generally about 10 in. long

253

On the leftis shown adiagram-matic ar-rangementof the com-ponent as-semblies ofa G.E.C.television re-

ceiver.

by 8 in. in height, and the number of linesmust coincide with those at the trans-mitter. Elaborate synchronising systemsensure that the spot in the receiver keepsstep with the spot at the transmitter, andnaturally a slight alteration has to be madeat the receiver end in order to adapt it forthe reception of the Baird or the Marconi-E.M.I. systems as just described.

The Vision ReceiverThe wireless signals are picked up by a

standard wireless receiving circuit, and inorder to preserve the high details specialforms of coupling are employed and thetransmissions take place on a very shortwavelength so as to enable a full range ofvariation to be covered without interferencewith other stations. At present the

254 NEWNES PRACTICAL MECHANICS

The Marconiphone Model 701 has a reflector to enablethe vertical cathode-ray tube to be viewed.

The Pye model shown here incorporates an auto -radiogram. Direct vision is employed.

February, 1937

The Philips receiver is fitted to a neatchromium stand to increase the height of

the viewing screen.

This is the smaller Ferranti Model, with adirectly -viewed screen. A cathode-ray tube isalso used in these receivers, a 10 -in. diametertube being provided and the approximate picturesize being 9 in. by 7 in., with a colour imagedescribed by the makers as" electric light white."

February, 1937 NEWNES PRACTICAL MECHANICS 255

This illustration of a relay of a Mannequin Parade shows the studio technique when the " Electric Eye" isemployed. The" camera" is in the centre foreground, and the operator is wearing headphones.

picture is sent out on a wavelength of45 megacycles, and the accompanyingsound is transmitted by standard broad-casting apparatus on a wavelength of 41.5megacycles. Thus, therefore, to receiveboth the picture and its accompanyingsound, two separate . wireless sets arerequired, but it is possible to arrangethat only one tuning control need beused, by adopting a modern super-heterodyne receiver. The variationsin signal strength coinciding to thelight and shade of the picture are ap-plied to the grid of the cathode ray tubeand modify the strength of the electronstream, thus giving rise to a variationin the brightness of the spot on the endof the tube and in this way the pictureis built up. The sound is fed to aloudspeaker just as in ordinary broad-casting.

Television ProblemsThis, then, is a brief outline ,of the

system as at present in use, but thereare many problems to be overcomebefore a perfect picture may be seenin the home. Firstly, the quality pro-vided by the vision receiver must bewell-nigh perfect if the picture is to befree from distortion. Where slight dis-tortion may be tolerated in a loud-spe4ker, any marring of a picture willoffend the eye. Owing to the veryshort wavelength used for the broad-cast, interference is experienced frommotor -car electrical apparatus such assparking plugs, and thus the aerial atthe receiving end has to be of a specialtype and erected as far from the road-way as possible. Usually, best resultsare obtained when the aerial consistsof a vertical wire measuring one-halfof the vision wavelength, and it is cutin the centre and two wires led awayto the receiver. These are sometimesscreened to avoid the picking up ofelectrical interference.

Furthermore, the speed of the spot-light trace on the end of the cathode-ray tube must be exactly in step withthe transmitter, and thus the time -basecircuit must not only be well -designed

and built, but must be placed in such a posi-tion that it is free from interference with theremainder of the apparatus. In a moderntelevision receiver, the various parts are usu-ally built as separate units, as this not onlyfacilitates testing, replacements,etc., but also

In this Marconiphone Television Receiver the reflectedmethod of viewing the screen is employed.

enables the apparatus to be disposed inside acabinet to the best advantage, both from apoint of view of convenience and of electricalefficiency. In the diagram of the G.E.C.apparatus which is shown, it will be seenthat the sound and vision receivers arecombined on one chassis, the time base onanother and the power pack or mains uniton another. Extremely high voltages areemployed with the cathode-ray tube, andit is usual to obtain 4,000 to 7,000 volts forthe anode, so that very high insulation hasto be obtained. The method of connectingthese separate units together also has toreceive careful consideration to avoiddistortion of the picture due to interferencefrom adjacent leads.

The Future of TelevisionThe end of the cathode-ray tube is gener-

ally viewed direct, as the picture is suffi-ciently large for adequate viewing by quitea number of people, and is sufficientlybrilliant to be viewed 'in the home underordinary domestic lighting conditions.In one or two receivers the manufacturershave placed the tube in a vertical positionand the lid of the cabinet is provided witha reflecting plate or mirror, so that whenplaced at an angle of 45° the reflectedimage on the end of the tube may be seen.In one case, a small tube is employed inthis way, and a lens is interposed betweenthe tube and the mirror to provide a largerpicture. The majority of pictures arebrilliant black and white, but it is possibleto obtain tubes which give a blue or greenpicture. So far it is impossible to providea coloured picture, that is, one in which

each part is reproduced in the originalcolours of nature. Attempts have beenmade experimentally to split up thescanning trace through filters to givea picture in natural colours, but havenot been entirely successful. Onemethod of achieving this object wouldbe a spinning disc in front of thecathode-ray tube suitably divided intothe three primary colours, the ar-rangement being in effect that eachpicture is framed in each colour inturn, the transmission being so con-trolled that the " light " portions ofeach picture are controlled by the colourvalue of the object or scene to betransmitted. In actual practice, ofcourse, the three primary colourswould have to be modified, as thesource of light (the cathode-ray spot)is not truly white. There is, however,little likelihood of such an arrange-ment being adopted for many years tocome, and it is also questionablewhether the present technique of trans-mission allows for a sufficiently steadypicture to be broadcast to enable thecolour to be obtained. Attemptshave also been made to project theimage from the end of the tube througha lens so that it could be shown in anenlarged form on a screen. No doubtthe time will come when the imagewill be projected stereoscopically andin natural colours, but this appears tobe a long way off. Certain mechanical systems are being experimented with,in an endeavour to avoid the use ofa cathode-ray tube and its limitations,but no details have been released bythe people using these systems andconsequently no details can be givenother than that a rotating prism isemployed in conjunction with a seriesof mirrors rotating at high speed.Whether or not this will provide thesame results as the cathode-ray tubesystems remains to be seen.

256 NEWNES PRACTICAL MECHANICS

The Arrangement of the Cathode-ray Tube and Chassis of the Cossor TelevisionReceiver. The Picture is Reproduced on the 13i -in. Diameter Cathode-ray

Tube, the size being Adjusted to Approximately 10 in. X 71 in.

February, 1937

February, 1937 NEWNES PRACTICAL MECHANICS 257

I ilk, It 1171 --r on A II\ lea Is .2 .11L-- 411 I I NO \ I ' a. l& 1... NM/ IM /V II NNW 411.--M II Uk -MI II M ..11 11Ik MN I& Nu u.MUM. =11., M PO M NOW 111 simEM. 'WV

THERE is probably no transport servicein the world which expends so muchtime and money on progressive de-

velopment as the London Passenger Trans-port Board. Thousands of pounds arespent yearly on experimental equipmentand a huge staff is constantly working toincrease the efficiency of the huge system,and comfort of the passengers. When onetravels on the existing underground trains,and notes the efficient and comfortablestandard which is maintained, it is some-what difficult to imagine any possible im-provement. The new tube trains, how-ever, which are shortly to be put into ser-vice, after exhaustive tests have beencarried out, incorporate many new featuresdesigned to increase comfort and give in-creased performance.

