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DEPT. 76, THE BENNETT

January, 1936 NEWNES PRACTICAL MECHANICS 217

A New Aid to SciencePROFESSOR W. D.

HARKENS, of the Uni-versity of Chicago, hasinvented an ingenious elec-tron -gun instrument. Thedevice simplifies the problem of obtainingpictures of the molecular surface structure bymeans of a photograph produced by electronbeams.A Portable X-ray Machine

CONSIDERED as the most importantachievement in diagnosing bone frac-

tures, a new high-speed portable shock-proof X-ray unit has been perfected. Itsadvantage is that patients need not be dis-turbed if they are in pain as the portableX-ray machine can be brought to the bed-side. Through a fluoroscope, the doctormay view ever.) ortion of the patient's bodyfor possible fractures.Fresh Milk and ButterTHEODOR HOFUIS, of Duisburg, Ger-

many, has constructed a tank called the" Hofais-tank." By means of a certainoxygen pressure inside the tank, it ispossible to keep milk and butter, placedinside, fresh for at least two months.

An Oil -burning Mail PlaneGERMANY'S newest trans -Atlantic mail

N-1 plane burns heavy oil. It is equippedwith two Diesel engines of the " Juno 5 "type. .The machine, which weighs W2 tons,has a cruising radius of 2,800 miles and cancarry 3 cwt. of mail. It can be launchedby a catapult from a ship.200 m.p.h. Air LinerTHE fastest British air liner ever seen

aloft recently made its first test flight.For an hour it raced round Hanworth Aero-drome. Her top speed, with ten passengersand two pilots, is known to be more than200 m.p.h. Economical cruising speed isexpected to be at least 190 m.p.h.

A New " Death Ray "A CLAIM to have invented a heat ray by

means of which aircraft could be des-troyed in a flash, is made by Mr. L. G.Andersol, of Melbourne. He states thathe has been advised by the United StatesNavy Departmept that his invention haslived up to its claims.The " Queen Mary's " Maiden Voyage

WE learn that the Queen Mary isscheduled to make her maiden voyage

VOL III. No. 28

I 9 3 6

MechanicsEdited by F. J. CAMMSUBSCRIPTION RATES :

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

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

8-11 Southampton Street, Strand, W.C.2.Registered at the G.P.O. for transmission by

Canadian Magazine Post.

Notes, News, and Viewsto New York from Southampton and Cher-bourg on May 27th, 1936.

Into the StratosphereI N a recent ascent, it is stated that theU.S. stratosphere balloon, Explorer II,

reached a record height of 74,000 ft., orabout 14 miles.

70,000 Degrees of HeatSOME remarkable illustrations of the heat

of the stars, and the tremendous amountof energy radiated by them, were given bySir James Jeans in a lecture at the RoyalInstitution. The sun, he said, is relativelycool at 6,000 degrees centigrade. Yet fromeach square inch of its surface it radiatesaway about 50 h.p. The area of the surfaceof the sun that would be covered by alocomotive would give enough energy torun all the railways in England. Sirius hasa temperature of from 10,000 to 11,000degrees, but the hottest stars of all are70,000 degrees.

The " Graf Zeppelin "THE Graf Zeppelin recently completed its

500th journey on its flight from Pernam-buco (Brazil) to Bathurst (Gambia).Earlier Zepps have made as many flights,but these have averaged about sixty mileseach, whereas the average of the GrafZeppelin's flights has been nearly 2,000miles, and it has flown over 900,000 milesin all.

Television in FranceANEW television studio in the Ministry

of Post's building in Paris, was recentlyinaugurated by Monsieur Mandel, FrenchMinister of Posts. Groups , of up to sixpersons are scanned entirely by mechanicalmeans. One -hundred -and -eighty -line defi-nition, and 25 frames per second are em-ployed.

Record for Light PlanesR. E. W. STITT, an American, will, assoon as weather conditions permit, take

off in his "Mosquito Aeroplane," in anattempt to break the world's non-stopflying record for light aircraft. The presentrecord of approximately 1,809 miles was setup by two airmen in 1931.

Bicycles of the FutureAN ultra -modern bicycle

has recently been pro-duced in America. It has asyren, speedometer, built-inlights, light switches, and

the tools are concealed in the saddle.

A Giant FunnelTHE funnel for the new motor vessel

Athlone Castle, now on the slips of theQueen's Island Shipyard, Belfast, had to bebuilt on the dock as there was no shed witha door large enough through which to takethe funnel after its completion.

The Light of the Sky at NightIT is stated that Professor Kaplan, of

America, has been carrying out experi-ments proving that between the stars thesky is not dead black. He has, it is re-ported, discovered more about the light ofthe sky,at night than any other man, but hischief achievement has been to reproducethis light in the laboratory. To make thisweird, dim light, Kaplan pumps a littlenitrogen into a glass container and passes onan electric current through the tube.

World's Fastest Fighting PlaneANEW single -seater Hawker monoplane

was recently tested out at Brooklands.The machine proved itself the fastestfighter in the world, although its speed wasnot stated.

A Binding Case ReminderWE again draw readers attention to the

fact that the Index to Volume II ofPRACTICAL MECHANICS is now available at7d. by post from the publisher, GeorgeNewnes, Ltd., 8-11 Southampton Street,Strand, London, W.C.2. Binding cases,complete with title page and index, cost3s. 6d. by post from the same address.Those readers desiring., a copy shouldapply at once as there are only a few copiesleft. A bound volume of PRAcricALMECHANICS is a Golden Treasury of know-ledge-a storehouse of the most reliablefacts and information on every branch ofmodem scientific progress, endeavour andinvention. A bound volume will enableyou to refresh your memory on somefavoured topic as well as have it to hand inyour workshop as a guide to workshopmethods and processes.

218 NEWNES PRACTICAL MECHANICS January, 1936

An unusual aerial view of the "Saratoga"with nearly one hundred combat planes

drawn up on its deck.

IN. many respects, the organisation andequipment of a Squadron of the Fleet AirArm involves vastly more serious and

complicated problems than in the case of asimilar squadron operating from a landbase. For not only is the provision of afloating aerodrome an obvious necessity,but the navigational problems involved inpiloting an aircraft from an aircraft carrierrequire the most meticulous calculation.Visibility at sea very often extends over arange of many miles, but it also often fallsto only a few hundred yards almost withoutwarning, and it is then no easy matter for apilot to find his way home to the carrierafter a long reconnaissance flight, unles hehas kept a very accurate record of his navi-gation during the flight.

Short flights, however, do not present thesame difficulties, and it was very early inthe World War of 1914-18 that aircraftdemonstrated their value as a means ofguiding the conduct of a major naval opera-tion. Although they were used almostsolely for reconnaissance duties and not inan offensive capacity, their services werefound to be invaluable. They sufferedfrom serious limitations, however, in thatif a " land " plane was used, their usefulrange was greatly restricted, while if aseaplane was used, it was incapable ofalighting with safety on anything but thecalmest sea. Even to -day, a seaplane isincapable of withstanding a swell which

Although Aircraft Carriers havenot yet Taken Part in a MajorNaval Engagement, it is Obviousthat such a Vessel is a FormidableFoe, as will be Gathered from

this Interesting Article

to even a small vessel represents a mostmoderate sea.

Aircraft in Naval OperationsLong before the construction of the first

aircraft carrier was considered, the Admiraltyhad appreciated the value of aircraft in anaval operation, and in the early months of1914, just before the War, they had pur-chased a tramp steamer which was then incourse of construction and had modified itsdesign for use as an " Aircraft Tender."The vessel, which was named Ark Royal,had a displacement of less than 7,000 tonsand was far too small to permit of the con-struction of a deck for landing. Actually,a small flying -off deck was provided on theforward part of the ship and two cranes wereinstalled for hoisting seaplanes on board.The Ark Royal was an invaluable vesselduring the early years of the War, but theimpossibility of effecting a landing, or ofeven taking a seaplane on board in roughweather, was a serious limitation.

Three more small vessels were taken over

by the Admiralty for service as aircrafttenders before the construction of the firstreal carrier. One was the Campania, apassenger liner which was completed in1916, and this vessel was particularlyinteresting in that a flying -off deck wasprovided which was equipped with specialwheeled trollies on which a seaplane couldbe mounted. These trollies enabled anormal seaplane to take off from the decklike an ordinary aeroplane, a feature whichconsiderably increased the value of thevessel. The other two tenders were theRiviera and the Engadine, the latter beingthe only aircraft tender present at theBattle of Jutland.

The First Aircraft CarrierThe first vessel to be constructed in the

form of an aircraft carrier as we know themto -day, was the Argus, a vessel of nearly15,000 tons which was originally designedas a passenger and cargo boat for Italianowners. Her construction had been com-menced early in 1914 at Beardmore's yard,but on the declaration of war, all work onthe ship was stopped and it was not until1916 that the hull was purchased by theAdmiralty and the design converted to acarrier. A complete flying deck wasfitted which extended to practically the fulllength of the ship, and a large hangar was

H.M.S. "Furious" is capable of a speed of 31 knots, and her clear deck expanse of 700 feet in length and 80 feet wide makes landing a comparatively simple matter.


H.M.S. "Hermes" was the first vessel to be designed and constructed especially as an aircraft carrier.

constructed beneath the flying deck. Afurther revolutionary change was effectedin the total abolition of funnels, andenormous horizontal flues were constructedto carry the boiler gases beneath theflying deck to discharge at the stern. Thehangar was 350 ft. in length and nearly70 ft. wide, and it could accommodatetwenty aircraft of both land and sea types.Fully equipped workshops were installedcapable of carrying out major overhaulsand, so far as accommodation and equip-ment was concerned, the Argus was a com-plete floating aerodrome. Two electriclifts were provided for raising aircraft fromthe hangar to the flight deck, and the flightdeck itself was equipped with wind -breakingpalisades which could be simultaneouslyraised along the sides of the deck to giveshelter to a machine on the deck.

With so many revolutionary features inher design, it would not have been sur-prising if the ship had not proved a success.In actual fact, however, the Argus was amost serviceable vessel ; she was the firstreally successful aircraft carrier ever built,although the fact that she was not com-pleted until September 1918, rendered herof no service during the War.

An Expensive ExperimentThe demands of the Admiralty were not

satisfied by the building of the Argus, and

in 1917 it was decided to modify the designof a cruiser, the construction of which wasbeing completed at Armstrong's yard. Thevessel, which had been named the Furious,was destined to prove an expensive experi-ment. As originally constructed, she car-ried two 18 -in. guns and was intended forservice as a light cruiser. The first modi-fication to her appearance was the removalof the front gun turret and the fitting of aflying -off deck with a hangar for seaplanesbeneath. The next alteration was theremoval of the rear gun turret and thebuilding of a flying -on deck over the aftend of the vessel. This deck was not asuccess, however, on account of the airdisturbance during landing due to thefunnel gases and eddy currents. Onceagain the ship was reconstructed and shewas finally completed in 1925 ; her funnelshad been removed and a clear deck fitted,and her present appearance is very similarto that of the Argus, which largely servedas the model upon which her final designwas based. In spite of her chequeredcareer, H.M.S. Furious has since proved aserviceable ship ; she is capable of a speedof 31 knots and her clear deck expanse of700 ft. in length and 80 ft. wide, makeslanding a comparatively simple matter.

The Aircraft Carrier " Hermes "So far, all the carriers constructed had

been converted from designs originallyproduced for ships of quite different pur-poses, but - about the same time as theFurious was appropriated for service as acarrier, the designs for the Hermes weredrawn up. The Hermes was the firstvessel to be designed and constructedspecially as an aircraft carrier. She is acomparatively small ship, having a dis-placement of barely 11,000 tons, but shehas the reputation of being a splendid seaboat with little tendency to roll in roughweather.

Her design includes one feature of funda-mental importance. Unlike the Argus andthe Furious, which were equipped with anunobstructed flying deck covering almostthe entire vessel, the Hermes was built witha conventional funnel and control turret,but instead of being placed on the centreline of the vessel they were built on anisland on the extreme starboard side at thewidest part of the deck. In this positionthey offer little obstruction to the landingor taking off of aircraft, and although theirpresence inevitably causes some disturb-ance of the air to a landing aircraft, yetmany pilots prefer their presence becausethey render the judgment of the height of amachine above the deck a much easiermatter than is the case with the cleardecks of the Argus and the Furious. Itis a curious fact that judgment of height is

H.M.S. "Eagle" is a heavy boat, having a displacement of 25,000 tons, but although it is such a large vessel it can only accommodate 20 aircraft.


H.M.S. "Courageous," flagship of the aircraft carriers, photographed from the air with some of hermachines arranged on deck. She carries a total of approximately 50 aircraft of three distinct types-fighters,torpedo bombers, and reconnaissance. These are raised and lowered into the hangars under the flight deck by

lifts, both of which are down in this photograph, and the wells can be seen.

,ffirk

extremely difficult unless there is someelevated object upon which to form one'sestimate, and it is therefore probable thatall future carriers will be of the Island type.

The " Eagle "A few months after the Hermes was laid

down, the Admiralty decided to appropriateand adapt yet another hull which had beenlying half -completed on the slips since theoutbreak of war. This vessel was theAlmirante Cochrane, which had been de-signed as a dreadnought for the ChileanGovernment. The hull was purchased latein 1917 and the design modified to that ofan aircraft carrier of the Island type,similar to the Hermes. The vessel, which wasrenamed the Eagle, took no part in theGreat War, as her trials only commencedin the spring of 1920, and she was notfinally completed until 1923.

She is a heavy boat for a carrier, having adisplacement of nearly 25,000 tons and hernormal complement of twenty aircraft is onthe small side for so large a vessel.

The " Courageous " and the " Glorious "The British Navy only possesses two

other aircraft carriers, the Courageous andthe Glorious. Both of these vessels werecommenced early in 1915 as part of theEmergency War Programme. Both ofthem were built as ordinary cruisers in theshort time of twenty months and they areto -day capable of a speed of 31 knots.They are modern vessels in every sense,equipped to burn oil fuel in the eighteenboilers with which each is provided. Theturbines, which are of the geared Parsonstype, develop over 90,000 horse -power.

For the first few years of their lives, bothof these ships served in their originalcapacity as cruisers, but by 1924, thenecessity for providing further accommoda-tion for squadrons of the Fleet Air Armcaused the Admiralty to decide on theirconversion to aircraft carriers. In theirmodified state, they are both carriers of theIsland type with a single streamlinedfunnel and the control turret situated onthe extreme starboard beam, and theynormally carry a complement of fourcomplete aircraft squadrons.

Whether aircraft -carriers will continue tobe of the Island type or will revert to thetotally clear decks of the Argus and theFurious is a much -debated question. TheJapanese favour the clear -deck type, alltheir carriers with one exception havingunobstructed decks, but the United Statesshow a clear preference for the Island type,and it is probably this design which willeventually prove the more popular.Largest Aircraft Carriers in the World

The largest aircraft carriers in the worldare the Lexington and the Saratoga, bothof which belong to the United States Navy.They have a displacement of 33,000 tons,and each can accommodate a total of 90aircraft. Not only is their machinery themost powerful ever fitted to a warship, butit operates electrically throughout. Theflight deck is nearly 900 ft. long and between85 ft. and 90 ft. wide, and a catapult isfitted to the bow of each ship which iscapable of launching the heaviest aircraft.These ships cost over £9,000,000 each andthey represent the climax of Americanpractice in the design of aircraft carriers.

Although no aircraft carrier has yettaken part in a major naval engagement, itis obvious that such a vessel is a formidablefoe, and it can be said with certainty thatthe fleet aircraft will be the deciding factorin future engagements.

An impressive photograph of nearly 100 planes, quartered on the aircraft carrier "Saratoga."


Recording Soundon Paper

The apparatus used for reproducing the sounds on a printed newspaper.

ANEW process of recording sound onpaper was recently demonstrated inLondon by M. Georges Rubissow,

the European representative of the Com-panie Funadora Fotoliptofono, S.A., ofBuenos Aires. The principal inventor ofthe system is an engineer, FernandoCrudo, who has specialised in differentradio and sound reproduction experimentssince 1923, and who completed his, re-searches in 1932.

The new invention, or rather the quitenew industry which is created by thisinvention, consists of the printing of theordinary paper or newspaper in the formof a square sheet of normal size. The print-ing is made in the ordinary way with ordin-ary printing ink, and the help of the ordin-ary cliche, with only one difference, thatinstead of characters phonograms areused which reproduce all sounds, as voice,several voices, music, choirs, etc., in themost perfect condition.

The cliche is very easily obtained by thewell-known microphone combined withamplifier and oscillograph, which registerdifferent sounds, voices, and music, etc., onthe negative, from which the cliche then ismade. The cliche, one or several, is givento the printer, newspaper printer, or bookprinter, who prints from it the sound pages,or the speaking paper. One hour after thevoice or the music has been registered, youcan get thousands and thousands of printedsheets which may be distributed like news-papers or like speaking books, etc., as theordinary paper is distributed at present.

Reproducing SoundsFor reproducing the sounds from this

printed paper you need only place it in theFotoliptofono apparatus where, with thehelp of a photo -electric cell., and ordinaryradio apparatus, you obtain the perfectreproduction of the voice, music, sound,etc., which quality is quite as good asgramophone records and even better thanthe talking film. The sound -paper record,during the reproduction, is not touched atall, because, it is only a beam of light whichstrikes the phonogram of these printedsound records, and that is why the soundrecord is practically indestructible. Thelight beam replaces the needles of a gramo-phone. There are absolutely no noises,such as the whirring of the motor with thegramophone.

The History of the FotoliptofonoMany leading electrical sound industries

throughout the world have been occupied foryears in trying to produce this speakingpaper. They used long pieces of paper,about one quarter of a mile long, on whichone or more phonograms had been put in aphotographic way, but it was practicallyimpossible to use such long rolls of paperstrips, and even more impossible to printthem, so they were not commercialised.

The sound record of Fotoliptofono,which may be printed at the rate of 50,000an hour, condensed in one sheet of about17 in. x 20 in., contains about one quarterof a mile of phonograms, so one sheetreplaces about one quarter of a mile ofpaper rolls, which were used by the previousinventors. What a big difference, inthe case of Fotoliptofono, to print one ordi-nary sheet, where other inventors found theymust have one quarter of a mile long stripsof paper, which, of course, is practicallyimpossible to print. And even if it could bedone, it would be of practically no interest,

Details of a New Processwhich may Make Possible theProduction of a Newspaperwhich will Reproduce theSound of Voices, Music, etc.

because you could not easily handle rolls aquarter of a mile long.

Quality of SoundThe quality of the printed record of

Fotoliptofono is extremely high. As youknow, the radio and the talking film haveobtained wonderful results, and applied toFotoliptofono, these results have greatlyimproved the process of sound reproduction.The ordinary gramophone generally uses3,500 to 4,000 frequencies per second.A very good cinema now gives about 5,000to 6,000 frequencies per second. The low-est frequencies that the gramophone cantake are about 200. The Fotoliptofono caneasily offer with ordinary print, about7,000 frequencies per second, but if they areput on the market, 5,000 frequencies, andeven then the quality will be much higherthan that of an ordinary gramophonerecord. The lower frequencies in Fotolip-tofono may easily begin at 16 frequenciesper second insteadinstead of hundreds as with agramophone.

Many people possess a good radio, and,for a few pounds, it will be possible to buythe Fotoliptofono apparatus which mustbe connected to the radio, in order tooperate the printed pages.

Further details of the apparatus used in the new process described on this page.


This impressive -looking saloon ivas built experimentally to test out the possibilities of the Diesel engine or high-speed purposes.

The Diesel Engine ExplainedASK any ordinarily well-informed

man -in -the -street how a Diesel en-gine works and, if he is at all inter-

ested in such things he will probably say," A Diesel engine ? Yes, of course-theycompress air in the cylinder, which heats itup, and then squirt in crude oil which isfired by the high temperature." Roughlyspeaking, he is quite right, although hisdescription is only partly true. There isfar more in the Diesel principle than that,and because this type of engine, especiallyin the smaller high-speed sizes, is rapidlybecoming more and more popular for roadtransport service as well as for industrialand marine drives, a rather more intimateaccount of the happenings in a Dieselcylinder will prove interesting.

In the first place, we ought to disillusionourselves about " crude oil." Crude oil isthe name given to the products of the oilwells before refinement, and is far toovaluable and too costly to be employed inits native state for use in Diesel or otherengines, because it contains the valuablelight oils and essences which are distilledoff in the refinery. Moreover, crude oil isalmost as thick as tar, and not at all suit-able for immediate use in an engine of anysort.

Diesel FuelsActually, Diesel fuels, of which there are

many grades, are quite highly refined pro-ducts, distilled from the crude after thepetrol and the kerosene and other con-stituents have been recovered. Also, whileit is true that the larger, low -speed Dieselscan be, and frequently are, operated, oncomparatively low-grade fuels, good effi-ciency and trouble -free running of high-speed Diesels calls fora carefully selectedfuel, of which more will be said later.

Returning, however, to the action in aDiesel cylinder, our man -in -the -street isquite right when he says that compressionof air in the cylinder raises the temperature.It is not always recognised, however, thatthe compression reaches the neighbourhoodof 500 lb. per square inch-over 30 atmos-pheres-and that the heat of compressionraises its tenperature to about 5000centigrade, at which temperature ironreaches a dull red heat.

Then, the statement that the fuel issquirted into the cylinder does not createquite the right impression. In order thatthe charge of fuel shall come into intimatecontact with the air, it must be injectedinto the combustion space as a very fine

For Mechanically -mindedReaders, the FollowingExplanation of what ReallyHappens in a Diesel Cylin-der will make Interesting

Reading

spray, and to do this it is usually forcedthrough one or more fine orifices at apressure which may amount to 3,000 lb.per square inch. The fuel is injected justbefore the completion of the compression

A

PRESSURE0 LBSFER SQIN.

EXHAUSTPORT. PISTON A

LOWER DEADCENTRE

A diagram showing the sequence of operations in an atomic Diesel engine.

moving spray of fuel-droplets averagingless than a thousandth of an inch indiameter so that, for example, a chargeconsiting of one two -hundredth of a cubicinch of fuel is ultimately divided into about50,000,000 droplets. These become stillmore intimately mixed with the air and,moreover, as their speed diminishes, theirtemperature rises, thus further assistingin rapid combustion.

The rapidity with which this action takesplace may be gauged from the statementthat from the commencement of injectionto the start of ignition, as little time as onesix -hundredth of a second may elapse. Itwill thus be clear that very careful designof the injection system and combustionspace, accurate timing, and also the use of

POSITION OF PISTONAT TOP DEAD CENTRE

POINT OF RIEL CUT-OFFVARIED sycouiRmos

COMBUSTION.

INJECTIONFUEL

stroke, and for maximum engine efficiency,complete burning of the fuel must beachieved very early in the expansion stroke.To ensure this, complete and intimatemixing of the air and fuel are essential, andin addition to the atomising action of thenozzles, ingenious designs of combustionchamber are used to give the air a swirlingmotion.

The Fuel SprayThis turbulence of the air is not simply

to cause a complete mixing of air and fuel,but to assist in a very important mechani-cal action. The actual speed of the fuelspray on injection may be anything up to300 miles per hour, so that relatively, thecharge of air is stagnant. As a result,tiny particles are torn off the swiftly

a suitable fuel are essential for perfectoperation.

" Diesel Knock "For example, if undue turbulence is

achieved, or if too much fuel has enteredthe cylinder when combustion starts, thesudden rise of pressure on ignition will beso great that the so-called "Diesel knock,"resulting in violent and even destructivevibration, will be set up. On the otherhand, if the fuel is of a type which takes along rime for complete combustion, therewill be uncontrolled burning, increasedshock on bearings, and troubles such asdamaged internal parts, in addition towhich it will be difficult to start the enginefrom cold-a matter of great importance,particularly with road vehicles.


rc) DIE=CASTING nrBy W. H. Delier

It is only within Recent Times that Die -castings have Come into Use Extensively, but theProcess Dates

IMPROVED technique, and the fact thatalloys having a low melting point andremarkable physical properties coupled

with stability, is leading to the increaseduse of die -castings. In many instancesthey are even being used to supplant partsfabricated from pressings with greatsuccess, as not only is assembly timereduced or completely cut out, but a muchcleaner and neater product possessing greatstrength is the result. It is hard to finda branch, at all events in the lighter typesof engineering, in which die -castings are notor could not be employed with success.This is borne out by the fact that to quoteeven a few instances, such castings are nowused in large numbers in the automobile,motor -cycle, electrical, small mechanical,gramophone and wireless, clock, instru-ment making, typewriter and calculatingmachine, and toy industries.

