HAN ICS...Army Certificates Auctioneers and Estate Agents Aviation Engineering Banking Boilers Book-keeping, Accountancy and Modern Business Methods B.Sc. (Eng.) B.Sc. r Estate Management)

-BUILDING THE WINGS

NEWNES

CTICALHAN ICS

NOVEMBER

SIGNS of theTIMES

The Budget has restoredPOLICE OPPORTUNITIES

The Air Force is to be increasedAVIATION MUST DEVELOP

Pay Cuts have been restored

CIVIL SERVICESuitable to both s xes. Ages '51 to 24.

PERMANENT, PROGRESSIVE,PENSIONABLE POSITIONS.

G.P.O. ENG. DEPT.CUSTOMS AND EXCISE, INSPECTOR OFTAXES, ETC. NO EXPERIENCE RE-

QUIRED. OPEN EXAMS.

MATRICULATIONThere are many ways of commencing a career,but Matriculation is the jumping-off board for

all the best ones.We prepare candidates for all

INSTITUTE EXAMS.TECHNICAL, ACCOUNTANCY,

SECRETARIAL, INSURANCE, ETC.

ENGINEERS andDRAUGHTSMEN

All Branches-Employers areadvertising for them.

TELEPHONY, RADIO and MOTORENGINEERING are expanding rapidly.There are lots of vacancies. Our postalcourses will make you eligible. Advice

on all careers Free.

Also ask for our NewBook (Free of Charge)

THE HUMANMACHINE

Secrets of Success

CAN YOUCHANGE MYEXPRESSION?

IF 80, YOU MAY BETHE ARTIST THATCOMMERCE 18

WAITING FOR.

Cfiti"44-11.414$0There are hundreds of openings in connectionv ith Humorous Papers, Advertisement Drawing,Posters, Calendars, Catalogues, Textile Designs,

Book Illustrations, etc.6s per cent. of Commercial Art Work is done by"Free Lance Artists" who do their work at homeand sell it to the highest bidders. Many Commer-cial Artists draw "retaining fees " from varioussources, others prefer to work full-time employ-ment or partnership arrangement. We teach younot only how to draw what is wanted, but how tomake buyers want what you draw. Many of ourstudents who originally took up Commercial Artas a hobby have since turned it into a full-timepaying profession with studio and staff of assist-ant artists; there is no limit to the possibilities.Let us send full particulars for a FREE TRIALand details of our course for your inspection.You will be under no obligation whatever.

Just try it for yourself,trace or draw the out-line and then put in

the features.

4,10, Art Dept. 76.

STUDY AT HOME IN YOUR SPARE TIME

OPEN LETTER TO PARENTSDear Sir or Madam,-When your children first arrived they brought with them a wonderful lot ofsunshine. Later you became proud of the intelligence they displayed, but still later you becameanxious as to what would become of them in the future. Perhaps you were anxious when you visua-lised them as grown men and women. Even with plenty of money it is not always easy to selectthe right career, and a parent is sometimes inclined to ask advice of some relative and in nine:y-nine cases out of a hundred that relative knows nothing at all about the possibilities of employment.Why not let me relieve you of some of your anxieties? In fact, why not let me be their Father?We do not profess to act as an employment agency, but the nature of our business compels us to keepan eye upon the class of men and women that are wanted and who wants them. There are somepeople who manufacture an article and put it on the market to sell. We do not do that, we work inexactly the opposite direction. We find out what employers want and we train our students to fillthose jobs. We have to be experts in the matter of employment, progress and prosperity. U youhave any anxieties at all as to what your sons and daughtersshould be, write to me, or better still, let them write to me per-sonally - Fatherly Advice Department - and tell me their likesand dislikes, and I will give sound, practical advice as to thepossibilities of a vocation and how to succeed in it. Yours sincerely,

YOU CAN HAVE A COLLEGETRAINING IN ALMOST ANY CAREERFOR A FEW SHILLINGS MONTHLYAccountancy ExaminationsAdvertising and Sales Manage-

mentA.MI. Fire E. Exam.Applied MechanicsArmy CertificatesAuctioneers and Estate AgentsAviation EngineeringBankingBoilersBook-keeping, Accountancy and

Modern Business MethodsB.Sc. (Eng.)B.Sc. r Estate Management)Building, Architecture and

Clerk of WorksCambridge Senior School

CertificateCivil EngineeringCivil ServiceAll Commercial SubjectsCommercial ArtConcrete and Structural

EngineeringDraughtsmanship. All branchesEngineering. All branches,

subjects and examinationsGeneral EducationG.P.O. Engineering Dept.Heati-g and VentilatingIndustrial Chemistry

Insurance MathematicsMatriculationMetallurgyMining, all subjectsMining, Electrical EngineeringMotor EngineeringMotor TradeMunicipal and County EngineersNaval ArchitecturePattern MakingPolice, Special CoursePreceptors, College ofPumps and Pump.ng MachineryRadio Service EngineeringRadio CommunicationRead -Making and MaintenanceSalesmanshipSanitationSecretarial Exams.ShipbuildingShorthand (Pitman's)Structural EngineeringSurveyingTeachers of HandicraftsTelephony and TelegraphyTransport Inst. Exams.Weights and Measures InspectorWeldingWireless Telegraphy and

TelephonyWorks Managers

If you do not see your own requirements above, write tous on any subject.

HOW TO STUDYIn your spare time when it suitsYOU. You fix your own time, youdo not GO to your studies-thepostman brings THEM TO YOU.There is nothing that a class -roomteacher can show on a blackboardthat we cannot show on a whitepaper. The lesson on a blackboardwill be cleaned off, but our lessonsare PERMANENT. A class -roomteacher cannot give you a privateword of encouragement, but a Cor-respondence Tutor can do so when-ever your work deserves it. On theother hand he can, where necessary,point out your mistakesPRIVATELY.

TO STUDENTSLIVING ABROADor on the high seas, a good supplyof lessons is given, so that theymay be done in their order, anddespatched to us for examinationand correction. They are then sentback with more work, and in thisway a continuous stream of work isalways in transit from the Studentto us and from us to the Student,therefore distance makes uodifference.

IT IS THE PERSONAL TOUCH EVERY DEPARTMENT IS A

WHICH COUNTS IN POSTAL COMPLETE COLLEGEEVERY STUDENT IS A CLASS

TUITION TO HIMSELF

Dept. 76, THE BENNETT COLLEGE, SHEFFIELD.

November, 1935 NEWNES PRACTICAL MECHANICS 65

French Radio Eye for Shipping

THE liner Normandie hasbeen equipped with new

electric apparatus devisedby a young Frenchscientist, M. Ponte.Its purpose is to de-tect at night all shipsDr other objects inthe vicinity of thegreat liner, andthus ensure protec-tion against colli-sions.

The Sun and Wireless ReceptionFOR the past eleven years, Dr. Stetson,

of America, has been experimentingwith an automatic recorder which recordsthe signal strength of broadcasting everynight. By means of these records it hasbeen found that sun spots influence theionisation of the upper atmosphere whichvaries the reception of distant broadcaststations. The sun follows in an 11 -yearcycle, and according to Dr. Stetson the bestwireless reception was obtained five yearsago and it will be poorest in 1939 and 1940.

A New Type of CraftANEW type of boat has just been

launched at Le Havre. It is called theocean glider and has received the name ofGenial. This original craft, furnishedwith two rafts each of 22 metres in length,provided with a motor of 100 h.p., andweighing 15 tons, will be used as a passengerboat between Le Havre and Trouville. Itcan carry 75 passengers and has a speed of22 knots. During the winter, it will beused on the French Riviera.

A " Sunshine " LampAN electric light bulb providing vitamin

F -ID, the " sunshine vitamin," has beendeveloped by Dr. Sperti, of America. Thisnew bulb, which is the result of more thanten years of research in selective irradiation,can be used in any electric -light socket, andprovides both the ultra -violet rays neces-sary to build up vitamin D, and sufficientlight -rays for reading and working. Thisdevelopment disproves the theory thatsunburn is essential for the development ofvitamin D in the skin.

A New Balloon RecordA NEW world distance record for balloonsr-lis claimed by the Soviet pilots, Romanov

JacticalMechanics

Edited b F. J. CAMM

VOL. III. No. 26

NOVEMBERI 9 3 5

Notes,

SUBSCRIPTION RATES :Inland and Abroad, 7s. 6d. per annumCanada - - 7s. per annum

News, and

Editorial andrAdvertisement Offices : " PracticalMechanics," 6eorge Newnes Ltd., Southampton

Street, Strand, W.C.2.Registered at the G.P.O. for transmission by

Canadian Magazine Post.

Viewsand Babykin, who have covered 1,437 milesin their balloon in fifty-six hours.

Modern House ConstructionAHOUSE of copper, designed to resist the

ravages of time and proofed againstweather, fire, lightning, and termites, is thelatest in modern house construction. Theprinciple involved in this kind of con-struction is an all -metal exterior fast-ened to an all -steelframework. Outsidewalls are composedof heavy copperplates backed bycomposition boardto give additionalstability. The roofis covered withsheet copper over awooden deck and insulation and sound-proofing are provided by a 4 -in. thicknessof spun glass between walls and roof, whichis said to have the insulation value of8 ft. of solid masonry.

The Shape of the EarthDISCOVERIES about the shape of theearth and differences in gravity were

recently disclosed by Prof. Meinsey, whomade a 23,000 -mile voyage in a Dutchsubmarine during his researches. Herefutes the suggestion that the earth is" flattened " at the Equator as well as

at the Poles. Hisexperiments in thesubmarine, he de-clared, proved thatthe earth is flat-tened only at thePoles. The professoralso discovered thatthere is a differencein gravity on theoceans and on thecontinents.

World's Longest Air -mail SystemTHE world's longest air -mail system was

recently inaugurated when the firstconsignment left Croydon for China.Henceforth, two mail liners will fly the newroute in each direction every week.

Plane Flies Like a BirdWE learn that M. Dubois

has produced a cycle -plane driven entirely by

man -power. The wings of the plane areshaped like those of a bird, and flap upand down during flight.

A Substitute for RadiumWE learn that the production of aninexpensive but powerful substitute

for radium is now possible on a commercialscale. The suggested substitutes for radiumare chemicals made active by bombard-ment with atoms of heavy hydrogen.Before the atoms are bombarded, they arewhirled about in a special mechanism, untilthey are given the energy of 5,000,000volts. By this method, and using sodium,enough can be made radio -active toequal the potency of 50 milligrams ofradium.

French Streamlined TrainTHE first streamlined train in France

recently started a regular service onthe P.L.M. Railways, between Paris andEvian.

Mysteries of the Cos-mic RayDR. R. MILLI-

KAN, world-famous physicist, isnow conducting ex-periments at FortSam Houston, SanAntonio, Texas, fromballoons, in a series

of cosmic -ray tests.

A Million -volt Generator

DR. W. BENNETT, of America, hasdesigned a new type of million -volt

generator, for use in the study of nucleardisintegration. Because it is much smallerand less costly than the models previouslyused for the same voltage, the new generatoris expected greatly to increase the possi-bilities for the study of the atom and itsnucleus. The generator will be used inoperating a high -vacuum tube at ex-tremely high voltages, to produce high-speed particles which disintegrate nucleiof atoms and change the chemical ele-ments.

66 NEWNES PRACTICAL MECHANICS November, 1935

Itow touild the

This Month we Deal

war& if I IV

ez.PIPs aitArni

with the Construction of the Wings

T0 cut a metal fitting out of a mildsteel sheet of 2 mm. thickness mightfrighten some amateurs.

Look at the illustration first of all, andcut a pattern in cardboard with the holescut in it. Place this pattern on the steelsheet and mark it with a thick pencil orchalk. Fix the steel in a vice having jaws

60

.182

562

at least 4 in. long, and chisel it off with theedge of a cold chisel. Hold your chiselalmost horizontally.

If you are obliged to hold the piece whichhas to be cut, beyond the jaws, give the chisela slight slant in order not to tear the metal.You will soon acquire the knack of holdingthe chisel at the correct angle for free cutting.

Fig. 18.-Thepylon which sus-tains the wings andpositions them inrelation to the fuse-lage.

of the " Flying Flea"

BendingOne ought never to bend a piece of steel

at a right angle, even for the smallestfitting, owing to the hammering necessarywhich cracks the metal.

Always interpose between the piece youhave to bend and the jaws of the vicea piece of steel of the same thickness whichhas already been correctly bent.

Pierce the holes some distance from theedges. Where the drawings do not showthe exact dimensions always leave betweenthe hole and the edge of the material adistance of 8 mm. to 10 mm. all round thehole.

All bolts on an aeroplane ought to bemade so that they cannot become loose.When it is a case of a piece which will oftenhave to be taken down, fix the nut witha split pin or a safety pin. In very carefulassemblages, use castellated nuts, or lock -nuts.

When one does not foresee the necessityof frequently taking the pieces apart, it isquite easy simply to burr the end of thebolt with several blows of the hammer onthe end of the bolt which extend 2 mm.beyond the nut. Before taking it apart,a few strokes with a file will replace thethread and remove the burr.

Every screw, axle, and wire bracing mustbe securely fastened, because if you neglectto fix, voluntarily, a dozen screws, it maybe that none will come loose ; but if youforget one only, and one which may beimportant, you can be quite certain thatthat one will come away.

As you construct, or file, or screw,always think that one day the piece uponwhich you are working will hold you sus-pended in space several thousand metresabove the ground.

The Main Landing GearThe axle is a tube 1.2 metres long in

36 mm. x 40 mm., reinforced internally withanother tube 800 mm. long in 31 mm. x35 mm. This makes a thickness of 4 mm.,and weighs 4 kilos. It is very heavy, butit is solid and will not bend. You will notbe afraid of damage when you are run-ning over bumps. A single tube wouldnot be sufficiently strong.

The play of 1 mm. between the two tubesallows one to be pushed inside the other.If they were both the same size, you wouldnot be able to get the inner one in place.A filling of hard wood is not suitable,because, although it is lighter, it only stopsbending, but will not prevent breaking.Its elasticity allows the metal to fracture,


and one day the axle will break under alight shock.

A collar is fixed on to the tube by a 6 -mm.bolt. It will prevent the tube from slidingin the rubber shock absorber, in the sameway that the block holds the latter underthe skid of the body.

Do not drill any hole in the axle at thisspot.

A piece of 8 -mm. rod goes through theaxle at its middle point, and a tube madeout of sheet metal of 1 mm. is rolled round.The rubber washers are then inserted be-tween the two metal washers and the wholeis held in place by a nut. This preventsthe axle from turning, by supporting it onthe front planking through the hole.

The axle bears down on the pad ofrubber of a thickness of 12 mm. cut fromthe tread of an old motor -car tyre (Fig. 19).This pad is fixed on the -6-mm. aluminiumwasher and held by two screws and aplate.

Elastic SuspensionThe rubber shock absorber of 12 mm.

diameter, which commences to stretch undera pull of 40 lbs., and which has a length of 1metre 90 mm., is fixed at each end into ametal fastening in metal of 1 mm. with abolt of 4 mm. One end of the shock ab-sorber is fixed under the axle by a screw in4 mm. x 20 mm. The shock absorberpasses behind the stop, and afterwardssix times round the axle, and under theskid, as shown in the drawing. One pullson it until it is just slightly stretched.The other end receives a wire 2 mm.diameter, which will be securely attached toa screw placed conveniently under the seatplanking. The screw prevents the last turnfrom slipping.

Before cutting the shock absorber, bind

it with rubber tape(two turns), andcut in the middle ofthe binding with aknife.

In its longitudinalview the suspension appears asshown in Fig. 19,which shows theaxle, its collar, itspad of rubber, thestrip of aluminium,the longeron of thefuselage, the skid which rein-forces it, and the lower stopwith the three turns of theshock absorber on either side ;which make altogether, oneach side of the body, twelve

11

turns of shock absorber. Themachine could roll on one wheelwithout stretching the shockabsorber, except over bumps.

The wheelsare fixed onthe endsof theaxle bywashersand col-lars (usinga 5 mm.bolt hori-zontally)cut outin metalof 2 mm.thickness. j

;TrO

Pieces of tube 40 mm. x 44 mm.diameter, of a length of 15 ram.,will also be quite suitable. In-terpose a washer between thewheel and the sleeve.

The WheelsThe dimensions of the tyres should be

450 mm. x 100 mm., which, when lightlyinflated, absorb most of the roughnesses ofthe ground. Only the bigger shocks willhave to be taken by the shock absorber.One blows up these pneumatic tyres so

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that theyhardly p re-serve theirroundness.Frequentlygrease theaxle.

The body ofthe fuselage is35 in. fromthe ground.It may seemrather small,but it is quitesufficient.However,make a care -

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Fig. 19.-The axle bears down on apad of rubber, cut from the tread of

an old motor tyre as shown.

ful inspection of the ground from which youare taking off, and flatten with blows from aspade any bumps which seem a bit too high.

The Control StickA tube traverses the fuselage from side

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to side underneaththe rectangularhole.

The centre of thetube is held be-tween two blocksand two cheekpieces by four bolts5 mm. diameter.Between thesestrips, and the 6mm. bolt and thewashers of 1 mm.,the control stickpivots. On the topof this stick is riv-eted a steel hook of2 mm., which willprevent your handfrom slipping off,and also will enable

Fig. 20.-Details of the framework of the wings.

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NEWNES PRACTICAL MECHANICS

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you to join the stick to the dashboard byrubber strips cut from an old pneumatictyre. These strips will relieve the pilot ofthe continuous pull of the stick in a forwarddirection.

The tube extends beyond the sides of thefuselage for about 50 mm. Two flaredsleeves prevent it from sliding laterally,and, if possible, without any play. Putwashers between the fuselage and thesleeves.

These sleeves carry the levers made from10 -mm. bar heated to a red heat, flattenedat one end and riveted at the other so thatthey will not come out of the sleeve. Thissleeve is fixed to the tube by a bolt of6 mm., taking care that the lever, whenlooking at it from the end of the tube, isat right angles to the joystick.

This latter disposition is for the controlof the wing, to which the eyes of thelevers, one on each side, will be fixed by acontrol cable.

2 OFF

Fitting the Rudder and Wing ControlThe control of the rudder and wheels can

be placed in position. Two cables5 metres long of 2.4 -mm. sectionsteel and extra flexible, will bepassed through the 6 mm. diameterhole in the joystick, and preventedfrom moving at the middle pointby the 5 mm. diameter bolt.Each double turn will cross

69

with the other in the 5 mm. diameter hole, I will prevent the cables from jumping out ofthen, in a similar manner, in the fork. Before the groove and jamming if they become

slack. This is a wise precaution, as jam-ming of the cable is much to be avoided.

/50

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Fig. 21.-Constructionaldetails of the main spar.

this, the joystick will have been filledwith hard wood, well greased with par-affin wax, level with the base of the stick.The fork, partly of wood and partly of

metal, should be filed round. The 4 -mm.rivet prevents the cables from escaping fromthe fork. It is flush with the outside ofthe joystick. A drop of oil will preventwear on the cables.

Each double cable, of a length of 2 metres50 mm., passes over the pulley. (This isa cast pulley and has a very wide groove :the diameter at the bottom of the groovebeing 40 mm. at least, which revolves onthe axis of a diameter appropriate to thehole through the centre of the pulley.) Anut on the interior of the fuselage at oneend, a bearing at the other, and a screw184 x 5 x 25 mm. fix this axis, which willbe slightly inclined by means of a blockunder the bearing in order that it can bealigned with the bottom of the control stick.

Finally, the double leads join up with theturn -buckle where they are attached by thegrip, adapted for cable of 4.5 mm. Bindeach free end and join the ends to the cable.They will be about 50 mm. to 100 mm.beyond the grip.

The little piece of strip steel of 2 mm.,fixed by two screws close up to the pulley,

The Wing SupportThe support consists of a pylon made of

tubes which sustain the wing and positionsit in relation to the fuselage, after it has beenfitted with its bracing wires.

It is made of two tubes in 17 mm. x20 mm., welded to two cheek pieces of 2 mm.separated by a block of hard wood andjoined by two bolts of 6 mm. (see Fig. 18).Where welding is not possible it can bebolted together. This is the head of thepylon.

The feet of the pylon, lightly bent (at redheat), are blocked with hard wood, and arepivoted at the U -piece in 2 mm. material,furnished with a 6 -mm. bolt. This isjoined to another piece of metalwork bytwo 6 -mm. bolts which go right through thecrosspiece, to which they give great rigidity.On the other hand, the metal piece is fixedby three 4 -mm. bolts to the three laths ofthe landing gear.

It would be better if the feet of thecabane were finished off by a transversetube welded on to them.

The head of the pylon is kept in positionby a tube about 300 mm. long-the exactlength will be decided at the moment whenthe wing is adjusted-and which is pivotedat either end on the 30 -mm. tubes made of

a 1.5 -mm. strip rolled.The axis tube of the foot is

fixed between two strips ofmetal, which will be bolted tothe motor when that is in place.

Fig. 22.-A sectional view of the wing, showing the rib construction.

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The Wing PivotThe tube of the head of the pylon is the

axis on which the wing will pivot. Forthat, a bolt made of screwed rod of 10 -mm.material, 200 mm. long, goes through thewing, and holds to it the metal piece whichis bent into a U and welded on to a tubemade of rolled strip of 2 -mm. thickness.The pivoting is assured by these two tubesrevolving one on the other, one being fixedon to the pylon, and the other fixed to thewing. In case it is impossible to weld, onecan arrange a metal fitting without a tube,but doubled. The tube will be so arrangedthat the metal piece moves freely on it, butwithout lateral play. Perfect adjustmentof these two tubes is useless ; whetherthere is 1 mm. or 2 mm. of play is of littleimportance, provided that they are ap-proximately round. A drop of oil is allthat is necessary.

/-5

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Choice of SpanThe wing span should be adapted to the

space in which it is to be constructed.The ideal is a room or apartment of 3

metres x 4 metres. The machine itself issmall, but this room should suffice for it.The wing is the largest part and has a spanof 4 metres.

The plane was first tried with a 51metres span, but it was decided to try 4metres as a test.

The first profile, with a flat lower side andthe tail turned up, showed itself perfectlystable, but it did not lift well. The machinemeandered across country, but it wantedthe full power of the motor, and it scarcelyclimbed at all.

Lateral StabilityIf one only wants to flutter, so to speak,

to learn to fly on little journeys of two or

/43

83

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three kilometres above a flat open plain,where one can land anywhere, then thisspan of 4 metres is possible. It is better

-3.3 -

Fig. 23.-Details of the ribs.Dimensions are in centimetres.

12

than a machine which only rolls on theground ; better than a " penguin " becauseit really flies " in the air," and the prin-ciple incorporated in the " Flea " will permitfaults of piloting which, in an ordinaryaeroplane, would lead to catastrophe. Itslateral stability is immense.

Commence in that way if your room willnot allow you to make a bigger wing. Thiswing of 4 metres for the standard model willbe suitable for the rear wing of another" Flea," or perhaps will be the means ofdoing a kindness to a pal.

If you are light (10 stone) and are onlythinking of short journeys, then a span of5 metres will suit you very well, but on 6metres you can weigh 12 stone, and youcan carry with you enough petrol for threeor four hours' flight.

Whether on 4-, 5-, or 6 -metre span, theconstruction is identical. You only haveto elongate, at your discretion, the ends ofthe wings (which means a few extra normalribs to nail) and alter the attachment of thebracing wire. The central part remainsunchanged.

Fig. 24.-All ribs which are not of the main seriesare designed and constructed in the same manner.

Dimensions are in centimetres.

This last wingof 6 metres, longerand deeper, andbetter arched, isdefinitely superior.

The Front WingThe framework

of the wing (Fig.20) is made up of18 ribs threaded tothe main spar whichis 6 metres long. Asmall rear spar of 5metres 20 mm. is


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Fig. 25.-Further details of the wing construction.

inserted into the tails of the ribs, whichare all of the same pattern.

The two ribs on the extreme ends are ofa different pattern, because of the taperingof the wing in plan.

The leading edge and the trailing edge(in treble strips glued together), with thesmall spar, triangulate the framework, whichdoes not need any other stiffener. And so.in the interior of the wing, except for thenailing of the plywood, there is not a singlepiece of metal. No fittings, no wires, noturn -buckles. The wing is supported onthe pylon by its centre at a place where the

gam

block is shown, while the system of bracingcables, joined to the wing, keeps it steadybut allows it to pivot about the axis.

The pivoting is 'controlled by the cablewhich joins the lever of the control columnto the small spar, to which this cable isfixed at the spots marked by the fourblocks. A spring, attached as shown, pullsdown the wing in front.

The Main SparThe spar is made of two flanges in

15 -mm. x 60 -mm. material, planed upto points and curved and maintained in

correct form by two webs of1.5 -mm. plywood, of whichthe grain is vertical to thedepth of the spar. The depthof the spar is 130 mm. (see Fig.21).

It is perhaps difficult to findordinary pine as long as 6metres free from knots. Thisgreat length, on the other hand,

is rather incon-venient fordelivery. Let usstart, then, withlengths of 3metres 20 mm.,which can be

Fig. 26.-The method of covering the ribs.

glued solidly together in the middle on thebevel.

Plane up at the same time the ends ofthe two 15 -mm. x 60 -mm. planks to alength of 400 mm., and they are thenplaced side by side and fixed together bya bolt. Take care that the surface is quiteflat and regular. After planing it pass afile or rasp over it in order to take off thepolish.

Join the bevels together with glue andalign carefully the two planks, which willbe temporarily fixed by two small nails.Glue all over this and press it carefullybetween two blocks in two vices or twostrong screw presses. Leave it for about24 hours in which to dry.

Next, prepare for the two wings twoblocks which can be of good pine or ofbeech. All the holes are of 11 mm. diameter.Get ready also five screwed 10 -mm. rods 180mm. long.

Assembling the SparAfter removing the two flanges out of

their presses and smoothing their four facescorrectly, drill a 11 -mm. hole in the middleand two holes 500 mm. apart at 1 metre300 mm. on both sides of the centre.Stated more exactly, these double holeswill be 3 mm. closer to the centre in theupper flange.

Place the two planks on two trestlesand glue them together. Make certain that


these two planks are quite parallel endto end.

Now glue on each side two plates of ply-wood F5 mm., 130 mm. broad and 500 mm.in length.

With the aid of a cord or a wire 2 mm.diameter and the king -post made of a tube1'5 metres long, pull up the points of theflanges in such a way that the thread,stretched between the points, passes at aheight of 230 mm. above the central boxedportion.

A temporary block, 40 mm. in height, willseparate the flanges at 300 mm. from theencl§.

Take care to see that the arch of theflanges, as checked by the thread, is ap-proximately equal to the right and to theleft hand. Next, provide both faces ofthe spar from end to end with strips of1 -5 -mm. plywood (nailing it with fine nails8 mm. long in a zigzag at every 15 mm.).Place the plywood strips side by side with-out overlap.

Altogether this 6 -metre -long spar requires1 square metre of plywood. It weighs15 lbs.

Construct in the same way the spar ofthe rear wing, but on a span of 4 metres,and with a curve of 18t) mm. under thethread. This spar weighs 11 lbs.

To facilitate the folding of the wings fortransportation along the road, place someblocks at the same distance apart as onthe front wing.

Let everything dry for 12 hours beforetaking out the screw rods and the blocks.

You will be surprised at the stiffness ofthese beams. They give the impression-

and a perfectly correct impression-of reallysolid bits of stuff, to which one could trustone's life. You can make these two sparsin one day.