More RoomIn the tube trains now in use, a special

compartment had to be provided to accom-modate the electrical equipment. On thenew cars, however, this equipment is housedunderneath the train in a specially designedcradle and thus the " engine -room " iseliminate dand extraspace isavailablefor 'passen-ger accom-modat i o n.A six - cartrain of thenew typewill haveapproxi m -ately thesame carry-ing capa-city as aseven - cartrain of theexistingstock.Each carwill carry40passengerand havethe usualtwo occas-ional seatsfor use dur-ing peakperiods.

r-1 1T1OFTHE

inrII- I NUM IIr". IL, IL_ 11.I Ilmmor WEN.4 mik

Many Novel Features areIncorporated in the NewElectric Trains Shortly tobe Put into Service by theLondon Passenger Trans-

port Board

Improved AccelerationAn existing six -car train has four

driving motors, totalling 960 h.p., whilst onthe new type twelve motors will be em-ployed giving a total horse power of 1,656.The acceleration will be at the rate of twomiles per hour per second and speciallydesigned control system will insure asmooth " get -away."

Fifty per cent. of the axles have beenmotored, this arranging for a greater pro-portion of train weight to be available foradhesion. A multi -notch system of control

.1111.1MOMMIIMOIMI

is employed which, by cutting out the start-ing resistance in small decrements, reducescurrent peaks and allows the acceleratingcurrents to be increased much nearer to theslipping point than has hitherto beenpossible.

Better BrakingA new braking system has also been de-

vised which gives a rate of retardation ofthree miles per hour per second. TheWestinghouse Brake & Signal Companyhave co-operated in the production, bydesigning an entirely new type of brake forindependent wheel braking. This systememploys eight air -operated brake cylindersmounted on each bogie, complete with auto-matic slack -adjusters. Electro-pneumaticcontrol is the result of much experiment andthe high rate of braking has been madepossible by using an automatic retardationcontroller which keeps the decelerationpractically constant over the whole speedrange. This type of control allows in-creased brake cylinder pressures to be usedat the commencement of braking when theco -efficient of friction is lowest. This gives

a gradualautomaticrelease ofpressure asthe frictionco -efficientincreasesand thetrain isbrought toa standstill.

The Trac-tion Motors

Thesemotorshave had tobe speciallydesignedfor use inthe limitedspace avail-able. Theyare rated at13 8 h. p.,giving atotal horsepower o f1 ,6 5 6, asalready

258 NEWNES PRACTICAL MECHANICS

stated. The motors are mounted on the in-side axle of each bogie and incorporate a newtype of roller -suspension bearing in theirdesign.

The bogies are of all -welded construction,are fitted with 31 -in. diameter wheels andthe wheel base is 6 ft. 3 in.

New Body DesignThree of the experimental trains are

streamlined to reduce wind resistance when

running on open stretches of line. A semi -elliptical nose at each end of the car in-corporates the driver's cab, whilst thewindows have been brought out flush withthe outside panels of the car. The windowpillars, slimmer than hitherto and of tri-angular section, give the general appearanceof one long window and give a better out-look. The bodies are carried on a weldedsteel underframe, the main longitudes ofwhich have been constructed to form airducts for use with the ventilating plantwhich is thermostatically controlled. Specialgears and wheels with silencing deviceshave been incorporated and in some casesthe car -sheeting has been sprayed with" anti -poise " composition.

Steadier lighting has been arranged froman independant 50 -volt supply, and diffusedlighting fittings give adequate light withoutshadows.

These fittings take the form of flutedoblong shades, housed in chromium -platedframes and are located in a line on eitherside of the centre roof section.

Each of the new cars is 52 ft. 51 in. long,

An underside viewof the car whichshows Crompton -West faceplate

control gear.

(Left) A wideangle of vision isobtained from thedriver's cab. Theseat has beenturned towardsthe camera forthis photograph.

and is fitted with two double and one singleair -operated sliding doors on either side.These are controlled electrically from the50 -volt supply.

Simplified OperationOn existing stock the cars have to be

interconnected by hand and thus a certainamount of delay is caused in coupling anddecoupling. The new cars, however, havebeen fitted with fully automatic couplers

February, 1937

which are operated by a push button in thedriver's cab. This allows, not only themechanical, but also the electrical andpneumatic connections to be made withoutthe driver leaving his position.

The semi -circular driving cab, of which aphotograph appears, is a vast improvementon the existing type. As will be seen,three large windows give a wide angle ofvision and automatic windscreen wipers arefitted.

The driver's seat is situated in the middleof the cab and the " joy -stick " type ofcontrol is employed ; one " joy -stick isused for driving the train and the other forbraking.

The amount of time, money and thoughtwhich have been expended in producingthese trains may be gauged, to some extent,by the details given in this article, and it isonly due to constant and careful experi-ment that we can claim, in Britain, to havethe finest underground railway system in theworld.

(Left) An impressive view of a new train showing thestreamlined driving cab.

(Above) This interior view of one of the new cars shows theincreased window space. The new lighting arrangement and

novel handstraps are two features worthy of note.

*PP

NEWNES PRACTICAL MECHANICS

Fig. 1.-The 2.4-c.c. " Elf " engine beside Kanga's 25-c.c. engine.Kanga was the first post-war petrol -driven record holder.

Fig. 2. -A three-quarter rear view of the model described showing theclock, and the petrol tank can be seen mounted into the wing.

A Petrol -Driven Model for2.5-c.c. and 3-c.c. Engines

THE 2.5-c.c. engine and the 3-c.c. enginesizes are now a proved success, andhave enabled constructors to make

really convenient sized light and portablemodels.

The 2.4-c.c. " Elf " engine is used in thismodel. The 3-c.c. " Grayson Gnome " isalready on the British market and there are

...... --By C. E. BowdenThe British Petrol Model Aeroplane

Record Holder

must be supported by a larger wing surfaceto keep the wing loading low, but we must

2 ° GFFSETTHRUST

63"- /71'2" - - 3 !/11

23d

several others that will shortly make theirappearance. Now, therefore, is the timeto construct one of these really smallpetrol models. There is the danger, how-ever, of attempting to make too small amodel.

A very small model for these engines canonly be made if strength and general dura-bility and the ability to withstand severeknocks is sacrificed.

In America, where the general flyingweather is far better, it is possible to pro-duce very light petrol models by the entireuse of balsa wood and paper covering.The size of the model can then bebrought down, and yet the model willfly slowly, as a light wing loading is stillobtainable.