Although die -castings haveonly come into use toany great extent generallywithin recent times, theorigin of the process datesback a considerable numberof years. As a matter of fact,it is close on one hundredyears since printers' type wasfirst cast by machine onpractically the same linesthat are in use for generaldie-casting at the presentmoment. Doubtless at thattime, the need for such arevision of methods waspartly brcaight about by thenatural desire for increasedproduction, but in all proba-bility the change was neces-sitated by the difficulty orimpossibility of makingsound and clear-cut smalltype by ordinary gravity -casting methods.

Sand -castingsDie-casting is essentially

a process suited to the pro-duction of certain types ofcastings in quantities. Inordinary foundry practice, apattern is used to form acavity in sand into whichthe molten metal is poured,an individual mould beingprepared for each castingrequired. On account oftechnical difficulties, it is im-probable that this method will ever besuperseded for metals have a high meltingpoint. Sand -castings, except for veryrough work, must be finished, at all eventsas far as important dimensions are con-cerned, by machining, and the preparationof unmachined surfaces to a conditionsuitable to receive a deposit which after-wards has to be polished, is a costlybusiness. By the adoption of the die-casting process, finishing operations arealmost entirely eliminated, but whereas

Nozzle

el nearly 100 Years

for sand -casting the preparation of a suit-able pattern is in most cases an expensiveitem, the provision of a suitable die is aconsiderable one and therefore cannot beconsidered as a paying proposition unlessthe cost can be spread over a large numberof castings. In comparing the cost of thecastings, it has to be remembered that adie-casting represents a finished machinedpart except perhaps for, say, a tappingoperation, so that where intricate machin-ing operations have to be carried out on apart, the high cost of the work so involved

Plvnyer,,

Cylinder

r.

Metal Level

Port

Meter/Po

fV

4o/.959eerCO'S 47.9

Fig. 1.-A cross section of the machine used for filling the d

might make a die more than worth whileon a relatively small quantity.

Although within the space of a singlearticle little more than a brief outline of themethod can be given, sufficient can be saidto convey to the reader the general prin-ciples of what is a really interesting process.

Whilst aluminium and certain types ofbronze can be die-cast, by far the greaterproportioh of die -castings are made inzinc -base alloy. This metal casts well andwith a good finish. Earlier die -castings

ies.

generally were confined to lightly stressedor purely ornamental parts that could bemade from lead or tin -base alloys. Thiswas on account of structural changestaking place in the then used zinc -basemetals with ageing, resulting in seriouschanges in the formation of the castings orin disintegration. Comparatively recentdevelopments have led to the introductionof zinc -base alloys in which these seriousdefects have been overcome and further,the mechanical and physical properties aresuch, that castings made from them cansatisfactorily replace those formerly madeof iron or brass for certain purposes.These facts have probably had much to dowith the popularisation of the process.

Die-casting MachinesMachines for the purpose of die-casting

follow more or less the same lines as regardsthe method used for filling the dies. Asection of this portion of the machine isseen in Fig. 1. It will be seen that thisconsists of a gas -heated metal pot, arranged

within which, in such a man-ner that it is almost com-pletely submerged in moltenmetal, is a cylinder havinga bottom outlet terminatingin a " gooseneck." Thecylinder is fitted with a pis-ton or plunger, and whenthis is at the top of its strokea port is uncovered throughwhich the molten metal flowsinto the cylinder and goose-neck. The means vary ondifferent machines for bring-ing the dies up to the nozzle,but when the dies are inposition the plunger is de-pressed, either by a handlever or air pressure, to forcethe molten metal into thedie cavity. As the dies arecomparatively cool thesolidification of the metaltherein is almost instan-taneous, so that the plungercan be raised again at oncewhen the surplus metal inthe nozzle drops back intothe gooseneck. The die isthen withdrawn from thenozzle, opened, and the cast-ing ejected. With modernhand -operated or semi -auto-matic machines, the labourinvolved in performing the

sequence of operations has been reduced to aminimum, and the rate at which castingsare produced must be seen to be believed.

As may be imagined, the most interestingpart of die-casting lies in the dies them-selves, for seldom are two jobs alike andfrom a die -makers' point of view, each hasto be dealt with in strict accordance withits peculiarities.

Die DesignA die for producing a part full of cored


holes, such as a carburetter body, must ofnecessity be a complicated piece of work,as, for holes that are other than at rightangles to the parting line, core -drawingmechanism has to be incorporated. It isthought, however, that the principle onwhich the dies are made and operated willbe best explained by taking simpler formsof castings as an example. The castingshown at the bottom left-hand of Fig. 2

is firmly attached to this half and somemeans of pushing the casting off is required.It will be noticed that there are three holes,arranged triangular fashion, drilled throughthe face of the movable die. Two smallerholes are also in the die adjacent to thesmall core -pins, but these do not show soclearly in the photograph. The purposeof these holes is to receive the pins set inthe ejector plate seen on the left-hand side

Fig. 2.-Some typical die -castings of handles, etc.

presents no difficulties as far as die -makingis concerned, it being a really ideal job fordie-casting methods. Perhaps it would beas well to explain that the dies are made inhalves so that the casting can be removed,and it is known as the parting line where thefaces of the half dies meet.

The die in which this particular part ismade, is shown separated at the right-hand side of Fig. 3. When together, thehalves are kept in alignment by the locatingpins protruding from the fixed half of thedie. In this half is sunk an impression ofthe top portion of the casting. The raisedpart on the opposite half corresponds inreverse to the inside of the casting as seenin the top left-hand corner of Fig. 2, theblind holes in the boss centres being formedby slightly tapered pins fixed in the die.On the left-hand side of the dies is seen therunner which matches up with the nozzleof the machine and through which themetal is admitted to the die cavity. Lead-ing from the impression in the fixed die andseen at the right-hand side, is anothershallow channel a few thousandths of aninch in depth. This is a vent throughwhich the air in the cavity of the die isforced out by the incoming metal. Thevent or vents must. be so arranged that noair can be trapped in the die, as, if this,happens, the cavity will not completelyfill.

Removing the Finished CastingThe layout of the die must be carried

out in such a manner that the casting comesaway on the movable half when the diesare opened. Usually on account of shrink-age, or to the presence of cores, the casting

of the fixed die. This device functions asfollows : when the dies are opened thetravel of the movable die is continued untilthe plate reaches a stop which pushes itforward. The small pins do the actualwork of ejecting. The purpose of the largerpins is merely to return the small pins to a

the sides of the castings call for carefulwork in the making of the die. These areprovided by making the projecting portionon the face of the movable die to fitperfectly, the sides of the opposite cavityin such a manner, of course, as not to pre-vent the die faces from bedding, the sidesof the plug, as it were, being milled away inplaces to leave the bars between. Whenejected from the die the castings appear asthose shown in the top left-hand of Fig. 2,that is, with the runner included. Therunner channel or gate in the die is cutfairly deep up to within about in. of thecavity where the depth is reduced toapproximately in. Thus, the unwantedmetal is joined to the casting by a verythin section only and is, therefore, easilybroken off.

Although still a simple proposition as adie-casting, the one shown in the bottomright-hand corner of Fig. 2 presents moredifficulties when the dies are considered.This will be apparent when the contour ofthe parting line of the dies at the left-handside of Fig 3 is examined. These dies aremade to cast two pieces at a time, thecavities being gated together. The ejectorplate and pins -are in the position that theyoccupy in the moving half of the die aftera casting has been ejected. This viewclearly shows how the plate is returned bythe four large pins as the dies are closed.

While it may be said that the exampleschosen are not strictly accurate jobs, theproducts from the dies are absolutelyuniform as regards dimensions. The sur-face finish of the casting depends upon

Fig. 3.-The dies for producing the castings shown in Fig. 2.

position flush with the surface of the diewhen ready for casting.

As previously mentioned, this die presentsno real difficulties on account of the partingline of the casting being absolutely straight.It may be remarked that for the castingsto be made with an absence of fin or" flash " at the parting line, the opposingfaces of the die must fit perfectly and, there-fore, flat surfaces are most easily producedwith accuracy. The port -like openings in

the manner in which the die cavities aremade free from scratches, and afterwardspolished, plus the matter of keeping themolten metal at the correct temperature.

In conclusion it is hoped that sufficienthas been mentioned to enable the reader tovisualise that to make complicated parts, orfine parts, such as gear wheels to almost anyreasonable degree of accuracy by thismethod is merely a matter of making correctshrinkage allowances and die designing.

WEARITE TEST INSTRUMENTS

THE service engineer will be interestedin the latest range of test instruments'from the Wearite range. In the

illustration at the foot of this page areshown the valve -testing unit, the oscillatorunit, the multimeter, and the meter unit.As may be seen, the instruments are madeto match up, and they are extremelyportable, and may be used individually oras a group to form a complete radio testoutfit.

January, 1936 NEWNES PRACTICAL MECHANICS

This aerial view shows left, the S.S. " Normandie," of the French line, the new Blue Ribbon ship of the seas, in the Hudson River, after her record -breakingmaiden voyage, and right, the S.S. " Europa" of the German line, a former speed queen of the Atlantic, is berthed almost adjoining her.

IN the hey -day of sailing ships, design wasa matter of tradition and experience.Shipbuilders built by eye alone. Some

remarkably perfect hull forms came fromthe building yards of those days. Theclippers of the Clyde attained speeds whichhave never since been exceeded under sail.

With the coming of steam, speed was notthe only criterion. Owners began to con-sider economy in coal. The number oftons of coal burned for every ton of cargocarried, is the standard by which themodern cargo boat is judged. At highspeeds, good design alone permits the savingof bunkerage space and horse -power whichbrings the running of the ship withineconomical figures.

Ship TanksActually to -day, we still learn by experi-

ment and experience. In the old daysexperience was picked up from the per-formance of each fresh ship which went offthe building stocks. To -day, that methodis too slow. The acquisition of experiencehas been accelerated by experimenting withship models in ship -testing tanks.

There are several such tanks in use.There is one at the National PhysicalLaboratory at Teddington. Thornycrofts,of speed -boat fame, possess another.. Theyare tanks about a hundred yards long bytwenty yards wide. Along the sides arerail tracks on which run a bridge spanningthe tank. The bridge travels at exactlycontrolled speeds up and down the tank.The models axe towed from it by a dyna-motor attachment which measures the force

The Queen Mary CrashingThrough the Sea at Thirty Knotswill meet Resistances Which area good Deal Higher than thoseOvercome by an Aeroplane Fly-ing at Four Hundred Mites anHour. In These Days of HighSpeeds in the Air we are Aptto Lose Sight of the Perfectionof Hull Form which Permitsof High Speeds on the Sea

needed to urge the model through the water.

Model Ships Cast in Paraffin WaxThe models are cast in paraffin wax,

scraped exactly to form, and finallypolished. They are ballasted down withlead so that they sit properly in the water.Sometimes the models are made in sections,bow, midships, and stern sections. Byfitting different bow sections, shall we say,to the same midships and stern sections,the effect of bow form can be studied.Similarly,. the other sections can be experi-mented with separately. A fact which hasemerged from this type of experiment isthat the shape of the midships section isunimportant provided that both bow andstern lines ease into it smoothly. From

this springs the square sectional midshipsshape of most modern cargo ships. It is ashape which is easy to build and gives agreat cargo -carrying capacity for the leasthull surface. A wartime discovery wasthat the addition of a large underwater,anti -torpedo bilge to ships over theirvital midships section, did not diminishtheir speed.

Skin FrictionBy far the largest factor in ship resistance

is the drag of the water on the hull. Thisis skin frictional resistance. It accountsfor nearly 85 per cent. of the resistance inall but the highest speed ships. Accord-ingly, in low -speed ships they build for thebiggest capacity for the least hull surface,and arrive at the bluff -bowed, short-stemedcargo boat exaggerated in form in the shapeof the canal -boat sectioned oil -tanker.

Wave ResistanceFor higher speeds, the resistance due to

the waves created by a ship becomesimportant. The wash raised by a shiprepresents energy which has originallycome from the ship's engines. Greatsavings in horse -power are effected bychoosing those lines which give least waveformation. A ship moving through thewater gives rise to no less than four systemsof waves, two system* from the bows andtwo from the stern. The bows cause ahump of pressure as they part the water.The outer edge of this hump travels out-ward at an angle and causes what we callthe wash of the ship. The inner edge

226 NEWNES PRACTICAL MECHANICS

follows the ship and causes a series ofwave %crests along its sides. Where theship begins to narrow again towards thestern and the water in streamline flowbegins to close in again, another pressuresystem starts which causes a wave hollowthat rises to a crest under the stern. Thestern system of waves can be killed if theship is designed correctly. The wave-length of both bow and stern wavesdepends on the speed of the ship. Bychoosing a suitable speed for a given overalllength of ship, the crests of the bow wavesmay be made to occur on the top of thetroughs of the stern wave. In this con-dition the wake of the ship is practicallysmooth and the only disturbance is therolling divergent wave from the bows.The opposite case is seen when a boat isforced above the most suitable speed for itslength. The bow and stern waves rein-force one another and a wave accumulatesunder the stern which has every appearanceof dragging back on the boat, as in fact, itdoes.

Naval architects from model experimentshave got this business of wave -making tieddown to an exact mathematical expression.From the length and breadth of a ship it ispossible to state the most economicalmaximum speed of which she will be capable.Or if a given speed is stipulated then theminimum overall length of the ship ispractically fixed by the stipulation. It isthus not mere chance that the fastest linersare the biggest. Ship -owners building for

January, 1936

wave -making charac-teristics of the hullform reasonable at highspeeds.

Cross -channel SteamersAn extreme form of

hull dictated by wave -making considerationsis instanced by cross -channel steamers.Limits of harbour ac-commodation andinanceuvreability donot permit these ves-sels to exceed about300 feet in overalllength. A 300 -footship has a most eco-nomical speed of aboutsixteen knots. Cross -channel steamers, how-ever, do about twenty-two knots. Such highspeed for their lengthhas only been attainedby building them withextremely long bows,which extend well past

What the " Queen Mary will look like when she makes hertheir midship sections.In this way the first

maiden voyage next May. crest of the bow wavespeed must allow die designers to give them is thrown back so that it coincides with thelength. Even then they have to resort first hollow of the stem wave. In most shipsto, special devices such as long hollow bow it is the second bow crest that is thrown insections and cruiser sterns to keep the this position.

AIEW ILAMF 1131116-11111TIR THAN THE SLNNEW type of mercury -vapour lampconsiderably smaller even than thesmallest domestic lamp bulb, yet

brighter than the sun, has just been per-fected in the Philips Research Laboratories.

It is claimed that this lamp will com-pletely revolutionise all industries depend-ent in any way upon super -brilliant illumina-tion. It will abolish the revolving shutterof the cinema projector, and already onesingle lamp is being used to floodlight alarge aerodrome.

This simpler form of lamp has a lightintensity of one -quarter that of the sun-nearly twice that of the cumbersome carbonarc, and two -hundred times that of theordinary electric lamp, which alone cancompare with it for size.

Enormous 'PressuresThe secret of the brightness of the lamp

seems to be the enormous pressures whichconstructional improvements have madepossible. It works at a pressure of no lessthan 150 atmospheres, while lamps havebeen working at twice this pressure, with abrilliancy twice as intense.

The magnitude of this advance in thetechnique of the mercury lamp may begauged by comparison of the followingfigures. Before the constructional dis-coveries which led to the present lamp, a mer-cury lamp of 9 Kw., with a luminous flux of500,000 lumens (about 40,000 candlepower),could not be made smaller than about threefeet in length, and about three inches indiameter. One of the new lamps of thesame power is no larger than the stump ofan ordinary lead pencil-an inch long, and aquarter of an inch thick.

Water-coolingThe discoveries which made this enormous

reduction in size possible were, summarily,the use of water-cooling (the lamp works ata temperature of from four to eight thousand

Although the Lamp is no BiggerThan the Stump of an OrdinaryLead Pencil it has a LuminousFlux of 500,000 Lumens(About 40,000 Candlepower)

degrees Cent.) and the perfection of amethod of applying this ; the quartzinstead of glass to withstand these terrifictemperatures, and the tremendous pressuresreferred to above, and finally the discoveryof a method of sealing thick tungsten wires

into the quartz tubes. The electrodes areof mercury, with specially prepared tungs-ten wire points.

Floodlighting, searchlights, spotlighting,photography, are among the more obvioususes for this amazing little lamp ; it is alsoclaimed that it will be particularly usefulfor medical purposes, since its light iswhiter than any mercury lamp yet invented.Unlike the ordinary mercury lamp, it showsa continuous spectrum, including almost thefull quota of red-a band usually absentfrom mercury light.

Experiments are now continuing withan even smaller lamp which will be at leastone -eighth brighter than the sun.

The size of the lamp may be gathered by comparison with the hand shown holding it.

January, I936 NEWNES PRACTICAL MECHANICS 227

ADEVICE that will be found extremelyuseful for lathe work is a tool -holderwhich will take tool steel of small calibre,

such as f -in. round cast steel. Such a tool -holder helps the amateur over the difficultyof forging tools out of bar -cast steel. Itallows him to make a tool for a special jobwith the aid of a blow -lamp and with noforging : for the tool steel can be easilyfiled in the vice to the cutting shape re-quired, and two or three tool -holders will

Fig. 1.-A form of holder for right- or left-hand side tool work.

Fig. 4.-A cutter made from round sled.

provide him with the means of applyingthem to any turning job.

There are many patented holders on themarket, which are extremely useful tools,but if the cost of these is a consideration, itmay be avoided by making the holder one-self. The job is quite simple, whilst per-sonal preference in the matter, and abilityto suit the tool to the type of tool -postfitted to the compound rest, will be anotherpoint in favour of making it.

A Simple HolderIn Fig. 1, is shown a simple form of

holder for right- or left-hand side tool work.It consists of a mild or cast steel bar of asize suitable for the tool -post (if of the open -side type as Fig. 2), and is sawn across atthe ends so that two side faces form equalangles with the.side of the tool.

From these side faces, and slightly slopingdownwards back from the face, holes a in.in diameter, shown in dotted lines in theplan view Fig. 3, are drilled to take thesmall tool bits which are made of f -in. casttool -steel rod. At the point of intersectionof the holes, and above them, a hole(tapping size for a is -in. Whitworth set-screw with square head) is drilled.

This set -screw will hold the round cutterfrom whichever side it is inserted, and the

atheW6rkMATEURS

.6A17'Wyers

overhang of the cutter, which is quite small,will be available for facing or side cutting.The cutters should be made in variousshapes of cutting edge to suit the job inhand. The slight downward or backwardinclination of the holes will give the toprake of the tool.

If the holes are filed a I in. square afterdrilling, square tool steel may be used forthe cutters. If round steel is used, the topsurface of the cutter can be filed down togive width as shown in Fig. 4.

Square and Round CuttersAn advantage of the square hole is that it

gives more stock in the cutter with which to

Fig. 2.-Details of the tool -post.

form the shape of the cutting edge, but anadvantage of the round cutter is that it canbe tilted round to get an appropriatebottom rake. In the case of the squarecutter, however, it will have to be groundsideways to obtain the rake for differentjobs.

For inside boring a good tool can be madeas shown in Fig. 5. Here we have a straighthole in. or Tog in. in diameter, drilled rightdown the tool from one end but to one sideof the stock, so as to leave room for a pinchscrew. This is shown in the end view Fig.6. The hole for the cutter and the hole for

LATHE WORK FORAMATEURS

By F. J. CAMM

96 Pages

1 /- or 1/2 by post from Geo.Newnes Ltd., 8/11 Southampton

Street, Strand, W.C.2.

the screw are first drilled. For the cutterhole, run the drill in the three -jaw chuckin the lathe, and feed the stock of the cutter -holder up by a centre hole in the other endin which the point of the back poppet headcentre will rest. The blank is held fromrotating by a shifting spanner on the squareof the stock, and resting against the lathebed to prevent rotation of the stock.

The hole for the pinching screw A, will bedrilled right through, tapped to size for the*-in. screw, and then cleared for half itslength to clearance size, i.e. A- in., the otherhalf is then tapped. The slot B, is thensawn down the stock into a -in. hole C,which has previously been drilled across the

Fig. 3.-The dotted lines show the position ofthe holes for the small tool bits.

A

O

Figs. 5 to 7 (Left).-A side andfront view of an inside boring tool -holder and (above) inside boring canbe accomplished with a cutter of theshape shown when fitted in the holder.

stock. With this holder, inside boring canbe done with a cutter of the shape shown atFig. 7. The end will have to be set roundwhen red hot, filed to shape, and thenhardened and tempered.

Cutter of Large DiameterThe cutter should be made of large

diameter, as, if the inside turning is of anydepth, the tool will be too springy. It willbe found that a Fin. diameter will be suit-able for most work, but for small modelwork, and work in non-ferrous metal, thecutter may be as small as diameter.These dimensions will depend on the sizeof the work generally undertaken. It isadvisable, when using any of these toolholders, to keep the cutter edge in as nearto the tool -holder stock as can be conveni-ently managed. This is, of course, de-pendent on the shape of the job in hand,and the ease of getting close up to the sur-face to be turned.

A split holder is better than one in which.the cutter lies in a hole and is pinched by aset -screw, because a very much increasedsurface of the cutter comes in contact withthe holder, and the heat generated incutting is more readily and fully radiatedaway from the cutter to the mass of metalin the holder or stock.


Fig. 1.-Showing the finished model hydroplane.

THE construction of the hydroplane" Jildi Junior " was undertaken as amatter of interest to see if the applica-

tion of a few petrol -model aeroplaneprinciples, both of design and construction,would help to forward the cause of the15-c.c. type speedboat.

It was noticeable that the 15-c.c. class ofboat was, as a general rule, rather slow, andusually had difficulty in even keeping theline taut on a circular course. It had alsobeen fairly obvious for some time that the30-c.c. boat had become so fast that shortlya limit to its popularity for the majority ofconstructors might possibly take place.Obviously then, there was an opening forthe development of the 15-c.c. class boatprovided its speed capabilities could beraised.

How then should the problem be tackled ?The 15-c.c. two-stroke " Atom Minor "engine which had proved its worth in flyingpetrol model aeroplanes seemed to be a suit-able power unit to start off with, and thewriter was thoroughly conversant with itsmoods and peculiarities.

From various tests that had been madewith engines of different powers on mysmall outboard full-sized speedboat, I wassatisfied that where limited power is avail-able, weight of the hull is all important. Ihave heard well-known model speedboatmen argue that weight is not important,and in fact that it is necessary in order toobtain a stable and even -running boat.

Undue WeightI feel that experience with full-sized speed

HULLPLATE OF SHEET STEEL

BOLTED TO STERNOF HULL yie THICK

STERN

STAINLESS STEELPROPELLER SHAFT

Fig. 2.-Theconstructionof the skeg,propeller, and

shaft.

A 15-cc PETROL-

By Captain

A Feature of the Construction of thethe Present Record Holder in Class C

strutted on the Lines

hulls fitted with various powered enginesand different numbers of passengers, soonmakes one realise that this is a mistakenview, and that where an undue weight isrequired to keep a hull stable, there is some-thing wrong in the design of the hull.Either the thrust line, weight distribution,planing angles, or planing surfaces areincorrect.

" Oiga Alba," Mr. Rankine's famous30-c.c. boat has a very light hull. Thiscraft is capable of over 40 m.p.h. I con-sidered that if the weight could be reducedby incorporating aircraft methods of con-struction, the somewhat limited power thenavailable from 15 c.c. could be madeto yield more speed. Ally thisweight reduction to a form of hullas streamlined as possible, and thereis the possibility of doing somethingthat will advance thespeed of the 15-c.c.class of boat.