The RibsCover a board measuring 300 mm. x 1,500

mm. with white paper, and mark out on itthe profile of the rib as follows :

Draw a straight line (Fig. 23) at 50 mm.from the lower edge. On this line draw 15perpendiculars spaced 100 mm. apart, andmark them in accordance with the drawinggiven. For example, 2-0 marks the pointof the leading edge, -7 and 8.1 are therespective distances to the line of the lowerside of the upper side of the wing, and soon right up to the tail of the rib, of whichthe trailing edge is 3 cm. above the line.This line is the chord of the wing.

Join all the points together, and this willgive you the form of the profile of the wing.

Two laths in 6 -mm. x 12 -mm. materialare held between nails 2 mm. long, of whichyou will have cut off the heads, and whichmark out the lines required.

At 320 mm. from the leading edge markoff the line for the axis of the bolts of thespar. Place the 6 -mm. x 12 -mm. lathson either side of this line, leaving a freespace of 70 mm. This is where you willthread the spar on to the ribs.

Join the two flanges by a web of ply-wood 1.5 mm. thickness. Keep the grainin the position shown by the arrows. Nailit every 25 mm. with nails of 8 -mm. length.Dismount it and the rib is now retainedin form.

Now nail the leading edge and the fourgussets.

In this way construct 22 ribs.With a cutting compass lighten the ribs.

This should prove a simple matter, andshould remove about 20 grammes from eachweb ; it is very little, but it will lighten theset of ribs by half a kilo, and that is cer-tainly proper aviation practice.

The rib weighs 160 grammes. It requiresten minutes to nail it up.

The ribs which are not of the main series-the ribs 8 and 9-each one repeated fourtimes over, will be designed and constructedin the same manner in accordance with thedrawing (Fig. 24).

One can prepare the webs and laths infive hours. All 31 ribs can be nailed up inone afternoon, although you should allowseveral hours for rubbing up with sand-paper.

The batch of 18 ribs weighs 3 kilos.One square metre of plywood of 1.5 mm.

makes webs for eight ribs.You will find it very easy to nail two nails

in three seconds, but if you utilise a box ofnails put on a slant. This slope will havethe effect of making the nails roll until theirheads are all pointing downhill. With apair of pinchers you can then easily pick upeach nail, and bring it under the hammerwith the point about 1 mm. from the wood ;at your first blow the nail is stuck into thewood. Take away your pincers, and withone more blow the nail is driven home.

You will get along quite fast, and willavoid damaging your thumb and fingers.

Take the pot of glue well away from thebox of nails.

"FLYING FLEA"" LE POU DU CIEL"

EVERYTHING FOR THIS WONDERFUL MACHINE

Complete Wings orFuselages, Spruce, MetalFittings, Wheels, Ply,Nuts and Bolts, ScrewedRod, Dope, Glue, Ribs,Main and Rear Spars.

Send stamped addressedenvelope for Lists.

LAY BUILDINGS, LONDON ROAD,

CHELMSFORD - ESSEX

"LE POU DU CIEL"EVERYTHING FOR THE FLYING FLEABuy from the constructors of this amazing littleaircraft-Spruce, Ply, Metal Fittings, Wheels,Complete Wings or Fuselages in any stage ofconstruction-in essentials

ANYTHING AND EVERYTHINGSend stamped addressed foolscap envelope for lists

E. G. PERMAN & CO.24,5'6 BROWNLOW MEWS,

GRAYS INN ROAD, LONDON, W.C.I

WE SUPPLYALL PARTa ,01001011"FORBUILDING/AO' -

Build this wonderful 'plane and learn thedelights of flying. We supply all parts exactly to theinventor's specification. Complete fuselage, wings, orany separate part. Save yourself time and trouble andensure that your " Flea " will be completely airworthy.

Write for full details of parts and prima.0. SZOMBATY,

Marshall's Yard, 3a Seaton St., London, N.W.I

F YOU ARE INTERESTED IN

BUILDING THE " FLYINGFLEA," THESE FIRMS ARE

AT YOUR SERVICE.

FLYING FLEACOMPONENTS MADE TO YOUR

SPECIFICATIONS.

WRITE FOR QUOTATIONS.ENGINEERING DEPARTMENT,

Britannia Works, Lincoln.KEENEST PRICE

for all Materials, Manufactured Partsand complete FLYING FLEAS.DUNSTABLE SAILPLANE CO.,

MEI Luton Aerodrome, Barton, Beds.=

WHEN REPLYING TO ADVERTISERSPLEASE BE SURE TO MENTIONip) "PRACTICAL MECHANICS." -sot

November, 1935 NEWNES PRACTICAL MECHANICS

THE STORY OFCLEOPATRA'S

NEEDLEThis Interesang Relic is die LargestHewn Stone in this Country. ItWeighs z 86 tons and Rises to a

Height of 7 o ft.

CLEOPATRA'S NEEDLE is the largestand most interesting hewn stone inthis country, and its story is a fascin-

ating blend of romantic history and mechan-ical ingenuity. The mere quarrying of thismighty block of granite was a remarkablemechanical achievement, for it is 70 ft. longand weighs 186 tons, or somewhere aboutten times the weight of the largest stone atStonehenge. It was split off a red granitecliff at Syene (or Assouan) about fifteencenturies before Christ. The workmen cuta long groove in the solid rock, and drilledit with a series of holes. Wooden pegswere hammered into the holes, the groovewas then filled with water, causing the pegsto swell, and the tremendous pressure splitoff the block in a clean line. It was thenrolled by means of levers, or perhapsdragged on wooden runners, to a spot nearthe river Nile, and placed upon an enormousraft made of palm trunks lashed together,and partly supported by inflated bladdersor skins. Here it remained till the winterfloods reached the raft, and it was thenfloated seven hundred miles down the riverto Heliopolis, and the pillar-with others-was set up in front of the great Temple ofthe Sun, where it remained for 1,400 years.

Years of LabourIf this venerable relic could only speak,

what amazing stories it would tell ! Itwould speak of the toiling slaves who de-voted long years to quarrying, shaping andpolishing the pillar-the lettering was cutsome centuries later. Probably half aman's lifetime was taken in the mere pre-paration of the pillar, and placing it on theraft. We know that a similar pillar, whichis now in front of the Church of St. JohnLateran, at Rome, was thirty-six years inpreparation ; and it is obvious that movingsuch tremendous masses by slave labourwithout modern machinery must have beena matter of inches or less in a single day.It is likely that the patriarch Abrahammay have stood and watched the slavesworking on this mighty task, and Josephand Moses must often have walked underits shadow when it was finally placed beforethe temple. We know that both these his-toric persons were closely connected withthe city, for Joseph married the daughter ofa priest in this temple, and Moses was edu-cated in all the learning of Egypt in theCollege there. This old pillar must alsohave witnessed the panics caused by thePlagues of Egypt, the mourning for the" First-born," and the exodus of the Israel-ites. Centuries passed and it still stood

Cleopatra's Needle, whidi stands on the Embankment in London and round which is woven a fascinating story.

erect when Anthony wooed Cleopatra, butseven years after her death it was removedto Alexandria and set up before Caesar'spalace, and it is quite possible that Josephand Mary may have seen it when theypassed by with the Holy Child, sometwenty-three years later. Fifteen morecenturies elapsed, the glory of Egypt haddeparted, and the proud palace of theCaesars crumbled to ruin, but this mightypillar still rose proudly erect, defying thehand of time. Then, about three hundredand fifty years ago, the sea encroached uponthe land, and by washing away the sandsundermined the needle, which fell but re-mained intact. It was still lying there in1798 when Napoleon conquered Egypt.Later Nelson destroyed the French fleet atAboukir Bay, and in 1801 a fierce battle wasfought within sight of the Needle, and SirRalph Abercrombie defeated the French andadded Egypt to the Empire. The victori-ous troops conceived the idea of bringing thepillar home as a trophy of victory, and ourbrave soldiers cheerfully gave a part oftheir scanty pay for the purpose. TheWar Office, however, vetoed the idea (beingalmost as purblind then as later) and all thatresulted was that the Obelisk was moved afew yards, and a brass tablet was placedupon it recording the victory.

Offered to England as a GiftIn 1820 Mehmet Ali, the then ruler of

Egypt, offered the Needle as a gift toBritain on the accession of King George IV,but it was refused. When King WilliamIV came to the throne in 1831 the offer wasrepeated, together with a promise of freetransport, but was again foolishly declined.In 1867 the Khedive sold the land on whichthe Needle lay, to a Greek, who was aboutto break this precious relic up for buildingstone, and it was only saved by the inter-vention of General Alexander, who had forsome years been pleading with the govern-ment for its safe removal to England.Seeing that the matter was now criticallyurgent, he approached Professor Wilson,who guaranteed the money for its removalhere. The work was entrusted to Mr. Dixon,C.E., and a sum of £10,000 was agreed forthe cost. Mr. Dixon went to Egypt, andunearthed the monolith, which was nowburied in sand. An iron watertight cylin-der was constructed, about a hundred feetin length and of much greater diameter thanthe Needle. The precious obelisk was en-cased in the cylinder, which was pointed ateach end, and quite water -tight.

The Olga steam tug was hired to tow it toEngland, and left Alexandria on September21st, 1877, with its precious burden. For


twenty days all went well, but when crossingthe dreaded Bay of Biscay on October 14th,a violent storm blew up, and the cylinderwas flung about in every direction, andfinally sank at the after end, leaving thefore part almost vertical. At midnight thecrew of the Olga believed that it was foun-dering, and thought that it would carrytheir small craft down with it, so the towrope was cast off and the tug went on toEngland with the sorrowful news of thedisaster. But Cleopatra's Needle was notso easily lost, and the pontoon floated aboutfor sixty hours till the storm abated, andvas then picked up by the steamer Fitz-maurice and towed into Vigo Harbour.After a few weeks' delay it was brought toEngland, and set up on the ThamesEmbankment.

Partially Destroyed by a BombEven then its adventures were not over.

The venerable monolith which had gloweddusky red in the mystic flame of the Pillarof Fire, which to Pythagoras and Solon, asalso to Caesar and Cleopatra, had been anancestral monument, and which had heardthe thunder of Napoleon's guns, was allbut destroyed by a Zeppelin bomb duringthe Great War. The base of the pillar, andthat of the flanking lions, is deeply pitted andscarred by an aerial torpedo which wroughtfrightful destruction, but which happilycaused no injury to the ancient inscriptionswhich cover each of the four faces. Fornearly two thousand years these hiero-glyphics were an unsolved riddle, but thediscovery of the celebrated Rosetta Stonemore than a century ago provided a key tothe riddle, and they have now been trans-lated. It has been discovered that the in-scriptions on the Needle were cut by twodifferent kings, the first by Thothmes III,and the second, two centuries later, by

Rameses II. These were the two greatestkings of ancient Egypt, but the translationis devoid of special interest, being mereboastful references to the importance of thekings.

The letters, however, are most fascinating,as they represent the world's first form ofwriting. It is said there were twenty-fiveletters in the Egyptian alphabet, and alsomany signs-as in Chinese-which repre-sent complete words. Although the fingerof time has somewhat defaced the signs, itis still possible to recognise some of them,and for the benefit of those interested I willmention a few of the letters.

An Eagle is A, a leg Bu, a Bowl ka, asitting lion Lu, an owl Mu, a human handTi, a chicken ui, and a zig-zag na.

So next time you walk down the Embank-ment have a good look at Cleopatra'sNeedle, for no other stone in all Britainhas so fascinating a story.

Underground Aerodromes

UNDERGROUND aerodromes costingfrom about £1,000 to £6,000,000 arenow under serious contemplation in

America. Such airports are not only de-signed to serve the regular commercial air-lines, but are proposed as impregnable out-posts in the scheme of national defence.

An underground aerodrome to serve theneeds of nation and community in war andpeace, has been laid out in plans and modelsby Harvey Wiley Corbett, co -architect inthe construction of Radio City, and FrancisKeally, well-known for his advanced ideasin modern architecture, in association withaeronautical engineering experts.

The underground aerodrome is designednot only to serve incoming and outgoing air-way lines, but it also brings air and groundtransports together in a way that greatlyexpedites the transfer of passengers, mailand express, thereby reducing the expenseof such operations. With aeroplanes speed-ing mail to all points of the compass, theabove experts propose to extend the under-ground pneumatic mail -carrying systemwhich handles 10,000,000 letters and small

An Aerodrome of the Future which hasmany Outstanding Features

packages under the streets of New Yorkevery 24 hours.

The underground aerodrome dispenseswith vans, which are generally held up in citytraffic. The underground pneumatic tubecarries mail at a speed of 1 mile per minute,between post -offices and airports. In timeof war, the experts say, the undergroundairport would be a formidable unit in thenational defence system. It affords the

security for an air force, and it pro-vides for the swift reception and dispatch ofpersonnel and equipment. The pneumatictubes would provide certain transit fordocuments and military dispatches. Thesurface of the underground airport is bowed,to facilitate the take -off of departing 'planesand to slow up the incoming ones. Con-cealed ramps, flush with the airport surface,provide a means of admitting on arrival,'planes with passengers and mail, to thelevels below.

Two interesting photographs of the underground aerodrome showing the internal construction.


DOMESTIC WIRT

The Second Article of a Short Series

WHEN a bell is operated by twopushes, complications arise as towhich push has caused the bell to

ring, and so an indicator board should befitted as, with three or more pushes, a boardbecomes essential. The indicators consistof a small electro-magnet in series with eachpush, and in front of each magnet a freely -moving pendulum armature is mounted, sothat when the circuit is closed, it commencesto oscillate and thus indicates from whichpoint the summons came. This arrange-ment is quite suitable for most ordinarywork, but when installing, buy a box withat least two more holes or windows than areat present required ; thus if an extra pushis added, it is only necessary to add a new

nJ

An Instructive Serieson Installing ElectricBells, Improving Exist.ing Bell Installations byFitting Indicators, andObtaining the GreatestService from ElectricalApparatus which Con.stitute One of the MainItems in a Modern Home

zzczd

Fig. 1.-A bell circuit incorporating an indicator

indicator to the board, and connect it inseries as before (see Fig. 1). The abovetype of indicator is only suitable when theperson called is within hearing distanceof the bell, and will arrive at the board intime to see one indicator moving, but inthose cases where the person may be somedistance away, a mechanical reset move-ment is needed. This consists of a similarelectromagnet which comes into serieswith the push when it is pressed. The

board.

circuit is closed andthe indicator drops infront of the window,and is reset by pressinga small lever.

Electrical IndicatorsElectrically -reset in-

dicators can be ob-tained. It is not worthwhile making up one'sown indicators, but itis cheaper to buyready-made ones andmount them on home-made boards, thanto buy complete in-dicators. Various in-dicators and circuitsare shown in thesepages, and from theseany normal connec-tions can be workedout. It is sometimesnecessary to have twobells in circuit, one

with a high note and the other low, orone bell may be replaced by a buzzer.Such circuits areuseful when wiredup, as it is possibleto locate the personringing by the toneof the bell. In such

cases the indicator boards can be mountedtogether or on separate floors. Withlong runs and indicators in circuit, itwill be found necessary to have a largervoltage battery, and cells should be addeduntil satisfactory working conditions result.It is in this connection that the transformerproves very useful. In exceptionally longruns, a relay can be incorporated to operatethe bell. Run double -wire from the pushto the relay and battery (a single cell wouldbe sufficient to operate it) and the localcircuit consists of a bell and battery.Relays can also be used in the bell circuitsto switch on lights and open and close otherswitches. Connect them in series with thebell operating relay, and not in the bellcircuit, otherwise, if a relay is connectedin series with a bell, the intermittent currentpassing through it will not hold the contactsclosed, so that apparatus in the local circuitdoes not function properly. If a bell isdesired to be used in conjunction with avisible signal, this may be connected inseries with it. It must, however, be of asmall capacity, as a large filament will notheat up, and this saves the cost of anextra relay and battery (see Fig. 2).

Fig. 2.-(Left) The application of two relays to work a visiblesignal and bell. Note that only one battery is used in the local circuit.(Right) Simple application of a relay on a very long run.


Fig. 3.-Thecircuit and bellwiring for acontinuous - ac-

tion bell.

11111111111111111111111

111111111111111111111

11111111111111111111111

I1 HMI 1111111111111111

II

teEserrma CORD

Burglar AlarmsFor burglar alarms, a continuous -action

bell is essential, since a cunning man mightopen a window slowly, hear the alarm start,and of course immediately close the win-dow before the alarm has had time to awakenanyone. With the knowledge that alarmsare fixed, he can beat a safe retreat, or ifdetermined to enter the house, dismantlethe alarm. This is possible unless it is sofixed that the circuit is closed even whenthe glass is removed. With an ordinarybell circuit, it is possible to close the circuitand open it again so quickly that the bellgives only one or two feeble strokes, notsufficient to awaken even a light sleeper.A continuous -action bell prevents this,since once the circuit is closed the bell willring until reset (Fig. 3).

A letter -box alarm is very simple to con-struct and install, and is wired in parallelwith the front -door bell, so that if an in-dicator circuit is used, the summons willcome from the front door. The com-ponents are cut from -in. sheet brass,and may be fixed directly on to the door, ormounted on a small panel (see Fig. 5).The contacts are so arranged that theyonly close the circuit while the letter isactually being pushed in, thus the bell willonly ring for a few seconds. This has theadvantage that if a newspaper is pushed inand left in, the bell will not ring con-tinuously, which would prove most annoy-ing if the paper was brought some timebefore the household's awakening. Wiresare connected to the moving arm and theside bracket, and this is bent so that when

Fig. 4.-A push with side leads for operation on adesk, etc.

the arm is pushed out through 40°it makes contact, but on pushingit farther the contact is opened, andthe bell stops ringing.

Clean ContactsThe improvements that can be

made to quite an ordinary circuitwithout affecting the main wiringare many and varied, and it is tothese little extra points that atten-tion is drawn. The user seesnothing of the wiring or battery ; itis only the pushes and their ar-rangement that concern him. Forbedrooms, all pushes should befitted with an extension socket, sothat in times of illness it is onlynecessary to plug in a pear pushand length of flex to reach tothe patient's pillow (Fig. 6). Wherepear pushes are fitted in an invalid'sroom, these also should be providedwith sockets so that extension wiresmay be fitted. This will be foundvery useful when a person movesfrom a bed to a window seat ;the extra push is removed at nighttime so as not to be in the way.In studies and offices, extensionsare often needed, but these should

take the form of flat -backed pushes withthe flex leaving through a bushed holein the side. They are also very usefulin a dining -room and do not lookout of place on the table, if they are ofthe china type (see Fig. 4). Sometimes anextension bell is required, and this shouldbe connected in parallel with the usual bell.In such cases, a small two -pin socket isconnected in parallel with the bell, and theextension bell has a two -pin plug attachedthrough a long length of flex. Extension -bell sets are often very useful, and consistof a small bell and a single dry cell mountedin a small and portable case, which is con-nected through a length of flex to a pearpush.

To FRONTDOOR PUSH

Pivors

CONTACTS

Fig. 5.-A home-madeletter -box alarm.

ARM MOVED BV ifETTER.

Locating Faults in WiringFaults in bell circuits are comparatively

easy to locate, due to the shortness and lowresistance of the runs. If the bell startsringing and continues to do so even whenthe push is disconnected, it indicates thatthere is a short on the push circuit, mostprobably caused by a staple. When a bellwill not ring, test the battery with a volt-meter, preferably one of low resistance,examine all contacts, and if these seem theleast doubtful, clean and smear with

Fig. 6.-(Above) A push with extension socket andplug, and (below) a pear push with a socket for exten-

sion leads.

vaseline. Repeat the procedure for thepush and bell, as it is important to cleanall contacts, since it may be the cumulativeeffect which is causing the trouble.

The Lighting CircuitBefore attempting any alterations to a

lighting or power circuit, one must be quitefamiliar with the wiring rules and regula-tions, and in cases of hire-purchase in-stallations one must make application inwriting before any alterations are under-taken. We cannot deal with the wiringrules, as readers are expected to have a.working knowledge of them. The two -point circuit is perhaps the most usefulthat can be applied to domestic work, andevery room that has two doors or entrancesshould have a switch by each door. Intheory this seems obvious, but in how manycases is it installed ? Bedrooms should alsohave two -point control, a two-way switchbeing fitted by the door and a two-way pearpush on a length of flex over the bed. Inthe case of corridors with stairs and severaldoors opening on to them, three- and four -point control can be fitted, in fact there isno limit to the number of points that can beinstalled. When modifying a circuit totwo -point control, first examine the presentone and determine the feeding wires, alsoobtain the necessary cable of the correctsize, and two two-way switches or a two-way pear push. With a pear push it isnecessary to have a three -plate ceiling rose,from which the switch is suspended on alength of triple flex.

THE HOME MECHANICENCYCLOPIEDIA

By F. J. Camm3/6, or 3/10 by post from George Newnes Ltd.,

8-11 Southampton Street, Strand, W.C.2.


The Sun Life Office building, Montreal-one of thelargest commercial structures in the British Empire-

is a typical example of ferro-concrete construction.

THE coming of ferro- concrete repre-sents a very remarkable developmentin building and engineering practice

during the last few decades. Concrete it-self is of course no new discovery. Manyof the great buildings of the Roman era werechiefly constructed of this material. Thewalls were made of concrete, leaving thecorners, doorways, and window spaces tothe masons, and domes were also made fromconcrete, which had the great advantagethat the thrust ceased immediately thematerial had set. The great Dome of thePantheon at Rome is made of concrete, as isalso the larger and later Dome of SantaSophia at Istanbul, which vies with thatof our own St. Paul's, although built morethan a thousand years earlier.

For the benefit of the uninitiated, it mightbe mentioned that concrete consists ofbroken stones or gravel, thoroughly mixedwith Portland cement and plenty of coldwater. The proportion of cement to stonevaries somewhat according to circumstances,and most failures of concrete are due to badmixing, or skimping the cement. Thegrain of the concrete is determined by thesize of the broken stones used, and whenfinely sifted small chippings of granite, oreven sand, are used, the resulting blocktakes a very smooth surface, and cannot

Aodern AiracieJ- ivy

=3erto -CoacreteFerro -Concrete Construction Consists of a Con-,erete %lulling Having an Interior Skeleton ofSteel -work. Such Ituildings are Chiefly luilt inEart lqua_le Zones as they are Enormously Strong.

be easily distinguished from a solid massof stone.

This property enables the architect toproduce ornamental designs, mouldings,etc., very cheaply by setting the concretein specially prepared frames, and suchornamental work costs no more than plainblocks. A further and very interestingdevelopment, which is seen both in Spainand California, is concrete sculpture.

Concrete SculptureThe artist works upon the mass of con-

crete while still soft and wet, and so canproduce figures, foliage, and other designsat a fraction of the cost and labour involvedby chiselling in stone. The enormous newcathedral at Barcelona, and several newchurches in Hollywood (California) and LosAngeles, exhibit this remarkable new art,which at a distance resembles the mostelaborate work of the mediaeval sculptors,but when close up is found to be definitelyrougher and lacking in intricate detail.

As its name implies, ferro-concrete consistsof a concrete building having an interiorskeleton of steel -work. Such buildings areenormously strong, and have been largelyused in earthquake zones.

A complete frame -work of steel girders isconstructed and jointed together; thenconcrete is placed over the steel -work, andforms a solid wall which is both quake -proof and fireproof. Buildings like this will

rock violently without suffering any struc-tural damage, and they cannot burn.

Ferro -concrete is used extensively for diving towers.This fine example at Coate Water (Wilts) is 33 ft.above the surface of the water, which is 10 ft. deep.

It cost about £700.

(Left) The Rocky House, Barcelona, and (right) the New Severn Bridge, Stourport.


Ferro -concrete plays a large part in the constructionof skyscrapers in New York.

There has therefore been a great develop-ment of ferro-concrete building in all earth-quake areas, and especially along theCalifornian coast from 'Frisco to Los Angeles;in Japan, Jamaica, Sicily, and many otherplaces. Perhaps the most remarkable ofthe cities is Los Angeles, with its marvel-lous Hollywood Terminal Building, thechurch of St. Vincent, and in the WilshireBoulevard, and Grauman's Theatre, all ofwhich display daring and elaborate designsin concrete.

The Terminal BuildingThe Terminal Building is of course a sky-

scraper of some thirty stories or so, withboth a tower and spire rising above the mainmass of the building, which is relieved fromheaviness by parallel vertical strips orpilasters running right up the walls. Thisis a fine example of modern commercialGothic, and the main doorway shows veryelaborate concrete sculptures. St. Vincent'sChurch also boasts very flamboyant de-corations, which at a slight distanceclosely resemble the work of the mediaevalsculptors.

We have shown that ferro-concrete con-struction gives a high degree of safety fromfire and 'quake perils, but it has furtheradvantages, viz. :

Economy of cost, since a large amount ofunskilled labour can be used, and theconcrete can be cheaply and thoroughlymixed by machinery.

Reduction of the period of construction,because this method is speedy and elimin-ates the slow hand labour of bricklayersand masons.

" Large window space, because thestrength of the structure is in the steelframe, and so large areas of window glasscan safely be used.

Larger rooms and less restricted floor space,because the steel lining of floors permitsvastly greater spans without interior wallsor pillar supports.

Decoration is cheaper, because wet -con-crete sculpture can be used, or pre -castmouldings formed at a very low cost.

Ferro -concrete bridges have some furtheradvantages over both steel and stoneworkstructures. They are not liable to thecorrosion which involves such heavy ex-pense in painting metal ; and they havegreater rigidity than steel, and can be built

'in much longer spans than any stone orbrick -arched bridge.

Modern BuildingsThese advantages are so important, that

nearly all large modern buildings are builtmainly of steel and concrete, and even whenthe outer walls are of masonry or brickwork,the strength and solidity of the structuredepend on ferro-concrete. It is interestingto examine one of these buildings in courseof construction, because the buildingmethods are quite different from thoseemployed on old-fashioned structures.

In commercial structures or residentialblocks the steel frame is always erectedfirst, the walls being put in long after.

The new cathedral at Barcelona wellillustrates the altered technique and manyadvantages of ferro-concrete building.This, by the way, is said to be the greatestchurch of its kind in the world, and soambitious a plan would certainly not havebeen attempted but for the manifold advan-tages of ferro-concrete. The building wascommenced during the period of prosperity(for Spain) caused by the Great War.Barcelona is the greatest city in Spain, andits citizens were anxious to excel all othercities in the Peninsula. Their own ancientcathedral, built in the eleventh century, is

The great new Cathedral at Barcelona-snapped tenyears ago when half-finished-showing vertical method

of construction.

small and hemmed in by buildings, and thefaithful longed to construct a vast buildingwhich would tower above the houses andexcel even the glories of such historic cathe-drals as Seville and Burgos. But thesesplendid fanes were built during an age ofintense faith and abundant resources, andonly modern technique made it possible toattempt to surpass them. The dominatingidea of the cathedral is height, its slenderpinnacles (each almost as high as our ownSalisbury Spire) and central and westerntowers soar above the close -packed housesof the city. On the hill of Tibidabo, justoutside the city, there is another concretechurch (the Sacred Heart) also of almostmodern construction-started about 1914,and finished in about a couple of years.Here the architect has imitated the outlineof a medieval fortress. The famous" Rocky House " in the city is a largemodern block of flats, built in ferro-con-crete and having a most striking effect.

Buildings of Great Size

ful Sun Life Building, which dominates theCity of Montreal, is claimed to be one of thelargest commercial structures in the Empire,and the gigantic Royal York Hotel in therival city of Toronto is said to be theEmpire's greatest hotel building.