A Robust ModelHere in this country we require a

reasonably robust model which means acertain amount of weight. This weight

O

CLOCK

O

not have too much weight or our very small2.5-c.c. engine will not be able to fly themodel. We must therefore compromise.The model to be described is a successfulcompromise, and ' has proved itself anexcellent flying good stabilityin reasonable weather. It is simple tobuild, and has various features in its

DIHEDRAL. ANGLE - /0°

.-12-Fig. 3.-A planview of themodel. Scale1 in. = 12 in.

- 22"

1' 1-k-construction which help to keep

4 weight down and yet retain agood factor of safety, and a robust

model.The weight complete, ready for the

air, is 2 lb.,including clock control forduration of ight. A 2-4-c.c. " Elf " engine,obtained from a Canadian manufacturer, isinstalled, but any good 3-c.c. engine will be asuccess provided a suitable propeller of finepitch is fitted which will allow the engineto revolve at about 3,500 to 4,000 r.p.m.

It is a mistake to cut the re-volutions down on these verysmall engines. They gain

/341 their power on high r.p.m.,T ' which allows a good gas seal

6 between piston and cylinder.A fine -pitch propeller of about12 in. diameter is usually verysuccessful. The " Elf " uses a12 in. diameter and 6} in.pitch.

260 NEWNES PRACTICAL MECHANICS February, 1937

It is possible to cut down the weight asthe Americans frequently do by dispensingwith the clock control for duration offlight, and limiting the petrol supply.

But in this country I do not consider thatthis is desirable owing to its highly popu-lated areas. In the interests of safety, therun of the engine should be controllable towithin a second or so of any desired dura-tion. There is then no danger of the modelflying ouside the flying field. Furthermore,a definite clock control makes the prelimin-

T

" bell " battery of 1,4 volts, and using a verysmall 3 -volt rectangular 2 -oz. battery forflight, because I find this size and shapemore convenient for my method of batteryinstallation. This will be explained lateron under " Ignition Details." I have notfound that the 3 volts of such a small bat-tery has damaged the coil.

The cylinder is an aluminium castingwith a thin steel liner. The bore is 0.542 in.,the stroke a in., and the piston displace-ment 24 c.c. The make -and -break mech-

r- Pknem...TAM-V.1=1 t=. CLOCK;

3&"

4

DouBLE LINES DENOTE 3 Pcv FORMERSREMAINDER - 118"84L.S4 l/PRAINT

CRoSSP/ECESFig. 4.-A side view of the model.

ary test flights safe for the model, as will beexplained at the end of this article underthe heading " Flying the Model."

A model of 14 lb. sounds attractive, but acontrollable machine of 2 lb. is far moresatisfactory, and it has been found that themodel to be described can fly on about halfthrottle. This proves that the wing load-ing is sufficiently light. Actually the modelflies quite slowly and glides very well.

It has been designed for stability and easeof construction rather than beauty of line,although in actual fact the model looksquite well.

The EngineThe " Elf " engine was one of the first, if

not the first, really small engine of 2.4-c.c.that was put on the market commercially.It has set the fashion for another reductionin size for commercially supplied engines.It is a four port two stroke.

Fig. 1 shows the " Elf " engine, side byside with a 25-c.c. engine, and gives someindication of its minute proportions.

I now have two of these engines, and bothare excellent little power producers. Thereis, of course, no import duty on the engine,as it is of Canadian manufacture. Theengine is very carefully made and naturallyto very fine limits, and therefore requirescareful running in on the bench with fre- -quent applications of extra oil. This canbe done whilst the modelis being constructedif the little engine and its wooden base uponwhich it is mounted are screwed down tothe bench.

Its chief peculiarity besides the smallnessof its size is the fact that three piston rings arefitted to the piston, whereas on most smallaero commercial engines to -day, the pistonare fitted without rings. The next mostnoteworthy point about this engine is thata 2 oz. coil and 4 oz. condenser are used, andthe coil operates on only 14 volts with aspecial miniature Champion sparking plug.The engine will therefore run on two 14 -volt" pencil " flash -lamp cells which, together,weigh 1 oz. The ignition weight is thuscut down considerably, as the ordinary6-c.c. and 10-c.c. model engine uses at leasta 4 -volt battery for flight. Actually on mymodel I have been starting on a ground

14

anism is of miniature automobile type.The carburetter is of the single jet type andfed from a float chamber.

The engine weighs 4 oz. The spark coiland condenser weigh 24 oz., and the pro-peller about 4 oz. The engine runs, withthe normal standard propeller provided, atabout 3,500 r.p.m., when it produces 2.8 lb.per brake horse power hour. The engineruns approximately 40 minutes on oneounce of fuel at this speed, and with thepropeller supplied, the engine develops astatic thrust of 9 oz. The carburetter has apetrol adjustment screw but no air adjust-ment. A mixture of petrol and oil be-tween 8 to 1 and 10 to 1 is suitable. Theengine is very sensitive when warming up,

Fig. 5.-Thegeneral arrange-ment of the

fuselage.

STRENGTHEN/HQSTRINGERS OFf(4")(06".5eRacEATNOSE ONLY

CELLULOIDWINDOWS

EL.-FACHABLEELEKTRONNOSEPIECEionvENGINE

model from Figs. 3 and 4, which shows alldimensions necessary. Fig. 5 will also helpboth at this stage and later when the fuselageand its fittings are being made.

The cheapest way to make this drawingis on ordinary white kitchen paper whichcan be bought in long rolls at Woolworth's,or any stores. Next a stout board that willaccommodate the fuselage side elevationmust be obtained. The drawing of thefuselage side view is then placed on thisboard. The drawing is then covered with

greaseproof paper, so that thedrawing can be seen through thepaper, but the fuselage construction

, will not become stuck to the draw -6 2m bg y glue. Construction of thefuselage can now begin.

The FuselageThis is almost entirely made

from balsa wood, but, due to itsconstruction, is very strong. It isof rectangular form in order thatit shall be simple to construct forthe newcomer to model work. Thetop and bottom longerons are of4 -in. by 4 -in. square " medium "balsa wood. These longerons arelaid along the longeron lines on thedrawing and are kept in place by

means of small pins on either side. Twolongerons are placed in position top andbottom, one above the other, so that bothsides of the fuselage are made simultane-ously.

Now 4 -in. by 4 -in. balsa uprights areglued in position everywhere except at No.1, 3, 7, and 13 formers (see Fig. 4). At thesespecial positions 3 -ply wood formers areplaced because these are the points wherewire fittings and strains occur. These 3 -plyformers, except No. 1, are all cut from * in.thick 3 -ply and well fretted out in the centrefor lightness. They are of rectangularshape and their dimensions can be drawn outfrom the side elevation and the plan viewof the Tull -sized drawings. No. 1 former isBALSA BLOCK N5PREVENT

-""UNIT COMING FORWARD

CLOCK HEREBALSA PLATFORMSerArco.e.ezcrANGLE OF ACIOENCE

DETACHABLE UNDER-CARRIASE MADE FROM/4 Sive. PIANO iviREFAIRED wing SILKCOYEREZ7Z544.44.

and requires the spark well retarded. Thestarting is normally easy provided theminute petrol ducts are kept clean, and thecontact breaker points are also kept clean.