This last matter ofstreamlining is by nomeans all important,but it must help,however much the die-hards will tryto point outthat at the ALUM/AI/UM ANGLEspeeds atwhich theboats travel,wind resist-ance has noeffect.

Finally, I

SHEET STEEL MEG

PHOSPHOR BRONZEBEARING BRAZEDTO SAES

BALL THRUST RACETAKEN FROM Ax,

MAGNETO -N

SHEET STEEL BLADESBRAZED INTO PHOSPHORBRONZE HUB

Q.111.11%

DURALUMINSTREAMLINEDHUB EXTENSION

SCREWED ON TOPROPELLER SHAFT

CROSS BEARER

CUT OUT FORLIGHTNESS

Fig. 3.-Details of the enginebearer and method of mounting

the engine.

considered that the planingsurfaces should offer as littleresistance as possible by skinfriction, but at the same timeshould be of ample surface sothat the hull could skid over thewater without any suggestion ofdigging in.

Nearly 25 m.p.h.These then were the under-

lying ideas when I settled downto design " Jildi Junior." Theresult was encouraging, for therecord was immediately put upby a considerable increase inm.p.h. The actual speed clockedfor the 300 yds. being 24.78m.p.h. There is no doubt thatwith more care and thought onfuture hulls, this speed will begreatly increased in the 15-c.c.class.

I do not wish to claim that my boat iseven a good one, I feel sure that it can beconsiderably improved, but I feel that itsform of construction may be of interest tospeedboat fans and may possibly form foodfor thought in the 15-c.c. class even if thereader discards the majority of the ideasthat went to form the design.

I should mention that having built thehull which I am now about to describe, Ifound that I had even then constructed itfar too robustly, and I hope a considerableamount of weight will be saved on my nexthull of the series.

Perhaps also an explanation of the boat'sname is necessary, as I haveheard several people, whilstlooking at the hull at regattas,suggest that the Hindustaniname of the boat was rather aboastful one.

I think this is due to a mis-interpretation on their part ofthe word jildi. Actually itis an exhortation to " go

quickly." I feltwhen naming it thatthere was no harm

EXTENSION OF BEARERTO REAR FLOOR OF HULL

AFT OF STEP

R/GHTHAND ASH ENGINE BEARER

in telling it to get a move on. I should notlike to tempt fate by giving the boat a namethat included speed as an accomplishedfact !

At the time of building " Jildi Junior " Ihappened to be living in Scotland, and myfriend Mr. Rankine, of model speedboatfame, was interested in my project. Hekindly consented to fit the engine with aminiature of one of his extraordinary simpleand efficient carburetters. I consider thesecarburetters are splendid instruments forracing, as there is no uncertain tap twiddlingand making of mixtures, just when the over-excited competitor is launching his aero-plane or his boat for some attempt for a cupor a record.

Anyway, up went the speed of my " AtomMinor " engines, and in particular the oneto be fitted to " Jildi Junior." A littlejudicious opening of ports also assisted. Asthe reader is probably familiar with the" Atom Minor " engine I will only give ashort description. The engine has beenfully described in PRACTICAL MECHANICS.It is a two stroke, constructed chieflyof a light alloy and with a cast-ironcylinder liner. The cubic capacity is 14.2


ENGINED HYDROPLANEC. E. BOWDEN

Hydroplane " jildi junior,"for .15-c.c. Boats, is that itof a Model Aeroplane

c.c. and the weight with flywheel as fittedfor " Jildi Junior " 1 lb. 14 oz. A Boschgreen band sparking plug is fitted. Theignition is by non -trembler coil weighing8 oz., the dry battery weighing 15 oz., andthe condenser 2 oz. The " Atom Minor "engine used was one -of the latest produc-tions of A. E. Jones, Ltd.

This engine was put on Mr. Latta,'s well-known small brake and put under load. Itwas found that with the added r.p.m. gainedby the special carburetter, and the increasedport areas, that misfiring set in at the higherspeeds. The ignition contact -breakerspring had to be substituted for a muchstronger one, and a slight modificationmade to the gear. (The production aeroengine is not designed for this big increaseof speed.)

The Transmission and PropellerThe propeller shaft is a simple stainless

steel shaft with no universal joint at thepropeller end. The propeller is attacheddirect to the shaft and there is a plainphosphor -bronze bearing carried by theskeg. A small magneto ball -race is used asa thrust race to take the thrust of the pro-peller. This is fitted hard up against therear end of the plain streamlined phosphor -bronze bearing (see Fig. 2).

It is a very debatable point whether auniversal joint should be used in the pro-peller shaft at the propeller end and soreduce the angle of the thrust line with theplaning surfaces.

SOLID BALSANOSEPIECE

r/85w6. W/RE ATTACHMENT FOR4/NE TO POLE FOR CIRCULARCOURSE RUNNING

FORMERS /11/1. 3 PLY

I

which isis Con-

STERN381 3 -PLY

COCA'P/T BEAD/NC/4413,/"4 BIRCH

zFA/RING %/6B/RCH STRIPSCOVER/NG HULL.

Manyconsider this is essential. I do notpropose to enter into an argument on thesubject, more than to state that I came tothe conclusion in the case of this boat, thatI 'wished to obtain a certain amount of downthrust on the front plane, and I wished tokeep the frictional losses on transmission aslow as possible in view of the small enginecapacity.

In view of the above, it was decided toeliminate a universal joint at the propellerend. The advisability of fitting a universaljoint or not is bound up in the planing anglesof the hull. Very fine planing angles andgreat speed probably do require a universaljoint to reduce the thrust -line angle.

Details of the skegThe skeg has a triangular plate made of

sheet steel -31.1 in. thick. This is bolted tothe stern bulkhead. To this plate a sheet -steel skeg is brazed which is composed of

-in. thick material. At the bottom end

COCKPITIFORMERSyoe 3 PLY

SCALE/"

/NC NES

zek"

BEVELLED Y2" AT STERNTAPERING TO STEP

9%i"

BATTERY COCHP/T

/0// /2 /3

fi- 'STEP

Fig. 5.-A side and plan view of the hydroplane.

SOL/0 BALSANOSE

BOTTOMSTRINGER

BIRCH

STEP

787-Hicir 3 -PLYBACKBONE UPON WHICH

WHOLE HULL /S ASSEMBLED

Fig. 4.-The general ccnstructionof the hull.

of the skeg a phosphor -bronze bearing, withits forward end streamlined, is brazed. Astainless steel propeller shaft ofdiameter passes through this bearing, andat the rear end of the bearing a small ball -thrust race is located to take the forwardthrust of the propeller. This ball race is anold magneto race. The propeller hub, whichis made of phosphor bronze, is next threadedon to the shaft and kept in position by agrub screw, which is located on the shaft byan indentation in the latter. On the extremeend of the shaft a duralumin streamlinedextension is screwed on to a right-handthread as the propeller revolves anti-clockwise, looking from the stern of thehull.

The propeller has two blades of highaspect ratio, and is 3 in. in diameter with a9 -in. pitch. The two blades are constructedof sheet steel twisted to give the correctpitch, and with very sharp leading and trail-ing edges. These two blades are brazed intosaw -cuts in the phosphor -bronze hub.

There is a small knuckle -joint to take thedrive from an extension of the engine mainshaft. A steadying bearing of duraluminis located in the last former of the cockpitnear its base, whilst the stern tube is merelyconstructed by making a hole in the floor ofthe hull where the propeller shaft goesthrough from the engine to the skeg bearing.The shaft is then placed in position, andinside the hull, around the shaft and hole,'Mastic wood is pressed. The shaft is thenrotated a few times to ensure that it is freeand the plastic wood allowed to dry. Theresult is an excellent stern tube with verylittle labour. Although suitable for a high-speed hull, this would not do for a displace-ment hull where a constant pressure ofwater is doing its best to find an entranceinto the hull via the stern tube.

The Engine Bearers and MountingThe two engine bearers are made from

ash 1 in. wide. (See Fig. 3.)The bearers form an important part of the

hull's backbone. Upon the top of thebearers there are two pieces of L-shaped" angle iron " of aluminium. The ends ofthese aluminium bearers are placed acrossthe longitudinal ash bearers and kept inposition by coarse -pitch wood screws. Theupright sides of the L-shaped aluminium


bearers are drilled to receive the twobottom longitudinal crankcase bolts of theengine. Reference to Fig. 3 should makeclear this method of attachment.

The Construction of the HullAs it was anticipated that it might not be

all smooth sailing with an experimentalhull, the construction was on the robustside. A central backbone of Fin. three-ply,and the two ash engine bearers alreadymentioned, formed the foundation.

Reference to both Figs. 4 and 5 should bemade during this description, and if thereader is considering building a replica, heshould first of all produce a full-sizeddrawing from Fig. 5, whilst Fig. 4 will give ageneral idea of the construction.

It will be observed that a number ofclosely spaced transverse formers of care-fully fretted out 1 -mm. thick plywood areattached to the main frame mentionedabove. These formers are stuck intotheir correctly spaced positions with cellu-lose glue. This glue can be obtained at any'ironmonger's and is waterproof.

Whilst the glue is setting hard, theformers are kept upright by placing woodenblocks on either side of each former. Whenall formers are set hard in position, a shapednosepiece is carved from solid balsa woodand stuck in position. The stern former,of course, is not fretted out forlightness, and where the opencockpit is situated, the formersare of 116- -in. three-ply, as theyare not supported by the toparches as in the case of all theother formers. Along the bot-tom outside corners of the form-ers, nicks are cut and fin. x -in.square lengths of birch are firststeamed to the necessary bendsand then stuck to the formers.In this way the foundation of the" hard chine " is formed. Whilstthe glue is drying, where eachformer contacts with the lengthsof birch, a piece of cotton is tiedto keep the two in position.These are removed later. It should bementioned here that all the woodworkdescribed is model aircraft material andcan be obtained from any good modelaircraft stores.

The ignition coil is tied down to the floor,aft of the step and immediately in front ofthe stern former by wire straps, and stuckdown with glue. All necessary ignitionwiring is carried out at this time as well, andled along the floor to the main cockpit.

Birch Stringers for the Hull

Next, the entire hull has lc -in x -in.square lengths of birch stuck on to theformers in the form of " stringing " as inaircraft practice. The birch stringers areplaced approximately 1 in. apart and, whilstthe glue is drying, are kept in position bysome lengths of model aeroplane elasticwrapped around the hull. When the wholeis dry this elastic is removed, and some fiatstrip balsa wood, 4,- in. thick and 11 in.wide, is stuck along the sides of the hull atthe bottom edges to form a firm chine.

One tip with regard to the perhaps, un-familiar method of " stringing." Eachlength of x -in. birch should be placedon the outside edges of the formers. It is amistake to cut nicks in the formers to takethe stringers. The formers will then showup when the hull is covered with silk and sospoil the clean unbroken longitudinal line.Where the stringers touch the formers, asmall blob of glue is placed.

After stringing, the bottom floor of thehull is stuck into place with plenty of glue.The floor forward of the step is composed of1 -mm. thick three-ply, and is difficult tostick down owing to its slight vee formation.But by wrapping the entire hull withelastic, and inserting suitable -sized wedgesbetween the elastic and the plywood bottomwhere the concave vee is, the three-ply willbe forced to the bottoms of the formers inits correct vee shape. In order to take theline from the pole in circular course racing,18 S.W.G. spring steel wire is formed into aseries of eyes, and this adjustable attach-ment has its ends of wire bound and gluedto formers Nos. 5 and 8. (See Fig. 5.)

A second cockpit is left for the 4 -volt rect-angular dry battery between Nos. 11 and12 formers ; Fin. thick balsa slats are usedto construct the sides for this cockpit, sothat the battery fits snugly. The top is leftopen and the battery is covered with oiledsilk wrapped round it to prevent damage bywater. An oiled silk tobacco pouch isexcellent for the purpose.

Now the whole hull is carefully sand-papered around the chine area to clean upthe balsa slats, and any uneven spots arefilled with plastic wood and afterwardssandpapered off. A knock -off ignitionswitch is also fitted just aft of the batterycockpit. This switch has a bamboo arm

STR/P5 OF SORBO RUBBERTO PREVENT DAMAGE TOHULL BOTTOM

END OF j/2 OUTCKWOOD C TTO TAKE PROPELLER

3 PLY WOOD 5/0E5 TOFORM A BOX FOR TOOLS

Fig. 6.-A suitable combined starting bedand tool box.

END OF Y2frTli/CK WOOD CUTIN V SHAPE ATTOP TO TAKEMRWARD FARTOF BOAT

extending upwards 6 in., so that the boatcan be stopped by hand whilst travellingaround the circular course. The whole hullis then varnished with a coat of clear cellu-lose. This gives a waterproof finish inside.

Covering with Silk and FinishingThe final operation is the covering of the

whole hull with damp silk, doping, andpainting.

A large pot of photo paste is obtained andsome paste liberally smeared over the out-side of the bottom floor to the step. Asuitable piece of thin model aero jap silk isthen stuck down on to the floor. This isthen sprayed with water from a scent spray.It is then worked and carefully stretchedwith the fingers until no wrinkles can befound anywhere. The sides are thentrimmed off by scissors and stuck over theedges.

When dry this silk covering will contractabsolutely taut. Now proceed in a similarmanner with the rear floor aft of the step.After the silk is dry cover the whole turtle -shaped top with one large piece of silk,having smeared photo paste along the edgesof the chine, nosepiece, and stern. Spraywith water and stretch the silk as before,trim off, and finish. When dry and con-tracted, if the silk has been well put on itwill be without a wrinkle. The advantageof using photo paste is that if any part isnot satisfactory, it can be wetted again andunstuck and the offending wrinkles workedout.

When dry, the whole is doped with full-strength aeroplane clear dope. This can beobtained from any aerodrome or from themakers direct.

" Jildi Junior " was doped with cellondope. It is essential to use full-strengthdope and not model dope. This gives thenecessary stiffness to the hull to preventdistortion by engine torque and vibration.

The hull when dry will now be very strongand light, and can be given two coats ofwhatever coloured paint the constructorfancies. " Jildi Junior " is painted whitewith the name in red lettering. The wholeboat weighed, with engine, coil, battery andpetrol, etc., on its record breaking run,6 lb. 4 oz.

The Petrol TankThe tank is a small cylindrical affair of

brass, 21 in. long and 11 in. diameter. It iskept in position to the rear cockpit formerby an aluminium strap. It is airtight anda rubber tube is led to a football bladderhoused in the bows. Having filled up withpetrol the filler cap is screwed on and theoperator blows up the bladder to a poundor two's pressure by mouth, squeezing thebladder's extension rubber tube betweenhis forefinger and thumb. He then placesthis tube on to the air inlet tube of the tank.The carburetter will now be pressure fed,and the system is far lighter and more simplethan the usually more complicated methodof valve and bicycle pump, etc.Operational Tips

A piece of blind cord is used to start up,the operator passing one end under thegroove behind the flywheel. (See Fig. 3.)

By grasping both ends, whilst a friendgingerly holds the hull down on the starting -up bed, the operator can rapidly turn theengine over compression through pulling onone end of the cord and releasing the otheras it nears the flywheel. A few pulls overcompression with the carburetter inletpartially choked and then a final pull withignition switched on, should start the engine.A few seconds throttled down to warm upand the boat is attached to the line, thethrottle fully opened, and, at the samemoment as the engine screams into activitywith its 8,000 r.p.m., the hull is placed on tothe water and given a slight push to take upthe line evenly, and away goes the craft.The tank holds sufficient fuel for five to sixlaps on full throttle. A suitable startingbed and combined tool box is shown inFig. 6.

A -

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(Left) El Escorial,

ILL1fl -.7

ft II tilln!!tlit!!ntil.tti,

Spain, the world's greatest architectural white elephant. This view of part of one facade of the Escorial, gives a fair impression of itsharsh, ugly prison -like style, and (right) the leaning tower of Pisa.

Some Crazy BuildinssVERY many living creatures are ac-

complished builders, but man alonecan originate. The comb of the bee,

the web of the spider, the city of the ants,the dam of the beaver, and the nests ofbirds, beasts, and fishes are all built to apattern, and never alter. Two newlymated young birds are said to build a nestas exquisitely beautiful and perfect as that

The two leaning towers of Bologna, Italy.

of their parents, who may have enjoyedseveral seasons of house -building, butthough these humbler creatures need serveno apprenticeship to learn their craft, yetthey can never excel the work of theirfellows.

Man, however, is a creature of brain, andnot of instinct, so he must devote long yearsof toil to acquire skill and knowledge, buthaving done so there seems no limit to hispossibilities, as we showed in our article on

" The Evolution of the Home." His creativepowers, which enable him to originate, havesometimes produced freak or fantastic re-sults. Crazy buildings are of many kindsand types. Some are so futile and uselessthat they are dubbed " Follies " by com-mon consent. Meanwhile, we will considersome other crazy buildings, and among suchthe " leaning towers " certainly deservemention. There are many such throughoutthe world, but the leaning tower of Pisa isby far the most beautiful and striking. Itwas built in 1174, is 179 ft. high, and leans14 ft. Two questions are usually askedabout this-and all other-leaning towers.Why does it lean, and why does it NOT fall ?

9. c,eong,E Crazy Buildings are of ManymKinds and Types. Some hadm their Origin in a Crazy Brain, 1Ki or were Caused by a Subsin dente of the Foundations,

whilst others have been De. gliterately Designed by Archi.

m tests to Prove a TechnicalK1 KR

ER Point ER

KimmEmmsEnrovmmiomwammmmum

Why it does not FallThe reason it does not fall is that-ac-

cording to a well-known principle ofdynamics-a vertical line drawn from thecentre of gravity of the tower falls withinthe base. No building falls so long as thisprinciple is adhered to, but directly it movesfar enough for this vertical to fall outsidethe base, the tower comes down. Somehave supposed that certain leaning towershave been deliberately designed by archi-tects who desired novelty, and understoodthe principles necessary to ensure safety ;but I think in most cases the " lean " wascaused by a subsidence of the foundations.There are two more remarkable leaningtowers in Italy, both in the ancient city of

Bologna. The Torre Asinelli (built 1109) isno less than 318 ft. high, or nearly as loftyas the Dome of St. Paul's, London. It is4 ft. out of the perpendicular, and so leansvery much less than the Torre Garisenda,which is less than half its height, and over:hangs 7 ft. England has a number of lean-ing towers, and one of these is said to leanat exactly the same angle as the tower of Pisa.This is the handsome square tower ofTemple Church, Bristol, which leans 5 ft.,and makes a very striking effect. The Spireof Salisbury Cathedral also leans 4 ft., butit is so lofty (404 ft.) that the overhang isnot very noticeable. It was caused by alater architect adding the spire, which hadnot been planned originally, and thereforethe foundations were not strong enough forit. Architects sometimes had their ownprivate joke, and there is an interestingexample of this in Sir Christopher Wren's

The leaning tower of Bristol, Temple Church.


town hall at Windsor. The lower partforms a kind of market hall, and Wrenplanned it without supporting pillars. TheMayor, however, objected that it would beunsafe without a double row of pillars, sothe architect added them. He made themall 2 in. short, so that they did not, and stilldo not, support the floor above, which, how-ever, still stands after three centuries !

The Crooked HouseIn mining and salt -producing districts

leaning buildings are very common. TheCheshire salt district is full of toppling andlop -sided houses, especially in Middlewichand Northwich. But the gem of all Britainis the " Crooked House " at Himley inStaffordshire, which I acclaim as England'scraziest building. A century ago it wasa village public -house, known as the" Glyime Arms," and remarkable for noth-ing save the solid work of the builders,which was demonstrated some ten yearsafter it was finished when the ground sank

under one end, and tilted the whole struc-ture like a doll's house with a brick underone end. The amazing thing was that thehouse was quite undamaged. Not a ceilingcracked, not a wall bulged, not a floor gaveway. It was as sound as a bell ; but quiteuninhabitable, all the same, until somethingwas done about it. All the floors had to beraised at one end to permit furniture tostand in its place, and the shelves had to beslanted so that they were actually hori-zontal, although they naturally appear tobe leaning.

Even to -day the structure is astonishing,but it is less " crooked " now than formerly,because about twenty years ago there wasanother movement of the earth, and it re-covered about two feet of its lean. If weexamine the house from outside it looksexactly like a sinking ship which is goingdown by the head. The inside effects arestill more striking. All doors and windowsslope steeply, and only the hanging lampsare really vertical; benches, shelves, andtables have to be made horizontal, or noth-

ing would stand on them, but inside thecrooked house they appear to slope steeply.The most remarkable of these items is thelong table in the back room, which has notbeen " corrected " sufficiently. It seems todope up, but actually runs down, so that ifa billiard ball is rolled down the slope itstops half -way, then turns back and rollsoff at the upper end ! The grandfatherclocks also have to be set at a curious angleto the walls, because if they were parallelto the " uprights " of the building theywould be so much out of the vertical thatthe pendulum could not swing. When thehouse first tilted, every clock stopped !

This remarkable " crazy building " hasbecome quite celebrated in the Midlands,and thousands visit it every year.

Jezreel's TowerSome crazy buildings had their origin in

a crazy brain. The most remarkable ofsuch structures in all Britain is probablyJezreel's Tower, which stands at the top of

(Below) The Crooked House,Himley, and (left) a room insidethe Crooked House, showing themysterious table. A billiards ballplaced on the sloping surface ofthe table appears to run up -hill,

and falls off at the top end.

Chatham Hill in Kent. It is a gigantic,ugly, square, unfinished building, looking asif it were intended for an hotel, but itsorigin was much more romantic. Jezreel;was a religious fanatic, who obtained a greatfollowing among the more ignorant localpeople. He claimed that the " coming ofthe Lord was at hand," but that all thosewho put their faith in the prophet Jezreelwould rise to Heaven with him on the Dayof Judgment, and meanwhile he (Jezreel)was immortal. The sect raised a consider-able sum of money to build a temple on thehill -top which would serve as a place ofworship until Der Tag, and then they wereto assemble on its flat roof, and thenceascend to Heaven. Unfortunately Jezreeldied before the building was finished; and thissomewhat blighted the prospects of hismovement, although, when I visited theplace shortly before the outbreak of war,there were still a number of " Jezreelites "in the locality. I do not know if the towerstill stands, it would certainly take somepulling down.

There is a crazy building in Hampshire,which also had a religious origin, though ofa much less sensational kind. It is knownas the Farringdon Folly, and during thethirty years it was building it attractedmuch attention. The rector of the village,Mr. Massey, was a wealthy but eccentricindividual, who conceived the idea of erect-ing a freak structure. Nobody knew whatit was, or what it would become. He actedas his own architect, and kept two menworking on it daily for thirty years ; veryexpensive materials were used, many of themoulded bricks are said to have cost 208.each, and the total expenditure was over£20,000. I visited it when under con-struction, and it was like a builder's night-mare. There were passages which lednowhere, and inner rooms complete in everyway but having neither door nor window.The exterior was bizarre in the extreme,having two lofty but unsymmetrical towersplaced near the middle for no apparentpurpose, and a paucity of outside windowsand doors. The rector never divulged itsreal purpose, and the secret died with him.Since then it has been taken in hand by amore practical mind, and has been com-pleted. It is now a village hall, and school,but I am informed that the interior stillcontains queer passages leading to nowhere,and rooms which cannot be used. Oldinhabitants still style it " The Folly."

World's Record White ElephantI fancy the world's record white elephant

must be the famous Escorial near Madridin Spain, whiclbhad its origin in the feveredbrain of the fanatical King Philip, whosebeard our gallant sea -rovers so well andtruly singed. A great critic has called it." the grandest and gloomiest failure ofmodern times," and in the records of build-ings it is the most monumental waste inhistory. It was intended to be a RoyalPalace, and also to house a community ofmonks, but the site selected was a bareand barren hillside, as bleak as Dartmoor,so the people for whom it was intendedsimply would not stay there. The RoyalFamily refused to live in their palace, andonly a handful of monks used the mon-astery. The ground -plan was Philip's ownidea, and characteristically futile. It wasa grid -iron, having the Palace as theHandle, and the Monastery as the Grid, inmemory of the martyrdom of St. Lawrence.And over this vast surface is spread a maze

(continued on page 266)


adeo- eCha111..C.4-

In This Sixth Article of the Series we Deal with theDiscovery of Atmospheric Pressure

WE live at the bottom of an ocean ofair which is some two hundred milesdeep. Air is a material substance.