The style has developed still further in theU.S.A. New York's amazing skyline con-sists of an incredible number of giganticbuildings, all of which are wholly, or mainly,of ferro-concrete. They rise before theobserver in every shape-spires, pyramids,or rectangular blocks. They are so loftythat some of them are literally cloud -capped-like mountains-when the lower air iscloudless. The spectacle is repeated to alesser degree in all the great American cities,and notably Chicago, 'Frisco, and LosAngeles, but the whole subject of the sky-scraper is too big for this article, anddemands a story to itself.Buildings in Northern Europe.

Ferro -concrete building has developedgreatly in Northern Europe, and especiallyin Germany, where modern architects haveevolved some daring new styles to suit theirnew medium of expression.

The Centennial Hall at Breslau is a gigan-tic circular building, with a lofty domedcentre. The interior shows vast concreteribs supporting the roof in a very bold anddaring fashion. Very original, too, is the

mushroom " restaurant built on thetower of the old fort at Cologne, and pro-jecting beyond it like the cap of a mush-room. The Exhibition at Leipzig has manyfine ferro- concrete buildings ; one of thefinest is the gigantic Hall of the ToolManufacturers, with a vast " classical "façade with concrete pillars.The Einstein Tower

But one of the most original designsknown in modern concrete construction isthe work of Herr Erich Mendelsohn, whodesigned the amazing Einstein Tower atPotsdam. In shape it resembles anenormous jack -boot, and the architect hasobtained a monolithic effect, i.e., the build-ing appears as if carved from one huge blockof stone. Concrete lends itself to this,because it can be constructed almost with-out joins, and the few that exist can be" rendered " over with fine cement and sodisappear. It is presumed that the strange

(Continued on page 80)

The British Empire has many ferro- The Royalconcrete buildings of great size. The grace-

York Hotel, Toronto, is said to be thelargest hotel in the Empire.


Thomas

AaAterJ o Aec4anic.J.

Newcomen, who was the First to Construct an Engine, the Motivefor which was Derived from SteamPower

INVENTORS, during the early days ofmechanics, were invariably looked uponas plausible schemers, if not as actual

scoundrels. Their inventions, it was con-sidered, were put forward purely and simplyas money -making schemes, devoid usuallyof all practicability, and, quite often, of allpossibility. Inventors, indeed, during thattransitional period of the seventeenth andeighteenth centuries which saw the rise ofmodern mechanics, were the most distrustedof men.

It is probably owing to these facts thatwe know even less about the life history ofone of the most original minds in thehistory of the steam engine than we do aboutthat of Shakespeare. The title, " Fatherof the Steam Engine," has often beenapplied to James Watt. More properly,however, it should be given to a muchearlier inventor, one Thomas Newcomen.[Watt was merely a scoundrel with little, if any,knowledge of mechanics, and who filched theideas of others.-Ed.]The Newcomen Engine

All that we know about Thomas New-comen is that he came of an old Devonshirefamily and that he lived in Dartmouth.Whether he died rich or poor is not known.Being of a retiring disposition (so it is said),he did not concern himself with the currentaffairs of his day. It is thought, therefore,that after he had perfected his engine andhad supervised its erection in various partsof the country he retired to Dartmouth, inwhich town he died towards the middle ofthe eighteenth century. No monumentmarks his burial place, however, nor is anyrecord of his death to be found.

Newcomen probably combined the tradesof blacksmith and ironmonger in Dart-mouth. How he first became acquaintedwith the problem of obtaining motive powerby means of steam is not, and perhapsnever will be, known. It is thought, how-ever, that Newcomen was fully conversantwith the work of Dr. Denis Papin on thesteam engine (outlined in the last article ofthis series), because, in his " atmospheric "engine, Newcomen utilised Papin's basicidea of causing the pressure of the atmo-sphere to drive a piston downwards into acylinder after a partial vacuum had beencreated underneath it by the condensationof steam. Thomas Savery, too, lived atModbury, some fifteen miles away fromDartmouth, and since Savery's engineobtained considerable renown at the time,it is quite impossible to think that New-comen was not fully acquainted with itsoperating principles. It has been assertedthat Savery, on hearing of Newcomen'sengine, threatened the latter inventor withproceedings on account of a supposed in-fringement of his patent and that New-comen, rather weakly, agreed to grantS ',very an interest in his " atmospheric "engine for a term of years. Whether thisstory is true or otherwise, there is no doubtof the fact that Newcomen's " atmospheric "1engine did not infringe Savery's patents,for the Newcomen engine operated upon anentirely different principle.

" Atmospheric " EnginesNewcomen invented and built a number

of his " atmospheric " engines, each modelbeing a substantial improvement upon itspredecessor. His first engine was madeabout the year 1705, and a Dartmouthglazier, John Cawley (or Calley), assistedin its construction and had a part interesttherein. The engine was not immediatelysuccessful. Gradually, however, Newcomenintroduced improvements, with the resultthat before many years elapsed there were

attached by means of a chain to a pump atone end and to a piston at the opposite end.The piston, which was about a foot or evenmore in diameter, was leather bound andit was free to move up and down within alarge cylinder composed of cast brass(cylinder boring was unknown in thosedays). The cylinder was usually placeddirectly above a hemispherical boiler, fromwhich steam was admitted to it directlyby turning on a cock. The simple formof safety -valve devised by Dr. Denis

Probably the last -remaining Newcomen engine in this country. For many years it stood in a field nearAshton-under-Lyne, Lancs, before being purchased as a relic by Mr. Henry Ford and being shipped to

America.

few large mines of any importance whichdid not employ a Newcomen engine forpumping purposes.

The principle of Newcomen's engine willbe apparent from a short study of the dia-gram given on the next page. A rocking oroscillating beam, pivoted at its centre, was

Papin was fitted to the steam boiler.

Cooling SystemsWhen the piston reached the top of its

stroke, steam was admitted into thecylinder. In Newcomen's earliest engines,the cylinder was then immediately cooled


by having a stream of cold water directedagainst its exterior walls. Afterwards,Newcomen surrounded his cylinder withcold water, but, finally, he caused a jet ofwater to be injected into the cylinder bythe turning on of a tap. These methods ofcooling the cylinder caused the steam tocondense. A partial vacuum was createdbelow the piston, whereupon the latter wasimmediately driven downwards by theexternal pressure of the atmosphere. InNewcomen's early engines, the operationof the piston was exceedingly slow. Hisimproved engines, however, gave an operat-ing efficiency of 16 or 20 piston strokes per

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The working principle of the Newcomen engine.

to produce a vacuum at definite intervals onthe underside of the piston. The actualpower of the engine is derived from thedownward pressure of the atmosphere inforcing the piston downwards in thecylinder. At the same time, it was en-tirely through the vacuum -producing powersof steam that the Newcomen engine derivedits motive power. Hence the Newcomen" atmospheric " engine was the world's firstsuccessful steam prime -mover.

For the successful working of the New-comen engine, an attendant had to be em-ployed continually in order to open andclose the water -injecting and the steam

minute, a speed which, in those days, wasconsidered eminently satisfactory.

Piston rings were quite unthought of inNewcomen's day, and in order to preventthe escape of steam past the piston, thelatter was bound at its edges with leatheror even cloth. Still further, a layer ofwater, derived from a supply tank, was keptcontinually on the upper surface of thepiston in order to provide an effective seal.

The World's First Successful Steam Prime -moverIt will be seen, of course, that in New-

comen's " atmospheric " engine the workis not actually performed by steam power,but rather that the steam is merely utilised

cocks. This task was usually assigned toboys, the work being easy althoughmonotonous in the extreme. About theyear 1713 a lad named Humphrey Potter-" the lazy genius " he has subsequentlybeen called-devised a very simple methodwhereby the continual opening and closingof the steam and water cocks by hand couldbe done away with. The lad, Potter, merelytied lengths of string to the cocks andattached the other ends of the strings tothe rocking beam of the engine. By thismeans, the engine was made to operate itsown valves. Humphrey Potter's planworked well, although it is said that New -cornea himself instantly dismissed theyouthful genius for his inattention to the

engine, dubbing him a " lazy little beggar."Suffice it to say, however, that in 1720 Potterwent over to the Continent. He seems tohave been last heard of in Hungary, inwhich country he erected a large Newcomenengine to pump water out of a mine.Potter's original idea of causing the valvesof the Newcomen engine to be workedautomatically was afterwards greatly im-proved upon and it became a standardfitting on all later engines of the Newcomentype.

Newcomen's first commercially workingengine was erected at a colliery nearWolverhampton. It was reasonably suc-cessful. Soon afterwards, another engineof a similar type was built for a colliery atNewcastle -on -Tyne. A third Newcomenengine was erected at Leeds, whilst a fourthwas erected in 1714 at Austhorpe, in York-shire. The Austhorpe engine possessed apiston of no less than 23 in. diameter. Itsrate of working was 15 piston strokes perminute and it drew water from a mine shaft111 ft. deep. Newcomen and Cawleyobtained the sum of £250 per annum forits erection and its maintenance in work-ing order. Cawley, the Dartmouth glazierand partner of Newcomen, erected theengine, but he died three years afterwards-in 1717-whilst engaged in superintend-ing the engine's working.

Cornish Tin MinesNewcomen, now alone, next proceeded

to erect his improved engines at the Cornishtin mines, where a great demand for pump-ing engines had arisen. The first New-comen engine erected in Cornwall was builtat " Wheal Fortune " tin mine, nearPenzance. This engine had a pistondiameter of 47 in. It pumped water froma depth of 30 fathoms. Afterwards, New-comen erected another of his engines at" Wheal Rose " tin mine, near Redruth, inCornwall. H re the engineer employed wasJoseph Hornblower, a Staffordshire manand a member of a family which sub-sequently became justly celebra ed in theperfection of the steam engine.

Newcomen's engines were extremelywasteful of fuel. They were slow inoperation and, often enough, unreliable inthe extreme. Despite all this, however,Newcomen's original engines continued tofunction for many a year after they hadfirst been erected. As late as the year1852, a Newcomen engine could be seen inactive operation at a colliery near Glasgow,whilst only two years ago the remains ofa Newcomen engine, which for decadeshad stood in a field near Ashton-under-Lyne, Lanes, were purchased by Mr. HenryFord, the famous motor -car manufacturer,and removed bodily across the Atlantic forrenovation and reassembly in the FordMuseum at Detroit. To this day may beseen at Elsecar, in Yorkshire, a collierypumping engine which was originally aNewcomen " atmospheric " engine, butwhich has, at some period in its history,been converted to steam working.

outline of the tower has some reference tothe theory of Relativity.

In our own country we have numerousfactories, bridges, and other structures inferro-concrete. Among public buildings sobuilt is the huge Ministry of Pensions build-ing at Acton, the England Pavilion, andthe Stadium at Wembley. Nearly allmodern factories are built this way. Thereare some private houses; several streets ofthese can be seen at Welwyn Garden City.Most of our new arterial roads are also offerro-concrete, and many fine new bridges,

MODERN MIRACLES IN

FERRO -CONCRETE(Continued from page 78 )

among which the splendid single -archexample over the Severn at Stourportdeserves special mention.

It will be interesting to observe how theidea progresses, and what new designs can

be produced by means of this highly prac-tical material.

Films in ReliefA DEMONSTRATION was recently given-in the Grand Hall of the BrusselsInternational Exhibition of a new type ofcinematograph, invented by an Italian,M. Gedini Giovanni. The invention is anew stereoscopic apparatus. The audiencewatches the screen through specially tintedglasses which makes the scenes appear quiterealistic.


Inventors of the Aeroplane//'he

(names of &pig, Renson, and Aringfellow Will no auk be Qinfamiliar to (-Most

(eaders but adirectly ghese cave acre were ,gesfionsible for Considerable gioneer(Work' in the avelofirnent of the Aerofilane

Fig. 1.-A view of the Henson -Stringfellow model of 1844-7.

WHO invented the aeroplane ? Inspite of the almost universal appealof aeronautics to -day, I suppose that

not one person in a thousand could give asatisfactory answer to the question. Per-haps the names of Wilbur and OrvilleWright are the most familiar amongst thepioneers, but one must in fairness admitthat the aeroplane of to -day was inventedmore than sixty years before the WrightBrothers achieved the first successful man -carried flight. This memorable eventoccurred in 1903, and in the race for develop-ment during the last thirty years the namesof the real pioneers have been almost for-gotten. In fact, it is only in recent timesthat the work of Cayley, Henson, andStringfellow has become appreciated at itsproper value. The modern aeroplane wasnot created, constructed, and flown by any

The wing span is 20 ft.

had occupied the minds of such men asRoger Bacon and Leonardo da Vincithroughout the ages, Cayley was the firstto apply his mind scientifically to the prob-lem, and to explain the principles on amathematical basis. He was not a prac-tical engineer himself, and though heundertook various experiments to gatherdata in support of his theories, he left thenext generation to develop them intopractical form.

His one practical effort was made late inlife and never got beyond the stage ofrough sketches. It was an interestingproposal however and, some years ago, asmall model was made at the ScienceMuseum to show the form which it wouldhave taken (see Fig. 2). The " wings "are really large circular lifting screws andare set on two spindles at an obtuse angleto each other, thus giving a dihedral angle.The wings were to be revolved to providethe necessary lift by means of a power unitin the body of the machine, which was alsoto be used to rotate the two propellers inthe rear.

Cayley's proposed machine was not soimportant a contribution as his paper on" Aerial Navigation," which was publishedin 1810, and which not only laid the founda-tions of the modern science of aeronautics,but also formed the inspiration for Henson'sinvention and patent of 1842. Cayleydeclared his belief that the transportationof passengers and goods at speeds of100 miles per hour was a possibility, andhis statements were based upon his re-search and calculations and not upon idleprophecy. He advocated the use of acurved wing section, he stated the prin-ciples underlying stability, and he suggestedthe dihedral angle; he showed how direc-tional control could be attained by the useof rudders, and he outlined all the funda-mental features of a flying machine, in-cluding an estimate of the amount ofpower required. In fact, , Cayley's workat the beginning of the last century pro-vided almost all the knowledge necessaryfor the accomplishment of mechanicalflight. It remained for others, however,to apply the knowledge in practicaldevelopment.

arrant MOA.

one man ; it was gradually evolved over aperiod of about one hundred years by afew scientists and engineers, each of whomcontributed to the final achievement, andamongst the very few who made substantialcontributions, these three must take thepremier place. Indeed, if it had not beenfor the work of these men, the aeroplane ofto -day might not exist.

Sir George CayleySir George Cayley was born in 1774.

As a scientist he soon acquired an inter-national reputation, and although specula-tion on the practicability of human flight

Fig. 2.-A model of Cayley's proposed " Aerial Carriage." The helicopter -type wings were designedto provide lift, while forward motion was to be provided by the propellers at the rear.


William Henson's " First Aerial Project "It was in 1842 that William Henson, then

37 years of age, filed his famous patent for" The First Aerial Project," and, in doingso, attracted to himself almost world-wideinterest. To what extent he obtained hisideas from Cayley's writings is not knownwith certainty, but there is no doubt that,directly or indirectly, Cayley was his in-spiration. It was one thing, however, todiscuss scientific principles ; it was quiteanother matter to produce a cut-and-driedplan for the construction of an aeroplanecomparable in size with a modem air-liner-which is virtually what Henson did-and we cannot be surprised that his planswere received with ridicule.

Henson proposed to construct a largemonoplane with a wing span of 150 ft.His patent specification and drawingsdescribe the construction in great detailand, with the exception of the lack ofailerons, he described every essentialfeature of the modem aeroplane, even downto the use of streamlined wires for bracingthe wings. He proposed to use a steamengine of 30 h.p. for driving the twin air -screws, and he proposed to launch hismachine, the weight of which he estimatedat 3,000 lb., by allowing it to run down asteep incline.

Henson had undoubtedly made a fewexperiments with gliders to gather data forhis design, but he was of too ambitious anature and too lacking in patience andperseverance to wade through all the stagesof development. Instead, he jumpedstraight to what he conceived as thefinal form his machine would take andwithout any practical results to back uphis claims, and in face of popular ridiculehe attempted to form a company to exploithis invention.

Perhaps capitalists were wiser in thosedays than they are to -day ; at any ratethere was no response to Henson's appealfor funds, and, having failed to raise thecapital necessary, he resolved to constructa model instead. In this he was assistedby his friend John Stringfellow, a lacemanufacturer, and an amateur mechanicof considerable skill.

Stringfellow possessed just those quali-ties which Henson lacked. He was en-thusiastic, but he was level-headed. He hadpatience and ingenuity, and it is notdifficult to understand why he eventuallysucceeded where Henson had failed.

Stringfellow's main interest undoubtedlylay in the engine rather than in the aero-plane, and to him fell the task of designingand building a steam engine for the modelwhich they constructed between 1844 and1847.

This historic model, which is now pre-served in the Science Museum, has a wingspan of 20 ft., while the wings have a

Fig. 3.-The engine of the Henson -Stringfellowmodel, constructed by John Stringfellow.

chord of 3.5 ft. The wings are rigged withflat steel wire from six streamlined masts,while the engine and boiler were carried inthe " car." The two airscrews are 3 ft.in diameter and were originally made withfour blades each, but as four blades werefound no more efficient than two, thenumber was reduced. The airscrews weredriven in opposite directions at a speed ofabout 300 revolutions per minute by meansof multiple cord belts from the large pulleyon the crankshaft, and it was stated thatthe thrust at this speed was over 6 lb.,

with the boiler pressure at 100 lb. persquare inch.

A view of the model is shown in Fig.1, while the engine is shown in Fig. 3.The boiler and furnace are, unfortunately,now missing

It will be seen that the undercarriage ofHenson's model consists of two long mem-bers which are attached to the bottom ofthe car and which carry three wheels,apparently for use on an inclined planedown which the model was to glide forlaunching. Such a method of launchinghas serious disadvantages for a pilotlessmachine-as Henson would have realisedhad he been a mathematician-because thechange of attitude necessary at the end ofthe launch is very difficult to adjust before-hand without introducing instability.

During the construction of the model,Henson and Stringfellow lived at Chard,in Somerset, and in 1847 the model wastaken by night on to the Bala Downs, twomiles away. For seven weeks they con-tinued their experiments and trials, butthe machine would not support itself forany distance, always gradually losingheight. Perhaps the engine was not suffi-ciently powerful, or perhaps the thrustdeveloped on the ground was not main-tained in the air. One thing is certain,however, and that is that the model wasfar too large for initial experiments and itslack of stability exposed it to the mercyof ground currents and may have preventeda successful flight.

In spite of every effort, success was notattained, and, discouraged by repeatedfailures and by the financial loss, Hensongave up. He abandoned the work, mar-ried, and in 1848 he emigrated to America.By this " retirement " Henson lost muchof the credit due to him for his invention

and for his work in laying the founda-tions of the design of the modern aero-plane. In retrospect, however, we canappreciate his work in proper perspec-tive and we can but admit that theaeroplane as known to -day was inven-ted by Henson in 1842.

Stringfellow's AchievementHenson's departure for America marked

the beginning of a new stage in the historyof power -driven flight-the stage whenStringfellow, undeterred by failure, con-tinued the work alone with the fixed inten-tion of demonstrating, at least to his ownsatisfaction, the possibility of power -driven,heavier-than-air flight.

Stringfellow modified the original designin several important directions. He adopteda smaller and more convenient scale for hismodel, he devised an ingenious system oflaunching whereby the performance of themodel could be largely ascertained prior torelease into free flight, and, finally, he con -

Fig. 4.-A replica of Stringfellow's model showing the launching device.


ducted his experiments in the calm air insidea long room. These modifications in theplan culminated in success in 1848 and themodel flights which were made at Chardand later in London demonstrated that aheavier-than-air machine could supportitself while travelling through the air, anevent of outstanding importance in thehistory of flight. It seems extraordinaryto -day to realise that this event occurrednearly ninety years ago and it seems evenmore remarkable to recall that more thanfifty years were destined to elapse before asuccessful man -carried flight was achieved.

Stringfellow's model of 1848 had a wingspan of 10 ft., the wings tapering to pointsat the ends. Right- and left-hand airscrewswere fitted, 16 irk in diameter, and the totalweight of the model, including fuel andwater, was under 9 lb. The construction ofthe boiler is unusual and it is interesting tonote that it conforms in principle to thatdescribed in Henson's specification althoughit was almost certainly designed by String-fellow. It is made of thin copper sheet, silversoldered at the joints. The cones, which arefor the purpose of giving additional heatingsurface, are connected with the steam drumabove and with water chambers below. Theboiler was fired by means of a lamp burningnaphtha or methylated spirit, but the lampis now unfortunately missing.

It is interesting to note that some yearsafter the experiments of 1848, the engineand boiler were acquired by a firm of lacemanufacturers of Tiverton, and for aboutfifty years it was used to drive a small lacemachine in the factory. The engine is nowpreserved in the Science Museum togetherwith the remains of the model aeroplane.

When the model was acquired by theMuseum, its condition was much deterior-ated. Many parts were missing altogetherand those which still remained were in toodelicate a condition to permit reconstruc-tion in its original form. Fortunatelyhowever, many notes and sketches existedwhich enabled an almost perfect replica tobe constructed to show the original form.The photograph of the replica (Fig. 4) alsoshows the method of launching devised byStringfellow, without which he might neverhave achieved success.

The launching device consisted of ahorizontal member which was supportedon a stretched wire by means of two deeplygrooved wheels. A smaller horizontal stripwas attached beneath the main member insuch a way that it was free to slide upon it,its movement being limited by stops whichworked in long slots. When in position forlaunching, the model was suspended by aloop of string attached to the front of thecar, the top of the loop passing over a pinon the launching device. The rear part ofthe model was supported by a verticalmember which engaged with hooks onthe model.

When ready for launching, steam wasraised and the model restrained until theairscrews attained full speed. It was thenreleased and permitted to run along thewire until the lower member of the launch-ing device encountered a stop on the wire.This caused the loop of string to be released,thereby freeing the model in front, and itsinertia served to draw it off the rear sup-port and to launch it into unrestrainedflight.

The great advantage of this method oflaunching was that trials could be madewithout actually releasing the model, andthereby risking serious damage, until theperformance of the restrained model ap-peared to indicate that a successful flightcould be expected. The stop on the wirecould then be set to the point where the

model became self-supporting, and it wasfound that the usual run required wasabout 22 ft.

The First Successful Model FlightThe first successful flights were made in

the packing room of a disused lace factoryat Chard. The room was nearly 70 ft. long,but only about 12 ft. high, so that thelaunching wire had to be placed fairly lowin order to leave the model room to climbduring flight. There seem to be no con-temporary accounts of the experiments,but they were described a few years laterby Stringfellow's son in a small pamphlet,in which he writes : " The inclined wire forstarting the machine from, occupied lessthan half the length of the room and leftspace at the end for the model to clear thefloor. In the first experiment, the tail waswas set at too high an angle, and themachine rose too rapidly on leaving thewire. After going a few yards, it slid back,as if coming down an inclined plane, atsuch an angle that the point of the tailstruck the ground and was broken. Thetail was repaired and set at a less angle.The steam was again got up and themachine started down the wire,and, upon reaching the point ofself -detachment, it gradually roseuntil it reached the farther endof the room, striking a hole inthe canvas placed to stop it. Inexperiments the machine flew wellwhen rising as much as one inseven."

The experiments were wit-nessed by numerous otherobservers, but, in spite of this,the momentous achievementattracted singularly little atten-tion at the time. Perhaps thereason for this was that String-fellow was not interested inself -advertisement or commer-cial development, and his solemotive was to satisfy himselfas to the possibility of mech-anical flight.

Further experiments tookplace in London during thesame year and a flight of 40 yd.was finally achieved.

Stringfellow's Later WorkString fellow's " rest " was a long

one-in fact it was more than fifteenyears before his enthusiasmwas again aroused-by the for-mation in 1866 of the Aero-

nautical Society ofGreat Britain, whichlater became the RoyalAeronautical Society. The immedi-ate cause of Stringfellow's revivalof interest was the holding in 1868of the first Aeronautical Exhibition,at the Crystal Palace. He had beenasked to contribute to the exhibi-tion, and actually supplied threeentries, a light steam engine ofabout 1 h.p., a high-pressure boiler,

and a fine working model of a triplane.The triplane is naturally the most in-

teresting of the three exhibits, and althoughno records exist to show that it ever madean unrestrained flight, it is of historicinterest, since it is the first machine tohave been constructed with superposedplanes. It had been shown mathematicallythat an efficient wing, or aerofoil, as weshould term it to -day, must be long inproportion to its breadth. If much weightwas to be supported, this necessarily im-plied a very long wing, which presents ob-vious mechanical difficulties-or else theuse of superposed planes as adopted byStringfellow.

These three pioneers, Cayley, Henson,and Stringfellow, can together claim to havelaid the foundations of the aeroplane ofto -day, and although at the time theirwork attracted scant attention, we can to-day appreciate the full value of theirexperiments. To Cayley we owe the theoryof flight, to Henson and Stringfellow we owethe practical application. The work ofthese three covered a period of over seventyyears and the fact that the practical workwas confined to models does not in any wayreduce its importance.

Fig. 5.-The engine andboiler of John Stringfellow' a model.The very light construction is animportant feature and the completemodel, including fuel and water,weighed less than 9 lb.


Building a Balsa ModelAeroplane

Below are given Constructional Details of the AustralianWakefield Cup Entry-the "Milton Special "-a Feature of which is its Remarkable Stability.

Showing the finished model in the hands of a modelaeroplane enthusiast.

THE Milton Special, the constructionof which is described in this article, isthe machine that came fifth in this

year's Wakefield Contest. It is remarkable

3"DIHEDRAL

BALSA BLOCKN" X

PINS

SIM ilEVATION

Side elevation, wing -planand plan of fuselage.

for' its stability, due inno small measure tothe sweep back of itswings and the turned -up wing tips. It was flown in the contestby Mr. S. R. Crow, the English Autogirorecord holder, its best time being 3 minutes33'5 seconds.

The construction of the model is quitesimple, as it is built " on the flat."

Prepare a full-size drawing of the model,and pin this down to a flat board. Takingthe side elevation first, pin down the twomain longerons of i-in. square balsa (mediumhard) and cut and glue into position theupright struts, also of the same section balsa.Next finish one side of the fuselage by gluinginto position the diagonal struts. Repeatthis procedure, thus making two identicalsides. Stand the two sides verticallyon the plan view, and put in the crossstruts, holding the stern and forward endsof the longerons in position with rubberbands whilst the glue is drying. Whenthoroughly dry, insert small sewing pins intoupright struts for the undercarriage fixing.

The Tail Plane and FinThe tail plane is constructed from 116 -in.

bamboo by bending it in the flame of acandle and inserting the ends into the sides

of the fuselage. The fin is made in the sameway, and inserted into the top, making surethat all joints are well glued. The noseblock is cut from a piece of hard balsa andan 18 -gauge brass bush is inserted. Thepropeller shaft is made from 18 -gauge wirepassed through the bush from the rear.The rear hook is of 18 -gauge wire cementedinto the balsa sternpost.

The propeller is carved from a block ofmedium hard balsa, measuring 16 in. x 2iin. x 11 in. as shown in the side elevation.The propeller is bushed to take the 18S.W.G. shaft, and a small metal plate isglued to the front. This plate is of brassand is shaped to fitthe front of the pro-peller, a small hole

f PONT flAVATION Of WING

looBAMBOO

20 GARE

"x1-7, OR

being drilled in theplate and prop, asshown, to allow themeend of the propeller (Continued on page 116)


Working <Model SteamEngines

R

ti

-±14041

1

THE model steam engine to bedescribed in the present article isof the horizontal type, and is

provided with a double-acting oscillatingcylinder which allows of a very compact lay-out. Figs. 1, 2, and 3 give the general viewsof the engine, from which it will be seen thatthe cylinder and crankshaft are mounted onside frames fixed to a baseplate, which inturn is mounted on a plinth. The cylinder,which has a bore of in. and stroke of 1 in.,is directly coupled to the crankshaft, to theend of which is fixed a spoked flywheel.