The piston is an aluminium casting andhas three piston rings.

The DrawingA full-sized drawing must be made of the

DETACHABLE7.71IL WHEEL,

PORE HooKs70 RETAINTAIL UNITBY ELASTICBANDS

WIRE HOOKS PROTRuONG FROMFUSELAGE (ATTACHED R) SPEGAZ3 ay FORMERS To TAKE ELASTICRETAINING BANDS WHICH HOWCOIL /NS/DEENGINEMOUN7WGHERE

POSITION

3oz. 3 vow- PLASH -LAMP BATTERYSLIPPED BETWEEN FUSELAGE ANDBANDS WHICH//OLD REAR SPRING LEGSacavozecARR/AGE TOGETHER .

4/m68/ AN LIGHTWEIGHT WHEELS

made from 4 in. thick 3 -ply as it is the nose-piece and has to withstand extra strain.

Before fitting these 3 -ply formers, all theuprights must be glued in and the glue sethard. To keep the bottom set of uprightsfrom sticking to the top through any excessof glue, little slips of grease proof paper arepushed between the bottom and toplongerons where the uprights meet the

February, 1937

/85w.G. P/avo WIRE Hooirs.40oEDAFTR CAST/Na.EL 457/C BANOS RETAINEivahvE Atoov ma ToFUSELAGE.ENGINE ZoosBOLT On 'HERE

2/A

NEWNES PRACTICAL MECHANICS 261

!/4 DEEP Box 7,5 Fir/Nro .5paARE Cur INFRONT FUSELAGE

FORMER

Fgoiktr ViEW REAR 14zw.Fig. 6.-A front and rear view of the wooden pattern for acast elektron mounting for the " Elf" or other 3-c.c. engine.

longerons after the bottom set of uprightsare glued into position. The top set ofuprights can then be glued into position.After all are set hard the pins can be re-moved from either side of the longerons, andthe two fuselage sides can be separated.

The rectangular 3 -ply formers can nowbe inserted and lightly bound and glued tothe longerons in their correct positions.Leave fitting No. 1 or nosepiece former

the model by inserting wood pack-ings of various thicknesses until thenecessary corrections are made. Thiswill be explained later under " Flyingthe Model."

There are two methods of makingthis mounting. No. 1 method, althoughit may sound more difficult, and per-haps the only real difficulty in thewhole model, is far the best method.

A casting is made in elektron whichis a very light alloy, 40 per cent.lighter than aluminium alloy.

A simple wooden " pattern " ismade up in 3 -ply wood 116- in. thick asin Fig. 6. The pieces of wood are gluedand pinned with very fine model nails.

The pattern is then sent off to theBirmingham Aluminium Casting Com-pany, Smethwick, Birmingham, whowill make up four or half a dozencastings for a shilling or two each.

These castings can be used for futureengines, and the nosepieces are standard-ised so that engines will be interchangeableon the other models that the constructorwill doubtless make.

If the constructor thinks that this castingmethod is too expensive or not worthwhile,it is possible to make a similar nosepiece upwith brass brackets bolted up to a 3 -plycircle and a 3 -ply square bolted up to the

Fig. 7.-A view of the model m flight.

until we have discussed its special shape andconstruction under " Engine Mounting."A streamline rail end to the fuselage ismade from a small piece of solid balsa wood.

The Engine Mounting and Fuselage FittingsThe engine is mounted on a detachable

nosepiece which is an electron casting.Fig. 6 shows details of this mounting, whilstFig. 5 will show it in position on the fuselage.

This mounting will save endless damageto both the engine and the fuselage for it iskept in position to the fuselage by rubberelastic bands, and can be knocked out ifthe model makes a bad landing or strikesany object that it was not intended to flyinto.

It will be observed that the mountingis located to the circular No. 1 former by araised square built integral on its backplate which fits into a square cut out in theNo. 1, / in. thick, 3 -ply circular former.There are wire hooks on the mounting andwire hooks bound on to the No. 3 former(3 -ply). Elastic bands of just sufficient ten-sion to take the engine thrust keep themounting hard up to the nose former.

The idea is simple, but extremely efficient,for not only does it prevent damage if therubber tension is correct and the mountingcan knock out, but it allows the engine tobe withdrawn in a moment for adjustments,and it also allows alteration of thrust lineand offset thrust to be made when testing

The rest of the model is comparativelyplain sailing.

Now look at Fig. 5, and it will be seen thatthere are various wire hook fittings thatmust be attached to the 3 -ply formers bybinding with thread and glue. 20 s.w.g.piano wire will do for these.

First of all there are the hooks lookingforward from No. 3 former. These allowelastic bands to hold in the engine. Thenon the same former there are hooks lookingupwards. Also at former No. 7. Thesehooks accommodate elastic bands to keepthe wing in position. At former No. 13,there are similar hooks to keep the front endof the tailplane in position, whilst there is asingle hook right at the stern of the fuselageto keep the stern of the tail down by meansof a band from this hook to a hook fixed tothe bottom end of the rudder or fin.

These wire hooks are all located about1/ in. from the top run of the fuselage sothat no unsightly bands go round or crushthe fuselage, and yet there is sufficientelastic band to cause a springing effect, toprevent damage to either wing or tail unitif it receives a blow.

The undercarriage is detachable (see Fig.9). Therefore two brass, or better still, ifobtainable, two duralumin tubes are boundacross the bottoms of formers Nos. 1 and 3.These are also glued, and have to accom-

Fig. 8.-The finished model, showing the clock mounted just behind the wing.

rear of the circle. This method is satisfac-tory, but not so rigid, of course, as the brassbrackets may bend and become damaged.It is also heavier.

BRASS TUBES ATTACHED 10 FUSELAGE

CATCHES FORELASTIC BANDS\

IBOUND &

'SOLDERED

BALSA FAIRING_BOUND WITH SILK S. DOPED

14 S.W.G. SPRING STEEL WIRE

Fig. 9.-Details of the main chassis.

modate 14 s.w.g. wire prongs. Two smallertubes are bound across the fuselage at for-mers 13 and 14, for the detachable tailwheel. Finally a wire hook is placed point-

ing downwards on eachside at former No. 7. Anelastic band passed fromthese hooks and aroundthe bottom of the fuselagewill keep the little rectan-gular battery for flight upto the bottom of the

fuselage.A few strengthen-

ing stringers of -in.by 4r -in. spruce areplaced around the

nose between Nos.1 and 3 formers.These help tomerge the rectang-ular fuselage into a

rounded nose(see Fig. 5.)

(To becontinued.)

41,1INIM/I1ar

262 NEWNES PRACTICAL MECHANICS February, 1937

-111-11E ILATI'1ST I

QUITE a new interest has been createdin the interesting hobby of modelrailways by the advent, last year, of

an entirely new system of small gauge electricrailway, introduced by Messrs. Bassett-Lowke, Ltd., of Northampton.