Consequently it possesses weight, and it isobvious that it must exert a pressure uponour bodies. As a matter of fact, the airsurrounding us presses upon every squareinch of our bodies with a weight equal toapproximately fifteen pounds. A full-grown man, therefore, supports a totalweight of air equivalent to several tons onthe surface of his body.

Such facts are plain and straightforwardones, and they are well known to everybodypossessing the least knowledge of scienceand mechanics. Time was, however, whenthe fact that air possesses weight was notrealised. The reason for this is to be foundin the fact that the air presses equally on allportions of our bodies. If, for instance, westretch out a hand, the upward pressure ofthe air on the under surface of our hand is15 lb. per square inch. and the downwardpressure of the air on the upper surface ofour hand is exactly the same, as is, also, theair pressure at the sides of our hand. Con-sequently, it was not until men found somemethod of removing the greater part of theair from a certain area that the resultinginequality of air pressure began to showitself and the pressure of the air becamedemonstrable beyond the slightest doubt.

Creating the VacuumThe story of the discovery of atmospheric

pressure and of the means of creating thevacuum, that marvellous condition ofemptiness which has made wireless and tele-vision possible in their present form, andwhich bids fair to enable us to wield stillgreater powers, goes back to the time ofGalileo, the famous Italian mechanician,astronomer and physicist. " Nature ab-hors a vacuum," the early natural philoso-phers had cried, and later generations ofscientific men had implicitly believed inthis dictum. Even the great Galileo foundno reason to question the assertion.

In 1641, the Grand Duke of Tuscanycaused a new well to be sunk for the purposeof raising water to supply the fountains inhis grounds. The new well was a deep one,and although the Grand Duke had had thebest pumps installed, he found that theywould not work. Galileo was brought toinspect the pumps, but he was unable to saywhy they would not work. Indeed, hesent to the Grand Duke the remarkablestatement that although Nature abhorred avacuum and would, therefore, allow waterto be pumped by suction, yet she did notabhor a vacuum greater than that equivalentto 32 ft. of water ! Galileo had found thatwater could be made to rise 32 ft. in a pipeby means of pumping or sucking, but thatunder no circumstances would it rise fartherby these means.

Evangelista TorricelliAbout this period, a student of Galileo's,

Evangelista Torricelli by name, began to be

struck by the fact that there was no satis-factory explanation of the fact that waterwould not rise by suction to a heightgreater than 32 ft. So much thought didthe young Torricelli give to this undoubtedfact that in 1643, hardly a year afterGalileo's death, he announced to the worldthe fact that water rises by suction in apipe not in consequence of the hypotheticalabhorrence by Nature of a vacuum, butsimply in virtue of atmospheric pressure.Torricelli had found by experiment that

3d'

vowWAROFD

Torricelli's experi-ment. He showedthat the height ofthe mercury columnvaried slightly fromday to day, thusproving thatatmospheric pressureunderwent daily

alterations.

MERCURYCOLUMNIN GLASS

TUBE.

ZESswiMOS%

BASIN CONTAININGMERCURY.

water would rise by suction to a height of32 ft. in a tube, and that under no circum-stances would it rise higher. Torricelli hadpreviously conceived the idea that thecolumn of water in the tube was sustainedby the pressure of the atmosphere on thewater outside the tube. If such is the case,he argued, then the pressure of air againsta liquid heavier than water should only beable to sustain a shorter column of thatliquid.

In his experiments, Torricelli employedmercury or quicksilver, a liquid which isthirteen times heavier than water. Hefound that a column of this liquid wouldrise to a height of 30 in. or there-abouts and no more. He showed that theheight of his mercury column variedslightly from day to day, thus proving thatthe atmospheric pressure underwent dailyalterations.

The BarometerThus came into being one of the world's

fundamental measuring instruments, thebarometer, or weight -measurer. Torricelliat one stroke exploded the ridiculous ideaconcerning Nature's abhorrence of a vacuum,and gave to scientific men and, indeed, tocivilisation in general, an instrument whichhas been of inestimable value ever since.Torricelli's discovery was Blade in 1643, adate which we have already noted. Fouryears later, in 1647, Torricelli died. TheTorricellian experiments, however, weretaken up by other men. Of these latterexperimenters, one in particular, BlaisePascal, a Frenchman, deserves our at-tention, for he conclusively proved thecorrectness of Torricelli's assertions.Pascal's Letter

The following is a letter written by M.Pascal to his brother-in-law ;

" I have thought of an experimentwhich, if it can be executed with accuracy,will alone be sufficient to elucidate this sub-ject. It is to repeat the Torricellian experi-ment several times in the same day, withthe same tube and the same mercury ;sometimes at the foot, sometimes at thesummit of a mountain 500 or 600 fathomsin height. By this means we shall ascertainwhether the mercury in the tube will be atthe same or at a different height at each ofthese stations. You perceive, withoutdoubt, that this experiment is decisive ;for, if the column of mercury be lower atthe top of the hill than at the base, as Ithink it will be, it clearly shows that thepressure of the air is the sole cause of thesuspension of the mercury in the tube, andnot the horror of a vacuum ; as it is evidentthere is a longer column of air at thebottom of a hill than at the top ; but itwould be absurd to suppose that Natureabhors a vacuum more at the base than atthe summit of a hill. For, if the suspensionof the mercury in the tube is owing to thepressure of the air, it is plain it must beequal to a column of air whose diameter is


the same as that of the mercurial columnand whose height is equal to that of theatmosphere from the surface of the mercuryin the basin. Now, the base remaining thesame, it is evident that the pressure will bein proportion to the height of the columnand that the higher the column of air, thelonger will be the column of mercury thatwill be sustained."

Pascal applied the above test on Septem-ber 19th, 1648, on a mountain in centralFrance named ' Puy de Dome." As heclimbed to the summit of the mountaincarrying the barometer with him, he foundthat the height of the mercury columnprogressively decreased, until at the summitof the mountain the mercury column wasthree inches less in height than it was at thebase of the mountain. The experiment wasrepeated subsequently again and again, butever with the same result. Thus wereTorricelli's assertions concerning the natureof atmospheric pressure finally confirmed.

The Invention of the Air PumpTorricelli's investigations in the subject of

atmospheric pressure were followed bymany important physical and mechanicalresults. Probably the most important ofthese was the invention of the air pumpwhich was made in 1650 by Otto vonGuericke, the now celebrated and somewhatromantic burgomaster of Magdeburg, inPrussia. Otto von Guricke was the firstone in history to show by direct experimentthat air possesses weight and, also, todemonstrate the exceedingly great pres-sures which can be set up by such aninvisible medium.

Von Guricke, early in his career, realisedthe fact that air can, in many respects, betreated like water. He devised means ofpacking it into vessels and, also, of emptyingvessels of it. Guricke's first notion was tofill a strong wooden barrel with water and

then completely to close the barrel, leavingmerely a delivery tube through which thecontents of the barrel could be drawn outby means of a suction pump. By thismeans, von Guricke thought that he wouldleave a completely empty space in thebarrel. When, however, he found that airpassed through the pores of the woodworkand between the joints he enclosed thebarrel in a larger one and filled the spacebetween the two barrels with water. Airstill entered the barrel after the containedwater had been drawn out, and it becameevident that a mere barrel would neversuffice for the purpose of creating a vacuumwithin.

An Interesting ExperimentVon Guricke next made a large hollow

metallic globe. This had a delivery tubeconnected to a pump. The globe was notfilled with water. The air was merelypumped out of it by means of the handpump. At first, the pump was easy tooperate. Quickly, however, the resistanceof the pump rose with each stroke, until atlast it was as much as the strength of twomen could do to operate the pump. Sud-denly, when this stage of exhaustion of themetal globe had been reached, the devicesuddenly collapsed with a loud noise. Ithad crumpled up just as if it had beensqueezed in the hand of a giant, therebydemonstrating the power of atmosphericpressure.

The ingenious burgomaster next made astronger hollow globe. This time, however,the globe was made in two separate portionsor hemispheres which, under normal con-ditions, could readily be drawn apart.When, however, the globe was exhausted oreven partially exhausted of air, it wasfound utterly impossible to separate the twohalves. In one of Guericke's famous experi-ments, a platform was slung from the lowerhalf of the exhausted globe, and on the

platform were placed heavy weights.Despite this, however, the bottom hemi-sphere of the globe refused to be drawnaway from the upper one, the two halvesbeing kept together by the external pressureof the atmosphere.

" Experiment of the Magdeburg Hemi-spheres "Guricke's most famous experiment was

one which he caused to be performed beforethe Emperor, Ferdinand the Third, atRatisbon, in 1654. The experiment, whichdemonstrated in a spectacular manner theeffects of atmospheric pressure, later cameto be known as the " Experiment of theMagdeburg Hemispheres." Two separatemetallic hemispheres when joined togetherformed a metal globe. This was exhaustedof air by means of von Guricke's air -pumpand an endeavour was made to pull the twohalves of the globe apart by means of ateam of powerful horses harnessed to theopposite halves of the globe. The attemptfailed and thus demonstrated to all presentthe enormous force with which the pressureof the atmosphere kept the two hemispheresof the metal globe together when the airhad been removed from within.

In the hands of English mechanicians,such as Robert Boyle and Robert Hooke,the air -pump became an instrument ofscientific precision. Its use made possiblemany experiments which, previously, hadbeen impossible. The creation of a vacuumor, to be more precise, of a partial vacuumwithin an enclosed vessel has, perhaps, givenmore practical benefits to the world thanany other single principle. To Otto vonGuricke, therefore, the worthy burgomasterof Magdeburg, must go the credit of notmerely devising a single mechanical in-strument but of formulating a principlewhich has been of inestimable servicethrough the history of mechanical, electrical,and other scientific invention.

AN exhibition portraying theorganisation and operation of theair service over Empire air routes

was opened by the Secretary of Statefor Air on Thursday, December 5th,at the Science Museum, South Kensing-ton, S.W.7, and will be on view tothe public until January 31st.

The exhibition, which is organised andstaged by Imperial Airways, Ltd., ispopular in character, both in scope and

THE EMPIRE'S AIRWAYEXHIBITION

treatment, and illustrates the developmentof air communications within the Empireby means of models, charts, maps, and

photographs. It includes models ofevery type of air -liner which has beenowned by the Company since itsinception, and sectional models ofthe new air -liners which are now underconstruction.

A part of the exhibition is devoted tothe design of air ports and includes a

large model of a modern combined land andair port, and dioramas of three famous Em-pire airports. There is also working models

showing the part which wireless playsin the control of aircraft when flyingin fog or above cloud ; the visitor,by pressing a button, is able to hearthe voice of the captain calling forhis position and the replies fromwireless stations on the ground.

Interesting ModelsThere are sections devoted to the

building of a flying -boat and a landmachine, and to aero engines. Oper-able models of a wind tunnel and atank enable the visitor to gain someidea of the part which these instru-ments play in the design of air -liners.

The exhibition should prove ofconsiderable educational interest atthe present time, and serves to showthe remarkable developments whichhave taken place in air transportduring recent years ; by way ofcomparison, the earlier historicaldevelopment in aviation canbe seen in the usual gallery ofthe National Aeronautical Collec-tions in the Museum.

One of the models on view at the exhibition. It shows a new Short " pickaback" dualflying -boat for the Atlantic route, now under construction at Short Bros., Rochester.We hope to publish an article on this unusual form of aircraft in the nest issue.


Pelmanism Brings Out YourPossibilitiesLET PELMANISM MAKE

1936 YOUR YEARWHEN 1936 ends, you would

like to look back on it asthe best year you have

ever passed.You would like to feel that some-

thing stupendous had happened to youin 1936, that made your Success inLife sure.

You would like to enjoy life ; toreally enjoy it this means not onlypleasures that come with extra money,but zest of living that comes withawakened mind, with quickened men-tal powers.

You would like your affairs to pros-per, and your income to increase.

You would like to cease worrying,and to become confident in yourselfand in your future.

All these good things, and manymore, are possible for you.

If you really wish to realise them,Pelmanise !

Change Your DisappointmentsInto Victories !

Pelmanism shows you how to so useyour natural, and too often unsus-pected, talents that you yourself canchange your disappointments intovictories, and attain the prosperityand the enjoyment of life that are thesure results of the Pelmanised mind.

You have within yourself a greatstore of abilities, of which youprobably use only an infinitesimalpart.

Pelmanism will reveal to you thesehidden abilities, and possibilities, andwill show you how to use them for youreverlasting benefit.

The Success of Pelmanismand of Pelmanists

Pelmanism is a twentieth centurymind -training system based on soundprinciples of modern psychology.

Pelmanism has stood the test of nearlyhalf a century of Success.

Pelmanists now number more thanhalf a million-men and women inevery walk of life.

Pelmanists themselves tell of theirSuccess in life. Every day quantities ofletters flow into the Pelman Institutetelling of the benefits Pelmanists owe toPelmanism.

The Results of Right ThinkingSuccess results from an orderly mind,

an obedient mind. Great people,famous people are lifted above the rank

and file, by the power of their minds.They know how to think, and thinkingright, they act right. They don'tfumble, they don't bungle, they don'twaste time and effort. Their minds areso controlled that they function with theaccuracy and ease of a well-oiled mach-ine.

People whose minds are trained thePelman way have time and money forthe diversions and amusements thatboth rest and stimulate the active civil-ised man and woman of to -day. Pel-manists don't just grind.

Once your mind is Pelmanised, andyour life reorganised, you will be sur-prised and delighted to see how muchmore pleasure you get out of every singleday.

All Work and No PlayOnce you set your mind to functioning

the Pelman way, you will not only bemore prosperous, but you will have moretime. Your life will never be all workand no play after you have become aPelmanist.

There are a number of indications thata mind does not function well. Forexample : lack of concentration-mindwandering, a faulty memory, timidity,self-consciousness, pessimism, quicktemper, a feeling of frustration.

Pelmanism soon eradicates thesefaults, and substitutes in their places thequalities that win: ability to concen-trate, reliable memory, courage, self-confidence, cheerfulness, even temper,punctuality.

A Real Acquaintance withYourself

No matter what school you may haveattended, no matter what the extent ofyour knowledge, you can still acquiresomething of inestimable value throughPelmanism, because Pelmanism is thesurest means towards the establishmentof a real acquaintance with yourself.Pelmanism points the road that leads toyour success.

The Course is given by correspondenceonly. Each Pelmanist selects his or herown time for the study of Pelmanism,consequently each Pelmanist is free totake as much or as little time as he or shedesires for the completion of the Course.The Instructors at the Pelman Institutestand, in their relation to Pelmanists,as friends, and Pelmanists are invited towrite freely to the Instructors con-cerning any problem that may arise.If you sincerely desire that 1936 be foryou a great improvement over 1935, donot put off your decision to become aPelmanist. Fill in the coupon at thebottom of this page, and mail it to -day.Take the first step now.

That Pelmanism sharpens the percep-tions, cultivates the mind and developsthose qualities that make for Success,there can be no doubt. Read what aBank Cashier just wrote us :

" Pelmanism has had the greatestinfluence in my life. I have now anobject in life, and know I am on theright way to realise it. Depression,moodiness, indecision are all removed-the result-Happiness-and what canthat lead to ? My whole outlook ischanged, not just for the better, but forthe best."

If Pelmanism can do so much for otherpeople, what can it do for you ? Wehave published recently a book called" The Science of Success " that tells justwhat Pelmanism is, just what Pelman-ism does, and gives the experiences ofPelmanists, related by themselves. Fillin the coupon at the bottom of this page,mail it to -day, and by return of post youwill receive a copy of " The Science ofSuccess," free of charge, post paid.Read this book carefully. You will seewhat men and women in every walk oflife say of Pelmanism. You will see

that no matter howdiscouraged, howtired one may be,Pelmanism re-stores confidencein life, developsself-reliance, andsets one's footstepsdefinitely on thepath towardsSuccess. Or, if youfind it convenientto do so, call at

the Pelman Institute, Pelman House,Bloomsbury Street, London, W.C.1, andhave a talk with the Director of Instruc-tion. The interview entails no obligation.

Send for a free copy of " The Science ofSuccess " and read more of what men andwomen say of the successes and benefitsthey have derived from a CorrespondenceCourse of Pelmanism.

I---------------I

, TO THE PELMAN INSTITUTE,i 130 Pelman House,

Bloomsbury Street, London, W.C.1.Please send me a free copy of " The

Science of Success," containing fullparticulars of the Pelman Course.

NAME

ADDRESS

OccupationAll correspondence is confidential

PELMAN (OVERSEAS) INSTITUTES :PARIS, 8o Boulevard Hausmann. NEW YORK,272 North Avenue, New Rochelle. MELBOURNE, 396Flinders Lane. JOHANNESBURG, P.O. Box 4928.DURHAM, Natal Bank Chambers (P.O. Box 1489).DELHI, So Alipore Road. CALCUTTA, 202 CloveStreet. AMSTERDAM, Datnrak 68.


Spinning Iron Pipes

riANY thousands of miles of cast-ironpipes are made annually for layinggas and water mains. The old

method of manufacture was by pouring themetal into a sand mould set in a verticalpit. Modern needs find this method tooslow, and a process has been devised forspinning the pipes from the molten metalby centrifugal force. A hollow water-cooled cylinder acts as the mould. It is setrotating at a high speed and advanced upto a pouring ladle containing cast iron at1400 degrees C. From the ladle a trough ex-tends to the back of the mould. The white-hotmetal flows down the trough, falls off on the

deuce,coal pits. The oreis smelted to pigiron, convertedinto steel, andfinally cast intobillets or rolled

into sheets all in the one works. Perfectcontinuity of process is preserved. Hand-ling is reduced to a minimum. Themost modern methods of by-productrecovery and fuel economy are practised.

A battery of 16 coke ovens makingmetallurgical coke for an installation of threeblast furnaces, is fired by the blast -furnacegas. Otherwise, this gas would largely goto waste. The coking of the coal suppliesby-product coal gas, sulphate of ammonia,road tar, and motor benzole. The coal gasis sufficient in quantity to supply the wholeof the fuel requirements of steel reheatingfurnaces and of a first-class modern boilerhouse. The steam from the latter supplies

Centrifugally casting Stanton-Delaoond spun iron pipes.

wall of the whirring mould, and is flung outradially in a dense even layer which almostinstantly sets. The mould is caused totravel slowly away from the pouring ladle,so that it is gradually lined with metalthroughout its whole length, until the com-plete pipe is cast. The rotation of themould is then stopped. It is opened andthe pipe is withdrawn to be sent to annealingfurnaces. Before going to stock, the pipesare subjected to a hydraulic test. Butfailures are few because the process gives adense casting unusually free from flaws.

New British Steel Works

CORBY, one of the most modern steelworks is said to be an outstandingexample of the perfect engineering

layout. It is a self-contained works-mining its own iron ore and owning its own

sufficient power to run the whole plant.From the blast furnaces the pig iron is run

direct to batch mixing pots where it is kepthot by gas firing. At intervals it is run toone or other of the Bessemer converters.In these converters, which resemble largecupolas pivoted on trunnions, a blast ofhigh-pressure air burns out the impuritiesfrom the pig iron and changes it into steel.The process is exceedingly rapid and needsa high degree of experienced control to getsuccessful results. The steel is cast intoingots and taken straight to soaking pits,where it is kept hot ready for working androlling.

The steel made at Corby is a mild steelwhich finds extensive use in the tin-plateindustry and in the making of solid -drawnmild -steel tubes. Before tariff restrictionswere placed on foreign steels, these needswere largely met from abroad. The new

plant marks a revival of the Bessemer pro-cess after its neglect for many years inEngland.

Freezing the EarthLARGE-SCALE refrigeration was the

unusual device employed by engineersfaced with the problem of sinking a

deep shaft through swampy ground. Amillion gallons of water per hour wererequired to feed the condensers of the newTir John Power Station at Swansea. Thechosen source of supply was a dock over amile away. An overhead pipe line ofadequate size was impracticable. A tunnelwas therefore decided on. But the inter-vening ground was too boggy to bear tun-nelling unless they went down to solid rock.At the power station end the rock was levelwith the surface, but at the dock end it was173 ft. down through mud, sand, and wetgravel strata. Where shafts are sunkthrough ground of this nature, it is usual toemploy caissons and compressed air to keepback water. Here the excavation was toodeep for this method, so they resorted tofreezing the ground solid for nearly 200 ft.down.

Holes were drilled round the site of theproposed shaft, and flow and return pipeswere inserted. A refrigerating plant wasbrought on to the site and coupled up tocirculate brine chilled to 40 degrees belowzero. Progress was slow and steady.After three and a half weeks freezing, trialbore holes showed that the site was sur-rounded by a wall of ice extending down tosolid rock. Excavation was started withthe refrigerating plant still at work. For90 ft. down excavation was easy, but lowerthey, found that they had overdone the job. .

The whole of the ground had become ice-bound, and was so solid that they had toblast their way through it.

Plywood Barrel MachineAN ingenious machine has been in-

vented in Germany for making barrelson the plywood principle. The

machine, fed with sheets of beechwood,veneer and glue, shapes, forms, and sticksthe body of the barrel in one operation.The ingenuity of the invention lies in thearrangement whereby three plies of woodare stuck together with a non -overlappingjoint. Ends for the tops and bottoms of thebarrels are separately made on anothermachine, and are then rammed home in thebody of the barrel. The barrels are sostrong that they can be dropped from aheight of 6 ft., when full of water, withoutbursting. Special glues are used whenliquids are to be handled. Light, strongbarrels of this kind will find ready com-mercial use, as they save considerably onfreightage charges when compared with thesteel drums in use at the present momentfor handling such materials as tar, asphalt,flours, powders, and solid chemicals. Asthey are cheap in manufacture they can be


nveni n E Pro'scrapped at the receiving end, and so savethe charges for returning empties.

Oil CentrifugesFEATURED at recent engineering

exhibitions have been centrifugalseparators designed for marine use.

Their purpose is the separation of oil frombilge water when the fuel tanks are beingpumped out. They are similar in construc-tion and principle to the common type ofdairy cream separator. The mixture of oiland water, whirred at high speed, separatesthe water which is thrown outward, and oilwhich remains as a central core. Suitablyarranged spouts guide each to its properoutflow. Shipowners find that the installa-tion pays for itself many times over in thevalue of oil recovered. It is probable thatan international regulation will requireseparators to be fitted to all oil -burningships.

Oil centrifuges find application too forpurifying diesel oils from traces of dirt andgrit. This operation is highly necessary asthe injection nozzles of diesel engines areextremely susceptible to blockage by solidmatter present in the oil.

A New Jointing MaterialANEW jointing material for aluminium

has recently been produced, thatshould mark a great advance upon the

construction of cycles, motor -cars, aero-planes, etc. The discovery consists of amedium called " Alunise " (formerly named" Alusol ") whereby it is now possible tojoin aluminium, hiduminium, duralumin,and other similar alloys, with a strengthequal to that of the original material.

Bicycles Built with a SpannerBICYCLES which can be taken topieces, new parts substituted, andrebuilt in a few minutes are now being

put on the market by New Hudson, Ltd.,Icknield Street, Birmingham. Instead ofconstructing the frame of tubing, channelsection steel not unlike miniature girders,is used. They are in five separate partsheld together by steel bolts and a simplewaterproof bracket.

A High -wing SeaplaneIT will soon be possible to travel by air to

Mandalay, in Upper Burma, by air. Anew type of high -wing seaplane is under-

going trials at Rochester. Driven by fourengines, each developing only 90 h.p., itis the smallest four-engined air -liner so farconstructed.

Rhodesia's New BridgeTHE third longest single -span bridge in

the world has just been completed inthe wilds of Southern Rhodesia. Its

single arch rises 280 ft. above the Sabiriver and is 1,080 ft. long. This span isexceeded only by those of the SydneyHarbour Bridge and the Bayonne Bridge,south of New York.

Noiseless Tube RailwayLONDON Transport engineers think

they have solved the problem of thenoiseless Tube Railway. Owing to the

fact that the temperature of the air in theUnderground never varies by more than10 degrees, it has been possible to lay anew type of " soft " steel rail welded in onecontinuous piece. Sleepers carrying thenew track are laid in a special concretebed which, besides absorbing vibration andnoise, allow for possible variations due toheat.