Engine Side FramesThe main side frame, A, which supports

the cylinder steam block and one of thebearing plates, can be marked out on apiece of A -in. sheet brass to the dimensionsgiven in Fig. 5. Cut the frame to shape

/6

Figs. 1 to 3.-(Left) A sideelevation and plan of the finishedengine, and (above) a view of theengine with the cylinder omitted

for clearness.

of the angles areflush with the edgesof the frames. Drill-A -in. holes throughthe angles andframes and rivetthem togetherwith brass rivets,

as shown in Figs. 1 and 3.The two bearing plates, C, can be filed to

shape from pieces of brass A- in. thick, afterdrilling a --in. hole in each for the crank-shaft, and A -in. holes for the fixing screws.After filing the lower parts down to A in. inthickness, hold one plate in position on themain side frame and carefully mark on thelatter the position of the two holes for thefixing screws. These holes are drilled andtapped to receive A -in. bolts. Locate theholes for the fixing screws in the side frame,B, in the same way, and drill and tap themfor A -in. bolts.

Baseplate and PlinthCut the baseplate out of a piece of A -in.

sheet brass to the dimensions given inFig. 4, and drill and tap the six holes totake A -in. bolts for fixing the side frame

Tapped for 3/-32 Bo/ Cs

4/8"

with the aid of a small cold chisel and hack-saw and carefully file down to the scribedlines. The dimensions for the other sideframe are given at B, Fig. 5. On the insideof each side frame, lightly solder a length ofA -in. angle brass so that the bottom faces

Figs. 4 and 5.-Plan ofbaseplate, showing settingout of holes for fixing boltsand screws, and details ofside frames and bearing

plates.

The Constrructi©n0f a Double-actingOscillating Hori-,zontal Engine isDealt witil in ThisFourth Article of

the Series

angle pieces, the positions for which areindicated by dotted lines. The other fourholes can be drilled in. diameter to takewood screws for fixing the baseplate to theplinth.

It is usual in a model steam engine of thetype described for the plinth to be a lightiron casting, but in the present model aplinth of hardwood such as oak, willanswer the purpose quite well. Theplinth is in. longer and wider than thebaseplate, and it will be seen that the topedge is bevelled all round to meet the edgeof the baseplate. A fixing lug is providedat each end of the plinth, and these consistof pieces of Fin. sheet brass f in. wide re-cessed into the wood leaving in. project-ing. Each lug plate is fixed to the plinthwith two wood screws from underneath, afin. hole being drilled in each projectingend.

The CrankshaftFor the crankshaft a piece of bright steel

rod A in. diameter and 2j in. long will berequired, and another piece the samediameter and in. long for the crank-pin. The crank webs can be marked out

>k>F< /4

4) 4)

--A-51*7/6

1< /is


on a piece of sheet brass .11; in. thick, andthe two holes drilled through for the shaftand crank pin. Cut the webs roughly toshape with a hacksaw, and file down to thescribed lines leaving the edges as square aspossible.

Slip the webs on the shaft in the positionindicated in Fig. 6, leaving a space of 1 in.between them. Next, press the crank pinin place so that an equal amount projectson the outside face of each crank web, andsweat the whole together, allowing thesolder to run well into the four joints.File the projecting ends of the crank pindown flush, and then cut away that partof the shaft between the webs. File therough ends flush with the inside faces of thecrank. The flywheel, which is a six -spokedone, 21 in. diameter, should have a plain

hole through the boss, and can befixed to the shaft with a grub screw.

311 3/1->V6K"

TFr

L211 ,

out and filed to shapefrom a piece of sheet brassA in. thick. The cylindercovers are also A in. thick,and each cover is fixed inplace with fourbolts, holes for which aredrilled and tapped in thecylinder flanges. As thepiston rod passes throughthe front cylinder covera stuffing box has to beprovided. This is madewith short pieces of brasstubing, and a brass discwith a hole in the centre,a good sliding fit on thepiston rod. The gland, K,must be a good push fiton the piece of tube whichis_ soldered in the central

Fig. 6.-Details of shaft and balanced crank.

Cylinder DetailsAs the cylinder in the present model is a

double-acting one, it will be a little moredifficult to construct than the single -actingcylinders previously described, but withpatience, and careful soldering, a service-able cylinder should result. The finishedcylinder will be equal in power to twosingle -acting cylinders of the same bore andstroke.

The cylinder has a bore of * in. and a

M

Fig. 8.-Side view of finishedcylinder and piston -rod head.

stroke of 1 in., and for the cylinder barrelselect a piece of solid drawn brass tubing* in. inside diameter and 111n. long. Thetubing should be at least A- in. thick, andif it is sufficiently true it will only requirecleaning out with a piece of very fine emerycloth wrapped round a piece of dowel rod ofsuitable diameter, using a little machine oilas a lubricant. File the ends of the tubesquare till it is exactly 1 in. long, and drillthe two holes, E, F, near the ends of thetube, on a common centre line.

The port block, G, which is sweated tothe cylinder barrel, can be fashioned out ofa piece of 1 -in. by f -in. stick brass, oneside being filed concave to fit the cylinderbarrel after the holes for the steam portsand pivot pin have been drilled. For thelatter cut off a piece of *-in. mild steel rod1 it- in. long, and cut a thread on each end,as indicated. File the recess in the face ofthe block, as shown at H..

The two flanges, J, which are soldered tothe cylinder barrel, flush with the ends, are1 in. diameter, and are cut away to fit theport block, G. These flanges can be cut

N\''' !% '\*AO,

tir mg II,

I /P2"

Fig. 7.-Sectionalview of cylinderand steam distri-buting block, anddetails of steam

ports.

0

hole in the front cylinder cover, and thestuffing box space can be lightly packedwith a piece of oily cotton waste afterthe piston rod is in place.

The piston rod is a piece of *-in. steelrod 21 in. long, screwed at one end for thepiston rod head, and at the other for thepiston, which is formed with three brassdiscs, two of which must be a good fit inthe cylinder barrel, and the third one, ofsmaller diameter, fitted between the other

two so as to provide a packing space,as shown in Figs. 7 and 8.

The piston -rod head, M, shownin Figs. 1, 2, and 8, can be fashionedout of a piece of brass Ar in. thick.It is split across the centre, and theend cap is fixed with two 116 -in.steel screws.

HOBBIESNEW ANNUAL

Edited by F. J. CammAn established favourite withevery mechanically -minded boy.New and up-to-date models for epthe junior workshop, fully andlucidly explained with a wealthof helpful diagrams and sketches.Cover and frontispiece in full

colour.

From All Booksellers3'6 net

GEORGE NEWNES LIMITED

N

2 3 /1V6.

Steam Distributing BlockThis is shown at N, and can be made

from a piece of I- in. by A-in. stick brass.Two long A in. diameter holes are drillednearly through the block, as indicated, andthe steam and exhaust ports are drilled tomeet these holes at an angle, as shown at P.The relative positions of these ports aredetermined by the throw of the crank,and the distance of the centre of the pivotpin from the centre of the crankshaft, asshown in the bottom diagram in Fig. 7.The scale at the foot of Fig. 7 will enablethe size and position of steam and exhaustports to be checked. The lower pair ofports are the steam ports, and the upperones the exhaust ports. The outer ends ofthe two long communicating ports can beenlarged to A in. to take the ends of thesteam and exhaust pipes.

The hole through the centre of the blockmust be drilled a good fit for the pivot pin,after which the recess can be filed across thecentre of the block, as shown. The workingfaces of both blocks should be carefullyprepared by rubbing them in turn on apiece of plate glass, using pumice powderand machine oil as an abrasive medium.Assembling the Parts

Having got the piston to work smoothly,take the steam distributing block and neatlysolder it to the main side frame in theposition shown in Figs. 1 and 2, with theopen ends of the long ports pointing awayfrom the crankshaft. Now take the crank-shaft and slip on two collars, R (Fig. 2), theone on the flywheel side having a smallgrub screw for fixing it to the shaft. Slipthe other bearing plate with the small side -frame on the other end of the shaft, andafter adjusting so that the shaft turns easily,screw down the angle bracket to the base -plate. After passing the cylinder pivotpin through the central hole in the steamblock, slip on a thin steel washer and ashort piece of brass wire spring, and screwon the nut for adjusting the tension.

Finally, connect up the piston -rod headto the crank pin and apply a little finemachine oil to all the working parts.


A SCALE MICIDEIL Cif TI IIE""ClUILEN111AIRY""

Fig. 1.-The completed model, which is 21 ft. 2i in.long, 2 ft. 6 in. wide, and 5 ft. 9 in. high.

"IAM happy to name this ship theQueen Mary, and wish success to allwho sail in her." The crack of the

christening bottle, the clank of guidechains, and the deepening sound of a greatship entering her native element-thus ayear ago, with cheering and hope, waslaunched Britain's challenger for that elusiveand coveted Blue Riband of the Atlantic,and soon-next spring-she will set forthto prove her worth.

Throughout her notable career the QueenMary has been featured and commented onby writers and critics until all the worldmanifests an interest in her.

In October the Cunard -White Star linerBritannic carried across the Western Oceana huge model Queen Mary to give an earlyglimpse to Americans of the beauty oftraditional yet progressive nautical design.How the Model was Made

In connection with this model there aretwo interesting facts. It is the largest shipmodel ever constructed in England, and itwas constructed in the record time ofthree months, whereas normally a work ofthis type takes at least six months.

For nearly thirteen strenuous weeks thecraftsmen of a well-known model shipyardhave been worked day and night tocomplete the model to time, and havedeservedly achieved a world's record.

In the first place, directly the order was

This Interesting Ship Model,which is Built to the Scale oflin. to the foot, is the Largest ofits Kind Ever Built in Englandapproximate length 21 ft. 2i in., breadth2 ft. 6 in., and height 5 ft. 9 in. In the caseof a model of a finished ship, hundreds ofphotographs are specially taken of the shipto assist the accuracy of the details, but thismethod, of course, could not be used for theunfinished Queen Mary.

Timber yards all over the country weresearched for wood for the hull, which waseventually carved from long planks ofseasoned African mahogany, and whenhollowed out was large enough to hold nineof the workers. The planks, each about2 in. thick, were roughly sawn to shape andthen bolted and glued together to form arough outline, which was finished off totemplates made to the various sections of

Fig. 2.-The finished hull ready for painting.

placed, the model -makers received all theexternal working drawings, giving allvisible detail as far as was then known.

The scale was i in. to the foot, making the

the hull. The inside of the hull was carvedout before bolting the planks for two rea-sons-to lighten the weight of the model,and because there is less risk of the wood

Fig. 3.-A stem view of the boat showing skilled craftsmen adding the final fittings.


Fig. 4.-The model nearing completion.

moving when done by this method. Thencame one of the most skilled operations inthe woodwork, to shape the hull by meansof hand tools and templates to the exact formof its huge prototype, as a false cut wouldruin the model. It was then smootheddown with glass-paper and received anumber of priming coats and fillings, oneafter the other, with long intervals in be-tween for drying.

The scores of decks and deck -house partswere of New Zealand kauri pine and closegrained hard wood, accurately constructedfrom scale drawings, and these parts werethen painted and all the decks were care-fully lined out by hand to represent plank-ing. Actually over two miles of this lininghad to be done for the Queen Mary's deckexpanses.

In the Metal -working ShopThe correct drawings to scale were sup-

plied for each small part-winches, ventila-tion cowls, funnels, davits, bollards, anchors,propellers, etc. In the case of the moresolid fittings such as winches, castings weremade in the foundry in gun-metal, brass, orsome non-ferrous metal, and were thenfinished by hand, and small details added tothem by skilled model -makers. Othersthat were hollow, like the funnels, or flat,like window frames and sidelights, werewrought from sheet and strip metal, or, likestanchions, were turned from fine rod.

The funnels, which in the case of theQueen Mary were of considerable size, were

rolled in sheet brass, and the banding andedging were riveted on and soldered.Before painting, all the small ladders,

31(MMI64!

and opinions vary as to the most attractivefinish, because when the ship is at sea thecolour of these depends on what is reflectedin their plate glass-grey, green, or blue,according to the weather. The Dutchmodellers nearly always use mirror glass ornickelled metal, but with this model a newexperiment was tried by using bexoid in amottled green, which gave a very successfulresult.

Completing the ModelWhen ,each part, large and small, was

finished, a careful check -over was made tosee that nothing had been omitted, other-wise the completion of the model would bedelayed, if only for one small winch orbollard.

The great hull was taken from the paintshop and set up in a specially prepared dust -proof room, and a staff of six skilled crafts-men began the assembling.

They drilled the hull and fixed eachlittle sidelight, and then the building up ofthe decks was commenced. Stanchionswere fitted and handrails threaded, com-panion ways secured from deck to deck,masts and funnels erected, deckhouses, hugeventilators, davits, lifeboats, and all thenumberless deck fittings placed intoposition.

Fig. 5.-Loading up the model for transport to London.

syrens, staging, etc., were tried in position,and removed for plating in bronze, silver, orgold. Some fittings are painted in correctcolours, while others are plated. Then thereis the glazing of port -holes and windows,

The last hand -rail was made fast, and theQueen Mary was ready for the inspectionand approval of the owning company's navalarchitect, a worthy deputy of Britain'sfuture " Queen of the Seas."

Refrigerator Rail -Road CarsIN an age when refrigeration is rapidly

becoming recognised as an essential infood preservation, rail -road companies

are not backward in using it to keep food-stuffs, flowers, and vegetables fresh in transitfrom producer to market. The LondonMidland and Scottish Railway has just putinto service a fleet of large insulated re-frigerator cars. These are of double -walledwooden construction. The cavity betweenthe outside planks and the interior plywoodlining is packed with crinkled aluminiumfoil. The refrigerating units are two tanksin the roof containing solid carbon dioxide,known commercially as dry -ice. The gasgiven off by the evaporating " ice " is ledaway outside the cars. The cooling circu-lation is provided simply by contact of theair in the car with the cold undersurface of

THE WORLD OF SCIENCE

the tanks. Cold air sinks down amongstthe cargo and displaces warmer air from thefloor.

The use of crinkled aluminium foil as apacking in place of asbestos, cork, or slagwool is an interesting modern development.Aluminium as a metal is a good conductorof heat. The real insulator is the little air -cells between the layers of the metal, and ashiny metallic surface prevents passage ofheat by radiation across these cells.Liquid Oxygen Explosives

ACIGARETTE soaked in liquid oxy-gen flares up like a firework when

lit. Modern safety explosives are adevelopment of this principle. Cartridgesof cellulosic material, harmless in them-selves, are made explosive by soakingthem in liquid oxygen. Unlike dynamiteand blasting powder, the mixture does nottouch off easily, but requires a definite flashfrom a detonating circuit to fire it. Theexplosion develops a powerful disruptiveforce. The cartridges themselves are inertand can safely be stored without specialprecautions. Moreover, if they fail to gooff they become rapidly harmless again asthe oxygen evaporates. Accidents due todelayed firing are thus obviated. A Frenchmining syndicate regards the method withso much favour that it has installed a liquidoxygen plant producing 300 gallons an hour.The plant is situated in the middle of itsarea of operations.


ALL RADIOQUESTIONSANSWERED

FREE

FOR various reasons, push-pull ampli-fication of the " straight " kind,as opposed to Q.P.P. and Class B,

has been very much neglected during thepast couple of years, and constant inquirieshave been received from readers for a reallyup-to-date set of comparatively simple typewith push-pull output. Push-pull is cer-tainly very desirable when a really largeoutput is required, and particularly whenquality reproduction is of prime importance.It is to meet the requirements of manycorrespondents that we are being so boldas to revive push-pull amplification, andto prove that it is ideal for modem con-ditions.

A Modern CircuitThe P.M. Battery Four is in every

respect a modem receiver, and providesexactly the type of reception that is beingdemanded by more and more listeners,.who fully realise that quality and punchare of even greater importance than longrange and the ability to separate twotransmissions emanating from stationssituated many thousands of miles away.We are aware that every listener at sometime or other likes to have by him a power-ful receiver ideally suited to the receptionat perfect quality of the nearer stations.There are many constructors, moreover,who fiuid it worth while to have two separatereceivers, one with which to go" globe-trotting " and the other forlocal work and for the benefit ofthe " family," who place ease ofcontrol and quality of reproductionbefore everything else. This re-ceiver forms an excellent " second "receiver for those who come withinthe latter category.

It will be seen from the circuitthat the arrangement is on verystraightforward lines, and that itis entirely devoid of any " extras "that make a circuit look compli-cated, but which do nothing toimprove performance. Air -coredcoils of sound design andofa type pro-viding good selectivity are used both

THE P.M.BATTERY FOUR

A Modern Battery -operated Re-ceiver with " Mains " Output,Ample Range, and a Degree ofSelectivity Sufficient for Most

Purposes-and at Low Cost

in the aerial and in the inter valve circuits.Both coils are of the H.F. transformer typeof which the primary is untuned, and bothare fitted with built-in wave -change switch-ing so that the number of external connec-tions is reduced to a minimum.

Distortionless Volume ControlThe first valve is ' a variable -mu H.F.

pentode, and this provides a really largemeasure of amplification besides forming anideal distortionless volume control. Thedetector circuit follows conventional lines,and includes a reaction condenser thatgives a smooth control of volume and alsoenables selectivity to be increased whendesired. It is also amply decoupled, witha result that there is no danger of in-stability or L.F. oscillation, whether the

set is used with an eliminatoror with an H.T. battery thatis past its prime.

These three viewsof the finishedreceiver will helpin checking theconstruction and

wiring.

Every Questionmust be accom-panied by the

Coupon onpage iii of Cover

It is the output stage, however, thatmerits most attention, since this includestwo modem valves in a modern push-pullcircuit. The degree of amplification givenby a push-pull stage is more than doublethat of a single valve, the output actuallybeing something like two and a half timesthat of a single L.F. valve. Push-pull hasthe further advantage that it is practicallydistortionless, due to the fact that the twovalves tend to cancel out any distortionthat might otherwise exist.

A Balanced Output StageIn designing the push-pull output stage

of the receiver very great care has beentaken to avoid any possibility of instability,and it is for this reason that stopperresistances have been included in the gridleads to the two valves. Still further toensure perfect stability, however, the twohalves of the secondary winding of the inputpush-pull transformer are shunted by meansof small fixed condensers. It might at firstappear that these precautions against in-stability are unnecessarily complete, butthis is not the case. Theoretically, twovalves used together in a push-pull circuitshould be perfectly matched, which meansthat they should be chosen from the makers'stock with great care. There is generally anextra charge made for accurately matchedpairs of valves, however, and besides this,they cannot be obtained from the localdealer. In saying this we realise thatmodem valves of the same type have almostidentical characteristics-but there are

slight variations. But by usingthe deooupling arrangementsreferred to above, the valvesfor the P.M. Battery Four neednot be perfectly matched, andthus ordinary ones can be boughtdirect from stock without resultsbeing impaired in the slightestdegree. Triode output valvesare indicated in the theoreticaldiagram, but pentodes may beused if greater efficiency is de-sired, and these are specified.


I USE THEM AT WORK -AND AT HOMEAWLPLUGS

.712,

......FOR ALL FIX! NG. PURPOSES

"I use Rawlplugs at work for fixing anythingfrom machinery to shelves-and they'venever let me down. So it's natural that Ishould use Rawlplugs at home when there'sa fixing job to be done. Things like towelrails, hooks, pictures and dozens of otherarticles can be fixed in a few minutes theRawlplug way. I find that they save moneyand always give a neat job. Have you a

Rawlplug Outfit in yourtool kit ?"Complete Outfits:1/6, 3/6 or 5/6Illustrated literature

free on request.The

RAWLPLUGCO., LT D

Rawlplug House,London, S.W.7

RAWLPLUGPLASTIC WOOD

WOOD IN PUTTY FORM" Here's a line that saves pounds in repairbills. Rawlplug Plastic Wood is like puttyto handle, yet when it's dry it is just likeordinary wood. It's wonderful for repairingcracks in tables and floors, filling in holes,making mouldings, and repairing thingslike knife handles and kiddies' toys. It isa fine adhesive, in addition to its otherqualities. When Rawlplug Plastic Wood isdry it can be stained or painted, cut andplaned-in fact it can betreated in exactly the sameway as ordinary wood."

Available i ntubes at 6d.and I - or intins from 9d.upwards.

It 17,

"CLIX" PREVENT CLICKS!If you were to ask any radio service engineer, which was the most common faultfound when servicing receivers, the answer would be "contacts." Extreme careis always taken in the wiring up of a job, but just because valveholders, plugs,sockets, etc., are small components their contact quality is often overlooked.For years now the designers of sets described in " Practical Mechanics " andall the British radio publications have consistently chosen CLIX, because Clixhave and still do specialise in producing the finest and widest range of PerfectContact Components. To prevent Clicks-Ask for CLIX.

CLIX SPADE TERMINALSAn important feature embodied in each of the 3 sizesof Clix Spade terminals is the metal shoulder piecewhich prevents acid creeping up to the leads. Thewiring contact is positive metal to metal and the jaw inall models is designed to give full surface contact withsmall, medium or large terminal stems.No. 2-is Standard for Accumulator contacts or H.T.

connections to set. Prices: Large 2d. SmallNo. 3-is Heavy Duty model intended for bringing

aerial or earth leads direct to set without havingto make breaks or joins. Lead-in hole in in-sulators allows leads up to -Ar" diameter tobe used without stripping insulation tape fromwires. Supplied with Red or Black insulators.

Price 3d. each.

CLIX CONNECTION STRIPSSome users call these Terminal Strips, but actually theyare for Plug and Socket contacts with Terminals tofacilitate wiring (Note illustration). There are four typesavailable with engraved markings as listed below. TheseClix Connection Strips make for speedy contact whileat the same time you do secure perfect contact. We re-commend Clix Solid Plugs at 2d. each for use with these.Type "A." Engraved Mains Aerial. In -Out. 6d. each.

"B." Engraved A I .A2.E. - - . - 7d." C." Engraved -L.S.-. Pick-up. - 8d.

"D." Engraved A.E. or L.S. (See illus.) 6d.

CLIX " MASTER " PLUGSThe most important feature in these is the efficiencyof the pin, which is non -collapsible and is so con-structed that it will give perfect contact with thevarying sizes of sockets so often found in differentmakes of H.T. batteries. These Clix plugs give fullsurface contact in sockets up to k" diameter. Theyare supplied with long or short insulators andstandard markings. Price: VA. each.There is a model for Heavy Duty work, on the

lines described for Clix Heavy Duty SpadeTerminals. The Plugs cost 3d. each.

Then there is a model for Mains work. Price:4d. each. Finally, there is a 5 -amp. modelwhich costs 4 -id.

CLIX VALVEHOLDERSThe Clix valveholder V.5 is a low -loss type withceramic base. Designed for short-wave work. TypeV.I is our well-known standard type, while Type V.7is excellent for short and ultra short work wherebaseboard mounting is preferred. Details and pricesof the full range are given in new FolderFree for a postcard.

gLECTRO LINX LIMITED, 79a ROCHESTER ROW, LONDON, S.W.I OnEver since "Practical Mechanics" has been published, Mr.F. J. Camm has specified ClixPerfect Contact components. Be on the safe side-" Use CLIX and prevent CLICKS."


Preparing the ChassisSome readers may prefer to purchase

the chassis ready drilled, but those whoprefer to drill it themselves should startby marking out and drilling the four holesfor the valveholders. These are all 1 in.in diameter, and their positions can readilybe determined from the scale wiring plangiven. After mounting the valveholdersit will be found most convenient to fix inplace all those components that are situ-ated underneath the chassis, starting withthe push-pull input transformer. Afterthat, the two component brackets can befitted and the reaction condenser andvolume -control potentiometer attached tothem.

It will be seen that the fixed condensersand fixed resistances are not attached to thechassis, but are supported by their con-necting wires. The next step is to mountthe third component bracket, variablecondenser, and coil assembly on the uppersurface of the chassis. Again the correctpositions (which are not too critical, by theway) can be found by making referenceto the wiring plan. One point that shouldbe watched, however, is that the condensermust be exactly in the centre, so as to makethe drive central. It should also be notedthat the end of the condenser spindleshould be in line with the front edge of thechassis-not overhanging, as might besupposed. This is because the collar on

List of Components for theP.M. BATTERY FOUR

One Two -gang Condenser, " Baby "type, with dial (J.B.).

One Two -coil Assembly, typeT.D.S. (Colvern).

One Reaction Condenser, .0003mfd., C3 (B.T.S.).

One Pre-set Condenser, 0003 mfd.,C4 (Ward & Goldstone).

Four Fixed Condensers : two -5tubular, C7, 010 ; two 1tubular, type 250, C5, C6(T.C.C.).

Four .0002 Fixed Condensers,type M, 08, C9, C11, C12(T.C.C.).

One 50,000 -ohm Potentiometer,El (B.T.S.).

Four Fixed Resistances : one 1

meg., .R2 ; one 30,000 ohms,B3 ; two 10,000 ohms, B4 andB5 (Amplion).

One Input Push-pull Transformer,type D.P.36 (Varley).

One H.F. Choke, type H.F.8(Bulgin).

Three Potentiometer Brackets(Peto-S cott).

Two Terminal Strips : A. E. andL.S., P.U. (Clix).

Six Plugs : G.B. -1, G.B. -2,G.B.+, H.T. H.T.+1,H.T.+ 2 (Clix).

Two Spade Terminals : L.T.+,L.T. - (Clix).

Four Valves : VP215, D210, twoY220 (Hivac).

One On/off Switch (three-point)(Graham-Farish).

Two 5 -pin Valveholders (Clix).Two 4 -pin Valveholders (Clix).One 120 -volt H.T. Battery.One Metaplex Chassis, 10 x 8 in.,

with 3 in. runners (Peto-Scott).One 9 -volt G.B. Battery.One 2 -volt Accumulator.One Loud Speaker (Amplion

Harmona).

Top and Sub -chassis Wiring Diagram of theP.M. 4, attery Four

ILON-OFF SWITCH

LT--

ToL.S.

M.8

V4

Tioo GANGTUNING

COND:e

F

TRIMMERS

I0

GANGED COIL UNIT. MB.

)N1oCAP

LIA2

SPECIAL NOTEIt is important to use the specified speaker (Amplion Harmona) for the P.M. BatteryFour. Details of this high -quality but low-priced speaker appear on page 102.

HT- HT -f2 H7.41 LT- LT+

C3. REACT CONO;(2-0003 k Fa -

CENTRE TERMINAL.


You'll

need these

Sx0eAND

EittrIvxBATTERIES

specified for the

`BATTERY

FOUR'For L.T. Exide DTG, 2 volt, 20ampere hours - 4/6, or with ExideCharge Indicator 5/For H.T. Drydex Super -Life, 12ovolts I06For G.B. Drydex Mont - 1 /-

Obtainable from Exide Service Stations and allreputable dealers. Exide Service Stations give service

on every make of battery.

Exide Batteries, Exide Works, Clifton Junction, nearManchester. Branches at London, Manchester,

Birmingham, Bristol, Glasgow, Dublin and Belfast.

FOR ECONOMY & EFFICIENCY

HIVACAs Specified

13210 SpecialDetector 3/9

P215 EconomyPower Valve 4/9

Y220 Low ConsumptionOutput Valve(Two required) I V

Value Guide "P.M." Free.