New Methods of ConstructionThis railway, known as the Trix Twin

Train, is " 00 " gauge of in. between rails,and incorporates many new methods of con-struction. The locomotives are propelledby specially designed electric motorsworking off either 14 volts a.c. or 12 voltsd.c., with a system of wiring the track andcontrol whereby two trains can be operatedon the same track at the same time, re-versing, stopping and starting, the commonreturn being made through the centre rail.The track also has the special feature of beingmounted on a moulded Bakelite base withneat snap connections, making it rigid whenbuilt, yet easily detachable for transportand packing.

AccessoriesTwin train accessories include goods

vehicles of every type, overbridges, signals,electrically controlled points, buffer stops,and, last but not least, an excellent range ofstation buildings.

Mr. C. Grasemann, Publicity Officer of theSouthern Railway, was quick to realise thepotentialities of this novelty and, in col-laboration with him, Messrs. Bassett-LowkeLtd. have just placed on the market anactual scale model, representing one of thenew electric trains, which will run on

N TWIN TIRAINS

A Southern Suburban electric train.

Further Developmentsin Gauge " 00 "

the London -Portsmouth service, when theelectrification of this line is finished in Juneor July. This model outfit consists of motorcoach, two trailing coaches, an oval of

the new " Southern Electric " the electricmotor and reverser had to be entirelyredesigned, the motor being incorporated inthe front bogie of the coach and thereversing mechanism in the rear bogie. Theresult is most successful and the generalappearance and outline most realistic.

Restaurant CarsBesides the 1st -class coach and the brake

The motor -coach chassis showing the motor and reversing mechanism.

track, controller and connection, completein a distinctive box, and costs 55s. Tomaintain the correct outline and detail of

A model of the Southern Electric motor -coach

third supplied in the set, Messrs. Bassett-Lowke, Ltd., are also making RestaurantCars and 1st and 3rd class CompositeCoaches. All the vehicles are bogie onesfitted with automatic couplings, and arenearly 7 ins. long. The general arrange-ments are standard with the steam trainsets now on the market, but this model isthe first attempt to give a real scale appear-ance to the " 00 " gauge Twin Trains.The set is made up in an attractive boxcovered with green enamelled paper and amulti -coloured label specially designed bythe Southern Railway Company.

Unique TrainsThis is one of the most unique trains sets

ever placed on the market and should domuch to popularise the well-known electricsystem of the Southern Railway, whichalready has 1,396 miles of track electrifiedand 2,294 electric vehicles in service.

This fascinating model set is now obtain-able from Northampton or from the retailBranches of Bassett-Lowke, Ltd., at 112,High Holborn, and 28, Corporation St.,Manchester. All the leading toy dealerswill also have this new line on show.

February, 1937

The Theft of CyclesTWO officers from Scotland Yard

recently called at my office, notto arrest me as perhaps many of

my enemies might wish, but to ask myassistance in drawing the attentionof cyclists to the great increase in thetheft of bicycles, and to ask theirco-operation in making it easier forthe police to restore those bicycles,when they are found, to their rightfulowners. Thousands of bicycles arestolen every year, and in many casesonce the thief has achieved the objectof the theft, namely, to escape fromthe police, or to escape from the sceneof another crime as quickly as pos-sible, he abandons it.

In many cases the police are unableto identify the machine from themeagre description which the ownergives to the police in the district inwhich its loss is reported. It is oflittle use to tell the police that youhave lost a B.S.A. bicycle. ' Theyprobably have hundreds of them.It is necessary for you to give theframe number, description of the con-dition of the bicycle, and a list of acces-sories. A good deal of this troublecould be avoided if every owner of acycle kept a note in his diary, and athome (to avoid any possibility of itbeing mislaid), of the frame number.Additionally, he should write his nameand address and the frame number ona postcard, using ink or an, indeliblepencil, roll it, place it in the seatpillar tube and plug the end of thelatter with a cork.

My associated paper The Cyclisthas dealt with methods of foiling thecycle thief in recent issues, and I regu-larly receive letters from readers of itasking my assistance in the recoveryof &bicycle which has been stolen.

The Army, the Navy and the AirForceOWING to the shortage of recruits

for the services I understand thatconditions of, service are to be madeconsiderably easier in the future. Inthe past it cannot be denied that theArmy and the Navy have not held out

NEWNES PRACTICAL MECHANICS

much attraction for recruits. You donot expect armchairs and feather bedswhen you join one of these services,but a good deal of the brusqueness ofthe Sergeant Major is unnecessary andhas acted as a deterrent. A littlepower given to a man who has risenfrom the ranks will sometimes turnhis head. The justice meted out to aprivate with a grievance has oftenbeen of primordial character. Allthat is to be changed, and thosereaders who are on the threshold of acareer should bear in mind that bothof these services offer excellent oppor-tunities to men. of the right physiquewho do not object to the necessarydiscipline and who are not squeamish.The Air Force is a branch of the ser-vice which in the future will probablybecome the senior service. The op-portunities in the Air Force arenumerous. I shall be glad to advisereaders as to the best methods ofentering any of these services.

The TruthMY views are not necessarily

yours, and it is quite possible,as I indicated when I started thisfeature, that you will disagree with meat some time or another. I mentionthis because a reader wrote to me theother day violently disagreeing withmy remarks about inventors.

Letters from readers are alwayswelcome, and I carefully read andreply to all of them. Those, however,who threaten to discontinue theirpurchase of the paper unless I publishmore matter about a certain subject,or refrain from expressing criticisms

263

leave me quite cold. It is the correctfunction of a periodical to criticise, tocomment, and even to advise. At aperiod when it seems almost indecentto tell the truth, the press of thiscountry is still a free press, though itmay be muzzled in political directions.A technical journal is not fettered norshackled in this way ; and when youdisagree with my point of view, it isalways wise to remember that quiteoften I disagree with xou !

Contributions from ReadersON my desk is a note from a

reader who wants to enter journa-lism. He thinks that by taking myadvice and by my influence his entryto the street of ink could be renderedmore easy than by treading -the thornypaths of provincial journalism andencountering the hard knocks ofadversity which are the lot of thestruggling scribe. My advice is thatthere is no royal road into any pro-fession, nor is there any reliable meansof avoiding the drudgery from whichvaluable experience is gained. Tothose who aspire to write for technicalpapers I would say this : Get a job ina factory, become apprenticed, applythe knowledge you have gained atschool, spend at least five years in thisway, gain experience with a variety offirms, and then you will be able towrite for the information of others.A youth of seventeen cannot beexpected to do more than regurgitatethe knowledge he has gained at school,and editors have no need to buy suchmaterial, which cannot bear the stampof authority.

"PrW"..MEWT,WWWIRPrrierimr^,"^""FRWMPIF

264 NEWNES PRACTICAL MECHANICS February, 1937

°ALTON'S WHISTLEMICROMETER ADJUSTMENT

PISTON

OUND, as everyone knows nowadays,is due to vibrations or waves. Soundwaves which are capable of being

heard by ordinary human beings rangefrom about 60 to 40,000 semi -vibrations asecond, whereas those undulations whichwe know as heat, begin at 65,000,000 vibra-tions, whilst visible colours range from 400to 900 trillions.