A Battleship Built in SectionsIT is stated that France's new 35,000 -ton

battleship, which is now under construc-tion, will be 794 ft. long and will draw

264 ft. of water. Work was commencedon 654 ft. of the battleship on Oct. 22ndlast in the Salon dock at Brest. Whenthe 654 ft. section has been floated theremainder will be joined to it. The reasonfor this is that the Salon docks are too smallfor the construction of the whole length ofthe vessel at once. The ship is expectedto be completed by the end of 1938.

An Automatic TypewriterTO watch the Auto -typist shown on this

page, deftly writing personalised lettersat the rate of 125 words a minute,

spacing and tabulating the lines' with fas-cinating sureness, is an experience that willintrigue even those who are familiar withprecision machinery. Yet the Auto -typistis so simple that any intelligent junioroffice worker can be taught, in less than anhour, to operate it. The pneumaticprincipal employed is identical with thatincorporated in over one million player -

LETTER SELECTOR

The Auto -typist shownherewith can be set tostop automatically forthe insertion manuallyof special references ordata. Then, at a touchon the button shown,the pneumatic mechan-ism starts again, to stoplater if necessary, a lineor a paragraph furtheron, or to complete theletter to the last full stop.

IreSSpianos. The machine operates on A.C. orD.C. from any electric -light socket, andcosts no more to run than an electric fan.At the normal speed of 125 words perminute, and including time necessary forthe insertion of stationery, typing of date,name, address, salutations, and an occas-ional record change, an Auto -typist willproduce from 100 to 250 letters a day,according to length.

SEVEN FEATURES OF THEAUTO -TYPIST

1. The Auto -typist is pneumaticallyoperated-fast, silent, trouble free.

2. Nearly every make and model oftypewriter can be used on the Auto -typist, including noiseless models.

3. Auto -typist records are rolled onspools, making them easy to file away,easy to handle, and easy to insert inthe machine.

4. Records can be changed on theAuto -typist in five seconds. It is notnecessary to " line them up." This isdone automatically and means animportant saving of time.

5. There is no large metal box underthe Auto -typist to catch the record.It is constantly kept neatly rolled ona spool, an important feature in pro-tecting it from tearing as well as agreat convenience.

6. Auto -typist records are not woundforward by gears, likely to stretchand tear the paper. For that reasonAuto -typist records will outlast thoseused on machines that operate electro-mechanically.

7. With a Selector Auto -typist youcan automatically skip or automatic-ally select any desired portion of therecord.


you must not use the decompressorof two-stroke engines to stop theengine until it is throttled back.

If you use it at open throttle, you may burnthe valve of the decompressor, which willcause a leakage of power.

To stop the throttled engine, always usethe decompressor to avoid back -fires as theairscrew stops.

The length and diameter of the exhaustpipe, i.e. its volume, is important to ensurethe emptying of the cylinders, their cooling,and full power. The pipe shown in Fig. 40is given as a guide, but your engine makerwill advise you on this point. You can flyjust as well without exhaust pipes, but itwill be found advisable to fit one.

The Fuel FilterThe use of a fuel filter is absolutely

indispensable in the carburetter deliveryline, and should be fixed to one of the armsof the motor support. However cleanyour spirit may be, you will always finda little dirt in the filter, and often water.You cannot prevent it, and you mighthave a stoppage at any time whilst inflight. There are plenty of good filters onthe market ; get a car model and not amotor -cycle filter, as the latter is too small.

The Petrol TankAs with the prototype, the tank is placed

in front of the spar. It holds 12 litres, i.e.two 5 -litre cans of fuel and a good measureof oil hours' flying). Sheet brass,although a little more expensive thantinned sheet, should be used for the tank asthis will last for a considerable time.

Cut a sheet of 4 mm. thick brass as shownin Fig 35 (shown last month) just wideenough to go between the central ribs of thewing and about 800 mm. long. At eachend hammer the edge for a width of 5 mm.over a piece of metal of .6 mm. to make ajoint. Join together and insert a singlerivet of copper at each end ; then hammerflat.

After marking off with chalk the positionof the bends, pass a plank, supported on thebacks of two chairs, through the hollowdrum thus formed, and bend it accordingto the template, and cut out in 3 mm.plywood.

This template, which follows the profileof the wing, except that it can project abit on the curve of the upper surface,should be able to be forced gently into thebent drum.

While pressing on the plank, cut out witha carpenter's compass a disc of suitablediameter for a brass screw stopper (as froman oil can or other container). You hadbetter try this job out first on a piece of

iiihiTc//A,HEI

This Month we Deal with its Engine Accessories, the

Instrument Board, and Give Instructions for Flying

brass. Next cut out the lower hole about50 mm. diameter.

Over this latter hole, rivet a 1 -mm. brassplate drilled with two holes, ready to taketwo valve stems from a motor cycle tyre ;see that the holes are drilled so that theirwashers are not up against the edges of thelarge opening. After riveting solder care-fully.

The Fuel GaugeNow rivet and solder the small piece of

rolled metal which will carry the aluminiumrod, and also the float of cork measuring40 mm. by 40 mm. A piece of .3 mm. steelwire unravelled from a spare piece of cableand straightened out, should be fixed to thealuminium rod vertically above the fronthole. Passing through the valve body (youwill have dispensed with the rest of thevalve) the rod enters a 8 mm. glass tube(such as that which is in soda watersyphon) closed at one end, and fixed at theother to the valve by a ring of treatedrubber. At the end of the steel wire is asmall black bead. This forms a gaugewhich will always tell you how much fuelyou have left.

Jam your template of plywood into thetank, and, letting the edge rest on a metalblock, flare out the edge with light taps ofthe hammer for a depth of 5 mm. Whenthis has been done on both edges, place thetank flat on one edge on a piece of brass.Push down your template to the bottom to

ensure that the shape is maintained, andmark off along the flared edge, one side ofthe tank. When you cut this out with theshears, leave a spare edge of 5 mm. allround beyond the flare of the tank edge.Turn up the edge of the flat plate by handwith flat -nose pliers and bend it over theedge of the tank. Then turn it over again,hammering all along the joint. Hold upthis work along the nose by a bar of metalshaped as shown in Fig. 35 (shown lastmonth) held firmly in a vice and pressedup from the inside. After the first side hasbeen done, put the float and its wire inplace (but not the valves) and fit the secondface. You will have to cut a 40 -mm. holein the first side through which to insertyour metal bar for hammering over thesecond side.

Soldering

All along the turn -up, spread a littlesoldering paste or killed spirits, and solderwith a hot iron. This is quite easy on anedge already jointed. Also solder thestopper seating and a disc of metal to closethe opening in the first side. Rinse withhot water, and test for leaks with a litre ofspirit. The finished tank should weigh1 kilo. 500 mm. If you are anxious to makelong flights, make another tank which willbalance the first on the other side of thespar. It can hold 22 litres, so that youcan have sufficient fuel for a 4 hours' flight.

-30 - -

Fig. 40.-Details of the exhaust pipe. The pipe shown is given as a guide to the constructor, and themaker of the particular engine employed should be consulted


The PipingThe valves from the tyre tubes of which

you will have cut off the head, will befurnished under their feet with a washerof fibre, passed with the aid of a pieceof wire through the filling opening andscrewed up tight by a nut. The valves andthe wire receive a glass tube, and the othersa petrol cock ; these are joined by a tubeof hardened rubber (insoluble in petrol),threaded on to each of them. A littlealcohol varnish (insoluble in petrol) makesthe fixing permanent. Remember thatbenzol may, in time, affect the rubber.If you are careful to bring the ends of alltubes flush together, you need not fear theobstruction of the pipes by the swellingof the rubber, and the arrangement will lastfor several months. The elasticity willprevent breakage. Soldered and screwedjoints should not be used.

The two cocks are joined by a collectortube in brazed red copper (you can get Tpieces ready-made in the shops). Ahardened rubber piece joins the collectortube to the filter, before the carburetter.The length and flexibility of the tubepermits the wing to pivot freely. Lookover this hardened rubber tube often, andline it with a coiled spring (the guide tubeof a Bowden assembly) to prevent itsswelling. Drill a 2 -mm. hole in eachfilter cap to let the air in as the fuel is used.The piping is so arranged that a singledrop of fuel leaving the tank, will arriveunder gravity, at the filter.

The Oil System

An oil can of 2 litres (tins as sold by oilvendors) can be fixed behind the spar nextto the tank (see Fig. 37). Change its filterto the side. The weight is 300 grammes.Place a dropper under the oil tap (two corksin a large glass tube) to control the flow ofoil (3 drops a second : five hours' supply).Use large pipes of 6 to 8 mm. interiordiameter and beware of freezing in winter.Do not try to regulate the flow by thetap otherwise you may starve the pump.The weight of the tanks does not affect inany way the movement of the wing :it would not matter if they weighed 100kilos. The control movements in flight are,in practice, of small amplitude and theinertia of the wing is of very small effect.

A shock absorber rubber of 12 mm.diameter and 250 mm. long, holds the wingin front and controls the incidence ; it ishardly extended when the rear edge of thewing is raised to the full extent. It is fixedto a metal fitting of 1 mm. material fixedto the leading edge by three wood screws.At the lower end it is fixed to the foot of thefront tube of the cabane.

The shock absorber prevents the wingfrom falling whilst the plane is at rest, butis not of any use in flight. Many people, onseeing the " Flea," will fix their attention onthe central pivot of the wing, thinking thatyour life hangs on a 6 mm. bolt which fixesthe unseen tubular axis. They forget thatthe wing is mainly supported by the bracingwires.

The Instrument BoardThe dashboard instruments are delicate

and fragile, but they are also heavy. It isdesirable, therefore, to group them on thesame support-the dashboard-and to givethe whole assembly a certain independencefrom the machine. In this way, thevibrations of the engine are much reducedwhen they arrive at the instruments, andare only just enough to cancel out theinertia of their indicators without making

he needles vibrate. The dashboard proper(Fig. 41) is a 6 mm. panel pierced with thenecessary openings. In the middle is therevolution counter, on the right is the watch,on the left is the air -speed indicator and thebarometer is placed next to it, as shown.

This panel is nailed to a piece of hardwood making an angle with the piecemarked A (Fig. 41) which is of 1.5 mm.. ply-wood cut in a semi -circle, and edged with acane (cane for clearing sinks) on which isnailed the rounded vertical piece in 1.5 mm.material thus making a sort of box. Anarc in thin 6 mm. aluminium or duraliumtube, or a 10 -mm. cane, reinforces a plate of

celluloid of very transparent quality. Thedashboard is secured to the boxwork bysmall screws, and to the arc by small collarsof aluminium, held by an eyelet or a rivet.The whole assembly is placed on threepads of soft rubber (sponge rubber) leavinga gap of 10 to 15 mm. from the top of thecockpit. Three springs of 1 mm. steel, onlylightly loaded, hold it more or less in posi-tion between the two rear legs of the cabane.The altimeter, the most sensitive instru-ment of the lot, will be simply an ordinarybarometer. You can fix on the glass, adisc of paper showing the heights corres-ponding to the pressures marked on the

Fig. 41.-Showing the instrument board and position of the various instruments.


scale. A table of barometer readings isgiven below.

BAROMETER READINGS

(Average-Corrected)29.92 in. = 760 mm. = 0 ft.28.86 in. = 733 mm. = 1,000 ft.27.82 in. = 706 mm. = 2,000 ft.26.81 in. = 681 mm. = 3,000 ft.25.84 in. = 656 mm. = 4,000 ft.24.89 in. = 632 mm. = 5,000 ft.

Using the TableBefore leaving the ground, set the barom-

eter so that zero is opposite the barometerneedle. Let us imagine that at this mo-ment the pressure indicated by the needleis 76 on the original pressure scale. Whenin flight, at a given moment, the needlewill have moved say to the mark 70, whichmeans that you are flying at 2,000 ft. Agood place for the barometer is to hang itby three springs from the arc above thedashboard. At your right hand on thepanel, fix a few leaves of paper under alittle aluminium strip with a rubber ring,through which you can pass a pencilfastened with a string. Before you takeoff you can write on it notes of use for yourflight, things to think about when in theair, etc. During the flight, while flyingwith the left hand, you can make notessuch as time of climb, etc.

The CompassThis is held in front of the pilot and ahead

of the revolution counter at 40 mm. from theinstrument board, by two arms made of4 mm. rod of duralium or brass, bolted to

the bar. A thin red line, the " lubber's "line, is painted on the glass right along thecentre line of the machine.

The metal work, more or less magnetic,which comes near the compass may makethe needle deflect in the following manner :

N. N.E. E. S.E.S. S.W. W. N.W.9° 55° 104° 149° 194° 234° 287° 325°

Thus, when the " lubber's " line is pointedat 234° on the card you know that themachine is pointing towards the S.W. ; ifyou want to retrace your steps, turn untilthe figure 55° comes under the " lubber's "line, and you know that you are thenpointing N.E.

These corrections were made by placingthe machine with the engine running on acompass platform marked out to the exactpoints of the compass. This can be doneby anybody with strings and pickers, orcan be obtained at any aerodrome.

The MapholderAn aluminium box measuring 140 mm. by

190 mm. fixed to the left of the panel,carries two tubes of 10 mm. aluminium.Wind on them a strip of map of 180 mm.width, under a celluloid cover. Rightacross the celluloid is a black line per-pendicular to the line of the roller, and thishas a small 1 mm. brass wire fixed under awasher. The wire is between the map andthe celluloid, whilst the washer is above it.The unrolling of the map and the movementof the needle, enables one to mark the pointover which one is flying.

The Throttle ControlsThe throttle controls, with two handles

belonging to a motor -cycle, are fixed out-

side on the left side of the cockpit (Fig. 41)with a strip of steel fixed by two woodscrews, or rubber will be useful perhaps,to hold the throttle levers so that theywill not close themselves under vibration.

Speed IndicatorThe head of the speed indicator is made

of brass and soldered according to thedimensions given in Fig. 37 (shown lastmonth) and will be fixed at the end of atube under the wing, to the metal fittingwhich holds the bracing wire. A small Vmade out of 2 mm. material, screwed on tothe leading edge and bound on to the rod,will hold it steady. A 3 mm. or 4 mm.aluminium or copper tube will run alongthe leading edge to which it will be fixedwith small fastenings, and will join thepressure head to the manometer (indicator).This latter is made from a glass tube whichis inserted into a few centimetres of waterdiluted with alcohol, half and half, andcoloured with a drop of red ink. Thewhole assembly is carried in a test-tube,fitted with a cork as shown in Fig. 32(shown last month).

On the outside of the tube, graduationsspaced at 10 mm. apart, will be paintedin black except above the level of the liquid.This manometer functions very well whenone is flying smoothly without turning nearthe ground or up aloft in calm air, butbeing very sensitive it shows up all gusts ofwind. It shows a speed of 10 as well as120 kilometres an hour. When one isswerving, being pivoted or turning, theaccelerations rather spoil its indications.It would be better, therefore, to have agenuine airspeed indicator which is madelike a barometer, and is independent ofacceleration, centrifugal force, etc.

Charting the Ocean BedCI NE of the most important responsibil-

ities of the U.S. Coast and Geodeticsurvey, is the maintenance of accuratenautical charts, discovering new informa-tion for the use of merchant and navy ships,and correcting ocean depth data.

Two of the instruments which are used inthe current researches are the fathometerand the hydrophone. The fathometer,which determines depths, measures the timerequired for sound to travel to the bottomof the sea, and return to the survey ship asan echo. These tests are made at the rateof four per second, whilst the ship proceedsback and forth over the area at her regularspeed. The positions of these depths arefixed by radio acoustic, ranging from two ormore previously determined positions.These positions may be either shore stationsor station ships, or a combination of both.

The Sound ReceiverThe hydrophone, or sound receiver, picks

up sound waves in the water, changes theminto a radio signal and returns them to thesurveying ship. When a bomb, thrownoverboard and exploding in the depths,sends its vibrations in all directions, thehydrophone notes the time elapsed betweenthe explosion and the return of the radiosignal, measuring the time to one -hundredthof a second. Knowing the velocity of soundin sea water, the distance between thesurvey ship and each of the respectivestation ships or land stations can be calcu-lated accurately, even when separated byas much as 100 miles. The photographshows the captain and wireless operator of asurvey ship working at the hydrophone.

They are shown testing the hydrophonepreparatory to lowering it into the ocean inestablishing a hydrophone station. Thehydrophone is placed about a mile off shoreand is connected to a wireless hut ashore, by

means of submarine cable. The mechan-ism inside the hydrophone receives soundwaves which, in turn, are automaticallytransmitted to the surveying ship throughthe medium of the wireless hut.

Showing the wireless operator and captain of a survey ship operating the hydrophone.


Special

L

" POPULAR

FLYING"!6D -

THE NATIONAL AVIATIONMAGAZINE FOR ALLWHO ARE INTERESTEDIN THIS NEWEST MODE

OF TRAVEL

contents of the January " Popular FLYING" include:

HOW TO BUILD A FLYING SCALEMODEL

Sopwith " Camel."

RECORD BREAKING DOWN AFRICABy D. Llewelyn-who, last month, with Mrs.Wyndham, broke the CapeLondon Record.

REUNION MEMORIESBy Mr. A. A. Nicod, 60 Squadron, R.F.C.

Get " Popular FLYING "

FLYING OVER ABYSSINIABy a war correspondent on the Italian Front.

RECOLLECTIONS AND REFLECTIONSBy A. J. Insall, Curator of Photographic

Records Imperial War Museum.

THE HUN IN THE CHIMNEYA true war story.

to-day-now on sale

STRIKING PICTURES OF THE BYRDANTARCTIC EXPEDITION

REVIEW OF AIR POST STAMPSREMARKABLE TOPICAL AND

HISTORICAL PICTURESLATEST AIR NEWS FROM ALL

COUNTRIESCOMPLETE SHORT STORY, etc.

at all Newsagents and Bookstalls.

C. Arthur Pearson, Ltd.

GRAFTON ELECTRIC Co.One large section of our Latest List deals entirely withMeasuring Instruments, Volt Meters, Ammeters, etc.

Single RangeInstruments, Volts,or Amps from 4/6to 77/6, Moving Coiland Moving IronMilliamps from 5/9

Multi Range MetersPocket Type 6/120

v., 32 M/A. 8/ -Testing Sets Volts-Amps-M/Amps

From £2 Os. Od.to £12 12s. Od.

SEND NOW for our 1935.36 Catalogue, 3d. post free. Acknowledged byExperimenters, Model Makers and Educational Authorities as themost complete reference. DEPT. P.

54 Grafton St., Tottenham Court Rd., LONDON, W.I

"DUPLEX TAILSTOCK"B.G.S.C. LATHEPOINTS OF SUPERIORITY.

Weight (bench model) 85 lbs. Concentric adjusted bronzebearings. Ground mandrel and tailstock barrel. Multi-purpose tailstock. Compare with any other make, and

judge for yourself. List stamp please.

WARD & POLLARD,Engineers, Orchard Works, Plumstead High St., London, S.E.18

KEENEST PRICEfor all Materials, Manufactured Parts and completeFLYING FLEAS. DUNSTABLE SAILPLANE

co., Luton Aerodrome, Barton, Beds.

FREE FLYINGFACILITIES

It is proposed that a club be formedwith branches where sufficient support isforthcoming, of which the membershipfee will be little more than that chargedby any other club, and this will entitlemembers to FREE FLYING and FREEBUILDING INSTRUCTION OF

FLYING FLEAAIRCRAFT

Send stamped and addressed envelope for particulars to -

E. G. PERMAN & CO.24-25 BROWNLOW MEWS,

GRAY'S INN ROAD, LONDON, W.C.I


FLYING SCALE MODELS for the real

Fascination of buildingFun of flying

You have to try these kits yourself before you can realise the gripping fascination ofbuilding them up. How each part almost goes together itself on top of the full-sizedplan-the joy of using a cement which is firm in 30 seconds. And when finished youhave a model which will really do things and go places !

PERCIVAL GULL 3/6Flying scale model. Wingspan 18 in. Length In in. The plan forbuilding it is clear and straightforward, and being a monoplane is quiteeasy to make. The kit includes all printed and strip balsa needed,shaped balsa flying prop, hardwood wheels, balsa for scale prop, quick -drying cement, bottle of blue dope for touch-up and all else needed.Extra full instructions. Complete kit, carriage paid, for 3/6.

HAWKER FURY 6/6Wingspan In in. Length 17 in. Exact I scale. The Fuselage is builton Comet's Auto -line-up method. All control services are movable. Itis a good strong flier. The kit contains all balsa needed, double sizetube of quick -drying cement, carved balsa flying prop, sheet of silvertissue, bottle of aluminium dope for touch-up and all else needed.Complete kit, carriage paid, for 6/6.

WESTLAND WALLACEFlying scale model. Wingspan 18 in. Length 13 in. The plan is full of rea scale details, oilcooling radiator, wing'slots, navigation lights, elevator and rudder control wires, all riggingshown, auxiliary tail skid, and many more details. In fact the detail you would expect tofund in a really expensive kit. Full instructions and material for movable machine gun orScarfs ring for rear cockpit. Cowl is built up from balsa, you do not have to carve it out.Comet's famous Auto -line-up method of fuselage construction. A special feature is that thekit includes SILVER TISSUE. The kit is very complete and includes all printed and stripbalsa needed, shaped balsa flying prop, hardwood scale wheels, quick -drying cement, printedinsignia, etc. Boys over r3 should find it fairly easy. Complete kit, carriage paid, for 3/6.Send your Postal Order for these kits NOW. Get started on the finest hobbygoing. Your money back if you are not satisfied. You MUST state yournearest RAILWAY STATION, as the kits are sent by passenger train (carriageextra abroad). Send two ld. stamps for 16 -page catalogue showing over 30 models.Also has four pages of the most helpful instructions for building flying models.

P. M. SWEETEN LTD.Bank Hey Street, BLACKPOOL

FLYING SCALE MODELSYOU can easily build scale model Planes that really fly from our Kits-no

special skill or tools required. Kits absolutely complete with full-sized '

plans and instructions, Balsa, Cement, Dope, Tissue, etc.

We are sole Agents for the most famous American Kits and Accessories-6CIENTIIIIC HI -FLYER KITS. CONSTRUCT -A -PLANE INC. FELTS.

LAWRENCE W. BROWN KITS (The makers of real plane).GENUINE "PAULOWNIA" PROPS. and IMP "TORNADO" MOTORS

(as described In December Issue of this Magazine).

Over 80 different Kits in stock of all popular Models, such asFokker D7-13 x-Triplane--Nieuport-Goshawk-Mr. Mulligan, etc.

16' span I/9d. 20" span 3/3d. 25' span 6/6d.AU pod free. AU complete.

Learn all about this fine new hobby. A lid. stamp brings our 1936 ten -pageIllustrated Catalogue of all Kits and Accessories. Remember-we deal onlyin Model Plane Kits and Accessories.

MODEL SUPPLY STORES(Dept. P), 46 Derby Road, PRESTWICH, Lancs.

MORE FULVALUE! ALLL 'V

LINDBERFORG'ALUE MONEY

KITS are

This famous war - timefighter is a really SUPERDETAILED JOB. Shockabsorbing landing gear,working controls fromcockpit. Machine guns onSCARFF RING. A VERYCOMPLETE KIT.

CARR. 6/6 PAID

Illustrated Catalogue of Scale -Model Kits and Supplies, NA.post free.

BRISTOL FIGHTER F -2BSpan ion Length 13r, Weight ri ozs.Coloured red and yellow with black and reddetails, struts and scale prop., natural woodcolour, varnished.

NORTHERN MODEL AIRCRAFT CO.37a FOUNTAIN STREET, MANCHESTER 2.

MICROSCOPES FOR ALLSPECIAL OFFER OF 1,700BRAND NEW STUDENTS'PORTABLE MICROSCOPES,

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 DONE C D E

Model C. Height 5f in., sliding locus, magnification 25 x linear PriceModel D. Height 7 in., sliding focus, circulac, 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 , 100 x , in wood case,with set of Dissecting Instruments. ... Price

IMMEDIATE DELIVERY FROM STOCK. Post Free inGreat Britain.