Economy with Efficiency is a rareoccurrence in radio practice, but,there is always an exception toprove the rule. Mr. F. J. Camm, inselecting four HIVAC valves for his" P.M. BATTERY FOUR," includestwo Hivac types with splendid effi-ciency records, coupled with markedeconomy in current consumption

A further economy is shown inthe prices of all Hivac Valves.Against their counterparts, Hivacshow you a saving of 25%. ThatHivac are efficient is quite evi-dent, in the fact that designersof quality receivers make quitea habit of using and choosingHIVAC.

10 IVATHE SCIENTIFIC

VALVE

BRITISH w MADEHigh Vacuum Valve Co. Ltd., 113-117 Farringdon Road, London, E.C.I

%SHORT WAVE FAN'S

Got MA AZ I NE

No. 1

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The ACKNOWLEDGEDLEADERS in SHORTWAVES

BRITISH TELEVISION SO PPL ES, LTD.,BUSH HOUSE, DEPT. Pt. M., LONDON, W.C.2

There was a youngfellow of Diss

Married a carelessyoung miss !

Pots and Pans in sadarray-

Really caused HIM-no dismay-

With FLUXITE-nojob came amiss !

See that FLUXITE is always by you-in thehouse-garage-workshop-wherever speedysoldering is needed. Used for 30 years ingovernment works and by leading engineersand manufacturers. Of Ironmongers - intins, 4d., 8d., 1,4 and 2/8. Ask to see theFLUXITE SMALL -SPACE SOLDERING SET-compact but substantial-complete withfull instructions, 7/6.Write for Free Book on the ART OF " son "SOLDERING and ask for Leaflet on CASE-HARDENING STEEL and TEMPERINGTOOLS with FLUXITE.

TO CYCLISTS: Your wheels will NOT keepround and true unless the spokes are tied withline wire at the crossings AND SOLDERED.This makes a much stronger wheel. It'ssimple -with FLUXITE - bat IMPORTANT.

THE FLUXITE GUNis always ready to putFluxite on the soldering jobinstantly. A little pressureplaces the right quantity onthe right spot and one charg-ing lasts for ages. Price 16.

ALL MECHANICS W/LL HAVEN

FLUXITEIT SIMPLIFIES ALL SOLDERING

FLUXITE Ltd., Dept. P.M., Dragon Works, Bermondsey St., S.E.1


Vzit

C4

CI

1,1

.4tecr,o,Cs

Cu

C/2

,Q/ If awe Conraot. ay. 0A-

Pts

.19/80

The circuit diagram of the P.M. Battery Four.

the slow-motion drive has to fit over it,the spindle from this actually passingthrd'ugh the front of the cabinet.

The position is rather different in thecase of the wave -change switch rodon the coil assembly, since this mustproject, and the coil base is so placedthat it just lines up with the front ofthe chassis.

Simple WiringHaving mounted the various compo-

nents, wiring may be commenced.The method of making the variousconnections calls for little explanation,since it is evident from the wiringplan, but it should be explained thatseveral wires pass through the chassisfrom components mounted on theupper surface to others that are under-neath. The holes through which thewires pass are numbered on the twowiring plans, so that the " run " ofevery wire can easily be traced. It willalso be observed that two " earth -return "leads are attached to a wood screwfitted into the chassis just beside theon -off switch ; one of the leads is fromthe on -off switch and the other is from thevolume -control potentiometer.

To those who are conversant withtheoretical circuits it might appear thatthere are more terminals on the coilassembly than are actually required, andthat some of the connections are duplicated.This is explained by the fact that certainof the coil connections are brought out totwo terminals, one situated on each sideof the coil base. There is a very goodreason for this, which is that it ensuresshort, direct connections to the fixed vanesof the variable condenser and also to thegrid circuits of the first two valves.

" Earth -Return " ConnectionsIn making the connections to the com-

ponents on the underside of the chassis itwill be seen that several leads are taken to abolt (marked M.B.). These are " earth -return " leads, and it is therefore importantthat the head of the bolt should make gobdcontact with the metallised upper surface.To ensure this it is well to fit a large washerunder the bolt head, and also to place asimilar washer over the looped ends of thewires before fitting the nut.

Battery ConnectionsHaving completed the construction of the

receiver, the valves may be inserted intotheir respective holders and the aerial,earth, batteries, and loud speaker con-nected. The correct order for the valves is :Vl, VP215 ; V2, D210 ; V3 and 174, Y220.

HT -

6

It willwill be clear that the flexible lead fromterminal 6 on the second coil should bejoined to the anode terminal of the

H.T. - should be joined to the negativesocket on the H.T. battery, that markedH.T.+ 1 should be taken to a tappinggiving about 60 volts, and H.T. + 2 shouldbe given the full voltage of the battery.The two L.T. leads should be joined to thepositive and negative terminals respectivelyof the accumulator. There are three grid -bias leads, of which the positive one shouldbe connected to the positive terminal of theG.B. battery, G.B. -1 should be given thefull 'voltage of the battery, and G.B. -2should receive about 44 volts.

TrimmingThe first trimming operation that should

be carried out concerns the setting of thetwo trimmers on the two -gang condenser,for much depends upon their accurateadjustment. If they are ignored, or care-lessly set, the overall selectivity, as well asthe sensitivity, will be reduced.

Before dealing with the trimmer screws,however, the knob of the pre-set condenser,which is situated on the underside of thebaseboard, should be turned to its midwayposition, the aerial being connected to theterminal socket marked A2. This will givea good compromise between selectivityand sensitivity, and form a good basis forthe more delicate settings. Now tune in aweak station on about 250 metres and

turn the reaction condenser toits zero (anti -clockwise) position.After bringing in the transmissionas loudly as possible by means ofthe main tuning knob, slowly turnthe trimmer screw on the sectionof the gang condenser marked C2on the wiring plan by means of along narrow -bladed screwdriver.It should be found that there isa slight increase in signal strengthas a certain point is reached andthat volume falls off to a certainextent on each side of that optimum

A three-quarter front view of thereceiver showing the neat and com-pact arrangement of the components.

var.-mu valve.Of the battery leads, that

point. Find that point and thenrepeat the trimming operation onthe first section (Cl) of the conden-ser. Variation of this trimmer shouldin all cases reduce signal strength,but if not, find the best setting.

Now tune to a station higherup the wavelength scale and repeat the

marked I operations.

34"->14--3Vi

REAC770N14f4- 4 Como:e..

/I"Front view of chassis, giving dimensions for drilling the cabinet.

44"3/,t


To be completed in about 30 Weekly Parts V- eachNEWNES'

PLUM INGENGINEERING

30 EXPERTS ATYOUR SERVICE

NOT AND COLDWATER %VRIES

DRAINAGE ANC

SANITATION

LI Li-iTINGNEATINO ANDVENTILATION

Ht11,1Sil ANDPLIRLIC

MALI:WIGS

UNIQUE ILLUSTRATIONSMany hundreds of photographs have been taken to illustrateapproved methods. These wonderful action picturesform an education in themselves. In addition, the workcontains many diagrams illustrating systems of ventilation,heating and hot water supply.

A FINE LISTE. THOMAS SWINSON,

F.R.San.I., R.P.Lt. -Col. D. J. SMITH,

M.I.Mech.E., O.B.E.D. G. LEWISE. W. HOBBS, A.I.N.A.THOMAS BAYLISS

C. G. NOBBS, M.I.E.E.,M.I.H.V.E.

THOMAS FOSTERW. J. WOOLGARW. L. KILBURN, R.P.,

M.I.W.E.

L. C. C. RAYNER,'A.I.E.C.H. BARRATT, M.R.I.P.H.,

M.R.S.I., R.P.

HENRY H. BRUCE,A.M.I.H.V.E.

R. N. LE FEVRE,M.Inst.Gas E.

J. H. CLIFTONG. J. NASH

FREEWITH

PART 1

MESTICPART 1

OUT NOW

of CONTRIBUTORS:H. C. H. SHENTON,

F.R.San.I., Hon. F.I.S.E.PERCY MANSER, M.R.S.I.,

R.P.ERNEST B. PARTINGTON,

M.R.San.I., M.I.W.E., R.P.

R. G. CHAMPIONB. J. GARDNERH. L. EGERTON, A.M.I.H.V.E.

ARTHUR ORD, A.M.I.H.V.E.,R.P.

H. 0. THORP, F.C.I.S.,Cert.A.I.B.

W. FROST, F.I.S.E., M.R.S.I.,M.R.S.T.

JOHN C. GRAHAME. D. CLAYTON, M.R.San.I.J. BODGERH. T. HUMPHREYST. PALMERL. J. FOWLER, B.A.,

A.M.I.C.E., M.I.H.V.E.

TABLES and DATAWherever possible, the practical information has been compressedinto the form of tables which are admirably suited for referenceby the practical man. The full scope of " PLUMBING& DOMESTIC ENGINEERING " is given on facingpage-you will find it absolutely comprehensive.

LARGE FOLDING CHART(In 2 Colours)

Dealing with Standard Hot WaterSupply and Heating Systems


To all young men in the Buildingand Allied Trades

L'OR EVERYONE interested inthe erection and equipment of houses

and large buildings "Plumbing andDomestic Engineering " offers awonderful opportunity for an investmentwhich will yield a return of manyhundreds per cent on outlay.It is the first work of its kind ever pro-duced, and every contributor is an expert

on his particular subject. MasterPlumbers, Gas Engineers, SanitaryEngineers, Heating and VentilatingEngineers, have written the articles,which are packed with practical infor-mation.Each week you can obtain thebenefit of their vast experiencefor a small cost !

Scope of "Plumbing and Domestic Engineering"Systematic Examination of the Domestic

Services of a Building.

Pipes and Tubes for Water Supply andDrainage.

Lead Plumbers' wiped joints ; preparation oflead -to -lead and lead -to -brass, copper or gun-metal ; underhand, upright, branch, knuckle-taft, block or flange joints ; expansion jointsfor waste pipes ; jointing tin and tin -lined leadpipes ; copper bit joints ; burned or fusedjoints ; bending and fixing. Copper ; Com-pression and screwed joints ; unions ; bronzewelding or brazing ; bending, screwing andfixing. Iron ; Socketed pipes ; caulking withgasket and metallic lead ; screwed joints withsockets ; flanged pipes with insertion ; specialand patent joints, etc.

Sheet Lead and Sheet Copper Work.Flats; box, parapet and valley gutters, cesspools,step and cover flashings, soakers, hips, curbs,ridging, domes, dormers, finials, skylights, trapdoors, cornices, aprons, drips, rolls, laps, baletacks, welted seams, lead wedging, " burnt -in "mastic joints, etc.

Materials.Alloys, solders and fluxes ; cements ; com-position, preparation and uses of Portland, lead

mastic and rustic cements ; other jointingmaterials and compounds.

Calculations for the Domestic Engineer.Domestic Water Supply from the Mains.

Hot Water Supply.Tank and cylinder systems ; combined doublecylinder and calorifier systems ; combined hotwater supply and heating systems ; boilers andwater heaters-the " Ascot," the " Ewart," etc,

Main Drainage Systems.Modern drainage systems simply explained ; theone pipe system of drainage ; installation ofwash basins, baths and scullery sinks ; inter-cepting traps, disconnecting traps, petrol traps,etc. ; the ventilation of drain, soil and wastepipes.

Private Water Supply for Country Districts.Wells, pumping plant, windmill pumps, elec-trically driven pumps, petrol driven pumps.

Drainage Systems for Country Districts.Cesspools, the septic tank, the automatic sewagesiphon, earth closets, surface and sub -irrigationfilters, contact beds.

Heating.Warming of buildings, slow combustion stoves,gas fires and gas radiators, electric heaters, hot

Absolutely Comprehensive!" PLUMBING & DOMESTIC ENGIN-EERING " gives you a splendid opportunityto make yourself so proficient in your work youwill stand head and shoulders above the manwho THINKS he knows all there is to knowabout the subjects of Plumbing and DomesticEngineering.

Hand this Order Form toYour Newsagent at once Mr'Obtainable at all newsagents and bookstalls, 1 /-each part,or 1 /2 each part post free, from George Newnes Ltd.,8-11 Southampton Street, Strand, London, W.C.2.

To

Practical

water heaters ; low, medium and high-pressurehot water systems, etc.Ventilation of Buildings.Principles of ventilation ; houses, large buildings;the Plenum system, exhaust system, combinedsystems ; fans and fan motors, duct work, aircleaning and conditioning, up-to-date practicein cinemas and theatres, etc.Ships' Plumbing.Lead Burning with Blow Pipe, Gas Torch

and Oxy-acetylene Flame.Oxy-acetylene welding.

The Principles of Gas Fitting.Cutting, jointing, bending and fixing of pipes ;wet, dry, check and slot meters ; lighting burners ;fittings and mantles ; switch or distant controlsystem ; high-pressure lighting, etc. ; types andfixing ; water heaters, geysers.Gas Refrigerators-Principles of Electric

Wiring.With special reference to thermal storage waterheaters, electric refrigerators, etc.Glazing.Handling, cutting and packing glass ; types ofglass used ; glazing methods and fitments.including shop window glazing.Estimating for Plumbing Work.Business Methods for the Master Plumber.

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Undercarriages And WheelsFor Petrol Model Aircraft

y @OM;n @ 6. (430wden(Wade, of cOrwsh a.0.9.aecord for dower (-Model Aerofitanes)

It is essential that the undercarriage of a model aeroplane be re-liable and also strong enough to absorb the shock of landing withoutbreaking itself or the fuselage. Below are given some suitable designs

IT may be thought that the subjectchosen for this article is the leastimportant of all the component

parts that go to make up a successfulpetrol -driven model aeroplane.

From my own experiences, however,and from observa-tions of otherpeople's petrolmodels, I feel that asound undercar-riage with suitablewheels makes ormars an otherwisegood model.

It is essential thatan undercarriageshould be reliable,and not require re-pairing after everylanding. Also, itmust absorb theshock of landingwithout breaking it-self or the fuselage,and it must go oncarrying out thesefunctions withoutattention. Further-more, I considerthat one should at-tempt to eliminateall points of un-reliability both inthe engine and themachine itself. Apetrol model thatwill regularly take off, fly in a wind andland without damage, is to my mind anideal machine. Having obtained thatideal, the designer can then cast aboutfor ways and means to beautify his model.

I fear too many constructors start fromthe other end. They copy a pleasing look-ing full-sized design and hope for the best.This method seldom succeeds wherepetrol -driven model aeroplanes are con-cerned. In my early models, I suffered

reasons for these troubles, and to devisemethods of obtaining reliability in eachof these departments.The " Split " Type of Undercarriage

Firstly, let me say that, as in the caseof practically all theother petrol models

and serviceable undercarriage fitted to one of the author's petrol -driven aeroplanes.

from three main troubles, carburation(i.e. easy starting and reliable running inthe air), damaged engine mountings, andundercarriage troubles. I accordinglyset about attempting to analyse the

ALUMINIUM BRACKETS ATTACHED TO FUSELAGE

Fig. 2.-Construc-tional details of a splittripe undercarriage.

Fig. 1.-Showing a strong

DURALUMIN 'TUBES

STEEL TUBES

I have seen, I trieddesigning a sprungleg" split "type un-dercarriage, ratherafter the style of thefull-sized article.My reason then be-ing, that I consider-ed a heavy petrolmodel would re-quire some usefulspringing device,and yet have a clearspace between thewheels without anaxle to hit longgrass and so turnthe model overwhen taking off orlanding.

I conjecturedrightly that this un-dercarriage must bepositioned well inadvance of thecentre of gravity,and just behind theengine, to preventdamage to it, and

to keep the model from nosing over onlanding and in taking off. I havenoticed one or two examples wherethe undercarriage has been positionedfarther back, as in full-sized practice,but in every case that I have observed,difficulty has been experienced in takingoff in long grass or rough ground, andthe model has nosed over on landing.It is therefore very important to placethe undercarriage as far forward aspossible, with the wheels almost underthe engine, in a tractor model.

I originally feared that with theundercarriage so far forward, the tailmight not rise when taking off. How-ever, if the model is correctly designedwith the thrust line in the right position

and a tail plane of slightly lifting sec-tion, it will be found that this ex-pected trouble does not exist. A tailwheel will help to get the model goingin the first place. In Fig. 2 is showna sketch of the undercarriage of thesplit type. For those who must havean undercarriage resembling the full-sized affair of to -day I can say this


type functions fairly well up to a degree.But I soon found that I had to carryspare rear legs with me, as after almostevery flight these legs and their fasten-ings to the fuselage were damaged.

I then tried placing the spring tele-scopic legs at the rear, but I found thatthere was not enough movement, andafter the springs had fully compressed,the legs were forced into the fuselageand the plane suffered from brokenfuselage longerons.

It then became obvious to me that apetrol model with even a good flat glidedoes not land in the stalled position, forthere is no pilot, as in the full-sizedmachine, to conveniently pull the noseup at the last moment and " hold off "so that the aircraft practically dropsdown with a vertical and downwardmotion just before touching the ground.

The model, however, glides into theground, thus first imparting a backwardblow, which is then converted into anupward movement (see Fig. 3).The Two -legged Type of Undercarriage

The type of undercarriage about to bedescribed is specially recommended toanyone who is building a new petrolmodel.

Reference should be made to Fig. 4 in

AEROPLANE STALLED ON 10 GROUND

PATH OF GLIDE

GROUND LEVEL

PATH OF GLIDE _ PETROL MODEL

GROUND

BRASS TUBES ATTACHED 10 FUSELAGE

U

BOUND &SOLDERED

CATCHES FORELASTIC BANDS

BALSA FAIRING_BOUND WITH SILK & DOPED

VanDIA. SPRING STEEL WIRE

Fig. 4.-Showing the latest type of wheelmade up with special _" Dunlopillo " balls.

order to follow details of construction.The undercarriage for a 6 -lb. to 8 -lb.

petrol model is composed of two mainlegs of i-in. diameter spring steel wireturned out at the lower ends to formsteel axles for the wheels. The upperends may be either carried across tojoin the legs and then eventuallybound on to the floor of the fuselage,by thread and glue, if the undercarriageis to be a permanent fixture ; or theends may be turned in and cut off 14 in.after the bend. These projections canthen be fitted into a brass tube whichhas been bound across the bottom ofthe fuselage. The undercarriage willthen be detachable if the rear legs aresimilarly treated. In Fig. 4 is shown adetachable type of undercarriage, as thisis the most convenient for transportpurposes.

On my model, the " Blue Dragon,"which won the 1934 Sir John ShelleyPower Cup and holds the power drivenR.O.G. record, I used a non -detachable

%type for complete reliability for com-

fuselage. The details shownin Fig. 4 will make thisclear.

The two main legs arenow reinforced bytwo morestraight pieces of *-in.diameter wire for each leg.These reinforcing lengthsof wire are bound in severalplaces with florists' wire tothe main legs and soldered.

For the detachable un-dercarriage one of the re-inforcing pieces on each legis turned out at the top toform a catch to keep thestrong elastic bands inposition that are used tokeep the two legs firmlyinto the ends of the cross -brass tube. Small wirecatches are also solderedto the rear circular spring

Fig. 3.-(above) A full-sized aeroplane held off by the pilot to legs for the same purpose.make a 3 -point landing, and (below) a model aeroplane landing.

Fairing the Undercarriage

LEVE

petition work. I have flown this modela great deal, but no damage has everoccurred to the undercarriage.

However, on all subsequent petrolmodels I have used the detachable type,and have experienced no trouble.

A crossbar, ortiebar, is now fit-ted between thetwo main legs. Itis located abouthalfway up thelegs. This helps tosteady them andyet allows goodclearance for longgrass between thelegs. This tiebar is

made of Fin.diameterspring steelwire turnedup beyondthe rightangle ateach endand carriedon into the

two rear legs as de-scribed below. Theseturned -up portions are then bound withflorists' wire to the main legs andsoldered.

Next the two rear legs are formedas continuations of the Fin. diameterspring steel wire used in the crossbarand are in the form of large circularsprings. This allows the main legs togo backward and then upward on theforward impact of the model with theground. These circular springs are bentby hand in a vice,-not an easy job ifthe wire is a good spring steel, as it mustbe to do its shock -absorbing work, butit is quite possible. The rear legs arethen bent inwfords at right angles toform detachable prongs 14 in. long toinsert into the rear brass tube, in thecase of the detachable undercarriage, orin the case of the permanently fixedundercarriage the two rear legs arejoined across the fuselage and boundand soldered, and then bound withthread and glue to the bottom of the

The final stage in the construction ofthe undercarriage is now entered into.The two main legs and the cross -barare faired off for neatness and to reducehead resistance by a fairing of balsawood, which is then sanded to stream-line form, bound with silk strips, doped,and finally painted to the desired colour.

Firstly, the fairing for the main legs iscarried out by cutting two lengths offlat balsa it in. thick, the length of thelegs, and 14 in. wide. These strips areplaced on either side of the wire leg,with a strip of 4 -in. balsa sandwichedbetween in front and at the rear ofthe leg. Plenty of glue is alsoplaced in the balsa " sandwich." Thewhole is then bound with model aero-plane elastic and left to set dry. Afterthe fairing is dry and the elastic re-moved a sharp razor blade is used toshape the fairing to a streamline form,the final finish being given by sand-paper.

Strips of silk are then cut approxi-mately in. wide and the legs arecovered with a coating of a goodphotopaste. The silk strips are thencarefully bound round the fairing with

ELEKTRONWHEEL PLATES_HOLES THREADED

DURALUMIN TUBE _THREADED ATEPCHEND

SPONGE RUBBER "TYPE BALL _WITH HOLEPIERCED FOR AXLE 'TUBE

Fig. 5.-The " Dunlopillo" doughnut wheel.


ION

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r,

just overlapping edges. The whole issprayed with water and smoothed downand allowed to dry nearly hard. A. coatof full-sized aeroplane clear dope is thenapplied, after which the legs are paintedthe desired colour.

The crossbar between the main legsis faired in the same manner. The rearspring legs are, of course, not faired,but are merely painted to match.

It will be found that the balsa fairingbound in this way with silk and dopedweighs practically nothing but strength-ens up the legs tremendously.

The above type of undercarriage canbe used for " pusher " petrol models aswell as tractor. In fact, the writerfitted a detachable one to a flyingamphibian boat with success.The Wheels

The next problem to be considered isthe type of wheel to be fitted.

There have been many different typesproduced by petrol model enthusiasts.I will therefore content myself with de-scribing briefly my own experiences,and leave the reader to judge forhimself.

I originally had some aluminium discwheels made up for me by the DunlopRubber Company. These were formed bytwo spun aluminium discs with a dura-lumin axle sandwiched in the centreand hollow rubber tyres with a flange in-side sandwiched between the outsidecircumference of the aluminium discs.Rivets were then placed through the discsand the rubber flange to prevent thetyre pulling off in a cross -wind landing.

These wheels are still in operation.They were 4} in. diameter and weighed4i oz. each. Their chief fault lies in thedamage that is done to the edges of thealuminium discs.

Next the Dunlop Rubber Companyturned up some elektron wheels of asmaller diameter, and made me hollowair -inflated tyres to spring on to the rims.

These frequently came off duringlandings across wind with drift on, andthe tyres also became deflated after atime.

They were light, however. Dunlop'sthen made me up some tyres of solid butlight " Dunlopillo " rubber. Thesedid not deflate but easily came off andwere inclined to be lost.

I then asked the Dunlop RubberCompany to make me up some solidballs of special light " Dunlopillo "rubber with holes pierced through thecentre, the bails to be of 41. in.diameter.

Two small discs were then made fromelektron and holes threaded in thecentre. A duralumin axle bush was thenmade 1 in. long and threaded extern-ally. The two discs were then screwedon each end with the rubber ballbetween (see Fig. 5). The ball was thussqueezed up and formed a perfect" doughnut " wheel, that cannot bepunctured or torn off, and is also veryspringy and has excellent shock -absorbing powers.

It is certainly rather heavy. A wheelweighs over f lb. complete. But Ifound on my eight -foot span " BlueDragon " monoplane with Atom Minor

engine, that whereas the model had beenvery stable and a good glider before, itbecame superstable ; the reason of coursebeing that the C.G. is now lower. Fig.5 shows the wheels fitted to the " BlueDragon."

I fitted a pair of these wheels to an8 -ft. low -wing monoplane that is beingflown by a 9-c.c. Brown Junior engine,and the result is excellent; the extraweight low-down being a great advan-tage for a low -wing model.

Altogether I am most satisfied withthe result, and have now asked the firmto produce me some special balls of thesame light rubber but of only 3} in.diameter and pierced in the centre.These will be slightly lighter and make,up smaller wheels for the small 9-c.c.engined models now becoming popular,and yet be of sufficient diameter to en-sure good landings and happy take -offs.

The Dunlop Rubber Company ofBirmingham inform me that they cansupply anyone with the larger ballsready pierced in the centre for 2s. each.Anyone requiring these balls should askfor exact replicas as made in the mouldespecially produced for me. No doubtthey will also be prepared to supply thesmaller ball shortly.

Before having these balls made for meI searched everywhere for a light -weightrubber ball of the desired diameter, butwithout success. I also tried makingwheels up on the same principle butwith hollow rubber balls. I gave theseup owing to the constant trouble experi-enced through deflation of the hollowball.

A New Metal -Spraying ProcessTHE recommendation by the Radio

Interference Bureau of zinc -sprayedcoatings as a means of suppressing

interference caused by electro-medicalapparatus is the latest development of acomparatively new industry.

Metal spraying is carried out by means ofa pistol which is patented and manufacturedby Mellowes & Co., Ltd., Sheffield andLondon.

The process, which is known as Mellozinghas been found valuable by many industriesfor giving a metallic coating to metal,wood, glass, or almost any material, as it

COVERGUARD

FRONTPLATE

COMPRESSEAIR COIL

AIR -FEEDER

SILVERSTEEL NOZZLE

FRONT ,-,PLATE

COMPRESSEDAIR COIL

AIR -FEEDER

CONTAINER

s:NN's

STEEL '1 'CONTAINERNOZZLE

is possible for a delicate fabric, such assilk, to be Mellozed without damage.

Rust RemovedAll metal -work is sand -blasted before

Mellozing to remove any rust or scale andto provide a suitable surface to which themetal spray can adhere. With othermaterials, such as wood, plaster, brick,etc., it is only necessary for the surfaceto be dry and free from grease.

The metal to be sprayed is first meltedin a small gas -heated crucible, from whichthe container of the pistol is filled about

every twenty minutes.A Bunsen type flame un-der the container, the gasfor which is obtained byconnecting the pistol tothe ordinary gas mainsby means of a rubberhose, keeps the metal ina molten condition whilstspraying. The pistol isalso connected by arubber hose to a cora-

HANDLE

COMPRESSEDAIR COIL

Details of the pistol used for Mellozing.

pressed air supply of 60/75 lb. persquare inch, and when the molten metalflows to the nozzle, it meets the preheatedcompressed air, which very finely atomisesit so that minute particles of metal areblown at a tremendous velocity against thesurface to be covered and adhere firmly,forming a continuous metallic coating with afine matt finish, which is decorative in itself,and an ideal base for paint. The thicknessof this coating is approximately -004 in.,and the speed of application 8 to 10 sq. ft.per minute, but this coating can be in-creased to any desired thickness by allowingthe pistol to travel at a slower rate acrossthe surface to be Mellozed.

Owing to the comparatively low tempera-ture of the metal spray when deposited onthe surface to be Mellozed, it is possible totreat glass, wood, cloth, and inflammablegoods with safety.