Let us consider, very briefly, the compassof the notes given by one of the best knownmusical instruments-the organ-whichoccupies the whole field of audible vibra-tions, nearly 10 octaves ; the piano has about7 octaves. The pipes in an organ varyimmensely in both length and breadth, anda Galton's whistle is nothing more or lessthan a minute organ pipe.

For special purposes, pipes have beenconstructed varying in length from 20metres to 0-5 millimetres and in frequencyfrom 8 p.p.s. to 100,000 p.p.s.

Now the limit of audible sound vibrationsvary considerably in different people, manypeople being incapable of hearing the chirpof a grasshopper or the twittering ofsparrows, whilst there are others who claimto have heard specially constructed tuningforks giving vibrations of about 70,000 asecond. These intensely shrill notes pro-duce an undefinable uneasiness in a personwhich lingers for some time. There islittle doubt that some animals hear soundsquite inaudible to human beings. Humanaudibility also varies with age.

Pure NotesIn experimental acoustics, first import.

ance attaches to those sources of soundwhich emit pure notes, consisting of a singlefundamental tone unaccompanied by har-monics or overtones (see Fig. 2 ). The fluteand diapason pipes of an organ give thenearest approach to purity. Tuning forks,when vibrating in their simplest manner,give remarkably pure notes, and anotherextremely good example is an ordinary tinwhistle.

Calton's WhistleIn order to determine the limit of audibil-

ity in human beings and as far as possiblein animals, Galion devised a miniatureorgan pipe in the form of a whistle providedwith certain adjustments, blown by meansof a rubber pressure ball similar to thatused on scent sprays (see Fig. 3).

Experiment with Whistling KettleIf you happen to possess a whistling

kettle try the following experiment. Half -fill the kettle with water and place it on a

BY V+ E+ JOHNSON> M+A+WITH THIS TYPE OFWHISTLE IT IS POSSIBLETO DETERMINE THELIMIT OF AUDIBILITY OF

THE HUMAN EAR

Fig. 1. Edelman's Whistle.

gas -ring, with the gas turned half on, andleave it until the kettle is whistling shrilly.Then slowly turn the tap full on, noting therise in note until it becomes quite inaudible.This experiment will illustrate, in a veryintensified form, what you actually hear witha Galton's whistle

A Very Simple Type of Calton's WhistleObtain an ordinary penny tin-whistle-

it must be one that whistles with all theholes closed. Cut the whistle in two, justabove the top hole, and discard the bottom

Fig. 2.-In experi-mental acoustics,first importance-

IMPURE NOTE

-attaches to thosesources -of soundwhich emit purenotes.

PURE NOTE

half. Next, take a piece of metal rodwhich will just go in the bottom (un-fortunately these whistles are slightlytapensd) and push it into the whistle,blowing gently and evenly through thewhistle at the same time.

It will be found that the note rises as thecolumn of air is shortened.

Now construct a similar whistle, some-what longer, out of tin, copying thewhistling production part of it. Thewhistle must be the same bore itsentire length, and you will now beable to push a close -fitting metal rodup it as far as the whistling aperture.You will now have a true Galton'swhistle in its simplest form, moreespecially if the bore of the cylinderis not more than a quarter of aninch-the less the better. Now fit apiece of rubber tube and tworubber balls, one of whichshould be enclosed in netting(see Fig. 3). Next fit on tothe end through which the elmoving piston travels, a screwpiston and a micrometer « -gauge and you can measurethe length of the column ofair and the pitch of the notedepending on it.

The instrument as thus described can bepurchased from scientific instrument ma-kers for a little under a pound.

An improved instrument with a muchfiner tube and capable of going in a casewhich would fit in a waistcoat pocket andfitted with a scale, showing the pipelength and frequency, can be purchased fortwo pounds.

You can graduate your micrometer asyou like, but usually it is, I think, graduatedin centimetres (the distance between twoconsecutive threads on the piston screw)and millimetres, i.e. ten divisions on theturning head.

The best way of calibrating a Galton'swhistle is probably by means of what isknown as the Cathode-ray oscillograph forwhich see Newnes Television and Short WaveHandbook. If the whistle be used with astandard air pressure, you can obtain re-productibility in the pitch of the noteemitted, provided the temperature remainsor is kept constant. Sounds above humanaudibility can be detected by means of thesensitive flame method.

Edelman's Calton's WhistleThis very scientific whistle is a type of

small organ pipe consisting of a very shortcylindrical pipe with a sharp edge, uponwhich is directed a blast of air from anannular nozzle. The pitch of the note canbe varied by moving a piston at the closedend of the pipe-by means of a micrometerscrew shown on the left in Fig. 1. Thedistance of the nozzle from the pipe re-quires adjustment to suit sounds of varyingpitches and the micrometer on the right isused for accurately setting this position.So far as human audibility is concernedonly a few nozzle settings are necessary.

3.--Galton's miniature organ pipe in the form ofa whistle which was blown by means of a rubber bulb.

February, 1937 NEWNES PRACTICAL MECHANICS 265

Smeaton's lighthouse,now on the Hoe,Plymouth. Smeaton'sideas were so successfulthat all modem light-houses are built on the

same plan.

The Conquest o/ theEddystone Rock

By G. Long, F.R.G.S.The Eddystone is the highest summit of a vast Reef of ock,

about Fourteen Miles South-west of Plymouth

THERE are few more splendid examplesof human skill, courage, and inventivegenius than the building of the Eddy-

stone lighthouses. The work was one ofenormous difficulty and danger, and, evenwhen completed, disaster again and againoverwhelmed the slender tower in the midstof the waters, but in spite of this there hasbeen a warning beacon on this deadly reeffor nearly three centuries, and thousands oflives have been saved thereby.

The Eddystone is the highest summit ofa vast reef of rocks, which lies in deep waterright in the track of shipping, about four-teen miles south-west of Plymouth.

When the wind blows up the Channelthese rocks become the centre of a frightfulvortex of raging waters from which no shipcould hope to escape. The need for a light-house was fully understood for many yearsbefore a man could be found with the skilland courage to build one.

DifficultiesThe difficulty was twofold. The lower

part of the tower had to be built below high-water level, and even at low water the rocksare swept by rollers which completelycover it, so that the workmen had to wearlife belts, and cling to iron stanchions fordear life. Only three hours' work a day ispossible at this stage of the work, and thatonly in very calm weather. If in spite ofall this the foundations were successfullylaid, they would immediately be subjectedto a stupendous battering from the waves.Great waves rush in at a speed of sixty milesan hour and exert an enormous pressure onthe work. On the coast of the mainland apressure of three and a half tons to the squarefoot has been recorded, and there is reasonto think that this tremendous figure hasoften been exceeded on the exposed Eddy-stone reef.