BROADHURST, CLARKSON & CO. es FARR1NGDONLONDON. E.C.L-

5/-9/6

12/630/-

"COMET"RIGHT ON TOP!

The "COMET " Petrol Engine Model 1935 Awards:-

FIRST PRIZE : B.M.A.S. Power Competition at Cranborne.SECOND PRIZE: S.M.A.E. Sir John Shelley Competition at

Fairey's Aerodrome.FIRST PRIZE : B.M.A.S. " Hallum " Competition at Cranborne.

Mr. Brooks' Petrol Engine Model flew from Cranborneto the Isle of Wight, 35 miles as the crow flies I

Build one of these Models this winter, powered with the18 c.c. COMET ENGINE

THE MODEL AIRCRAFT STORES133 RICHMOND PARK ROAD, BOURNEMOUTH

Please send 2d. stamps for price lists.


Two views of a model of a Westland Wallace aeroplane, a kit of parts for which is supplied by F. P. Sweeten Ltd., 38 Bank Hey Street, Blackpool, for3s. 6d. A feature of this kit is that the cowling is built up from rings of *-in. sheet balsa.

MODEL AERO TOPICSM ANY readers have written to me for

further details of the AC: CO En-gine which I described in last month'sissue, particularly regarding dry ice. Thisis obtainable from Imperial ChemicalIndustries Ltd., Imperial Chemical House,Millbank, S.W.1, and consists of smallblocks sometimes referred to as frozen snow.It is used by ice-cream vendors to maintaina low temperature round the ice-cream con-tainer. Dry ice is frozen carbon dioxidegas, and its temperature is 110 degreesbelow zero.

Two of the model aeroplanesmade from kits of parts suppliedby the Northern Model AircraftCo. (Dept. C), 37a FountainStreet, Manchester. They alsostock a fine range of model aero-

plane accessories.

Another Miniature Petrol EngineFROM America comes details of a minia-

ture engine known as the Baby Cyclone.It employs a rotary valve system of car-buration. It is of one -sixth horse power,two-stroke, k -in. bore, j -in. stroke, and hasvariable speeds of from 500 to 4,000 revolu-tions per minute, with a 13k -in. propeller.The manufacturers claim that it will idledown until it just ticks over, the control beingby needle valve. The petrol tank weighs11 oz., and an exhaust manifold is included.Ignition is by means of a specially light coilweighing only 2 oz. The cylinder andpiston are of special alloy iron, ground andlapped together, the cylinder head is ofduralumin, and the crankshaft is of nickelsteel, drilled for lightness. The remainder

By F. J. CAMM

of the construction consists of die castings.The engine is 3i in. deep, in. wide (with-out exhaust manifold), and 4f in. high, itsweight complete with two standard flash -lamp cells being only 15 oz. The price inAmerica is 15 dollars 75 cents, and I supposethere would be an ad valorem duty of 33kper cent. on this.

The A C: CO Gas EngineINTERESTED readers may care to knowthat the gas engines which I described

last month and which I have referred toin the opening paragraph above are nowavailable in this country from The ModelSupply Stores, 46 Derby Road, Prestwich,Lancs. The prices which I gave last monthwere, of course, the English equivalentto the American price. The actual pricesin this country are 27s. 6d. and 42s. forthe 2 -cylinder model and 4 -cylinder modelsrespectively. The increase in price is due toCustoms duties.

Astonishing Petrol ModelAeroplane TripON July 21st of this

year petrol model en-thusiasts of the Bourne-mouth Model AircraftSociety set out fromBournemouth for Cran-borne, twenty miles northof Bournemouth on theborders of Wiltshire andDorsetshire. The objectof the journey was toobserve an attempt onthe British record forpetrol engine model aero-planes by Mr. A. E. Brooksof Leicester.

The model was the " SkyRocket," designed by him-

self, and fitted with an 18 c.c. " Comet "engine. The Society of Model AeronauticalEngineers' approved timekeepers strainedtheir eyes to keep the model in sight, butthey could not follow its progress more than

a little over ten minutes. An attempt wasthen made to follow the model by car, butthis proved useless.

Some days later, however, Mr. G. F.Baster, of the Bournemouth Club, receivednews from Mr. Stride, a model engineer ofEast Cowes, that the model had been found,and was in the custody of the Receiver ofWrecks, Custom House, Cowes, Isle ofWight. The " Sky Rocket " had beenrescued from the sea by the crew of acoasting steamer, fifty yards off the SouthBuoy, Cowes, on the morning after it hadbeen launched from Cranborne.

After salvage negotiations had beenconcluded with the authorities, the modelwas returned to its owner at Leicester withthe kind assistance of Mr. Stride. Themodel was somewhat the worse for wear,though the fuselage and undercarriage wereundamaged. The distance coveredthirty-five miles " as the crow flies," buta longer distance was actually covered.

The Baby Cyclone miniature two-stroke Petrol Engine with rotary -

valve carburation.

The sting of the report comes in its tail,however, as, though the model made sucha performance, no record can be claimedas the flight was not observed in its entirety.

244 NEWNES PRACTICAL MECHANICS anuary, 1936

Fig. 6.-The petrol -driven model biplane in flight.

FIRST of all a full-sized drawing shouldbe made up from the outline drawing inFig. 3 of the fuselage ( given last month )

taking great care to locate thrust line andangles of incidence of main planes, etc.,correctly. This also applies, of course, tothe wings and tail plane. It is best to keepeach component on a separate sheet ofpaper.

Over the drawing, a sheet of greaseproofpaper should be placed. The whole is thenkept down to the drawing -board by a fewdrawing -pins. The greaseproof paper willprevent the glue, to be used shortly, fromsticking the fuselage to the drawing or board.

Now take four suitable length longeronsof 1 in. x * in. square birch, place two alongthe upper line and two along the lower andplace tacks on either side to keep them inposition. Steam them carefully by holdingthe board over the spout of a steamingkettle, moving the board along so that eachportion of the longerons is thoroughlysoaked and heated. The spout of thekettle should be very close to the portionbeing heated.

Leave the longerons pinned down to the

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APetro[:=Drivenay COL E

(Continued from Faye 188board for the night in adry place. They will thenset hard in their correctshape.

The UprightsNow cut the uprights

to the correct length, alsoof in. x 1in. birch, and

stick each end into position whilst thelongerons are pinned out flat on the board.

When the underneath fuselage side iscompleted, place little pieces of greaseproofpaper between the bottom longerons andthe top two where the uprights have beenstuck to the underneath longerons. Thiswill prevent the two sides of the fuselagesticking to each other when the top up-rights are placed and glued in position.

Having glued the top uprights in positionyou now have the two sides of the fuselagecomplete. Leave for twenty-four hours toset hard and then the tacks can be takenaway and the two sides of the fuselage canbe handled up.

Now comes a rather ticklish operation,and one that must be carried out carefullyand 'accurately, if the fuselage is to be true.Lay the two sides on the board, but upright,and carefully fit No. 1 former.

This No. 1 former has to be first cut outto shape from in. thick three-ply wood.

It is circular and cut to the size of the

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Wee Noaes FOR4°k-7;1/Hi/VG Z24.3"-71c .9.4 At. 0 TZ,AllePENa/NE/WI/NT/NSa,446.4aysr Not

facAtE,e.

Fig. 7.-The detachable engine mounting, which is of the cone type, shown detached.

back of the engine mounting. The outsidediameter is 31 in. A rectangle is cut outin the centre into which is fitted thedetachable engine mounting. This No.1 former should have nicks cut infour places on its circumference, and theforward ends of the longerons bound andglued into the nicks. Great care should betaken to give a down -thrust angle for theengine of 8 degrees to the thrust line drawnstraight down the fuselage and through theleading and trailing edge of the tailplane.Careful reference to Fig. 3 should be madehere. In other words, the circular No. 1former is tilted with the top further for -

Fig. 8.-A further view of the model in flight.

ward. Also be very careful that this No. 1former is " square " with the centre linedown the top of the fuselage.

If it is not, the model will turn toorapidly during flight and may get into aspin.

Fuselage ConstructionThis part of the construction of the

fuselage cannot be hurried, and havingstuck and bound in No. 1 former, the nextformer, No. 2, can be stuck in and bound atits corners to the longerons. The wholeshould be then left to dry hard. Nos. 2, 3,4, and 5 formers are all made of it in. three-ply wood in the form of rectangles, themeasurements being taken from the full-sized drawing.

The centres of these formers should befretted out for lightness, leaving rims ofabout in. The distances between formersvary from each other (see Fig. 3).

The uprights already stuck in positionwill strengthen these three-plyformers, and should lie alongside theformers. Cross pieces of * in. x in. birchare now glued in to strengthen the tops andbottoms of the three-ply formers.

The forward part of the fuselage is madevery strong, as it has to take engine loadsas well as compression loads where thewings are retained in position by elastic, asdescribed later, and also undercarriage


Mocte[ Biplane6. c130.d.of Last Monthf s Issue)strains have to be allowed for.

When Nos. 1 and 2 formers are dry andfirmly stuck, Nos. 3, 4, and 5 three-plyformers are inserted in the same manner,bound at the corners, and glued. Cross-pieces are also inserted to strengthen topand bottom.

After these formers are dry, the remainingcross -pieces of 1 x / in. birch should becarefully cut to length, and the last former,No. 10, inserted first. This last former andNo. 8 are also made of three-ply frettedout.

Having placed the last former, No. 10, inposition, place No. 8 former in position.This former is where the leading edge of thetailplane will rest upon the fuselage.Finally stick in the remaining cross -piecesthat you have already cut to the correctlength, as shown in the drawing.

fore also be taken off anda rear float fitted if theowner later desires to ex-periment with the modelas a seaplane.

The tail wheel is merelya simple but light three-ply disc with brass tubebush on a wire axle. Twoforward and two rear wire struts are carriedfrom this axle up to the brass tubes on thefuselage. These wire struts are turned in-wards to form prongs to insert into thefuselage brass tubes.

The whole is kept in position with elasticbands to keep the prongs hard into the brasstubes.

The CabinNext a small cabin must be erected on

Fig. 10.-A front view of the biplane.

The Fuselage FittingsThe first fitting to be tackled is the stern -

piece. This is constructed of a small blockof balsa wood and is merely a streamlinedend shaped with a knife. It is then stuckon with glue to the last three-ply former,No. 10, already mentioned. The under-carriage, to be described later, requirestwo brass tubes to be bound across thefuselage bottom at Nos. 2 and 3 formers.These tubes are of 1 in. internal diameterto receive the wire prongs of the detachableundercarriage legs. After binding the twotubes along the bottoms of Nos. 2 and 3formers with thread, they should be smearedwell with glue to cement them firmly inposition as they will have some severeshocks to deal with.

Before leaving undercarriage details theconstructor should bind two smaller brasstubes across the fuselage at formers No. 8and No. 9. These tubes accommodate thewire prongs of the detachable tail -wheelmounting in the same way as the mainundercarriage. The tail wheel can there -

BRASS TUBES ATTACHED TO' FUSELAGE

Lis

BOUND &SOLDERED

CATCHES FORELASTIC BANDS

BALSA FAIRING_BOUNDWITH SILKS DOPED

1/8"DIA. SPRING STEEL WIRE

Fig. 9.-The plane during a flight across country.

top of the fuselage at the forward end (seeFig. 7). This cabin acts as the platform forthe top main plane. The angle at whichthe top of this cabin forms to the thrust linemust be carefully adhered to in order toensure that the main plane takes up thecorrect angle of incidence when placed ontop.

The cabin is constructed by gluing twouprights of balsa across the top of thefuselage, one at the front end just behindNo. 2 former, and the other at the rear,9 in. from the front upright.

A platform of 1 in. thick balsa slat isplaced and glued on top of these uprights,and again care should be taken to check upthat this platform is at the correct angle, asshown in Fig. 3, to the thrust line. Nowinsert uprights of balsa slat 1 in. thick every3 in. between the platform and the toplongerons. These will act as supports tothe platform and should be glued into place.Finally the cabin sides and a V-shaped frontof 1 mm. three-ply wood with windows ofthin celluloid are stuck around the cabin andheld in position by elastic wound round thefuselage until dry.

Next the front end of the fuselage, fromNo. 1 former to 151 in. back, should becovered with sheets of 1 mm. three-plywood. If it can be obtained, 0'8 mm. three-ply is even better and lighter, and is thematerial used by the writer.

This three-ply woodis stuck all along itsedges and at uprightsto the fuselage. Thewhole is kept in placeuntil dry by wrapping

old model aeroplaneelastic around the

Fig. I I .-Showing the construction of the detachableundercarriage.

fuselage.When eventuallycovered withsilk and doped,this forward end

of the fuselage


will be found to be very strong and resist allnormal blows and the compression strainsof the elastic retaining bands for the wings.

The EngineThe light " Brown Junior " coil and con-

denser are now kept to the floor of thefuselage inside by wire retaining straps, andare positioned immediately in rear of No. 2former. Wires are led out to the enginewith plenty of slack to allow the engine tobe knocked off or taken off its detachablemounts. It is unnecessary to give wiringdetails for the ignition as the Brown Juniorcomes to its purchaser ready wired up on itstemporary base.

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ikawbvivm.6.e.rat-er

/PELEASELek -kw

LEADSrNREEPLY PANEL

Fig. I2.-The automatic timing mechanism to regulatethe duration of flight.

Wires must be carried back to No. 6former where the automatic timing deviceto control the length of flight is fitted to athree-ply panel on the top of the fuselage.On this panel are also two sockets for thedetachable plugs to start up the model froman accumulator on the ground.

This timing device will be describedshortly, but of course will have to be con-structed first in order to fit to the fuselagebefore covering with silk. Two leads tothe small flash -lamp battery, that isactual flying, are brought out of the fuselagefloor just behind No. 2 former. Snap clipsare attached to the end of these leads, whichcan then be fastened to the flash -lamp bat-tery terminals.

The BatteryIn this model the flash -lamp battery is

kept on the outside of the fuselage by meansof rubber bands. This is done in order tokeep the fuselage free from the weight ofconstructing doors and a compartment in-side. Furthermore, the battery can be slight-ly slid along the fuselage for final weightdistribution and trim. On the writer'smodel this battery is found to be locatedimmediately between the Nos. 1 and 2formers. The whole fuselage should now becovered with damp jap silk.

Photographic paste is put along all edges,and the sides are covered first. Thusassume that we cover the left side first. Astrip of silk the correct size is cut. Thephotographic paste is then applied to theedges. The silk roughly put on. It is thensprayed with water from a scent spray.The silk is then worked and stretchedmoderately tight in all directions with thefingers until there are no wrinkles any-where. It is allowed to dry, when it willshrink up absolutely taut like a drum.

The opposite side is then covered.Finally the top and bottom are covered inthis manner in their turn. The advantageof using photographic paste as an adhesiveis that if a mistake is made the poorly -covered section can be unstuck by rewet-ting the silk with water, and the coveringcan be reworked into shape and the wrinkleseliminated.

51-z,ermize

Now give the whole fuselage a coat ofaeroplane clear dope to keep the model taut.Allow it to thoroughly dry, and then applytwo coats of coloured dope. One coat willsometimes suffice. My model is dopedwhite all over, and white requires two coatsto make a good-looking job. The fewer thecoats the lighter the job. Dope and paintweigh quite a lot.

The Automatic Timing Mechanism toControl Duration of Flight

This little piece of mechanism is mostessential, and is quite easy to make.

It is composed of a " Kodak self -timer "and a push-pull electrical switch of the

small variety.The " Kodak self -timer "

weighs approximately 14 oz.only, and operates on the air -leak principle. It can be set tooperate after any length oftime from a few seconds toabout four minutes. It is notdead accurate, but an approxi-mate setting can be obtainedsufficiently accurate to controlthe model and ensure that itdoes not fly out of the flyingground. It has the advantageof light weight and of having apowerful action, so that it canoperate the pull -and -push igni-tion switch. Fig. 12 should be

examined for constructional details, andthere should be no difficulty in making upthe control mechanism from this drawing.The timer costs approximately 6s. from anychemist, and the switch 6d. from any cheapstores. The two are mounted on a pieceof three-ply wood by the aluminium bracketshown in the diagram. The rectangle ofthree-ply wood with timer is then glued inposition on the top of the fuselage betweenformers Nos. 6 and 7 before covering thefuselage with silk. The two insulatedwires led from the timing mechanism arecarried into the fuselage, one lead beingtaken from the coil to the timer, where thecurrent is made or broken according tosetting, the other lead being taken for-ward through the fuselage to the positiveflash -lamp battery terminal.

The timing mechanism is situated at therear end of the fuselage because it will befound that after starting the engine andrunning it up on the ground battery, theoperator will have to move to the rear of hismodel before releasing it. The timer is thenin a convenient position, so that the smalllever on top can be depressed just beforereleasing the model for its flight. Thislever releases the timing mechanism so thatit operates after the given time as alreadyset on the timer by screwing up or unscrew-ing the milled head.

This action of screwing up or unscrewingthe milled head controls the speed of theair leak operating the " dashpot."

This explanation may sound lengthy, butit will be seen, on obtaining one of theseautomatic timers, that their operationis extraordinarily simple.

How the Mechanism WorksInto the three-ply panel containing the

timer there are also two electric socketsfitted. Plugs are placed into these sockets,and from the plugs leads are taken to anaccumulator on the ground. The wiring istherefore arranged so that when the twoplugs, positive and negative, are placed intheir sockets the engine is on contact, andcan be started up and warmed up, using thelarge battery on the ground.

Just before flight the Kodak self -timerswitch is placed on contact, thus cutting -inthe small 44 -volt pocket flash -lamp battery,which weighs 4 oz.

The two accumulator plugs are removedand the model is released for its flight afterpressing the self -timer release lever. Thevery limited capacity of the flash -lamp bat-tery is conserved in this way.

The UndercarriageOn this model the undercarriage has been

made detachable so that the model will packup into a small space for transport purposes,and also so that seaplane floats can be fittedif the owner wishes to experiment in thisdirection.

The undercarriage is quite a simple affairand is made up from spring steel wire andbalsa wood. It is practically indestructibleand does not require any lathe work. Avice and soldering iron and a knife are allthat are required.

Furthermore, it is designed to move in abackward direction first and then an up-ward direction when absorbing the landingshock of the model. A moment's reflectionwill make it clear that a petrol model glidesinto the ground at a flat angle and is notstalled on to the ground in a three-pointlanding as in the case of the full-sizedmachine.

The movement of the undercarriage inthe model must therefore be backward firstand then upward. If this sequence is notcarried out, either the legs of the under-carriage will break or the bottom longeronsof the fuselage will collapse.

The Wheel AxleIf the reader will glance at Fig. 11 he will

see the construction of the undercarriage.He will observe that there are two mainlegs of 4 -in. diameter spring steel wire bentinwards at the tops to form prongs to placeinto the forward brass tubes already locatedon the fuselage. The bottom ends of thelegs are bent outwards to form stub axlesfor the wheels.

To these two main legs, two strengtheninglengths of 4 -in. diameter steel wire arebound with florists' wire and soldered.

The top ends of these strengtheningpieces are bent outwards to form retaininghooks, to prevent the elastic bands, usedto keep the two legs tight against the fuse-lage, from slipping off.

About one-third of the distance from thetop of the two legs a cross -bar is carriedbetween the legs. This bar is also made ofthe same spring steel wire. It is turnedup at each end for 1 in. These turned -upends are bound to the legs with florists' wireand soldered. From this point the tworear spring legs are also attached by bindingand soldering. These rear spring legs aremade of the same spring steel wire and arein the form of two large circular springs.Their rear ends are turned inwards for 14 in.to form prongs to insert into the rear brasstube fitted to the fuselage. Two smallwire hooks are bound and soldered on toprevent the elastic retaining band fromslipping off.

(To be continued.)

A NEW HANDBOOK !

POWER -DRIVEN MODEL AIRCRAFTI /-, or 1/2 by post from George NewnesLtd., 8-11 Southampton Street, Strand,

W.C.2.

January, 1936 N EWN ES PRACTICAL-MECHANICS 247

Aaleta tataA Train Ferry Enables Trains to be Run on to a Boatby Means of Railway Lines .which Continue onBoard, and the trains are Run Off the Same Wayat the Other End, thus Dispensing with a Bridge

(From Left to Right). A view from the upper deck, showing the car park. The Swedish train ferry leaving Copenhagen Harbour for Malmo.A deck view, showing new patent davits which enable the boats to be launched even when here is a serious list on the ship.

THE oldest method of crossing a deepwaterway is by a ferry. Beforebridges were built, it was usual to cross

shallow rivers by means of a ford, and some-times the bottom of the crossing was pavedto enable wheeled traffic to pass throughwithout bogging. When the water was toodeep for fording, the ferry was the onlyalternative, and we know some of these werein use in Roman times. Thus, if we consulta map of the Roman roads, we shall findthat Ermine Street came to a dead end(after passing Lincoln), on the banks of theHumber, and since no man would build aroad merely to a river -bank, we may assumethat a ferry was established to continue thejourney.

The oldest ferry in Britain which is stillworking, is the famous Pilgrim's Ferry, onthe River Wey, below Guildford. It hasbeen running before recorded history, as weknow from a law -suit fought about its rightsin the fourteenth century.

Although modern mechanical progresshas largely superseded the ferry by a bridge,there yet remain places where the crossingis too long for a bridge, or where the costwould be excessive.

The Famous Free FerryMotorists on the West Coast of Scotland

know how many ferries are still running overinlets of the sea and lochs, and all Londonersare familiar with the famous Free Ferrybetween North and South Woolwich, andthe longer Tilbury -Gravesend crossing.These large steam -driven ferries can carry aconsiderable number of motor -cars as wellas hundreds of people. They are fittedwith hinged flaps by which vehicles candrive ashore. Before we reach the trainferry, these steam " floating bridges " arethe biggest ferries. The usual method ofpropulsion is by means of two long chains,which are stretched from bank to bank, andare picked up by a cog -wheel arrangementon the ferry, and paid out again behind, sothat the floating bridge hauls itself acrossby means of the chains. The advantage ofthis arrangement is that the huge unwieldyflat-bottomed boat cannot be deflected by

currents or tides, and is certain to arriveexactly at its landing -place. This, ofcourse, is of the utmost importance, because

INTERESTING BREVITIES

The oldest ferry in Britain which isstill working is the famous Pilgrim's

Ferry on the River Wey.The first train ferry in this countrywas run over a hundred years agoThe Americans constructed their first

train ferry in the late seventiesThe Danes inaugurated their first

train ferry in 1880

it is only here that a landing is possible.Floating -bridge services are usually run inpairs, with a third ship in reserve againstbreakdowns. There are good examples on

One of the electric deck winches.

the Thames ; and at Portsmouth, South-ampton, Plymouth, Cowes (I.W.), and fourat Liverpool. There are also steam -ferryboats in many places which carry motor-cars, of which perhaps the best known totourists is the Portsmouth -Isle -of -Wightcar -ferry service.

The idea of the train ferry is merely anextension of the floating bridge carryingvehicles, and the first for trains was run inthis country nearly a hundred years ago.

The First Train ferryWhen the railway age began, and the

steel highway extended northwards throughScotland, the engineers soon came up againsttwo great natural barriers, the Firth ofForth and the Firth of Tay. Further pro-gress was impossible unless the water couldbe crossed, and the only alternative was awide detour westwards. The first train -ferry was put in service between Grantonand Burntisland in 1849. It was called theLeviathan, but its tonnage of 417 wassmall indeed in comparison with the laterferries. The general design, however, wasmuch the same as we use to -day, the trainswere run on to the boat by means of railwaylines which continue on board, and were runoff the same way at the other end. Need-less to say the engines did not cross. Thisferry was found very useful, and wasfollowed soon after by a similar contrivancefor crossing the Firth of Tay at Dundee.These ferries worked well for some years, asit was not till 1891 that the mighty ForthBridge was opened for traffic, and the train -ferry was scrapped.