One of the largest wireless valve manu-facturers in the country has been usingMellozing pistols for five years for metallis-ing the outer glass bulb of wireless valves,and has found the process very successful.Other branches of the radio trade havefound Mellozing useful for giving a metalliccoating to wood panels for screening pur-poses, and for the manufacture of radiochassis from metal -sprayed plywood.

For the protection of iron and steel fromcorrosion by spraying with a coat ofcorrosion -resistant metal, such as zinc ortin, the Mellozing pistol is unequalled, andat a comparatively low cost, iron andsteel products may be made impervious tocorrosion.

More industries are becoming aware ofthe possibilities of the process for protectiveand decorative purposes.


4

1

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Fig. 1.-L.M. & S.R. Engine, No. 4357.

LMS

A Model Electric Garden RailwayFROM time to time, articles on garden

railway plants operated by manualpower, and also by steam locomotives,

have appeared in these pages. The first is,of course, a very simple system ; cheap,but somewhat tiring for the person workingthe engine, which is driven by a handlemoved by the hand of the driver and linkedto a single -throw cranked axle on whichthe driving wheels are mounted. Thesecond, where steam locomotives are em-ployed, is generally too complicated forchildren to work unassisted, and, therefore,an electric scheme is described below whichany person of average intelligence can workwithout supervision.Current from Mains

As the current supply will be taken from__,_,

:t04

1

4

1

1

,

1

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74"

3 %I - - -

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By E. W. TWININGAlthough There is Nothing in the AboveTitle to Give any Indication of the Sizeof the Railway, it is Intended That itShall be Large Enough to Carry JuvenilePassengers. This Constitutes Somethingof a Novelty, for Nothing of the Sorthas Previously Been Published and HasPerhaps not Been Previously Attempted

the ordinary house electric light mains, thewhole system must be foolproof, and becapable of being handled without risk ofshock. As most readers know, the usual

rl2 - -

method of transmitting current to the motorof the engine and returning it to the sourceof supply, is by making the running rails,that is to say, the rails on which the loco-motive and rolling stock travel, carry thereturn current to the battery whilst theoutgoing current is passed through a con-ductor rail on which a brush (carried by theengine) rubs. One side of the motor isconnected to this brush and the other tosome part of the frame of the engine, which,of course, is in contact with the wheels, andthey in turn are contacting with the rails.Now, if 220 -volt mains current were used todrive the motor, such an arrangement wouldbe extremely dangerous, as the personoperating the engine may receive a severeshock by touching one or other of theconductors whilst his feet are earthed.

14°'

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11000

TA ifrAI I I Y34 A

8'

Fig. 2.-G.W.R. Engine, No. 1005.


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AMPLION RESISTANCESare also specified by Mr. F. J. Camm.

A defective resistance cancompletely ruin the enjoy-

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ResistancesThey are colour coded, compact andsturdy, and all values are wire -wound,this method of construction giving themost reliable form of resistance.Send for Descriptive Folders "P. M."

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perfectly. Any handyman can erect. Fits all shapesof windows-square bays, round and oval.Most fittings SOLID CHUNKS OF BRASS and whole system is a

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IN FOUR QUALITIES.Strong (Brass) ... I ft.Light (Brass) ..

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Steel (Rustproofed)9d. ft.

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From all ironmongers. Ifany difficulty write fornearest stockist's name.

Beware imitations.Any length cut to order

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as illustrated.Each model has inclinablebody, swing mirror, stageclips, and is nicely finished inBlack Crystalline Enamel andbright Nickel Plating.SHARP DEFINITION ISOBTAINABLE and GOODWORK CAN BE DONEModel C. Height 5i in., sliding focus, magnification 25 x linear Price

Model D. Height 7 in., sliding focus, circular stage magnification 50 x

Model E. Height 7 in., rack and pinion focusing, magnification 50 xlinear, square stage ... ... .. ... Price

Model F. Height 7 in., rack and pinion focusing, triple nose -piece. 3lenses, magnifications 25 x , 50 x , 100x, in wood case,with set of Dissecting Instruments. .. ... Price

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BROADHURST, CLARKSON & CO.LONDON. 5.1.1.

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SCALE RAILWAYS IN MINIATURE"00" GAUGE IS

the most practical Gauge for the average home

Complete railway systems in miniature can besimply and cheaply built, accurately to scale.We have a large range of parts, accessories, etc.A fully electric layout comprising 20 -ft. track,loco., scale coaches, points, etc., costs under £5.

Scale Electric Locos from 37/6, Wagon parts 1/11 each.

Write for list and track samples, sending 3d. to

HAMBLINGS26 Charing Cross Rd.LONDON, W.C.2


Protected Conductor RailsThe obvious thing to do, in order to

render the system safe, is to avoid passingcurrent through the running rails, but torun two conductors, provide two brusheson the engine, and to cover the conductorsin such a manner that they cannot betouched by hand.

The layout of the motor and the neces-sary gearing in the engine is shown in theillustrations.

For all-round purposes no scale is moresuitable for carrying passengers than 1 in.to 1 ft., which gives a gauge between railsof approximately 41 in. Of course, if amore powerful locomotive were built wemight very well go to 1 in. to 1 ft. and agauge of 7} in., but the 1 -in. scale is thesmallest which can conveniently be adopted:the width of rail is sufficient for stability.On narrower gauges the trucks are liableto overturn because passengers do notrealise the necessity for sitting centrallyon the truck and balancing themselves.

Engine PrototypeAlthough it may not be universally

popular amongst model -makers, the 6 -coupled goods engine is one of the mostsimple types which can be adopted. Ithas the smallest number of wheels whichcan be fitted to a main -line engine, thewhole weight of the engine is available foradhesion and, if painted in proper colours,has a very good appearance. In Figs. 1and 2 are shown elevation drawings ofLondon Midland & Scottish and GreatWestern 6 -coupled locomotives.

Of course some of the railway groupspaint all their goods engines black, but itis suggested that the prototype be departedfrom in this matter of colour. I wouldcertainly paint the London Midland &Scottish engine the usual passenger colour,crimson red. The Great Western will, ofcourse, be middle Brunswick green, theLondon & North Eastern also Brunswickgreen of a slightly lighter shade, and theSouthern the well-known olive green.

The Electric MotorComing now to the motive power, in

Fig. 3 is shown a general arrangement ofthe mechanism in the after part of thelocomotive. The motor is, as will be seen,

supported in the firebox and back part ofthe boiler barrel. The particular motorillustrated is the Klaxon type EKU-SWR.These machines are made integral with agearbox, and this gearbox carries the motor.The particular type, bearing the code lettersmentioned, is made with quite a largenumber of gear ratios in the gearbox, andthe ratio selected is that bearing the num-ber 20119, which number is part of thecode reference. The output speed of theshaft, projecting from the gearbox, is 160r.p.m.

irl

u

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IIntermediate Gearing

It is perhaps unfortunate that it is notpossible to drive direct from this shaft downto one of the axles. There is not room, aswill be seen from the cross-section on theright-hand side of Fig. 3, to pass a chainstraight down over the side of the gearboxso that it will come between the framescarrying the driving wheels ; so it is neces-sary to introduce an intermediate shaft.The method of transmitting the power is

Fig. 3.-The arrangement of the motor and gearing.

through the medium of bicycle sprocketwheels and bicycle fin. pitch roller chains.There Will be on the gearbox shaft twosprockets of 14 teeth each, and on the in-termediate shaft two sprockets of 17 teeth,these driven from the motor. From theintermediate shaft only a single chain iscarried down to the rear coupled wheels,and here there will be no gear reduction;both the sprockets on the shaft and on theaxle will have 17 teeth.

For fixing all these sprockets, a special fit-ting will have to be made for each, since, whenthe sprockets are purchased, they will befound to have a screwed hole through themof approximately 11 in. in diameter. Steelbosses will have to be made and screw -cutfor mounting the sprockets, the inner boreof the diameter of the boss being equal tothe diameters of the shafts on which theyare required to fit. To prevent the sprocketfrom unscrewing from the boss a keep ringis turned and secured by about six cheese -headed screws. The arrangement of thesebosses may be seen in the cross-section onthe right-hand side of Fig. 3. The bossesare secured to their shafts by tapered steelpins.

Materials for Engine ConstructionWith the exception of the driving wheels,

their axles, and the coupling rods, the restof the engine can be made of wood, but ifwooden frames are made, metal bearingsare necessary for the axles, but it is stronglyrecommended that the frames of the enginebe made of metal.

The little Klaxon motor is not sufficientlyheavy to drive the engine and a truckcarrying one child passenger at a greaterspeed than 2 miles per hour. It is uponthis rate of travel that the gear ratio of160 r.p.m. in the gearbox and the chainreduction to the wheels has been calculated.These latter will make 134 r.p.m., which willresult in the rate of travel mentioned withdriving wheels of 5 -in. diameter. If higherspeeds are required, then some other andlarger motor would have to be adopted,introducing perhaps an Opperman gear.By increasing the size and scale of the engineand railway to 1 f in. to 1 ft. it would bepossible to fit a f-h.p. motor, which wouldbe capable of hauling three or four pas-sengers at a speed of perhaps 6 m.p.h.

4 N'


, (Left) The Floating Harbour, Bristol, and (right) the earliest harbours were like this. Hamble, to -day, is the same as when the Saxons landed.

averts oWATER transport is the oldest and

still the cheapest method of con-veying goods or passengers for long

distances, and its origin is lost in the mistsof time. Probably the earliest navigatorstried out their crude craft on such inlandwaters as lakes and rivers, and it may nothave been till centuries later that some for-gotten hero first ventured far out on thestormy ocean. When once sea voyages hadcommenced, however, men soon learned thatthis form of travel was impossible withoutsafe harbours. A harbour is defined as asheltered area of water where ships can liesafely, and most of the world's greatest har-bours have been naturally formed, and de-mand but little artificial aid to make themsafe. No doubt the first natural havenswere estuarine, i.e. situated at the mouthsof rivers, since such a position offered theadvantage of sheltered water, whilst theupper reaches of the river afforded anatural highway for small craft to penetratefar inland. Such advantages have causedthe building, and have fostered the growth,of many of the world's chief cities ; indeed,the two greatest cities the world has everknown-London and New York-are bothsituated at or near the mouth of a greatriver, and the same applies to a large

OM.

the SeaThe Evolution of Docks andHarbours forms the Subject of thisInteresting Article. It is Easy toTrace the History of Harboursin our Own Country and we Findthat the First Docks of which

the

Saxon Maws on the Thames

(Right) The en-tranceto the Float-ing Harbour atBristol, which ismore than 4 mileslong, and suppliesdeepwater at everywharf throughout

the city.

(Left) An aerialview of a pic-turesque harbour,the Golden Horn,

lstamboul.

number of the world's chief ports, andespecially to Rotterdam, Antwerp, Ham-burg, Bremen, Liverpool, Bristol, Hull,Glasgow, Southampton, Le Havre, Bor-deaux, Lisbon, Oporto, Montreal, QuebecToronto, and many others.The Bay of San Francisco

There is another important type ofnatural harbour, consisting of a shelteredbay of deep water, having a narrow en-trance. The finest of such in the worldis that of Sydney (Australia), which boastsan internal shore line of 188 miles, and thesplendid bay of San Francisco has 420square miles of sheltered water. Greater

New York Harbour has 150 square milesof sheltered water outside the actual riverarea, i.e. beyond the East and HudsonRivers. Portsmouth, Hong Kong, and Riode Janeiro are all examples of splendidnatural harbours. A third group of har-bours are those possessing natural shelter,but which are dangerous in certain direc-tions of the wind, and these have been madesafe by artificial breakwaters ; well-knownexamples of this type are Plymouth, TableBay, Marseilles, and Cherbourg. Finallywe come to harbours which are wholly


artificial, such as Madras, Panama, LasPalmas, and Zeebrugge of immortal memory.

The engineers designing a wholly arti-ficial harbour have many difficult problemsto consider in planning their enterprise.Soundings are taken to ascertain the depthof the surrounding sea and the slope of thesea bed. Certain mountainous islands can-not have a harbour because the sea is toodeep at the shore, as for example, Madeira.

The engineers must also search for rocksor shoals which can serve as a foundationfor breakwaters, and for headlands whichcan give some natural shelter. The tidaldrift must be carefully studied, or the newharbour may be silted up before it is evenfinished, and the size and direction of wavesmust be fully observed. When there aretwo breakwaters, one usually overlaps theother so as to give protection to shipspassing the harbour entrance. This en-trance must be narrow so that the innerpart of the harbour is well sheltered, butnot so narrow that it is dangerous to enterin stormy weather. The wreck of theS.S. Berlin, some years ago, is an exampleof the risks of entering a narrow openingbetween two breakwaters when a violentstorm is raging.

Crude HavensThe earliest sea Powers were Crete, Tyre,

and Carthage, and it is likely that the firstnamed constructed some crude havens aslong as 6,000 years ago, and we know thatthe splendid city of Carthage had a magni-ficent harbour many centures before Christ.It was founded 850 B.C. Turner has paintedDido's fleet at anchor in a marble basinof old Carthage, and the haven was awonder of the ancient world until itsdestruction by the Romans about 146 B.C.To -day only the partly -filled -up and ruinedharbour remains, and shipping has leftCarthage and now ties up at Tunis. Theharbour of Tyre was also ruined by enemyaction, and the oldest ports which are stillin use are Ostia, Taranto, and Brindisi, allof which were employed during the RomanEmpire, while the first mentioned is saidto date from the seventh century B.C.,though now but a shadow of its formerimportance.

It is easy to trace harbour history in ourown country. London, Southampton, andPortsmouth still stand on, or near, the placewhere Roman galleys anchored 2,000 yearsago, but no trace of the Roman harbourworks remain. The first docks of which we

Part of the harbour and Hans Aandersen mermaid,Copenhagen.

have any record are the Saxon hithes onthe Thames, whose name lingers in suchplaces as Rotherhithe. A hithe was a cutin the bank of a river to admit a ship, thesides of which were held up by stakes andbrushwood. It had the advantage thatcarts could come close up to the ship's side,and the vessel was not separated from hardground by an expanse of soft mud. We seethe importance of hard ground in theearliest name for a port-the Hard-as atGosport. A modern dock resembles ahithe, but is far bigger and is constructedof concrete instead of wood.Wet and Dry Docks

There are two kinds of dock, the wet andthe dry. The first is full of water and en -

(Right) The townof Southamptonhas developed intoour finest port, andcan accommodatethe world's greatestships. The illus-tration shows the

Berengaria atSouthampton.

,11"

(Left) A classicalharbour; entranceto the Hyllaenport at Corfu,where Ulysses was

Ai wrecked (Canon,Corfu).

ables the ship to tie up alongside, and thesecond is used when it is necessary to workupon the ship's hull. The vessel enterswhen the dock is full of water ; the gatesare then closed and the water is pumped out,leaving the ship high and dry. Dry docksare of two kinds, Floating and Graving,and the wonderful port of Southamptonboasts the largest of each kind in the world.The floating dock is built of steel, withhuge tanks below the floor of the dockproper. When not in use the whole struc-ture floats with the inner floor above thelevel of the water outside ; but when aship is to be admitted the dock must sinklow enough to admit her. This is done byadmitting water into the tanks, and whenthe ship has entered, they are pumped out,and the dock rises to the surface holdingthe ship high and dry. The advantage ofthe floating dock are twofold : firstly, it ismobile, and so can be transferred elsewhereif no longer required in Southampton, and,secondly, being mainly built of steel, thework of building it helped our two mostdepressed industries-coal and steel. Thisadvantage was clearly shown in the case ofthe Singapore floating dock, which wasmade by British labour, whereas a gravingdock would merely have employed cheapAsiatic labour to our own disadvantage.

A Stupendous DockThe King George V Graving Dock at

Southampton (opened in 1933) is simplystupendous. Its length is 1,200 ft., width135 ft., depth 59 ft., and its constructionrequired 750,000 tons of concrete. Thefloor of the dock is 25 ft. thick ; this isnecessary, not only to sustain the enormousweight of a 100,000 -ton ship, but also toprevent the water pushing through fromoutside. The dock holds 58,000,000 gallonsof water when full, and can be pumped dryin four hours. It is the only dry dock inthe world which can hold the Queen Mary,which is only 75,000 tons, and it will take

ships of 100,000 tons, if and when theyare built.

Of British ports, only two (London andLiverpool) exceed Southampton in tonnage,but these figures are made up chiefly ofsmall cargo boats, and no European portcan approach Southampton's record forthe number of big liners it accommodates,and only New York in the whole world canexceed these figures. Even Manhattan Is-land-wonderful as it is-is beaten by our


Hampshire port in the matter of tides, forSouthampton has four tides in twenty-fourhours, instead of two. This is due to theshape and position of the Isle of Wight atthe end of Southampton Water,which causeseach high tide to last for two hours. Thisadvantage, and the small rise on spring tidesof 13 ft. only, means that the port can ac-commodate the world's biggest ships at allstates of the tides, an enormous advantage.

Where the difference between high andlow tide is very great (as at Bristol, whereit is about 40 ft.) serious difficulties arise,and they become greater when bigger shipsare built. Not only are vessels unableto enter or leave the docks at low tide, butthey cannot float alongside the wharf, andfall over on the mud. This does not matterwith small ships, but may cause seriousdamage to the hull of a large vessel, orinjury to the cargo by shifting. The ancientport of Bristol has very cleverly overcomethis by the idea of a " Floating Harbour."

The channel of the River Avon, whichpasses through the city, is deep and wind-ing, and, at low tide, almost empty. Thiscaused much damage through flooding inwet seasons when the river was high, andas early as 1239 a new channel was cut toshort-circuit the bends-it was 18 ft. deepand 120 ft. wide. Since then the windingmain stream has been closed by huge gatesat Hotwells-just below Clifton Bridge-so that the water can be kept at top levelall day and ships can ride alongside. Alock permits entry or egress at all timeswhen there is enough water outside. Thisfloating harbour is more than four milesin length, and gives deep water at everywharf throughout the city.

A Floating Landing StageLiverpool boasts a remarkable floating

landing stage, 2,643 ft. long, by whichpassengers can enter and leave great linersat almost all states of the tide. It rests on

200 iron pontoons, and is connected withthe shore by 8 hinged bridges. Big linersstart from the north end and ferry or pleas-ure steamers from the other end, so itsometimes happens that careless passengersfor the Isle of Man find themselves en routefor New York or Sydney ! Such incidentshave actually occurred !

Although by no means our greatest port,the City of Glasgow deserves mention forthe enterprise by which it has overcomenatural difficulties. A little over half acentury ago, the Clyde near the city wasonly 180 ft. wide and 3 ft. deep, but sincethen by continual dredging it has become500 ft. wide, and is deep enough to permitthe Queen Mary to sail out when she iscompleted.

Modern docks are very rich in up-to-datemachinery, dredgers, floating cranes, fireappliances, grain -suckers, and many others,but the subject is so vast that it wouldeasily make a book by itself.

essesseeeeeeeeeeeeeeeeseeee

®06)

ci Smokeless Explosionsin Coal Mines

19(900(9c9SDSSC9c9SDDS,C9C4®®®@SSGSS®

BECAUSE large chunks of coal aremore valuable than small ones, and inorder to escape the fumes which ham-

per work and endanger life, certain coal -mining areas in America have discardeddynamite in favour of compressed -air" blasting." Specially -designed compres-ser-drives, motors and control devices for anew equipment built and introduced intothe mining districts, have met with out-standing success. With the new equip-ment the coal is " pushed " out of place byair -pressure.

Absence of FumesThe coal -dust and chips which are broken

out by the dynamite are difficult to handleand they bring much lower prices on themarket. With the absence of fumes, underthe new method, miners can start loadingcoal immediately after the " shooting " anddo not have to wait until the air clears.The mine level does not have to be vacated,as is the case when explosives are used.

15,000 -Pounds PressureWith the new method, a portable com-

presser stores up to 15,000 -pounds' pressure

Blasting coal with a compressed -air cartridge.

in a long metal cartridge. The latter is in-serted in a hole drilled in the face of the coaland a valve suddenly releases the air, which,in expanding, pushes out the coal in bigchunks. The steel cartridges are specially

designed and may be used over again.The entire operation is conducted at thecoal face, and cartridges are filled in 90seconds. Miners retreat to a distance of100 or 150 feet during the explosion.

ELECTROPLATING to -day is an almostperfect science and has wide applica-tion in both the decorative and the use-

ful arts.The art of making a bond of very great

mechanical strength between the platingand the underlying metal has been ac-quired. By scrupulous care in the pre -cleaning of the metal the bond can actuallybe made stronger than the plated metalitself. Experience in the use of correctamperage, voltage, and composition of theplating bath enables thick layers of platedmetal to be built up, and it is an acceptedengineering practice to rebuild in this waysuch articles as ball -races, cylinders, pistons,big -ends, crank shafts, and gudgeon pinswhich otherwise would have to be scrapped.Nickel is the plating metal used in suchcases. As pure nickel is of extreme hard-ness, the repair often provides a better wear-ing job than the original.

Protective coatings for steel are not con-fined to nickel and chromium. Zinc, tin,cadmium are extensively used as platinum

1rd %rra 214 V V <4.241,270,7aro)724,A.A.Artil,A Vlr AAAAA va vi4 r>4oa

QO

* Facts About *2,4 641,74'9 Electroplating tt

234

V 214 21,;4242z472.0 .g(s4 2r4 2:3,1 V..Atti14' 07 A A A Ac' Ddr as 147 1,47 7;47oametals. Cadmium, a silvery metal verylike zinc in properties, is used by wirelessmanufacturers to give the silvery finish tothe chassis of wireless sets. The Post Officeuses zinc to plate the steel parts insidetelephone systems. Tin-plate manufac-turers find that a pre-treatment with tinin the electroplating bath improves thecoherence of the thick coat which is after-wards put on by dipping in molten tin.

For purely decorative work ordinarysilver plate is being displaced by silver plateplated over with platinum or rhodium.Either of these metals have the silvery

white lustre of silver, but they are un-tarnishable. A final thin plating of electro-plated nickel silver with rhodium thereforegives the jolka permanent polish.

A material of very definite value inarchitectural decorative schemes is anodisedaluminium. It provides a material forhighly -polished metallic surfaces capableof taking lustrous coloured finishes. Ifaluminium is made the anode in a bath ofsulphuric acid it acquires a thin hard coatof aluminium oxide. By using dyes in thebath the film may be given permanentshades of great iridescent beauty and madeto appear exactly like coloured metal.Dyed or undyed, any degree of polishing maybe applied from matt grey to bright silver.A further elaboration is provided by mach-ining the aluminium before treatment.Aluminium oxide is the hard material ofcorundum, the ruby and sapphires. Itsextreme durability as a surfacing can there-fore be well understood.

Aluminium itself is originally made byelectro-deposition from its fused salts.


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268PAGES

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ettal- Jztvept onoplane

The completed model-the first concerning which detailed designs and full-size blueprints have been published.

Final Details of this Fine Flying Modelty grg eamm.

AS mentioned last month, I loaned the"model shown in the photograph aboveto the Model Engineer Exhibition, and Ihave not had an opportunity of photograph-ing the model in flight since then. It isdifficult to launch a petrol -driven model andthen to endeavour to pick hold of a cameraand photograph it. I have made arrange-ments, however, for the services of a photo-grapher on the next fine week -end.

The Ignition CircuitI HAVE received dozens of letters fromreaders who are building it, and one or two

of them have asked for details of the ignitioncircuit. This I have pleasure in giving thismonth in the diagram on page 110. It will

be seen that one lead from the coil goes tothe sparking plug, one primary lead beingconnected to one lead of a fixed condenser,and then earthed to any convenient pointon the engine cradle. The other side of thecondenser passes to the insulated contactbreaker and the two leads to the batteryand switch are led off as shown. Thisarrangement is far better than that norm-ally adopted where the accumulator is left incircuit, and in parallel with the dry cellwhen the switch is thrown over. In myarrangement the accumulator is cut out andthe dry cell cut in instantaneously, since theswitch is of the quick make -and -break type.I would repeat that the full-size blueprintslisted on this page will facilitate construc-

tion. The supply is limited,and is running short. The

The size of the model can be estimated from this photograph.

positions of the wings shownon the blue prints are veryapproximately correct, andonly a slight movement ofthe dry cell is necessary inorder to make the centre ofgravity coincide with the cen-tre of pressure. I have foundthat the thrust line is ideal,although in some cases it maybe desirable to bend the tailflaps up to improve longitudi-nal stability. A negative angleon the whole tail also im-proves stability, and this canbe arranged by adjusting thetube fixed to the rear of thetail before soldering it.

Inverted EnginesA LOT of readers have writ-

ten to me asking whetherit would be advisable to invertthe engine, as is sometimesdone. My answer to this is anemphatic No! It serves nopurpose whatever to do so,and merely provides one of thehumorous aspects of model

aeroplaning. It places the cylinder in itsmost vulnerable position, and it enablesoil to drain down on to the plug, thusgiving rise to misfiring and other ignitiontroubles. It does not lower the centre ofgravity of the machine at all, and I havefailed tb discover any sound reason forplacing the engine in any other than thecorrect position. Another disadvantage isthat you will put yourself to a considerableamount of trouble inverting the carburetterand tank arrangements.

BLUEPRINTS OF F. J. CAMM'SPETROL -DRIVEN MODEL ff

MONOPLANEThe following full-size blueprints =-4-

are now ready and may be obtained,at the prices mentioned, from thepublishers : George Newnes Ltd.,8-11 Southampton Street, Strand,London, W.C.2 :

Sheet 1, price 18. -----.--=-=

,-2- This blueprint gives the shape of-...-.- each bulkhead, the engine cradle, and 5

g the stiffeners.-7_E-- Sheet 2, price 18. ==

-=-----!Shows the rudder and tail full-size ,--with methods of fixing.

Sheet 3, price 48. Em-=-

E - Shows the fuselage full-size in sideff. elevation and plan, the holding -downm strap for coil, chassis construction, .

E rear wheel and suspension, switch -3E and ignition circuit, wing fixings and method of bracing.

Sheet 4, price Is. 6d.F---- Full-size plan of the mainplane, full-

size rib section and wing couplings.-E---

----3=Sheet 5, price 6d. ,-.-_-

E---

-ff Full-size plan of engine adapter for---3- the Atom Minor, Hallam, Grayspec, - Andrich, and Economic engines.5111111111111111111111M111111111111111111110111111111111111111111111111111111111111111111111111111111111111111111111111i


A Starting TipI HAVE found that the engine will start atthe first swing every time by injecting a

few drops of petroil (one part of oil to eightof petrol) in the induction pipe, and openingthe jet about 2/ turns. Allow the engine torun for about five seconds in this way andthen gradually close it down until it firesevenly and is two -stroking properly. Thenote of the engine will rise as the jet isclosed. The correct setting is somewhereround about one full turn.

I omitted to mention in my previousarticle that the hinges securing the trans-verse chassis numbers to bulkheads D and Fare bolted through blocks of wood gluedbehind each bulkhead for that purpose.The three-ply bulkheads alone would not besufficiently strong.