-The first of the Heroes of Eddystonewas Henry Winstanley, a country gentle-man living at Littlebury, Essex. He wasan amateur scientist, and an eccentricgenius who loved practical jokes, as hisfriends knew to their cost. A guest kickedan old slipper on his bedroom floor, and

immediately a ghost rose beforehim. In another room there wasa trick chair, which flung out itsarms and held fast the visitorwho sat in it. It was no doubtowing to this eccentric twist inhis character that we owe theremarkable shape of Winstanley'sLighthouse, which, as can be seenin the illustration, is more like aChinese pagoda than anything.

Started in 1696He started in the summer of

1696, and succeeded in fixingtwelve iron tie -rods in the rockbefore the autumn gales stopped

all work. The next summer a solid, roundpillar was constructed, 12 ft. high and 14 in.in diameter, and bound to the tie -rods.In the third summer the pillar was enlargedby two feet at the base, and carried up toa height of sixty feet. Supposing that thiswas lofty enough for safety, Winstanleyand his men determined to remain on thetower to finish the work, but the waves roseto the summit of the tower, so that theywere almost drowned and their provisionswere all spoiled. They were rescuedeleven days later. The fourth year wasspent in enlarging the structure, but its

wide, open galleries and fantastic projec-tions could not resist a great gale. In spiteof this it stood for seven years, and thebuilder was so proud of his work and so con-fident in its strength that he rashly said hewould like to be beneath its roof in thegreatest storm that ever blew.

A section of Smeaton's lighthouse.

His wish was fulfilled in November 1703.A frightful gale raged all night, and Win-stanley and the keepers were swept away.No vestige of the tower remained.A Constructive. Genius

Three years later John Rudyerd begananother. Although he was a silk mercerby trade, he seems to have been a con-structive genius. He determined to builda tower which should offer as little resist-ance to the wind as possible, so instead ofa polygon he chose a circle for his planand made the exterior of the tower quitesmooth. It was 92 ft. high and took fouryears to build. Instead of twelve tie -rodshe had thirty-six, each sunk from twenty tothirty inches deep in the rock. The rodswere perforated with holes, 252 in all, bywhich they were clamped to the timberswith jagged spikes. The lower part of thetower consisted of oak beams and courses

Winstanley's lighthouse, which, as can be seen, is rather of stone, all joined to each other by ironlike a Chinese pagoda. clamps. The upper part was all timber.

011.111111aws

266 NEWNES PRACTICAL MECHANICS February, 1937

A section of the present Eddystone lighthouse.

Rudyerd's Lighthouse was an absolutesuccess so far as resisting the winds andwaves was concerned, but it was destroyedby another element-fire.

It was completed in 1709, and in Decem-ber 1755 the top of the building caughtfire through some mishap with the candlesused for lighting. The keepers tried to ex-tinguish the flames with buckets of water,but it is no easy task to carry water to thetop of a ninety -two -foot tower. They weredriven down stage by stage, and finally hadto get on the rock, whence they were res-cued by a boat which put off from Ply-mouth when the fire was observed. Oneof the keepers died twelve days after, andwhen a post-mortem examination of hisbody was made, a mass of lead weighingnearly half a pound was found in hisstomach. He had swallowed the moltenlead when trying to put out the fire.John Smeaton

The third lighthouse on the EddystoneRock was built by John Smeaton, andwork began a year after the second had beendestroyed. Smeaton decided that the twoprevious towers had been deficient inweight, and he announced his intention ofbuilding a tower so solid that the seas shouldgive way to the lighthouse, and not thelighthouse to the sea. Also it must be fire-proof, and so would be built of stone.

It might be mentioned that Smeaton'sideas were so . successful that all modernlighthouses are built on the same plan.When working out his design he kept be-fore his mind the outline of a stately oaktree.

Every foundation -stone was dovetailedto the rock and also to its neighbours, andas the courses rose every stone was lockedto its fellow and a hard plug of marbleprojected into the course above. As thefoundation and lower part of the towerwere constantly swept by waves before thecement could dry, Smeaton's greatest fearwas that the cement might be washed outof the joints before it could set.

He overcame this difficulty by two cleverideas. In order to make certain that no

stone could be moved by the utmost forceof the waves, he inserted a number of oakwedges in grooves between the stones,whit when wetted by the sea -water wouldlock %verything solid. All joints werefilled up with cement and covered outsidewith plaster of Paris, which set hardquickly and kept the water out of thecement.

During the first summer nine courses ofmasonry were laid, and at the end of thenext the solid part of the tower was com-pleted, 35 ft. above the base.

The whole job was finished during thefourth summer, the lantern being 72 ft.above high-water level.

Smeaton had three narrow escapes dur-ing the progress of the work. Once he wasnearly drowned when his boat was caughtin a tremendous storm, once he fell over therock and dislocated his thumb, and finallyhe was almost smothered. A charcoal firewas being used within the tower for meltinglead, and Smeaton was overcome by thefumes. Fortunately his men found him,and dragged him into the open air, wherehe was revived with buckets of cold water.Smeaton's Lighthouse still stands, but it isno longer on the Eddystone Rock.

Rocked DangerouslyIt successfully resisted the wind and

waves till 1882, when it had become unsafethrough the undermining by the waves ofthe rock upon which it stood. The towerremained solid but the rock was breakingaway, and the lighthouse rocked danger-ously in gales.

A bigger and better Eddystone Light-house was then built by Mr. J. N. Douglas,Chief Engineer to Trinity House, who hadalready built the magnificent " Wolf," and" Bishop " Lighthouses. Mr. Douglas hadthe advantage of working in the age ofsteam machinery, and so easily surpassedSmeaton's great achievment.

The new Eddystone Lighthouse contains2,171 stones ; that is, 4,668 tons of masonry.Smeaton's contained only 988 tons, and hadfour living -rooms. The new tower has nineliving -rooms, each larger than those on theold tower, and is 130 ft. high, as against 70.

A sketch showing Smeaton's lighthouse and itssuccessor-now on the Eddystone.

Lighting FacilitiesElectric light was proposed, but was re-

jected because it was thought there wasinsufficient space for the engines anddynamos, and it was feared that the vibra-tion would endanger the tower. Oil lampswere installed in 1882, with an illuminatingpower of 250,000 candles, or about sixthousand times as much as Smeaton'soriginal light.

If we stand on Plymouth Hoe to -day andlook far out to sea, we can on a clear day seethe slender pencil of the New Eddystonerising above the water, and if we turn shore-wards we can see Smeaton's old light-house, standing on the historic Hoe. Thelower part, or solid stump, remains on thereef, but the upper part has been carefullyrebuilt on shore, and is a favourite venue forvisitors, who can climb to the top for apenny and see for themselves how mag-nificently the stones have been dovetailedtogether, so that after nearly two centuriesit is as solid as when it was built.

MELIA III LE STOPWATCHES

A

STOP watches are so useful in almostevery sphere of activity-wireless,motoring, flying, turning, racing-

that it is a wonder that more people do notown them. If you developthe stop - watch habityou will in- crease yourknowledgereliable infor- (6? 0 V)11))

and can givemation about

speeds and times insteadof making wild guesses.

One ofthe stop

watches inthe Arnold

range.