The Americans constructed their firsttrain ferry in the late seventies, by whichthe Philadelphia and Reading Railwaycarried its traffic across New York Bay, andin 1880 the Danes inaugurated their firsttrain ferry from Nyborg to Korsor over theGreat Belt, a distance of 14 miles. Thisservice-though greatly improved-is stillrunning, and the crossing now takes about1 hours. There is no country in Europe sosuitable for train ferries as the little king-dom of Denmark, which consists of a penin-sula and a string of islands spread across the


Trucks on board the Harwich -Zeebrugge train ferry.

entrance to the Baltic, and so forming thenatural highway from Europe to SouthernScandinavia. Nearly all the main throughrail services are maintained by means oftrain ferries. Thus the run from Copen-hagen (the capital) to Hamburg and themainland of Europe, first crosses the GreatBelt, 141 miles to the island of Fyen, andthen the Little Belt, a distance of 3 miles, toFredericia in Jutland.

European Train ferriesThere are two train ferries over the Baltic

to Sweden, one runs from Copenhagen toMalmo (about 6 to 7 miles), and from Hel-singor to Helsingborg over the narrowestpart of the Sound, which is here about twomiles wide. The main traffic however fromSweden to Europe,is by train ferry over theBaltic from Tralleborg (Sweden) to Sassnitzin Germany, which are the largest and mostup-to-date European train ferries yetrunning. The crossing takes four hours.

It is a strange fact, that although thetrain ferry was first installed in GreatBritain, it was not used to connect ourisland with the Continent until compara-tively recent years, although until aChannel Tunnel can be constructed, thetrain ferry is the only method of arrangingdirect through railway services fromLondon to various parts of Europe.

The Great War, which stimulated me-chanical ingenuity in so many ways, alsogave us our first cross -channel train ferry.

The work of supplying our armies withmen, munitions, and supplies imposed agreat strain upon our resources, and this ata time when every hour saved was of theutmost importance.

To load and unload a truck, place itscontents on a ship, land them, and againload and unload a truck involves muchlabour ; and if the truck itself could be runon the ship six operations would be reducedto two. Accordingly three train -ferrysteamers were placed in commission, andran regularly between Richborough (Kent)and France. When the war ended thevessels were taken over by " Great EasternTrain Ferries Ltd." and a regular servicebetween Harwich and Zeebrugge was in-

stalled, and worked by the L. & N.E.R. Co.Three steamers are employed, length 363 ft.,beam 60 ft. and engines of 3,000 h.p. Fourlines of railway track are mounted on thedeck, and there is room for 54 loaded trucks.This service is mainly used for goods traffic,and has been found especially useful for theconveyance of perishable articles, or heavyand awkward machinery involving risk ofdamage in transhipment. Thus a thousandtons of electrical equipment was run directfrom Newcastle to Ymuiden (Holland),1,100 tons from Manchester to Budapest, 700tons from Newcastle to Copenhagen.Among these loads were giant machinesweighing 63 and 58 tons respectively. Thewhole equipment of a factory travelledfrom Roubaix (France) to Lancashire, andfourteen trucks brought the SchneiderTrophy team from Italy to the Solent. Itis also useful for fresh fruit, and oranges are

now loaded loose in a truck in Spain, andtravel direct to the factory siding in Eng-land. This service, as mentioned, is mainlyuseful for goods, but important develop-ments are in preparation for throughpassenger travel from London to all parts ofEurope by the Short Sea Route. Theseboats are expected to commence running in1936, and it will then be possible to go tobed in England, and wake up on the otherside of the Channel, en route for Berlin,Rome, Istanboul, etc.The Southern Railway

Three vessels have been specially built 'forthe service by the Southern Railway in theNeptune Shipyard on the Tyne. They areeach named after a famous ThamesFerry, the Twickenham Ferry, Hampton,and Shepperton respectively. Coaling isa simple matter as the trucks are rundirect on board, and tipped into the hold.Each vessel will carry forty goods trucks,or twelve sleeping coaches, which stand onfour lines of metals. There is accommoda-tion for 500 passengers, and a special garagefor motor -cars on the upper decks will hold25' cars, which are driven on board up anincline.

Very great technical difficulties had to beovercome, owing to the great tidal differ-ences in the Straits of Dover. The dailyrise and fall varies between 10 and 20 ft., sothat an inclined slip from the ship to theshore was out of the question-the gradientwould be too steep for a heavy train. Thealternative was a lock which the vesselcould enter, and by which the level couldbe maintained at any state of the tide. Thelock at Dover is nearing completion, and asthe ships are already built, the service willsoon commence.

The ferry -steamers are each 360 ft. long,with a spied of 161 knots. The engines arecoal fired, with automatic stokers.

Although these ferries will certainly bethe most up-to-date in the world, the largesttrain ferry still remains in America. It is theContra Costa, was built in 1914, with a ton-nage of 4,500, and is working in California.

Train ferries will certainly speed up thecrossing to France, and abolish the trouble-some business of disembarkation with itslong delays. It seems likely that suchservices will be so successful that theChannel Tunnel will no longer be demanded.

The L.N.E.R. Harwich -Zeebrugge train ferry.


Lateral Control onLight Aeroplanes

By S. J. GARRATTA Method of Lateral Control Without theComplications of Ailerons, which Helps in theDevelopment of the Light Aeroplane Movement

THE future of aviation as a popularpastime is undoubtedly wrapped upwith the question of simplification-

both in design and construction-of theaeroplane ; but whether the simplificationshould be carried to the extent of dispensingwith lateral control entirely, as is done onthe " Flying Flea," is open to argument.

There seems to be little room for doubtthat the " Flying Flea " is destined to do agreat deal towards bringing flying withinthe reach of the man of moderate means,because the cost of outlay and upkeep isreduced to a fraction of the amount pre-viously necessary. It is now possible tofly as cheaply as to run a car.

The main reason for this great reductionin cost is the simplification brought aboutby the revolutionary design of the controls.In the ordinary system of aeroplane con-struction, the angle of incidence of the wingshas to be very carefully adjusted by skilled" riggers " to a fraction of a degree, and thewings are fixed in that position. But thisdelicate adjustment is quite unnecessary inthe case of the " Flea " because the angle ofincidence of the main wing is directly con-trolled by the pilot through the medium ofthe joy stick. With this novel arrangement,elevators on the tail are unnecessary and,therefore, the construction is very muchsimplified, the tail taking the form of a singlefixed wing. A shorter fuselage can be usedwhich further simplifies construction withconsequent reduced cost. The rudderarrangement, however, remains normal,except that it is controlled by the stickinstead of by the usual rudder bar.

Dispensing with AileronsAnother great step toward simplification

is achieved in the Flea " by dispensingwith ailerons, thus leaving the main wing inone piece devoid of any moving parts, theadjustment of the angle of incidence beingeffected by means of a simple hinge fixingand controlled by wire cables.

It is interesting to consider the effect ofthis simplification from a theoretical pointof view. The fore and aft control (obtainedby altering the angle of incidence of themain wing, the tail remaining fixed) appearsto be a very sound scheme and seems to beopen to no objection whatever, in fact, ithas probably all the advantages claimed byM. Mignet, the inventor.

The omission of the ailerons, although apraiseworthy step from the point of view ofcost, is not so sound technically, for there isno control at all laterally. Although the

SIDEWIND

Fig. 4.-Owing to the _

dral of the wings, the sidewind caused by the sideslip has the effect shown.

dihedral angle ultimately provides a form oflateral stability, it is only a secondary effectdue to sideslip. Banking for a turn, forinstance, can only occur after a sideslip, infact it is correct to say the aeroplane side-slips into a bank. , This is not necess-arily dangerous, and probably onewould get used to - I it, but it is a make-shift arrangement,

t..and one would ex -

3 I

Fig. 1.-Showing theforces acting on anaeroplane flying stead-ily towards the reader.

~CENTRE OFI GRAVITYI5

a I0I

pect the " Flea " to wallow about a gooddeal in flight.

To understand the reason why sideslipplays a part in the question of lateral

stability, we must'" look into the matter

// a little more closely.

(i Lateral StabilityIn Fig. 1 are

shown the forcesacting on an aero-

/I

/ I

I

Figs. 2 & 3.-(Above) Irregu-larities of the wind causing theaeroplane to tilt over on to itsside. (Right) When an aero-plane sideslips, the side windcaused by the sideslip has the

effect shown.

UNBALANCEDI- I FORCE.>1 PRODUCINGg ,SIDESLIP0I. II,

V

plane flying steadily towards the reader.The lift on the wings and the force ofgravity are both equal and both actthrough the centre of gravity, so there is nomoment or twisting force to cause the

Fig. 5.-Lateral control bymeans of a differential rudder.

machine to tilt laterally about the line offlight. Now, in gusty weather, the ir-regularities of the wind will soon cause theaeroplane to tilt over to one side as shown inFig. 2. The lift force remains in exactlythe same relation to the aeroplane, as inFig. 1, and tilts over with the aeroplane.The force of gravity still acts vertically,however, and both lift and gravity still actthrough the centre of gravity, so no matterhow far over the wings may be tilted, thereis as yet no restoring couple-or twistingforce-to bring it back to an even keel. Oncompleting a parallelgram of forces asshown in Fig. 3, it will be seen that there isan unbalanced resultant force acting side-ways through the centre of gravity whichtends to move the whole aeroplane side-ways towards the depressed wing ; butthere is still no tendency for the aeroplaneto resume an even keel. When the aero-plane sideslips under the influence of thisunbalanced force, other forces are broughtinto play, for owing to the dihedral angle ofthe wings, the side wind caused by the side-slip has the effect shown in Fig. 4. It willbe seen that the side wind is able to getunderneath the lower wing, so tending tolift it up, and at the same time it blows overthe raised wing, tending to push it down, soproducing a couple which tilts the aeroplaneback to the horizontal.

This is, of course, exactly what is re-quired, but the objection is that the aero-plane must sideslip first and in the act ofsideslipping, it will " yaw," or in otherwords, begin to turn. Rudder must beapplied to correct the yaw, and this furtherincreases sideslip.

Making a TurnPractically the same sequence of events

takes place when the pilot wishes to makea turn. On moving the rudder over, theaeroplane attempts to make a flat turn (i.e.to turn withoutabsence of bank, an outward sideslip occurs,the aeroplane then banking as a combinedresult of the sideslip and dihedral angle.As in the previous case it sideslips first andbanks afterwards. On a normal aeroplanethe wings would be banked by the pilot,through the medium of the ailerons, at thesame time that the rudder was just over,thus avoiding any tendency to sideslip.

The provision of ailerons would undeni-ably spoil the attractive simplicity of the" Flying Flea " and besides adding com-plications in the mechanical sense, wouldprobably become the legitimate prey ofinspectors, who would .have to certify themas airworthy at intervals, with resultantexpense and delay.

In the hope of assisting the developmentof the light aeroplane movement, theauthor and the editor of PRACTICALMECHANICS have evolved a method oflateral control without the complication ofailerons, in fact the controls retain thesimplicity of those on the " Flea." Thislateral control system takes the form of adifferential rudder as shown in Fig. 5. Therudder becomes two rudders, a small oneabove a large one, both on the same rudderpost and both connected to the same ruddercontrol in the pilot's cockpit, but the wiresto .the top rudder are crossed so that the

Fig. 6.-The large rud-der set for a turn

towards the right-hand side of the illustration.


two rudders act in opposition. The ruddereffect is then the difference between the tworudders and they, being mounted in differentplanes, will tend to twist the aeroplaneabout its longitudinal axis so as to cause itto bank automatically when making a turn.

The Differential RudderFig. 6 shows a diagram comparable with

Fig. 1, but with the differential rudderadded. The lift and gravity forces remainas before. In Fig. 6 the large rudder is setfor a turn towards the right-hand side of theillustration, and the forces acting on thetwo rudders will then tilt the aeroplane so

as to raise the outer wing, thus bringing theaeroplane to a banked attitude withoutwaiting for sideslip. In the case shown inFig. 2, where the level attitude is upset byexterior circumstances, a touch of rudderwill correct the incipient yaw and bring upthe dropped wing.

In making a turn, the rudder deflectionwould be reduced progressively as the aero-plane banks until, at the correct angle ofbank, the turn will continue even thoughthe rudder may have been brought back tomid position. This is quite a normal stateof affairs, for it is always necessary to takeoff rudder and bank after the turn has

fairly started. This would also be neces-sary on the " Flying Flea," because whenthe aeroplane is banked, the rudder has atendency to force the nose down ; on anormal aeroplane a steep bank actuallynecessitates the use of opposite rudder tokeep the nose from dropping, but steepbanks are quite unnecessary on light aero-planes to be used for straightforward flying,as distinct from " stunting."

It will be seen that the differential rudderadds nothing appreciable in the way ofcomplications, but it should prove a usefulcontribution to the furtherance of simplicityin flying.

he HomeON page 135 of last month's issue we

gave constructional details of a simplehome telephone. A disadvantage

of the telephone described was that thespeaker also operated his own receiver, andas a result, listened to his own voice. Witha twin line this could only be eliminatedby a method of switching, and this is shownin the illustration on this page.

This method of wiring also has the ad -

elephoneAn AlternativeWiring Planfor the Telephone Described

in Last Month's Issue

and receivers, it will be noted that thebatteries are in opposition, thus virtually

LEADS TO /11/CROPRONE

,141/CROPNONE -BELL PUSH

;h

71/FoRET/c4z Ch.ecuir4asrEo //Yszok-Z/z7 Foie A2EFERENcE.

vantage of cutting out the listener's micro-phone from his own receiving circuit,resulting in a definite increase in volume.

In this case, although it would appearfrom first sight that the current might takethe outside circuit through both microphones

dimensions can be given owing to the varia-tion in material such as phones and cigarboxes, but this omission should not hinderin any way. It must also be understoodthat an earpiece used as a microphoneleaves much to be desired as far as sensi-tivity is concerned, and the substitution ofcheap microphones would doubtless provebeneficial, but if economy is the prior con-sideration the earpiece will prove a reason-

able substitute.

.......,..441

It; A11 sa

.40

S i

47a 1L7- FLASHLAMP BATTERY

I

isolating the two circuits. It is stillnecessary to lift the receiver before callingup the other unit.

Construction of either of these unitsshould not prove difficult in any way. Itwill be appreciated that no detailed

The alternative wiringplan for the home tele-phone described last

month.


I W74gr'z,....,

E/YLARGED 14kwOF aqms

Chisels.-Tools coming within the generalclassification of " sharp edge tools."They are of several types, the main ofwhich are as follow :Bevelled -edge Chisels.-Made with bladesfrom in. to 1+ in. wide and used chieflyfor accurate or delicate work. Theyshould not be used for such purposes asmortising, since they are not very strong.Firmer Chisels.-Similar to bevelled -edgeones, but stronger, having a blade ofrectangular section. Are suitable fornearly every purpose.Mortise Chisels.-Made principally insizes from in. to in. They are muchstronger than the two former types andhave a blade of from in. to in. thick,according to size. The handle, insteadof being fixed on a tang projecting frontthe blade, fits into a socket formed in thelatter. (See Fig. 11.)

Countersink Bits.-See under Bits.Countersinking.-Countersunk holes are re-

quired chiefly when using wood screws,their purpose being to allow the head tolie flush with the surface of the wood.Countersinking is done by means of oneof the bits described under Bits, andillustrated in Fig. 6 (shown last month).

Cramp.-A device used for holding frame-work, etc., whilst the glued joints are

Woodworking forBeginners

(Continued from page 194 of last month's issue)

Figs. 9 and 10.-(Left)An ordinary brace and(inset) the shape of thejaws. (Below) A ratchet

brace.

setting. Also for pressing floorboardsclose together when they are being laid.(See Fig. 12.) " G " cramps so-calledbecause of their shape, are used for hold-ing boards on the bench top whilst plan-ing or otherwise working on them.

Cross -cut Saws.-See Saws.Cup Shake.-A defect occurring in timber.

(See under Shakes.)Dovetails.-Joints used for fastening to-

gether corners of drawers or other widepieces of wood. There are differenttypes, viz. Common dovetails. Lapdovetail=a neater joint in which thecuts in the timber show on the surfaceonly. This is the kind generally usedfor the joints at the front of drawers.Secret dovetail-a joint which combinesdovetailing and mitreing. When com-pleted it looks like a plain mitre, but is

0 0

Fig. 1 .-Different types of chisel handles. Grinding and sharpeningangles for a chisel are shown inset. On the right is a bevelled -edge

chisel with the handle removed.

Fig.12.-A joiner's cramp.

much stronger. Thisjoint is very difficult tomake and is not usedextensively in practice ;it is a recognised test ofthe joiner's skill.

Dovetail Saws.-See Saws.Drills.-The Archimedian

drill is the type mostoften used in woodwork,its purpose being to makesmall holes for nails. Thedrill points used in it areof the diamond -endedtype as shown in an ac-companying sketch. Theycan be bought cheaply,but are not difficult tomake in a form suitablefor light woodwork. Themethod is to flatten theend of a nail by strikingit with a hammer, andthen to file down the

end to make an angle of about 90 de-grees. The cutting edges should be sofiled that they have a " leading angle "of some 65 degrees.

Ebony.-A wood which is remarkable forits great density and almost black colour.It sinks in water and is extremely difficultto work. It is very liable to split and isthus cut into small sizes as early as pos-sible after the tree bas been felled. Itsprincipal use is for cabinet work, parts ofelectrical fittings and tool handles.

Elm.-A useful hardwood, reddish brownin colour, and has an open and often

twisted grain. There arefour . species growing inthis country, but thesmall -leaved type is mostcommon. Elm is verydurable when kept eitherdry or under water, butwill not stand alterna-

tions without rotting. It is most easilyworked when quite fresh, and for thisreason it is usual to store the timber un-der water. The wood is used for planksor piles in wet foundations, naves ofwheels, pulley blocks,wooden springs, or forany purpose where sud-den shocks have to bewithstood.

Exeter Hammer.-A ham-mer with a cross pane,the underside of whichis parallel to the uppersurface. The portion ofthe head through whichthe eye passes is rec-tangular in section. (SeeHammers.)

Files.-Obtainable in var-ious patternsand sold ac-cording to thetype, length,and cut. Themain typesare : Flat -

rectangular in sectionand in elevation. Hand -rectangular in sectionbut with curved edgestapering toward the tip.Triangular (or saw)-triangular in section,mainly used for sharp-ening saws. Half round-with one flat and onecurved surface. Round(or rat-tail)-circular insection.The " cut " of files isdetermined by the num-ber of teeth to the inch.For example, the bas-tard has about 16 teethto the inch, the secondcut 32 teeth, the smooth60, and the dead smoothup to 100 teeth perinch.Wood files are very liableto become quickly Fig.13.-An Archi-clogged when used on median drill.


Fig. 14.- Various chisels.From left to right theyare : Bevelled -edge orparing chisel, sash chisel,mortise chisel and socket

chisel.

resinous wood and shouldtherefore be frequently cleanedby means of a wire scratchbrush. The process is sim-plified if the tool is first dipped intowarm water. An alternative method ofcleaning is to scrape the filings out of theteeth with a strip of zinc sheet ; this re-moves the wood without damaging theedges of the teth.

Fir.-Otherwise known as spruce. It isgrown largely in the British Isles and isproductive of a useful soft wood generallyreferred to as white deal or spruce. Apeculiar characteristic of the wood is thatit contains a large number of small knots.These are hard and black, and in somesamples are " dead " and loose so thatthey easily fall out. This wood is verydurable and because of its whiteness isfrequently used for tops of kitchen tablesand for common joiner's work, such asfor floorboards, packing cases, etc. Theyoung trees can be made to grow verystraight, and in that form are often usedfor scaffold poles and ladders.

Firmer Chisel.-See Chisels.Firmer Gouge.-Also called outside -ground

gouge, due to the fact that it is sharpenedon the outside of the curve. (SeeGouges.)

French Glue.-See Glue.French Nails.-The ordinary kind of nails

which are circular in section. They areoften called wire nails and are obtainablein all lengths from about 1 in. upwards.(See Nails.)

Gall Nuts.-More commonly known as oakapples, are defects which occur in oakand are caused by the attacks of thegall -fly.

Glass Paper.-Otherwise called sand -paper.Can be obtained in a wide variety ofgrades from No. 3 (very coarse) byto No. and then to No. 0 and No. 00, thelatter of which is very fine. Glass-paper

should wherever possible be used in aglass -papering block or on a cork block,called a " rubber." It is important toremember that a plane should never beused on work that has previously beenglass papered, since particles or glass ad-here to the surface and will blunt theplane iron very quickly.

Glue.-Can be obtained in two kinds :Scotch glue, which is very strong anddark brown in colour ; French glue,which is clear and semi -transparent andrich amber in colour. French glue makesa closer joint, but is not so strong. Thereare other proprietary glues having anacetate base and which can be melted atvery low temperatures. These latter arebeing more widely usedthan the older fashionedkinds due to the greaterease with which theycan be prepared for use.They are also claimed tobe stronger than theother kinds, althoughthey are appreciablymore expensive.Scotch and French glueis sold in hard cakes bythe pound. Before useit must be broken upinto small pieces, soakedovernight in water, andthen boiled in a gluekettle. Sufficient watermust be added duringthe boiling process tokeep it quite fluid, andwhen ready for use itshould be of such aconsistency that it willrun freely from thebrush.

Fig. 15.-Firmer and paringgouges. At the bottom right thevarious curves of the edges are

shown.

Care should always be taken that dust isexcluded from glue, since this will seri-ously impair its efficiency. If a scumforms on the surface whilst boiling, thisshould be skimmed off.

Gouges.-These may briefly be described aschisels which are curved in the directionof their length. There are two maintypes of gouges, paring and firmer, andthese are described under their respectivenames. (See Fig. 15.)

Grain.-An understanding of the grain inwood is very useful in all woodworkingoperations. In very few cases does thegrain run parallel to the surface, andtherefore if the wood is planed in onedirection (with the grain) a smoothfinish is obtained, whilst if it is planed inthe opposite direction (against the grain)the surface tears away and becomes un-even and rough. This is particularly

true with hard woods, and it is thus al-ways wise to examine them before com-mencing to work. Not only must thegrain be watched when planing, but alsowhen performing any other cuttingoperation, such as chiselling.

Grounding Punch.-Also called a mattingpunch. Is used for matting the surfaceof wood for simple decorative purposes.A suitable punch can be made from asquare or round mild steel rod about I in.square or diameter and filing five or sixgrooves in each direction across one end.

Gullet.-The name given to the angle formedbetween the teeth of a saw.

Half Rip Saw.-See Saws.Halv ng Joint.-As the name implies, this

is a oint in which half the thickness (orwidth) of one or both pieces of wood tobe jointed is cut away. There arenumerous forms of halving joint, andsome of these will be shown next month.The corner halving is useful as a simplemeans of fixing the corners of a box orframe which is not called upon to bearany great amount of strain. The crosshalving is a much -used method of fixingany pieces of timber which cross each otherat an angle. Another name for the crosshalving is a notched halving, since anotch is formed in each piece of wood.

Hammers.-Of various types, such as, forexample : Cross pane (joiners'), straightpane (mechanics'), American (with clawend), Exeter (see under this heading),ball pane (mechanics'). Hammers aresold according to the type of head and toits weight, e.g. 8 oz. cross pane, 4 oz.Exeter. (See Fig. 16.)

Heart Shake.-A serious defect in timber.(See under Shakes.)

Jack Plane.-The kind of plane used forremoving the rough initial surface fiomwood. It may be obtained in variouslengths from about 10 in. to 14 in., havingeither a straight stock or a sunk handle.To set a plane it should be held in theleft hand so that the operator can seestraight down the sole ; the sharp edgeof the iron should then be seen as a blackline. (To be continued.)

Fig. 16.-(From left to right)-A cross -panel hammer, an Exeter hammer, a thin pane hammer (for settingplate irons), a ball pane hammer, and an American claw hammer.


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"HARMONA"

Permanent MagnetMOVING COIL SPEAKER

Specified

for the

"PINNACLE"

The Moving Coil Unit of the" HARMONA" is of entirely new design,it employs the very latest developmentin Permanent Magnet Construction-the New Type Nickel

PRICEAluminium Alloy Magnet.The resultant improvementin sensitivity and life -likereproduction is an outstand-ing achievement.