Model Aircraft at the Model EngineerExhibitionSHOULD like to congratulate my old

friend, Percival Marshall, on the success ofthis year's Model Engineer Exhibition. Heis doing work of national importance inencouraging interest in mechanics, and hemay truly regard himself as the high priestof the model and small -power engineeringworld. Quite frankly I was disappointedwith the model aircraft exhibits, particu-larly with the petrol -driven models shown.Quite obviously most of them had beenbuilt as units without any consideration forthe complete design. Nearly all of themwere built on the unit principle, thedesigners having first built a fuselage beforeconsidering how the chassis and wings wereto be attached. The wings had then beenbuilt before the fittings for them had beendesigned, the general result in most casesbeing a clumsy -looking square -section fuse-lage to which wings, tail, and engine wereattached as obvious afterthoughts. TheClub Exhibits were definitely poor in designand in workmanship, and with only onenotable exception could I award any marksfor ingenuity. Pins and glue were usedwhere small fittings should be made, and toomuch reliance was placed upon the coveringand the dope tastefully to camouflage care-less and unskilled work. There was toomuch decoration on them, some amateursapparently being unable to leave the paint-brush alone once they get to work. Thelines in general were disproportionate, andmany of the models were not up to exhibi-tion standard. If I may make a suggestionin all sincerity, it is that in future exhibi-tions the organisers have a Selection Com-mittee and ruthlessly reject models not upto exhibition standard and which only en-courage derisive remarks from members ofthe public who do not appreciate the

A fine model of the Hawker Fury, made by Messrs. F P. Sweeten Ltd., Blackpool.

patience, lack of equipment, and probablylack of skill of those who make them.

Encourage Model MakersIT is, of course, a nice thought to encouragemodel makers who are less fortunate than

others in these respects, but after all anexhibition is intended for the public and assuch should be designed to advance itstraditions. These remarks apply strictlyto the Model Aircraft Section. In theother sections one could but admire theremarkably high standard of workmanship,ingenuity, originality, and finish displayedin the model locomotives, boats, station-ary engines, machine tools, and the almostunlimited variety of models on view. Ihope that the influence of what I may callthe Model Engineering Section of theexhibition will inspire aircraft modellers todepart from the thread, pins, and gluemethods, the parts being held together moreor less by unskilled methods, of which faithand hope form the strongest part.

An interesting exhibit was that repre-senting the joint efforts of Mr. H. H. Grovesand Mr. Trevithick-a small steam -drivenmodel, powered by a flash steam plant.When I saw this modelat Fairey's Great WestAerodrome it failed to make a flight, andpart of the fabric was burned away from thefuselage. Quite obviously the power plantneeded to be enshrouded with aluminium,an improvement which has since beeneffected.

It is to be regretted that the Model Air-craft exhibits were not morerepresentative of the provin-ces ; the same old names withthe same old designs keepcropping up year after year,the idea apparently beingthat if they alter the shapeof the wing they have pro-duced a new " design." Somedo not apparently know thedifference between designingand copying, alas ! I makethese passing comments froman unbiased and disinterestedpoint of view, feeling that anexhibition of model aircraftshould not be parochial inits character and embraceonly the work of local Lon-don clubs.

The old London AeroShowing the assembled model of the Flying Flea- with half the Model Association was the

skeleton framework covered. precursor of the S.M.A.E. and

it was at my suggestion at one of their meet-ings in Great Windmill Street, Piccadilly,some years ago that they approached theR.Ae.C. for recognition as the body togovern the hobby of model aeronautics in anational way, and in succession to the oldK.M.A.A. They have done very little toadvance the call outside of London, and Isuggest that the Royal Aero Club mightusefully look into this situation, particu-larly as so many well-known people havedonated cups for National competition.

CompetitionsM ANY readers write to me asking whether" it is advisable to enter the model aero-plane competitions held during the summer.My advice to them is that if they are pureamateurs they will be competing againstprofessional model makers and as such startoff with a heavy handicap. I suggest thatthe S.M.A.E. while it is the controlling bodyshould rigidly exclude all models made byprofessional model makers and confinecompetitions strictly to amateurs. Itshould not be permitted, moreover, for onecompetitor to enter two models merely byplacing one of them in the hands of anominee. At present there is little to stop acompetitor so minded from doing this.

Flying Scale ModelsMR. F. P. SWEETEN, of 38 Bank HeyStreet, Blackpool, has sent me his

catalogue of realistic flying scale models.The Hawker Fury kit costs 6s. 6d. complete,with a full - size plan and all material.Other kits include the Curtiss Goshawk, theBoeing, the Pursuit, the Douglas Observa-tion, the Curtiss Falcon, the Curtiss Swift.There is an easy -to -build series, and a com-plete range of material. The well -illus-trated catalogue is free to readers.

Model of the " Flying Flea "AMOST interesting model of the " Flying

Flea " has been produced in kit form byMessrs. Williams, Ellis & Co. The completekit costs 3s. 6d., and it flies when correctlyassembled. All parts are ready-made andfinished, and .the price includes a plan andfull instructions.

Air -minded ModellersHERE is something to interest all air -

minded readers who are clever withtheir hands. The Skybird League haveoffered to co-operate with Skybird agentsthroughout the United Kingdom to run a


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Local Competition open to all, for the bestassembled Skybird Model Aeroplanes.Competitors may enter one or more models,the only stipulation being, the purchase ofthe materials from the local agent. Fivehundred Skybird Airports, value one guinea,500 books value 5s., and other prizes,together with Certificates of Merit, havebeen reserved for this competition.

The competition closes on October 31st-get in touch with the nearest Skybird agentat once for full particulars of this splendidopportunity.

Enq/necontactbreaker

Seconds

1411111111111111 11111111111111111111

insviated Contact Carburettor

Wire: Insulated Primaries

Suggestions WantedI SHALL be glad to hear from readers as tothe type of model they would like me to

design and make next. Do you wantanother petrol model ? A duration mono-plane or biplane ? Do you prefer a fuselageor pusher machine ? Are you interested incompressed -air models ? I should appreci-ate a post card from you. You willrecollect that I promised to design andbuild a Canard petrol -driven model, butdeferred it owing to requests from manyreaders for a design such as that just com-

Earthing Bolt 4; Voit drycell

SwitchArm

Details of the ignition circuit of the petrol -driven model monoplane.

There are now 325 clubs registered in theSkybird League and many hundreds ofassociate members. The movement pro-vides a most instructive and interestinghobby, the value of which is demonstratedby the success of the League, and thenumber of well-known people connectedwith aviation who have interested them-selves in its welfare. Sir Harry Brittain,K.B.E., C.M.G., LL.D., is president of theLeague, and Squadron -Leader Burge,O.B.E., vice-president. The list of hon-orary members includes such well-knownnames as Capt. G. de Havilland, Capt. H.Broad, Mr. K. Waller, Mr. C. W. Scott, Mr.Cathcart Jones, Capt. W. E. Johns (Editorof Popular Flying), Lieut. Ira Jones (authorof King of Air Fighters), and many others.

Congratulations!I HAVE received the following letter from

W. Rigby : " May I remark that I thinkyour petrol job at the Model EngineerExhibition a very fine job indeed, certainlyone of the best looking on show."

ficcumulatorSocket

pleted. If you are not building the presentdesign and are waiting for the Canardmachine, write and let me know.

Two Useful HandbooksFRESH impressions of my two books

Model Aeroplanes and Airships andPower -Driven Model Aircraft (obtainablefrom us for Is. 2d. each by post) are nowavailable. The first contains chapters onmaterials for model aeroplanes, how anaeroplane flies, methods of constructionand design, construction of model airscrews,designs for tractor monoplanes and bi-planes, a fuselage monoplane, a tail -lessmonoplane, model helicopters and orni-thopters, spar machines, gliders, flyingmodel aeroplanes, building airships, kites,full-size gliding, etc. ; whilst the secondvolume deals with the commercial petrolengines, how to make petrol, steam andcompressed -air engines, ignition systemsand carburetters, compressed -air models,steam -driven models, petrol -engine models,and wheels.

MATERIALS FOR THEFLYING FLEA

THOSE readers who are building the" Flying Flea " should remember that

advertisers in this journal are supplying thecorrect material at specially low prices.The Luton Aircraft Co., Ltd., who are de-signers and constructors of aircraft at LutonAerodrome, Barton, Bedfordshire, supplythe complete set of materials as listed onpage 7 of our October issue for the sum of£25. The material is specially selected. Thiscompany is, of course, proprietors ofthe wellknown Dunstable Sailplane Com-pany.

The Luton Aircraft Co., Ltd., will supplythe " Flying Flea " complete with a Scott

34-h.p. Aero Engine and ready to fly for£170 10s. The aeroplane complete, but lessengine and airscrew, costs £110 ; the frontmainplane, complete with tank fitting andcovered with dope, for £29 ; the rear main -plane complete for £19 ; the fuselage, com-plete with fitting, for £23 ; the rudder,complete covered and doped, £3 188. 6d. ;the chassis, complete with wheels and tyres,£6 5s. ; tail chassis, complete with specialwheels, £3 12s. 6d. ; the Scott Aero Engine,£50 ; the airscrew hub, £4 ; and the air -screw £7 10s. They issue a price list of allthe other parts which will be suppliedseparately or in toto.

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All -mains Portable RadioM EASURING only 10 in. x 7 in. x 6

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111

A universalportable receivermeasuring only 10 in. X

7 in. x 6 in.

A Lightning Stamp AffixerCAPABLE of stamping 150 letters per

minute, this amazing little machine isoperated by a single stroke of the plunger.It picks up, moistens, severs, attaches, andcounts the stamps and is so accuratelyconstructed that it never cuts the stamps.The model illustrated costs 4i gns., and isheavily nickelled, with a coloured bakelitehandle. A lighter model, with an alu-minium case, is available at a guinea less,

This ingenious device willaffix stamps to envelopes at therate of 150 letters per minute.

The address of the makers ofany device described belowwill be sent on applicationto the Editor, PRACTICALMECHANICS 8-11, Southamp-ton St., Strand, W.C. 2.

Quote number at endof paragraph.

whilst ether model is available without theenumerator at a reduction of 10s. 6d. [154.]

A Universal Pencil SharpenerFITTED with solid steel twin cutters, this

little machine is capable of sharpening

A pencil sharpener that can be adjusted to take pencilsof all sizes.

pencils of any diameter. The disc, shownin the illustration, is rotated until therequired hole is at the top, the pencil is theninserted, sharpened by turning the handle,and a flush -fitting drawer at the base of thesharpener catches the trimmings. Theattractive marbelite casing is obtainable inwalnut, rosewood, mahogany, or black, andthe price is 12s. 9d. post free. A specialclamp is supplied for Is. 6d. extra. [155.]

An anti -fume ash

barrel that willappeal to smokers.

An Anti -fume Ash BarrelTHERE are probably few things quite

so annoying as the acrid fumes from apartly extinguished cigarette. The ashcontainer, sketched on this page, is especi-ally designed to overcome this nuisance, asonce the cigarette has been dropped into itthe fumes are trapped in the upper part ofthe barrel as is shown in the cut -away insetsketch. The barrel unscrews in the centreand is thus easily cleaned. Moderatelypriced at ls. 9d. post free, the containermay be obtained in red, mahogany, black,walnut, green, or rosewood bakelite and ispractically unbreakable. [156.]

I12 NEWNES PRACTICAL MECHANICS November, 1935

A Letter Damper and SealerTHE illustrations clearly illustrate the

usefulness of this little gadget, whichwill be found a great time saver when alarge number of letters are to be sealed.The sponge rubber damper is gripped in anickel ferrule which prevents any possibilityof breakage, and the large base of thereservoir handle forms a convenient methodof sealing the envelope after damping.Supplied either in chromium -plate finish orin bakelite, they cost 18. 3d. post free. [157.]

A Handy Measuring OutfitCONVENIENTLY houses m a strong

wooden box, this set of tools will befound extremely useful to every handyman,and comprises a pair of spring dividers,

A complete measuring outfit suitable for the handyman.

outside callipers, a steel try -square, a 9 -in.three -fold steel rule, and an eight -bladedset of feelers which range from -002 in. to015 in. All the tools are of first-ratequality and the complete kit may beobtained for 118. post paid. [158.]

Snapshots after DarkSSIMPLE, safe, and efficient, the photo-

graphic lighting apparatus illustrated onthis page enables even the amateur to takedelightfully clear and natural snapshotsindoors, and eliminates the risk of that

An electric lamp that enablessnapshots to be taken indoors,thus dispensing with the use of

flashpowder.

startled expression on the face of the sitter,which is usually associated with flash -powder photographs. The lamp, whichplugs into an ordinary electric -light socket,gives an intensely brilliant and continuouslight, is made to suit all standard voltages,and costs 28. 6d. The collapsible alu-minium reflector is designed to increase theefficiency of the light by four and a half

Details of the letter damper and sealer.

times, and used in conjunction with thespecial wire stand enables the light to befocused in any direction. The reflector ispriced at 38., and the stand at 48. 6d. Auseful outfit, comprising a reflector, stand,lamp -holder, bayonet adaptor, and 9 ft.of well -insulated flex is marketed at 78. 6d.[158.]

A neat and compact perpetual calendar.

A Perpetual CalendarM ADE in a variety of colours to

harmonise with almost any type ofdesk fitting, the calendar illustrated isoperated in a flash, for by simply pressingthe lever at the top the dates changeautomatically. It has a great advantageover the " slip -in " type of calendar as nosorting and arranging is necessary. Theprice is 28. 9d. post free. [159.]

Slow -Speed Synchronous Motors

A WELL-KNOWN firm has just intro-duced an interesting synchronous

motor, which operates on quite a differentprinciple from the orthodox fractionalhorse -power type, and is in fact very similarto the motor employed in a synchronouselectric clock, working at a dead -beat rate ofrevolutions, 100 r.p.m. on 50 cycles. Amotor such as this has varied applications,such as aerating water, driving models,scientific apparatus, etc., where a slow andperfectly constant speed is required. Cur-rent consumption is practically negligible,and there is no interference with wirelessreception. The motors are available withone -cylinder and twin -cylinder pumps, andrun equally well in either direction, onlyrequiring theimpulse of thehand to startthem whenswitched on.They are 51 in.long x 4 in.wide x 6} in.high, and assupplied are suit-able for 230 voltsdirect off themains withoutresistance. [161.] An ingenious slow -speed motor.

The New

STUARTCATALOGUE No. 3

describes in 72 profusely illus-trated pages the full range ofStuart products-

Steam engines and boilers,pumps, petrol engines,fittings, screws, drills,materials, etc.

The Stuart centrifugalpump for fountain orwaterfall.

The Pump:20/ -

Electricallydriven:

£4:7:6`Please send now for " Cat. No. 3."

6d Post Free.

STUART TURNER LTD.HENLEY - ON - THAMES

The LeadingWirelessWeekly

Every experimenter, home -constructor, andall those interested in the technical side ofWireless should read " PRACTICAL ANDAMATEUR WIRELESS."Authoritative, comprehensive, it providesan unrivalled service in News, Designs, Tech-nical advice, and information of more generalinterest.Get a copy o" this great weekly paper to -dayand judge the merit and value for yourself.It is lavishly illustrated throughout.

PRACTICALand AmateurWIRELESS

Every Wednesday Threepence

On sale at all Newsagents and Bookstalls, or bypost 4d. from George Newnes Ltd., 8-11 South-ampton Street, Strand, London, W.C.2.


4 Glass Which Prevents Tare

Interesting Facts Regarding a Scientific Medium for

Diffusing Light and Heat in the Home or Factory

PPRESSIVE heat and blinding glarein summer and icy down -draughts inwinter are two serious discomforts

produced by ordinary window glass. Theabsence of a satisfactory glazing material,which transmits light without involvingthese discomforts, has hitherto proved aserious check to the fulfilment of moderndemands for good natural lighting indoors.

After exhaustive experiments, Dr. P.Modigliani, a chemist and an acknowledgedexpert on glass in Italy, has discovered asatisfactory method of opposing the heatrays of the sun. He has incorporated hisideas in a special glass known as Thermo -lux," now marketed in England. Thismaterial transmits sunlight without sunheat and yet provides undistorted trans-mission of the visible wavelengths of thespectrum, giving all colours indoors theirtrue values. It is best described as a com-pound glass of a three-ply nature withsmooth, brilliant surfaces. Between twosheets of glass is a central lamina consistingof numerous glass silk threads regularlyarranged. This centre is porous, and, sothat the air contained within may remainundisturbed, the edges are hermeticallysealed.

The advantages of this porous qualityare : (1) it has a very low coefficient ofthermal conductivity ; (2) a much lowerweight than sheets of other glass of equalthickness ; (3) a marked ability to absorbhigh -frequency sounds. The lamina ofglass threads also prevents the transmis-sion of incident heat waves by deviatingand reflecting them. The thickness of theinterlayer varies from 1 mm. to 3 mm.,according to the purpose required. Nor-mally white in appearance wit4 a satin -likesheen, " Thermolux " is also available inpale or dark shades of coloured amber,blue, pink, and marbled effects. Colouringis effected by introducing special threadsinto the glass -silk interlayer between thetwo panes of glass.

Even Illumination and Uniform HeatingIn a room where the windows are glazed

with this glass, light diffusion is complete.Rays of sunlight are distributed instead offorming patches on the floor. As light andheat rays do not pass in or out of a roomin the same way as they do with ordinaryglass, great lighting economy is effected inthe winter. Heat and glare are avoided inthe summer ; conversely heat and lightare conserved in the winter. At night thisglass viewed from inside an illuminatedbuilding gives the impression of finely -fluted mirrors. No curtaining is neededto ensure privacy, and it is possible toobtain artificial lighting effects closelyapproximating to daylight.

Previous MethodsHeat insulation is obtained in three ways :

by reflection from the outer polished sur-faces ; by diffusion ; by the oppositionencountered by the three-ply constructionand the interlayer of glass silk. Tests haveshown that the coefficient of heat trans-mission is about the same as that of abrick wall.

Hitherto there were two well-known

methods employed to obtain light -diffusingglass. The first consisted of altering thecondition of one or both surfaces of a clearglass by grinding, sand -blasting, acid treat-ment, or by impressing a rough pattern onthe glass during manufacture prior to cool-ing. In the second method, opaqueness wasobtained by a suitable adjustment of theworking and melting temperatures, theglass being allowed to cool in a disturbedcondition in which it thereafter remained.These glasses are generally known as opalglasses.

The particles which impart its milkyappearance to the glass are themselvestransparent. It is the same as the break-ing up of the sun's rays by cloud or fog,although the individual particles of moistureare clear and transparent. In other wordsthe diffusion is really due to the repeatedreflection and refraction of the light rays,in turn dependent upon the difference be-tween the index of refraction of the particlesin suspense, and that of the surroundingmatter. In " Thermolux " glass trans-parent glass threads of very small diametertake the place of these particles. Thismakes light volume control possible oradjustment according to requirements ofthe main factors of illumination : diffusion,refraction, and reflection. Various gradesof this glass are produced giving differentproportions of these three values.

Insulation of SoundIn addition to the efficient diffusion of

light and heat, glass of the type describedalso provides effective insulation of sound.The transmission of sound through amaterial is governed by three principles :(1) its air tightness; (2) its rigidity; (3)the non -homogeneous structure of suchmaterial. It has been proved that most ofthe sound striking glass is reflected back,but owing to the low thickness -to -area ratioof the panes themselves, and the windowsas a whole, that portion of sound energywhich is not reflected back vibrates thepanes, causing them to act as sources ofsound. The heavier, thicker, and smallerthe panes, the less will this membranefactor operate. Experts agree that ifdouble glazing is employed, two separateframes (preferably of dissimilar glazing)should be fixed to avoid conduction ofvibration of the outer panes to the innerones through the material of the frame.

The Glass of the FutureTo sum up : glass has now been pro-

duced that will permit a good gradation oflight intensity. By this means rooms canbe divided into brilliantly and softly litzones without sharp demarcations. Prac-tical insulation for sound and heat can besecured with glass of the same thicknessand yet infinitely lighter than ordinaryglass.

The characteristics of this interestingmaterial can be preserved indefinitely be-cause all exposed surfaces are highly polishedand therefore easily cleaned. Prismatic,cast, and figured glass are subject to rapiddiscoloration because of dirt trapped bytheir irregular surfaces.

Things are happening to -daywhich vitally affect you!

If you are about 18, perhaps you aregetting settled in your chosen work andalready feeling the strain of competition fora better position. If you are in the 40's,your family responsibilities are near thepeak, the necessity for money is tense-and younger men are challenging your job.And men of the ages between i8 and 45 facesimilar problems, in one form or another.

The most valuable employment securityto -day is the security a man creates forhimself-in himself! Through training, heis able to adapt himself to new conditions,to utilise experience without being handi-capped by habit I He masters jobs andmakes new jobs. He meets emergencies-and is not overwhelmed by them. Andthis is an age of emergencies.

For 44 years the International Corre-spondence Schools have helped thoughtfuland ambitious men to acquire the trainingthey need. To -day, with this need moreurgent than ever, this world-famous institu-tion offers greater opportunities than ever.Why not permit us to show you the way togreater security and larger earnings ? Ourexpert advice is free. Write to -day.

...COUPON FOR FREE BOOKLET...INTERNATIONAL CORRESPONDENCE SCHOOLS,

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Please send me your booklet containingfull particulars of the Course of Correspond-ence Training before which I have markedX. I assume no obligation.

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Incorporating a patentedfloating non-magnetic Jewelledlever movement, shock, vibra-tion, dust and sand proof.Time tested under seater, chro-mium patent gland case, 24 -hour dial. Leather strap. Cashprice 59/6 (luminous dial 2/6extra), or yours for 5- down.

made by the Supp.iers A WATtiriIMPERIAL AIRWAYS, etc.

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or send your order to -day to:-

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24/26 Ludgate Hill, London, E.C.4

INCREASEYOUR HEIGHT

BY XMASShort people can be made taller with the aidof a box of Challoner's Famous Formula-

H.T.N. TABLETSand easy system : well tried : harmless andsafe. No strenuous exercises or old-fashioned appliances. If one box is insuffi-cient, we guarantee to supply a furtherbox FREE of all charge. E.H. (Sutton)writes : " Results beyond expectations andI am as pleased as Punch." Act NOW!Send I id. stamp for full particulars in sealedenvelope Sample lid. Book on heightimprovement 3d. P.O. or stamps onlyColonial Return Air Mail /- extra.THE CHALLONER CO. (late of Bond St.)Department G93, Laboratory and Works :HYDE HEATH, AMERSHAM, BUCKS.

Around the TradeA Tool Chest for HandymenTHE hundred -and -one jobs that occur

in most households are undoubtedlysimplified if the householder is properlyequipped with tools. The best thing is tohave a complete set such as the G.T.L.tool chest and home repairing outfit.Here in one chest is everything likely to beneeded, actually well over fifty finest gradeSheffield tools, each neatly fitted in itsplace and fully guaranteed. An illustratedinstruction book on the use of tools is alsoincluded. Interested readers may obtainfree of charge from Guaranteed Tools(1933) Ltd., 12-13 Chiswell Street, Fins-bury, London, E.C.1, a sixteen -page book-let describing the G.T.L. tool chest andhome repairing outfit.

Modern Lathes

THOSEreaders interested in lathework

should certainly write to Messrs. Wardand Pollard, High Street, Plumstead,S.E.18, for details of their " DuplexTailstock" 3k -in. centre, back -geared, screw -cutting, boring, milling, and sensitivedrilling lathe. A feature of the machine is

Book of the Lionel Trains," covering acomprehensive range of model railwayaccessories. The care and precision in theengineering and construction of Lionel" 0 " gauge and Lionel standard (wide)gauge makes them outstanding in theelectric train field, and they incorporatemany ingenious features in their design.All trains have 3 -position automaticreverses, that is, by pressing a buttonsupplied with each set, at any distancefrom the track the train may be stoppedwith headlight alight and coaches illumin-ated. Another press of the button willsend the train either backwards or for-wards. Some models are also fitted withchug -chugging devices which producethe sound made by a real train going alongthe track.

The " Scruit " Connector

ON page 63 of last month's issueappeared a short article under the

above heading. Unfortunately the nameof the manufacturer of the particulardevice described was given as J. M. Blair ;this should have been the V.G. Manu-

A,realistic model aeroplane made by F. P. Sweeten, Ltd., 38 Bank Hey Street, Blackpool.

the tailstock, which is a combination screw -operated and lever -feed tailstock. It canbe changed from one to the other in threeseconds. When using the lever feed thehand wheel may be used as a dead stop tolimit the travel of the barrel, thus pro-viding an accurate method of controllingthe depth of the holes. Each machine istested with standard test bars and sensitivedial indicators before dispatch, and run ona test bed to ensure that all bearings,slides, etc., are properly adjusted.

A CorrectionON page 577 of our September issue we

gave under the heading of " LatestNovelties " details of a useful photographicdevice. The price of the device was givenas 2s. 6d., but this should have been5s. 6d. The number at the foot of theparagraph was 141.

Lionel TrainsGUITERMAN & CO., LTD., 35 and 36

4.0 Aldermanbury, London, E.C.2, haverecently produced a fine well -illustrated18 -page booklet under the title of " The

facturing Co., Ltd., Gorst Road, ParkRoyal, London, N.W.10.

Universal High -voltage ReceiversTHE usual all -mains receiver employs

valves having a heater operated at alow voltage, the necessary step-down fromthe mains voltage being obtained by meansof a resistance or a transformer. In theOstar-Ganz receivers special valves opera-ting with the full mains voltage on theheaters are employed and there are severaladvantages to be obtained from this typeof valve. The receivers which are obtain-able with these valves range from simplesingle -valve converters to ten -valve all -wave superheterodyne receivers, and thereare also some interesting amplifiers avail-able for use with pick-ups or microphones.There are also a number of kits for homeconstructors and these include receivers,radiograms, and amplifiers ranging in pricefrom £5 5s. to £15 15s. Details of thereceivers may be obtained on applicationto Universal High Voltage Radio Ltd., of28-29 Southampton Street, Strand, London,W.C.2.

November, 1935 1NEWNES PRACTICAL MECHANICS 115

BRILLIANT LIGHTINGFOR 'WINTER WORK

Mechanics, amateur and professional, andowners of email workshops, lathe sheds,observatories etc., should get the TilleyLantern. it gives a magnificent light andenables work to continue after dark, eitherin or out of doors. Can be placed anywhere.Wind and Rain proof. British madethroughout.

TILLEY LANTERN(Burns ordinary Paraffin)

Light of 300 c.p. for 6 hours for Id.

The Lantern is strongly made in stoutbrass, and there are no parts which can rust,corrode, or get out of order. Will burnsteadily anywhere, unaffected by weather,however severe. Get rid of all antiquateddevices and use this marvellously efficientStorm Lantern. You will then wonder howyou did without it before

Remit 313/- or can be sent C.O.D.Post and Charges Paid.

TILLEY LAMP CO. (Dept. P.M.) HENDON, N.W.4

-CHEMISTRY-EXPERIMENTS MADE EASY !Whether con are a novice or an experienced stude,,,sew) TO -DAY for the most complete and up-to-datemanual devotet to experimenta` chemistry-BECK'S BOOKLET OF TESTED EXPERI-MENTS. It contains, ,n addit on to over70 expertly chosen experiments, a list ofreliable, inexpensive equipment supplied byBECK'S. Semi Postal Order NOW.

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PATENT ADVICE

THE following information is speciallysupplied to PRACTICAL MECHANICS byMessrs. Hughes & Young, British and

American patent and trade mark agents, of9 Warwick Court, High Holborn, London,W.C.1., who will be pleased to send toreaders free of charge a copy of theirhandbook, How to Patent an Invention.

2006979. Electric Valve Excitation Cir-cuits. E. F. W. Alexanderson, Assignorto General Electric Co., New York,U.S.A.

This invention can be regarded as a con-verting apparatus for transmitting energyfrom a source of current. A plurality ofelectric valves is employed, each providedwith an anode, a cathode, and a controlgrid. A grid -excitation circuit is adaptedfor each of certain of the valves which im-presses upon the grid an alternatingpotential of the corresponding value tomaintain the selected valve normally non-conductive. The phase of this grid poten-tial is retarded with respect to the saidanode potential by more than 180 electricaldegrees, and an arrangement is provided forperiodically overcoming the grid potentialto render such valve conductive.