The speedometer of a car is not the mostreliable means of testing accurately thespeed of a car, the distance it takes to pullup, its rate of acceleration, but a stop watchin infallible. Because of this we shouldlike to draw the reader's attention to thefact that A. Arnold & Co., 19 ClerkenwellRoad, London, E.C.1, is a specialist in stopwatches of all types, sizes and prices, froma few shillings to several pounds, in chrome,nickel, silver and gold, for the wrist or thepocket, and in a variety of case styles.

It is always wise to deal with a specialist.You cannot expect to buy a reliable stopwatch at a general stores. The firm men-tioned have been specialists for many yearsin all types of timers, from the simple stopwatch with or without fly -back, to compli-cated split -seconds chronographs with KewA certificates costing several pounds. Theysupply a variety of dials for various purposes-sports, mechanical, dog racing, medical,etc., accurately calibrated for the purposerequired. Whatever stop watch you re-quire A. Arnold & Co. have it. Drop them aline at the address given, and explain yourrequirements. They will send you illus-trated lists and a quotation by return.

NEWNES PRACTICAL MECHANICS 267

14.:1Februarr:415"7TER'S OF MECHANICSNo. 18. 4 ,Romance of the

HAVE you ever stopped to wonder howthe highly complicated and many -coloured designs which are woven into

textile materials of all descriptions areproduced by mechanical means ? Timewas when the weaving of a design into clothmeant the expenditure of a truly enormousamount of hand -labour and, with the bestwill in the world, a hand -weaver and hisnecessary two or three assistants could onlyweave a design of a very simple andrestricted pattern into cloth.

Nowadays, woven fabrics of silk, cotton,wool and other materials can be obtainedwith all varieties of complex designs woveninto them. Such materials are turned outmechanically by means of Jacquard looms,or, as the latter are more simply termed inthe Lancashire weaving towns, " Jac-quards."

A Jacquard loom is really not a loom atall. Rather it is a mechanical contrivancewhich is mounted over a weaving loom andwhich, by modifying the automatic opera-tions of the latter, causes a pattern of a pre-determined design to be woven into thecloth which is turned out by the loom.

Many Different Patterns" Jacquards " are nowadays of many

different patterns, and since the recent intro-duction of mass -scale artificial silk andrayon weaving they have tended to becomestill more complicated in mechanical design.Nevertheless, their fundamental principleremains the same in all cases.

It is not easy to explain the precise work-ing of the present-day " Jacquard " inmerely a few words. The reader, however,will doubtless be aware of the fact that inordinary or " plain " weaving the shuttle(which carries the " weft " or crosswisethread of the fabric) is caused to pass underalternate strands of the " warp " or length-wise threads of the fabric which, in themodern loom, are mechanially raised for thispurpose. If, however, we arrange mattersso that not all the alternate " warp " orlengthwise threads of the fabric beingwoven are raised at the same time, but onlysome of them, it will be obvious that apattern will be formed in the finishedmaterial.

A Series of CardsThis is precisely the operation which the

Jacquard attachment to the loom performs.A series of cards bearing perforations arepassed through the Jacquard portion of theloom. These perforations cause a numberof wires to be raised automatically and thewires, having hooks at their lower ends,raise the " warp " threads of the materialwhich is being woven. The shuttle passesunder these raised threads. Consequently,a design is woven into the cloth, the designbeing determined by the exact number andarrangement of the perforations in the card.

A player -piano does much the same thing,but, of course, instead of translating anarrangement of perforations on cards intoa woven pattern, it converts a perforation" design ' on a roll of rough paper intoaudible sounds.

In the Jacquard loom, the necessary per-forated " cards " are all fastened togetherto form an endless band. The passage of

Weayins Industry

The True Story of JosephMary Jacquard Ort5Iinatorof the Jacquard Loom

all the cards through the Jacquard attach-ment to the loom causes the complete de-sign to be woven into the cloth. Since,therefore, the Jacquard cards form an end-less band when passing through the loom,

Joseph Mary Jacquard, from a portrait in the TownHall at Lyons.

it follows that the design is repeated on thewoven cloth again and again until the loomis stopped. The woven design is producedentirely automatically, at a high speed, andmore or less infallibly, since only an injuryto the Jacquard " card " can interfere withthe correctness of the woven design.

The inventor of this simple and almostfool -proof system of mechanical patternweaving which is now in universal employ-ment was a poor man of Lyons, in the southof France, Joseph Mary Jacquard, byname. He was born at Lyons on July 7th,1752, and he died near that famous town onAugust 7th, 1834, in a humble cottage of hisown choice.

PovertyJacquard's parents were poor country

folk, who had come into Lyons to pick up aliving by silk weaving. At the age oftwelve the young Jacquard found himselfplaced in a bookbinder's workshop andunder the severe necessity of having to earnhis own living. He had had little educa-tion. True it was that he could read a littleand could manage to write his name and totup figures, but the spectre of dire poverty

had walked more than once through theJacquard home, with the result that theyouthful Joseph Mary (the feminine " Mary "was-and still is-not infrequently appliedto male children in Latin countries), hadfound the task of learning how to assist at asilk -weaving loom of far more urgency thanthat of imbibing the art of the alphabet.

One of the characteristics of inborngenius is that it will grow and find an outletunder the most unfavourable conditions.It was thus with Joseph Mary Jacquard.Doubtless, also, his early training in hand -loom manipulation which he received fromhis parents accentuated his natural me-chanical ability not inconsiderably. Theyoung Jacquard quickly showed an intenselove for mechanics and for all constructionalmatters. In his childhood days he amusedhimself for hours on end by building uphouses, castles and other quaint models outof cardboard and brown paper. Then hewould make carts with wheels and putmodel horses between the shafts, and finallyhe tried his hand successfully at the con-struction of simple types of mechanism.

When Jacquard left the bookbindingestablishment to take up a job with a firm ofprinting -type makers, we are told that heinvented a number of useful tools for themaking of types, a fact which stresses theoriginality of mind of the youngster.

Jacquard was not very old when hisfather died. A year or two later his motherdied, also, and he was left an orphan withpractically no means.

A FailureAt this time, he fitted up for himself a

workshop complete with two or threesecond-hand hand -looms, and therein hetried to run a business in the weaving ofsilks. The business failed, however, and,to make matters worse (or was it better ?)Jacquard had by this time managed to fallhopelessly in love with a pretty young girlfrom the surrounding country.

The young pair decided to face the sternrealities of life together. They married,and, perhaps, it was the best thing they everdid, for, although poverty and distress stillcame their way, Jacquard and his wifeassisted each other mutually, and in the endfought their way to success.

The first thing Jacquard did after gettingmarried was to drift into a condition of al-most hopeless penury. After many trialshe managed to get a job as a labourer in aneighbouring lime works, and his wifehelped matters on considerably by makingstraw hats at home, and afterwards by open-ing a shop for the sale of them in Lyons.

And so the years passed on. Jacquardstill, in his spare time, worked away atmechanical hobbies, his one object being toinvent a mechanical loom which wouldrevolutionise the system