2007662. Valve Transmitter for ShortWaves. W. Prinz, Assignor to Tele-funken Gesellschaft fiir Wrahtlose,Telegraphie M.b.H., Germany.

In this invention a plurality of pairs ofelectron -discharge devices is employed,each device having a grid and anode, theanodes of the tubes of each pair beingconnected together through a linear con-nection devoid of lumped inductance andlumped resistance. The grid of each tubein a pair is connected to the grid of a tubein an adjacent pair through a similar linearconnection.

2009834. Electric Valve Converting Ap-paratus. B. W. Bedford, Assignor toGeneral Electric Co., New York, U.S.A.

This is another recent American inventionfor an electric valve converting apparatusfor transmitting energy between a supplycircuit and a load circuit. The inventioncontemplates the use of a transformer net-work and a plurality of electric valves forinterconnecting disc circuits through the saidnetwork. A special method for rendering thesaid valves alternately conductive and non-conductive in a predetermined sequence isemployed, a source of commutating poten-tial tending to rapidly transfer the loadcurrent of the apparatus between the saidvalves. Inductive winding is connectedin series with each of said valves, and adamped circuit is combined therewith forsubstantially short circuiting the potentialinduced in each of the said windings by adecrease of current in its associated electricvalve.

A STANDARD WORKHome Mechanics Encyclopaedia,by F. J. Camm. 3/6, or 3/10 bypost from Geo. Newnes Ltd., 8/11Southampton Street, Strand, W.C.2.

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REPLIES in BRIEF

D. R. (New Tredegar).-It is unusual tohave a 3 -pole motor; you probablymean a 3 -pole armature. In any case,if the machine is fitted with a wound fieldit will run from the transformer providingthat it can supply the necessary power. Ifthe machine needs rewinding then send usa sketch of it, indicating the sizes of boththe field and armature, etc. A tripolarmachine with a permanent magnet will notrun on an alternating supply.

F. W. (Colchester).-A 4 -blade fan wouldincrease the noise. We therefore do notrecommend the change. A 2 -valve wire-less set will, of course, work from a 60 -voltH.T. battery, but not very efficiently.

J. G. H. (Sheffield).-The " Flying Flea " isdesigned for the Scott engine, and we do notrecommend you to depart from this. Fulldetails are obtainable from the ScottMotor Cycle Co., Shipley, Yorks, who alsosupply the airscrew and the airscrew hub.The engines you have are quite unsuitable,too heavy, and of insufficient power.Many thanks for your appreciation.

BUILDING ABALSA MODEL AEROPLANE

(Continued from page 84)shaft to engage in it. Before bending theshaft to the correct shape, a small springis slipped on to the front.

The Action of the Free WheelThe end of the shaft is placed into the

hole in the metal plate, thus compressingthe spring, and as the rubber motor iswound this keeps the spring compressed andthe propeller engaged to the shaft. Onreleasing the prop, the rubber motor unwindsand turns the propeller, and when fully un-wound, the spring expands and disengagesthe end of the propeller shaft from themetal plate, thus allowing the propeller tofree wheel. The undercarriage is made from18 -gauge wire, shaped as shown in thedrawing, the rear legs being soldered to thefront. Balsa or celluloid wheels (bushed)are put on and the ends of the undercarriagebent up as shown.

For the wing, cut ten riblets and twelveribs, the riblets being the shaded part on theside elevation drawing.

Pin down the trailing edge and the twobottom spars, glue into position the ribswhich have been cut from lir -in. balsa sheet,and insert the riblets and the leading edge ;the sizes required being leading edge-136- in. x * in., trailing edge in. x * in., andthe spars * in. square balsa.

The wing tips are next added, and aremade from A- in. bamboo. The dihedral isnow steamed in, the wing tips being 3in.above the centre section. The two diagonalstruts are then cut so that the trailing edgeis in. above the leading edge, thismeasurement being at the point where thestruts are glued to the trailing edge. Allowthe glue to set firmly, and finally insert thetop spar. The machine is covered withmedium weight jap tissue, and given onecoat of dope. The rubber motor consistsof 20 ft. of + in. .x A in. elastic divided intoeight strands (four loops), making the motorshort but powerful. The wing position isapproximately that shown on the sideelevation.

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ezaziellf*astIf a postal reply Is desired, a stamped addressed enveiope 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 ill ofcover. Send your queries to the Editor, PRACTICAL MECHANICS, Geo. Newnes Ltd., 8-11 Southampton

Street, Strand, London, W.C.2.

POLISHING SILVER PLATING" I AM making up a preparation for polish -

ling silver plating, chromium plating,etc. It contains no acids and is thinned outwith water.

Could you advise me as to an ingredientto hasten drying, which can be mixed withwater to make it volatile, and the proportionto volume of water necessary to be effective?It must not be costly, as I wish to keep theexpense of the preparation as low as possible."(F. S. W., Oxted.)

YOU are up against a very difficult taskin endeavouring to incorporate a quick -

drying agent in your polishing preparation.As a matter of fact, no really satisfactoryagent of this nature exists, and this for thereason that if you mix a volatile liquid withwater, the volatile liquid evaporates first,leaving the water behind. It is true, ofcourse, that the volatile liquid, provided itis completely miscible with the water,entraps some of the latter liquid and thustends to hasten its evaporation. Neverthe-less, when solid ingredients are present, asthey will be in the case of your polishingpreparation, it is very doubtful whether theaddition of a volatile liquid will have muchbeneficial effect.

You might try adding about 20 per cent.of methylated spirits to your preparation.Better still would be methyl alcohol oriso-propyl alcohol, the latter being the lessvolatile of the two, but the cheaper becauseit is not subject to excise duty.

Methylated spirits, you will be aware,contains heavy ingredients which tend tomake its rate of evaporation slow. Itscores, however, in point of cheapness.

LEAD AMALGAM" AS an experiment, I melted about 1 oz.

of lead in a crucible over a Bunsenburner. I then poured into this about thesame amount of mercury, which caused themixture to splutter violently. I then let themixture cool, which set into a greyish,brittle substance which I easily crushed intoa powder. What is this substance, andwhat is it used for ? (I. H., Oxford.)

THE material which you prepared byadding mercury to molten lead is lead

amalgam, and, since you used equal partsof lead and mercury in its preparation, itwill be a 50 : 50 lead -mercury amalgam.Various lead amalgams can be prepared byvarying the proportions of mercury addedto the molten lead. As the proportion ofmercury is increased, the melting -point ofthe resulting lead amalgam is lowered,until, with a high percentage of mercury,the lead amalgam becomes almost plastic atordinary temperatures.

There is little use for lead amalgams onaccount of their brittleness. The only useswhich these amalgams have been put to arethe following :

1. As a substitute for an artist's drawingand shading pencil, the greyish lead amal-gam being soft enough to give a peculiargreyish shade to paper when rubbed on thelatter.

2. In the autogenous soldering of lead.The lead surfaces to be soldered are wellcleaned and made bright and a layer of leadamalgam is melted over them. They arethen brought into firm contact and a hotsoldering iron is passed over them withheavy pressure several times. The heatvolatilises the mercury in the amalgam butthe lead remains behind, thereby effectinga firm union of the two surfaces.

This method is not much employed at thepresent day on account of the considerableexpense of mercury. In experimentingwith the method, great care should be takennot to breathe the mercury fumes given offby the soldering operation, since they arepoisonous.

THE MANUFACTURE OF CELLOPHANE" (1) S it possible to make ordinary cello-

' phane, i.e. cellulose xanthate, inthick slabs at least I in. thick, and, if so, towhom should I write for a quotation ?

" (2) Text -books on mineralogy deal withthe crystalline form of minerals. Can yourefer me to any text -books describing thephysical characteristics of artificial crystalsand the different systems of crystallinearchitecture to which they belong ?

" (3) Can you refer me to any works on' liquid crystals ' ? Can you give me thename of a liquid crystal ' of the nematicclass normally obtainable which exists inthat form at (a) ordinary temperatures, ifpossible, or (b) slightly above ? Where canthese be obtained ? " (H. H., Epsom.)

(1)wE doubt whether it is possible to

procure cellophane sheets of atleast in. thick. However, you mightwrite to the Cellophane Company, 6-9Bird Street, Oxford Street, London, W.1,for a possible quotation.

(2) Any text -book of crystallographywill give the information you desire con-cerning the forms of artificial crystals.You might try the following :

Evans & Davies : Elementary Crystal-lography, 9s. 6d. net.

Tutton : Crystallography and PracticalCrystal Measurements, 2 vols., each 508.net.

Tutton : Crystalline Form and ChemicalConstitution, 108. 6d. net.

(3) There do not appear to be any exclu-sive works on liquid crystals. A. E. H.Tutton, the well-known crystallographer,in his Crystals (1911), devotes a chapter totheir description. They are also mentionedand described in all other crystallographicalworks. Ammonium oleate, para-azoxy-phenetol, and para-azoxy-benzoic acid aresubstances which can exist in the form of

(Continued on page 118)

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REPLIES TO QUERIES ANDENQUIRIES

(Continued from page 117)

small liquid crystals at ordinary tempera-tures and slightly above these tempera-tures. Ammonium oleate (and, also,other oleates) can exist in liquid crystalform at considerably elevated temperatures.Liquid crystals as such are not procurablecommercially. They are generally formedon the microscope slide. The abovematerials may be obtained from anychemical wholesaler, such as The BritishDrug Houses, Ltd., Graham Street, CityRoad, London, N.1.PHOTO -ELECTRIC CELLS" A RE the photo -cells used in the different

/forms of photographic exposure metersof a vacuum, gas, or liquid type, and are theypermanent ?

" Is it possible for me to construct aliquid cell sufficiently sensitive to work inconjunction with a low -reading milli -ammeter on the lines of those described in

Practical Mechanics,' and does the size ofthe container and amount of solution haveany bearing on its sensitivity or life ? Is itssensitivity dependent on the area of theplates, and can these be paralleled in anyway to reduce the area ? Will you pleasetell me what metals, solution and method ofpreparing either are the most sensitive andwould it be permanent if the cell were madewatertight ? " (R. D., Regent's Park.)THE photo -cells used for photographic ex-

posure -meter purposes are of the " self -generating " type, i.e. they generate acurrent of electricity which is proportionalin intensity to the intensity of the lightfalling upon the sensitive surface of thecell. The cells are of the vacuum type,such cells being very constant in actionalthough the current which they deliver isless than that produced in a gas -filledphoto -cell. All photo -cells used formeasurement purposes are supposed to bequite permanent, although, in this respect,it will be realised that they have not beenin general use for a sufficient length of timefor this claim to be fully substantiated. Agood vacuum photo -cell, however, is aconstant and reliable article.

Liquid photo -cells are not practicable forconstant service. For one thing, theirsensitivity varies very greatly, they are notvery portable, and they are not sensitiveto weak illuminations.

You can make a liquid photo -cell bytaking two pieces of copper foil (about 2 sq.in. in size), thoroughly cleaning thesethrough immersion in a solution of causticsoda, and afterwards thoroughly washingthem. The copper elements are thenimmersed in a very dilute solution ofcopper sulphate (prepared by dissolving a

grain of copper sulphate in 2 pints ofwater) and allowed to remain therein forabout 8-10 days-in sunlight, if possible.During this time, a delicate bluish film ofcuprous oxide will form on the surface ofthe copper. If, now, the plates, stillremaining in this liquid and separated fromeach other, are connected together extern-ally and matters are so arranged that oneplate is kept in the dark whilst the other isstrongly illuminated, it will be found that asmall current will pass in the externalcircuit as long as the illumination persists.Immediately, however, the illuminationceases, the current will also stop. Thesensitivity of such cells is mainly dependent

upon the efficiency with which the sensitivecoating on the plates is formed. Withinreasonable limits, the sensitivity of the cellis not dependent upon the area of the plates.Unfortunately, liquid photo -cells are notpermanent, this fact constituting one of themany reasons why they are not employedin practice. With a very delicate milli -ammeter, a reading could be obtained, butmore satisfactory results would accrue fromthe use of a microammeter or a micro -voltmeter.

ELECTRO-DEPOSITION

" I AM interested in electro-deposition andI would be pleased if you could tell me

the conditions necessary for the anodicoxidation of aluminium. The electrolyte, Ithink, contains chromic acid, but I do notknow the proportions. Could you tell me :

" (1) Composition and proportions ofelectrolyte ?

" (2) Composition of cathode ?" (3) Is it necessary for the aluminium

anode to be clean or does it matter if it isalready thinly coated with oxide ?

" (4) Particulars of current needed ?" (5) What kind of dyes can be used for

colouring the oxide sheet ?" (6) What dyes will colour it (a) green,

(b) blue, (c) red, (d) orange ?" (7) Can the process be carried out at

home ? " (J. H., Hampstead. )

THERE are two general methods inwhich the anodic oxidation of alumin-

ium may be carried out, viz. :(1) Chromic -acid method.-Three per cent.

solution of chromic acid as the electrolyte.A carbon rod or a strip of stainless steel(the latter is preferable) as the cathode.The bath should be maintained at atemperature of 45 degrees C. For the firstfifteen minutes, the voltage of the currentis steadily raised to 40 volts. It is main-tained at 40 volts for thirty minutes.During the following five minutes it israised to 50 volts and kept at 50 volts for afurther five minutes.

(2) Sulphuric -acid Process.-In this pro-cess a dilute solution of sulphuric acidforms the electrolyte and a strip of leadforms the cathode. The electrolysis isconducted at room temperature and asteady current of from 10 to 20 volts ispassed for thirty minutes.

In order to obtain the best oxide films onaluminium it is absolutely essential that themetal should be well cleaned previously,especially when it is intended to colour theoxide film.

To obtain the best results from thecolouring of the oxide film on aluminium,the dyeing process should take placeimmediately after the oxide film has beendeposited. Remove the metal from theoxidising bath, wash it well, and immerseit in a 2 per cent. dye solution in the cold.During half an hour gradually raise thetemperature of the dye bath to boiling -point, maintain it at that temperature fora quarter of an hour, and finally wash thedyed metal -coating in warm water.

Any basic dyestuff may be used for thedyeing of oxide films prepared as above, as,for instance :Green . Malachite Green, Brilliant Green.Blue . Methylene Blue, Methyl Blue.Red . Acid Scarlet, Lake Red D, Cerise.Orange . Methyl Orange, Orange II, Aura -

mine, Acid Orange, Safranine.Provided that the necessary direct -

current supply can be obtained, there isno reason why the anodic oxidation ofaluminium should not be carried out inthe home workroom.

November, 1935 NEWNES PRACTICAL MECHANICS I 19

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ENGINES. Build Butler's i-h.p. practical Modelpetrol Engine. Set of Castings, 9/9. InterestingCatalogues 3d. TAPS. Your own stocks, dies, taps,

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A.B.C. HORIZONTAL TWIN, cylinders drilled andlighted suitable for "Flea" with carburettor, magneto,exhaust pipes and tank £5.10 . 0:- Willoughby,Hillcrest, Merstham.

ENGRAVING'ENGRAVE ON METALS with the Vibrita Engraving

Machine, tallies, name plates, etc., speedily done. A.C.mains only. £3 complete. Particulars. - Lycett's,Skinnergate, Darlington.

LITERATURE

OVER 190 PAGES Illustrated Workshop Hints andCalculations in Calvert's Mechanics' Almanack, 1935.8d. post free. Endsor & Co., 5 Bridge Street, Man-chester.

MAGIC

CONJURING TRICKS, Catalogue 3d. Gordon andCo., 65 Chancery Lane, London, W.C.2.

PERPLEXITIES AND TANTALISERS.-" TheStrand Problems Book " is the finest collection ofpuzzles of all kinds ever assembled, mathematical,geographical, literary-acrostics and codes, by W. T.Williams (Tantalus) and G. H. Savage. Only 2s. 6d.net, from all Booksellers.-George Newnes, Ltd., 8-11Southampton Street, Strand, London, W.0.2.

METAL WORKMAKE METAL TOYS. Easy, profitable with

" SUCCESS " Moulds. List Free. Lee's, BentinckRoad, Nottingham.

MISCELLANEOUS

" HOME TOYMAKING," just published, 180illustrations of practical fascinating toys. 1/2.-Industries (below).

DOLLS' HOUSE BRICKPAPER. Roof, flooring,bedroom, kitchen and fancy papers. Complete set sixsheets, 1/6; 12 sheets, 2/6.-Industries, 13 GordonAvenue, Twickenham.

GENUINE BARGAIN. Original 2 guineas MindTraining Course. 5/- only. Leonard, 18 RamwellStreet, Bolton.

STOP SMOKING: Send 2/6 for complete treat-ment. Immediate results guaranteed. " Peacock,"7520 Bury Road, Bolton.

MODELS

TURNING AND FITTING for Model Makers.Scientific Instrument Making and Repairs.-S. Bowles,23 Beaumont Road, Hornsey Rise, N.19.

SCREWS, NUTS, WASHERS (special ModelEngineers' sizes). Everything for Electrical Re -windsand Repairs. Lists Free.-Lumen Electric Co.,9 Scarisbrick Avenue, Litherland, Liverpool 21.

HALF-PRICE MODEL RAILWAYS, stationaryengines, etc. Just like new. Many testimonials.November illustrated catalogue, 40.-Model Exchange,11 Friars Street, Ipswich.

AN INVALUABLE Handbook. ACCUMULA-TORS. Up to date, practical, dealing with every typeof accumulator, methods of charging them at home,care and maintenance. This little book also explainshow to erect a charging station. This is one of Newnes''Home Mechanic Books. Ask your Newsagent to showyou other Titles in this Helpful Series. Obtainable atall Booksellers, ls. each.-George Newnes Ltd., 8-11Southampton Street, Strand, London, W.0.2.

ARE YOU HANDY With Your Hands ?-If youlike making and mending things you ought to knowabout the Home Mechanic" Series of 1s. Handbooks.They cover a wide field, from model and toy -makingto motor -car upkeep and radio construction. Each iscomplete in itself and fully illustrated. Price ls. eachfrom all Booksellers and Newsagents (from whom a listof subjects can also be obtained).-George NewnesLtd., 8-11 Southampton Street, Strand, London,W.C.2.

" WORKING MODELS and How to Make Them."Edited by F. J. Camm, 3s. 6d.-'this book will appeal toall who are handy with tools. Contains complete in-structions for the making of every kind of workingmodel. Each model has been actually constructed inaccordance with the details given and subjected tostringent tests. The instructions and diagrams are soclear that even the most elaborate model can be builtwithout fear of failure. Obtainable at all Booksellersand Newsagents.-George Newnes, Ltd., 8-11 South-ampton Street, Strand, London, W.C.2.

MONEY -MAKING BOOKS

MONEY -MAKING OPPORTUNITIES constantlyoccurring ; highly recommended ; particulars free ;send postage. Messrs. Green, 17 Church Lane, Hull.

YOU WILL BE DELIGHTED with our money-saving Catalogue. Endless variety. Postcard now.Green's, 323 Albert Street, Lytham.

OPTICAL INSTRUMENTSASTRONOMICAL TELESCOPES. Reflectors.

Stands, large or small. Eyepieces. Microscopes andparts. All Optical Instruments. Write-Hackett & Co.,Manufacturing Opticians and Engineers, 51 MillersRoad, Brighton.

PATENTS

REGINALD W. BARKER & CO. (Estab-lished 1886), 56 Ludgate Hill, London, E.C.4. Patentand Trade Mark Booklets Gratis.

PHOTOGRAPHY

£500 worth good, cheap Photo Material, Fre-Plates, Cards, Papers, Chemicals. Cata'

and 4 Samples Fees.-Hackett's. Works JulyLiverpool 6.

POSTCARDS FROM ANY PHOTO. Time tofinish, four days. 25 1/9; 50 3/-; 100 5/-; 500 17/-;1000 30/-. Enlargements 1/-. Samples and ListFree.-Hackett's Works, July Road, Liverpool 6.

DON'T TAKE RISKS. Good developers meangood results. Our reliable stock developers keep twelvemonths after mixing. Satisfaction 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 free. Hackett's Works, JulyRoad, Liverpool 6.

AMATEUR PHOTOGRAPHERS sell your "Snaps"to illustrated newspapers throughout the world. Hun-dreds of pounds paid weekly in reproduction fees foramateurs' pictures. Make your camera a paying proposi-tion. Write immediately for free prospectus withoutobligation. World's Press, 194 Grove Road, ChadwellHeath.

BUY, EXCHANGE OR SELLSITUATIONS VACANT

YOU CAN USE YOUR SPARE TIME to Starta Mail Order Business that quickly brings you a full-time income. Follow the lead of others who areaveraging £12 per week net profits. Get away from adrudging routine job-join the big -money class. Noprevious experience necessary. Few pounds capitalonly needed. No samples or outfits to buy; no rent,rates or canvassing. New method makes successcertain.-Write to -day for FREE BOOKLET toBusiness Service Institute, Dept. 236c, 6 CarmeliteStreet. London, E.C.4.

UNDER COST! 150 sets Highest Grade LatheTools. Greenwood, Arnside Road, Southport.

30 WONDERFUL 5/- Self -blowing Gas Blowpipes,2/6 each. Greenwood. Arnside Road, Southport.

THE MYFORD ' 3' LATHE. The modern tool forAmateur and Engineer. Used by Technical Schools,Instrument Makers. Garages and Production WOrks.Moderate Price. Illustrated List from The MyfordEngineering Co., Neville Works, Beeston, Notts.

SANITARY AND WEIGHTS AND MEASURESINSPECTORS, R.ele ing Officers, Band leen ft Teach-ers, and R egist I ars co e in Mils' ant demand. Permanentwog esSive position:. Full de ails of entry lb o theseattractive ea: ems front (1.1'., 335U High Holbo.II,W.C.1.

POST OFFICE ENGINEERING. Coo.] positionsopen to youths and Inen age 17 to 40. For details ofvaeancies, salaries an .1 prospects, write N.T.O. Wept.3071, 335 Mgt' llolborn, \N .1:.1.

START your own 1,11S;IleSS in spare time. .Details -Macfarlane & Co., 27 Ilant ilton Road, ltutherglen,Scot lamb

STAMPS

NINE DIFFERENT SILVER JUBILEE STAMPS2d. Bequest approvals, Sanders, 90 Newlands,Southampton.

STAMPS FREE ! ! Twenty Unused, Colonials''Neurope." 1 Id. G. 11.11aniett. limingtott, Somerset

TOOLS

ELECTRIC DRILLS, geared type, 18/9-allvoltages A.C./D.C. reconditioned, new bearings, gears,shucks, etc. Powerful motor over 1/16 h.p. carryinghisi-class grindstone about 4 in. 14/9 all voltages.Powerful 6-v. motors 13/6. Used lathes, chucks, fret-work machines on application. Lists 2d. Machiningand casting undertaken. '2 -in. Drummond faceplate, sliderest 18/6. Ancel Ciue Co., 8 Highbury Terrace Mews, N.5.

TOOLS upon emy payments. Treadle Saw Benches,118/ power £3, Constructors' Saw Bench Fitments12/8, Lathes 25/-, Compound Rests I5/-, Foot Treadles35/-. Lists 2d.-Brown Bros.. Acciington.

GRAYSON'S steel mouse threads flex through conSuits. 5/- post free. -Below.

GLASS -BORING 0 ittits avoid risk.- Grayson &Company, 300 Campo I Sheffield,

UNDER COST! 150 A merican 6-0z. Soldering Irons,104 each, carriage paid. Greenwood, Arnside Road,Southport.

THE IDEAL JUNIOR 3" LATHE. SCBGCompBest. Quick Return to Saddle. Full divided Nut toapron. Illustrated List. -Willimott, Neville's Factory,thilwell, Notts.

NEW AND SECOND-HAND BARGAINS forWood and Metal Workers. Tools and Material. Call orstate wants. Aeon. 55 high Street, Battersea, S. W.11.

- - ------- -

WIRELESS

A DICTIONARY OF WIRELESS TERMS, byRalph Stranger. A Wireless Work of Reference thatshould be on the bookshelf of every keen amateur.Compiled by a master of lucidity, it gives the meaningsof all Technical terms in general use. Price 2s. lid.from all Booksellers and New sagents.-G eorge Newnes,Ltd., 8-11 Southampton Street, Strand, London,W.C.2.

FOR THE RADIO ENTHUSIAST.-" The \Vice-less Constructor's Encyclopredia," by F. J. Carnm(Editor of " Practical and Amateur Wireless "5, thirdedition. Compiled by one of the most accomplisheddesigners and writers on the practical side of Wireless,it covers the whole field. A veritable Treasury of Wire-less Knowledge. Price 5s., from all Booksellers andNewsagents.-George Newnes, Ltd., 8-11 South-ampton Street, Strand, London, W.C.2.

FIFTY TESTED WIRELESS CIRCUITS, byF. J. Camm, 2s. Gd.-This handbook contains everymodern circuit, complete with instructions for assem-bling, component values, and notes on operation.Obtainable at all Booksellers and Newsagents.-GeorgeNewnes, Ltd., 8-11 Southampton Street, Strand,London, W.C.2.

" THE MATHEMATICS OF WIRELESS," byRalph St ranger.-This book is essential to the amateurwho wants to gain a further knowledge of the subjectwithout loss of time-or temper! Fully illustrated, 258pages. Price 5s., from all Booksellers arts] Newsagents-George Newnes, Ltd., 8-11 Southampton Street,Strand, London, W.C.2.

WOODWORK

CABINET HARDWOODS, Oak, Mahogany, Ash,White -wood, Ply Woods, etc. Lowest Prices. SendCutting lists. Planing free. Speciality prime Jap Oak.all thicknesses.-Wilfred Parr & Co., March Works,Latica.ster Road, Leytonstone, E.11.

BAG- STATURE

COMMANDSSUCCESS

Commeirci»e Detoi's of the World -Famousow- Ross System 6d. P.O. or Stamps

or Complete System L2 2s.Marled I's m ule13, psplal cover

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In four Vol-t ones, stronglybound inCloth, lettered22 carat gold,1,568 pages,2,500 illus-trations and

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MODERN MOTORREPAIR

AND OVERHAULINGA Comprehensive and Authoritative Guide compiled by PracticalMen for the Use of the Mechanic, the Garage Proprietor and the

Motor Owner.

Why this Work willInterest You

1. Because experienced men in the Garage Industry

READERS' OPINIONS(TYPICAL OF MANY RECEIVED)

" I consider ' MODERN MOTOR REPAIR'the best text book on Modern practice for themotor user or repairer."-R. B. (Leeds).

" Congratulations on issuing ' MODERNMOTOR REPAIR.' I consider it the finest workever published on this subject."-G. S. M. (Leyton,E.10).

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" I must say as regards your ' MODERN MOTOR RE-PAIR,' that since I first commenced to serve my time as amotor mechanic I have never come across any books ofsuch practical value and in which one could place suchimplicit confidence. Again and again I have saved timeand worry over the 101 jobs which require to be done inany large public garage, and I have gained quite a reputa-tion amongst customers. This is well worth the time spentin perusing these volumes of compressed knowledge, with-out taking into account the considerable amount of enjoy-ment obtained. I must, as the Americans put it, hand itto you ' and your staff on the team -work which must havebeen necessary for such results."-N. A. J. (Glasgow).

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ooks are worth having and re -P. (Birmingham).

TICAL WORK FOR THE PRACTICAL MAN

consider it to be the best book of its kind yet published.2. Because it contains no frills and no padding.

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