25i-Fitted with Uni-versal Transfor-mer to match allTypes of Output

Values.

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

A defective resistance cancompletely ruin the enjoy-

ment of radio-and frequentlydoes. Moreover, it is oftendifficult to trace the fault, asnone but the most expensivetesting equipment can de-finitely locate it.Amplion 1 Watt Wire -Wound

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of all Amplion Products.

PRICElir EACH

ALL VALUES

AMPLION (1932), LTD.82 -84 ROSOMAN STREET, LONDON, E.C.1

EASY WIRINGAll Clix components, in addition to givingPerfect Contact, are easy to wire ; for instance,in Clix Chassis Mounting Valveholders thecentre socket of the 5 -pin and two sockets ofthe 7 -pin type are made longerthan the others; this reduces thepossibility of short-circuits and addsto the ease of wiring.Clix " Master " Wander Plugs andSpade Terminals are simply andefficiently wired, and the specialwire -to -wire wiring device makesfor certain and lasting contact.

All Clix components illustratedare specified for

"THE PINNACLE"Spade Terminals for L.T.

Large - 2d. Small -

Master Plugs for H.T. or G.B. Ifd.Clix Standard Chassis Mounting

Valveholders.4 -pin 8d. 5 -pin 9d. 7 -pin I/ -

Terminal trips.A.I., A.2.E., 7d.

LS. 6d.

Clix 1936 Folders"P.M." Free on

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LECTRO LINX LIMITED,79a ROCHESTER ROW, LONDON, S.W.I

High -FidelityReproduction

In our opinion Mr. F. J. Comm has chosen a most excellentcombination of Hivac valves for "THE PINNACLE." Readerswill, we believe, be interested in the information now givenconcerning the 4 -pin type Hivac variable -mu H.F. Pentode valve-one of the three types selected.

This Hivac VP2I5 (4 -pin) iswithout doubt the most perfectlyshielded valve of its type on themarket. As will be seen fromthe illustration, the valve is built MICA

ATup in such a way that the split SFPAR ORS

anodes are entirely enclosed in twoFaraday Boxes,thus producing thebest shielding system possible.

It is essential to shield theanode from the rest of theelectrode system in order toobtain the minimum anode con-trol -grid capacity so necessarywhen efficient high -frequencyamplification is desired.

ANODE

ikA IVATHE SCIENTIFIC

VALVEBritish Made

ANODE

BONDINGMICA

BOTTOMSCREENINGPLATE

lgiCREENING

FILAMENT

SPRING

CONTROL GRIDSUPPORT BORE

BACK SCREENINGPLATE

SCREEN GRIDSUPPORT

SCREENINGGRID.

CONTROLGRID

GLASSPIN,4

HIVAC VP215 (4 -pin)Illustration shows construction of the two

Faraday Boxes.VP2 15, 10/6. H210, 3/9. Y220, 10/6.

High Vacuum Valve Co. Ltd., 113-117 Farringdon Road, London, E.C.1


ALL RADIOQUESTIONSANSWERED

FREE

THE " Pinnacle " can truly be de-scribed as one of the very best batteryreceivers that has been described in

PRACTICAL MECHANICS. Regular readersknow what this means, and that it would bedifficult to give greater praise to any set.There is, therefore, no necessity to empha-sise the extreme efficiency of the receiver,or even to say that it is probably moreeffective than any simple three -valvebattery set that could be made at a reason-able price. Another point of great interestis that the set has been designed on strictlyeconomical lines ; every unnecessary com-ponent has rigorously been omitted, andnothing except real essentials has beenretained. This does not mean that thosevaluable refinements which are so popularon present-day sets have been omitted, forthe set has every feature which is generally

A three-quar-ter rear view ofthe complete receiver.

wanted by the average listener. Forexample, there is a remarkably smooth -working volume control which operates onthe first (variable -mu pentode) valve, whilstiron -cored tuning coils are used in bothtuned circuits. The " Pinnacle " is selec-tive enough for all requirements, but inaddition there is ample provision for modi-fying the actual degree of selectivity to suitany particular set of conditions.

A Handsome DesignThe special cabinet chosen is of very

handsome design, and can be bought eitheras a plain table consolette, or with a set oflegs so that the receiver may form a com-plete piece of furniture and may be stood onthe floor. The controls are few in number,but nothing has been omitted which mightmake for better reception, or which mightin any way simplify the operation. Thereare two tuned circuits, both of which maybe controlled by means of a single knob,although an accessible trimmer is provided,and this takes the form of a second tuningknob concentric with the first. By thismeans the very distant stations whichwould never be received in the normal waycan be brought in with ease ; all theadvantages of separate tuning condensers

THE -PINNACLE"An Efficient Three -valve BatteryReceiver Designed on Strictly

Economical Lines

are thus secured without the attendantdisadvantages.Variable Selectivity

It has been said that the sharpness oftuning is ample, and this statement mightbe amplified by stating that the Londonstations, when only about ten miles away,occupy no more than one degreeof the tuning scale, even whenthe aerial is connected to theleast selective tapping on the firstcoil. Moreover, either of thesetransmissions can be eliminatedmerely by rotating the knob ofthe trimmer condenser through asmall angle ; this is true proof ofthe correct matching, of the two

coils and their associ-ated circuits. Reactionis provided, but this isrequired only when dis-tant stations are beingreceived, or when ex-treme selectivity is calledfor, such as, for instance,when the set is beingused within two or threemiles of the local station.Both coils, and also thetuning condenser, are

Every Questionmust be accom-panied by the

Coupon onpage iii of Cover

adequately screened so that there is nodanger of " break -through " occurring.

It will be evident from the illustrationson this page that the set is entirely self-contained, the batteries and loud -speakerbeing all accommodated neatly within thepopular type of horizontal cabinet specified.

The " Pinnacle " is Easy to BuildThe whole of the constructional work is

of the simplest possible nature, and cansafely be undertaken by the beginner,even if he has never before attempted homeconstruction. The chassis, which is of themetallised-wood type, is supplied in ready-made form by Messrs. Peto-Scott, and it is

Another view of the " Pinnacle" which will help you in assembly.

The finished receiver in its cabinet andmounted on the neat pedestal.

a perfectly simple matter to mount thenecessary components. The positions ofall the parts can readily be determined bymaking reference to the wiring plans andalso to the photographs. Most of thecomponents are attached by means of

in. and Fin. wood screws, but the two -gang tuning condenser is fitted by meansof the three bolts which are supplied with it.A word of warning is called for in connectionwith this component, especially since twoof the bolts are used on the underside of thechassis for taking earth -return connections.Because of this the bolts must necessarilybe screwed up tight, and in doing thisthere is some danger of the tubular " legs "on top of the chassis breaking through themetallised surface, so that they do not makeproper electrical contact with it. Thiseventuality can be avoided in one of twoways : one is to place washers between thefeet and the chassis surface, and the otheris to avoid tightening the bolts unduly.

The twin screened high -frequency chokeis mounted by means of a -in. bolt, thelatter passing through the metal lug whichis joined to the screening cases. By adopt-ing this form of mounting the screen isproperly earth -connected to the chassis bymeans of the bolt head.


Constructional PointersTerminal socket strips are used for making

connection to the aerial and earth leads, andalso to the loud -speaker, and these aremounted by means of wood screws aftermaking two series of il-in. holes throughwhich the metal sockets may pass.

The reaction condenser and on -off switch,it will be noted, are mounted on the three-*ply front strip of the chassis, the latterhaving two -166- -in. holes for the purpose.The rest of the assembly is perfectlystraightforward and calls for no comment.

Straightforward WiringLittle explanation is called for in respect

of the wiring, since this can readily befollowed by referring to the large-scalewiring plans provided. Most of the con-nections are made by means of insulatedconnecting wire, and only a few of themrequire to be soldered. Those which aresoldered are the connections to the volumecontrol potentiometer and to the 1-mfd.fixed condenser. As can be seen from thevarious illustrations, the fixed resistancesand tubular fixed condensers are attachedto the various components by means oftheir own connecting wires, and thesecomponents have been placed in suchpositions that the wires do not need to beextended or even cut off short.

Battery ConnectionsThere are three flexible leads, these

being for the grid -bias battery connections,and they are passed through a hole madethrough the baseboard of the chassis nearto the G.B. battery clip. The only otherflexible leads are those which comprise thebattery -cord assembly, and these areattached to the terminals by forming loopsin their ends which fit over the terminalshanks.

After the wiring has been completed, andbefore the set is fitted into its cabinet, itis advisable to give it a preliminary trialand to set the trimmer on the rear half of thegang condenser.

Setting the TrimmerThere are very few preliminary adjust-

ments to be made, chiefly because of the

LIST OF COMPONENTS FORTHE " PINNACLE "

Two Dual -range Coils, A.D. and T.G. (Wearite).One Two -gang Condenser " Unitune " (Jackson

Bros.).One 0003-mfd. Differential Reaction Condenser

(Peto-Scott.)One 50,000 -ohm Potentiometer (Ferranti).Five 1 watt Resistances : 10,000 ohms, 30,000

ohms, 40,000 ohms, 30,000 ohms, 1 megohm(Amp ion).

Three .1-mfd. Fixed Tubular Condensers (Amplion).One 1-mfd. Fixed Condenser (T.M.C.).Two .0002-mfd. Tubular Fixed Condensers

(T.M.0.).One 3 -point On -off Switch (Snap Switches).One 5: 1 Niclet L.F. Transformer (Varley).Three Valveholders: two 4 -pin, one 5 -pin (Clix).One L.M.S. Screened H.F. Choke (Graham Farish).One Snap H.F. Choke (Graham Farish).Five Wander Plugs: G.B. -1, G.B. -2, G.B.+,

H.T. H.T. + (Clix).Two Spade terminals: L.T. L.T.+ (Clix).One 100-mA. Fuse, Type F.5 (Bulgin).-Two Component Brackets (B.R.G.).One Metaplex Chassis 12 x 10 x 3 in. (Peto-

Scott).One Cabinet (Peto-Scott).Two Terminal Sockets: B, Al, A2, and L.S. -

L.S.+ (Clix).One G.B. Battery Clip (Belling -Lee).One Speaker (Amplion).Three Valves, VP215, H210, Y220 (Hivac).One Accumulator Type D.M.G., 2 volt battery

(Exide).One H.T. Battery, 120 volts, Super Life (Drydex).One G.R. Battery 9 volts H.1001 (Drydex).

The Above and Underneath -chassis Wiring Plans of the "Pinnacle."

LS- L S +

J i.i him . Cs -

OM =9 11= MOmi. emm

.' H.F CHOKE 6 e4f .111Pi*. HT+

I r.n II ,,,, VaMEG,

G

R4. L.F. fRANSR.. LT+

.000 OH S,,

0002 MED. 5 Ca0 000

40.00 MS IR G. 11,

mOHMS

.41-. -- ".-- .1111111

2 MFD

O

SCREENED H F CHOKE

6. TOMB

6 <Ut) 000 2 HT-M F D...

viG B

C 3 : MED Cs -t-0 FUSE

04

LT -o

TO MB...T.

C4-a3 0

F c .r. F

I 2 DIFF REACT CONDR 0003 M FD'-r-r--r1

ON -OFF SW. II

M B.N1 ETA L LI SE D BASEBOARD


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Television is the comingboom in wireless-it willbring even greater pros-perity to the industry andcreate many more opportunities for acareer. Men who foresaw the broadcast-ing boom made good-be trained andprepared for this television boom whichmust follow as surely as night follows day.

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258

43/"

NEWNES PRACTICAL MECHANICS

TUNING CONTROL

2,8.1 DIVE REACT CONEYR

44"

WAVECHANGE SW

POT.AAETER

414"

Use the dimensions shown here when drilling the cabinet front.

fact that the tuning condenser is providedwith an external trimmer, but it is bestto set the star wheel of the othertrimmer to about its midway (half -in)position. When this has been carriedout it should be found that theexternal trimmer is somewhere nearits midway setting when any stationis tuned in. If this state does notobtain, a further slight alteration can,with advantage, be made to the starwheel.

For the benefit of beginners, itmight be preferable to explain brieflythe battery connections. Dealingfirst with the battery -cord assembly,the two spade terminals should bejoined to the corresponding (red andblack, or positive and negative) term-inals on the accumulator respectively.The high-tension negative wanderplug should be inserted in the negativesocket of the H.T. battery, whilstthe positive plug should be given avoltage of 100 to 120, according tothe exact battery employed. In anycase, the higher voltage is to bepreferred on the score of optimumperformance.

Grid Bias VoltagesThe grid -bias battery fits into, the clip

provided on top of the chassis, and theG.B. + plug should be inserted into the+ socket, whilst the G.B -2 plug isinserted into the 9 -volt socket. The bestposition for the G.B. - 1 wander plugdepends upon the actual voltage of theH.T. battery, but assuming this to be of thevoltage recommended, the plug should beplaced in the or 6 -volt socket ; if thebattery is only of about 100 volts, however,this plug should be given from 3 to 44.volts. No matter which battery is used, itwill be worth while to try different positionsfor the plug, choosing the highest one atwhich good quality of reproduction issecured. It is important to note that noalteration should be made to the G.B.voltages while the set is switched on ;switch off every time an adjustment is tobe made.

It is scarcely necessary to point out thatthe two plugs provided with the L.S.terminal sockets should be connected to thetwo " outside " terminals on the loud-speaker through a short length of twinflex. The earth lead should be attachedto the plug marked E, whilst the aerialdown -lead must be connected to the second

plug, this being inserted into the socketmarked A2.

WSW

This under -chassis view of the" Pinnacle shows the wiring andwill assist you in connecting up.

January, 1936

(clockwise rotation) position. Turn thewave -change switch to the left or rightrespectively, according to whether medium -or long -wave reception is required. Thenswitch on and tune to the desired stationby rotating the larger knob on the gangcondenser. When signals are heard, thesmaller (trimmer) knob can be adjusteduntil maximum volume is obtained. Areduction in volume can then be securedby movement of the right-hand knob.

It will have been observed in studyingthe circuit diagram that both tunersare fitted with primary windings havingtwo tappings by means of which differentdegrees of selectivity can be obtained.When testing out the original " Pinnacle "receivers, however, it was found thatample selectivity for all purposes could beobtained by connecting the aerial to thefirst tapping-that is, to terminal 2-onthe type A.D. coil, and by connectingthe H.F. coupling condenser direct to theend of the primary winding (terminal 1}on the T.G. coil. Should it ever be foundthat additional selectivity is required-forinstance, when the set is being used " underthe aerial " of a powerful transmitter-theaerial lead may conveniently be transferred

to terminal 3. Alternatively, leadscan be taken from terminals 1, 2,and 3 to the sockets marked Al,A2, and A3 respectively on the chassisterminal strip. Additionally, the leadfrom the tubular condenser, which isshown as being connected to terminalL on the T.G. coil, can be trans-ferred to terminal 2 or 3.

When all these connections have beenmade set the reaction condenser to zeroand turn the volume control to the full -on

A D

RUNNING MODELS FROMTHE MAINS

A FINE range of power units is nowobtainable from Shenphone Elec-

trical Products, 226, High Road, Ley -ton, E.10. The units are specially de-signed for the operation of model elec-tric railways, etc., and supply smoothcontinuous outputs for this work. Rec-tification is obtained by using a graph-ite anode -tungsten rectifier, which,being of the static type, has no movingparts to wear or require attention.Also, a longer life is assured with thistype of rectifier, a definite guaranteeof 2,500 hours being given. Many oftheir units include a reversing speedcontroller. Although this can, if de-

sired, be put out of action, it enables, whenin use, the operator to completely control themovement of his locos.

G.B-2The circuit diagram of the" Pinnacle. -

L S.

OHT+

r--OHT-

100 M.AFUSE


WEASTANDARD TESTING I INSTRUMENTS

0a.

0

THE WEARITE METER UNIT.A precision instrument conforming to let grade B.E.S.A.Specification with ranges (most of which are direct reading)as below. The Meter is a Moving Coil instrument 35"diameter. A special output arrangement incorporates aseries condenser for Output Meter requirements.

D.C. VOLTS A.C. VOLTS CURRENT0-10 0-10 0-2 5 mA0.50 0.50 0.10 mA0-500 0-500 0-100 mA(1.000 ohms per volt) (1,000 ohms per volt)0.20 0-20 RESISTANCE0-100 0.100 0-1,000 ohms0.1,000 0-1,000 0.100,000 ohms(500 ohms per volt) (500 ohms per volt) 0.1 megohm

CAPACITY INDUCTANCE'05 mid. to 4 mid. 5 to 120 Henries

Price Z6 . 17 . 6Other Instruments Include: -VALVE TESTING UNIT .. 24 17 8OSCILLATOR UNIT .. .. £6 15 0FREQUENCY METER .. £4 15 0

MULTIMETER .. £4 5 0

To WRIGHT & WEAIRE, LTD.,740 High Road, Tottenham, London, N.17Please send meliterature givingfull details of yourtest instruments,etc., also yourlatest catalogue ofcomponents andcircuits, etc. P.M. 1/86.

Name

Address

The " PINNACLE"uses these Wearite

NUCLEONIRON -CORED COILS

ONE A.D. (Aerial) COILONE T.G. (H.F.) COIL

Price each 12/6im8213

ELECTRADIXFINE TURNING METAL for brass -bearing bushes, etc. Solid

drawn, 15 in. dlam., I ci in. bore, 4 lb. per ft., sale 2/8 ; ditto, 2 -in.diem., 15 -in. bore, 31 lb. per ft., sale 2/6. Emery Cloth, GrindingDiscs, coarse, 65 -in. diam., 2/- dos. Larger, 9 -in. diam., 4/- dos.

TWO 8) -IN. DIAL CHART RECORDERS, for Draught or L.P.to 12 -in. water, 87/6 each.

CLOCK -IN Staffsine Employees Time Recorder, 70/-.ANEMOMETER. 6 -dial type reading 1-1,000,000 c. air metres

by Stanley, in pocket case, 50/-. Hill -Barnard Sphygmometer,0250 mllg., 10/-.

MIRRORS. 55 in. chant. Helix or Television. 1/6. Para-bolic Concave, 10 in., 20/-; 20 in., 25/-; 24 in., 30/-. Carr. fwd.Neon Lamps, 2/6 and 8/- each, with holder. Miniature Neons, 2/6.

VLIGHT AND RAY CELLS -Selenium Raycraft, 21/-;Kingston, 15/-; Raycraft outfit with relay and amplifier,45/-. Photo -Cells, for sound on Film, Television andRay Work, B.T.P., 15/- ; R.C.A., 25/-; DEC.... 25/- to701-. Beck Angle Prisms, mounted in carrier, 5/6.Micrometer adjusters for lens, 1/-. Eyepieces withprism and lemma for photo -cell inspection, 12/6. NewEver -Ready Service Inspector's Handlamps with BatteryHolder, 7/6.

THERMOMETERS. Panel, 21 -in. clock dial, 5 ft. of ether tube,for distant indicating, reading 0 to 100' C., 7/6 and 10/6. Straight0 to 100° F., 3 in., 6 in., and 12 in. for 1/4. Pocket, 5 in., Clinical,9d. R.A.F. Air Speed Aero Indicators, 10/6.

RADIO RECEIVERS. Complete and ready for use, no batteryor valves wanted with a crystal set, 7/6.DYNAMOS. Bargains.

FOR CHARGING OR LIGHTING.240 -watt Enclosed Dynamo, 12/20v., 12 amps, Ball Bearings, VeePulley, Type C, 25/-. Marinetype Switchboard with Ammeter,maximum and minimum AutoCutout Main Switch and Fuses.Field Regulator, 25/- or 47/8the pair.

DOUBLE CURRENT GENERATORS, D.C., 600 volts, 100 ma.,and 6 volts 3 amps., 40/-.

BINOCULARS AND TELESCOPES. Prisms, 55/-; Field,40/-; Precision, 15/-; Navy Telescopes, 24 -in. Gun Type, 17/6.Hand Range Telescopes, 25/-. Stick Periscopes. 35 in. by 15 in.Mirror and Cover, Swivel back, 6d.

COMMUTATORS. An opportunity for amateurs. Enginebuilt, 24 copper segments, mica insul. Worth 7/6. Sale, 2/6.

HEATERS Immersion heaters, 110 volts, 2/6 ; 220 volts, 3/6 ;hot plates, 110 volts, 500 watts, 3/6 ; 660 watts, 5/- ; 3 -heats, 220volts, Toasters, 7/8 ; 17/6 ; was beaters, 100-250 volts, 15/- ; bowlfires, 220 volts, bronze finish, 7/8 ; 8 kw. bar fire, 8/6 ; 1 kw., 220volts, 17/6 ; Electric Soldering Irons, from 5/6.

ELECTRADIX RADIOS218 UPPER THAMES STREET, E.C.4.

Telephone: Central 4611.

An old-fashionedPlumber of Poole

Went back (true totype) for a tool.

Thought madam, "Allright,

We've got someFLUXITE,

I'll do it myself -he's a fool ! "

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 " SOFT "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 ate tied withline wire at the crossings AND SOLDERED.This makes a much stronger wheel. It'ssimple - with FLUXITE - but 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 1/6.

ALL MECHANICS WILL HAVE

FLUXITEIT SIMPLIFIES ALL SOLDERING

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

For the

'PINNACLE'

these

AND

BATTERIES

are specified

FOR L.T.-Exide DMG, 2 volt,42 ampere hours I I

FOR H.T.-Drydex Super -Life120 volts I 016

FOR G.B.-Drydex H1001,9 volts 10d.

Obtainable from Exide Service Stations and allreputable dealers. Exide Service Stations giveservice on every make of battery.Exide Batteries, Exide Works, Clifton Junction, nearManchester. Branches at London, Manchester,Birmingham, Bristol, Glasgow, Dublin and Belfast.


"LILLIPUTIAN POWER."

Scale Model L.M.S. COMPOUND No. x ro8.An improved model of one of our most popular locomotives,whose prototy'pe is noted for efficient and economic workingover all parts of the L.M.S. system. These engines have ashapely and characteristic outline, and our re -built modelembodies all these features. Length overall, x5 inches. Gauge

Prices: Clockwork, 3216; Electric, d.c., 8 volts, 39/6, a.c.,20 volts, 44/6.

ENGINES.Are you in-terested in :Engines,Boilers,Cast-ings & Fit-tings, etc.? Ifso, write forB.12. ModelEngine Cata-logue,post fi(e

THAT IS the name of ournew Free Train Folder,No. 52, with all our popularlines-new and well known-depicted therein.Send for your copy at once.By return of post the post-man will bring this splendidtwo-colour pamphlet-brightblue and black-to yourdoor.

On January xst our newseason's Catalogue, New A.12,comes out, describing rail-way models-and their ac-cessories-from gauge " o"to 55 -inch gauge. A.12, price6d. post free.

Scale Model L.M.S. 4-6-4 Tank Locomotive No. 2536.For many years we have been asked for a model super -detailscale model Tank Locomotive at a popular price, and afterconsideration have decided upon the new L.M.S. Tank designedby Mr. W. A. Stanier. Length overall, 13 inches. Gauge "o."Prices : Clockwork, and Electric, d.c., 8 volts, £7 12s. 6d., a.c.,zo volts, with distant directional control, including' controller,£8 I7s. 6d.

The most popular gauge " o " scale loco-motives we have ever made. " ROYALSCOT" and "FLYING SCOTSMAN,"78/6 and 4 gas. respectively.

SHIPS.Does yourinterest liein: MotorBoats ,Yachts,Scale ModelShips,WaterlineModels, Setsof ShipFarts,Draw-jugs'? If so,you willwant 8.12.,6d. post free.

BASSETT-LOWKE LTD., NORTHAMPTON,London: 112 High Holborn, W.C.I. Manchester: 28 Corporation St.

MERCOReaders interested in " Model Railways inMiniature " MUST be interested in MERCOProducts, which have made such modelling possible.Send I d. stamp for full lists and MERCO buildingpaper samples to:

MINIATURE EXHIBITION RAILWAYS CO.64 Watson Street, Dundee, Angus.

NOTE : Readers in the London area should make a personalvisit to HAMBLINGS, 26 Charing Cross Road,W.C.2. Entrance opposite Charing Cross Road P.O.

"O 0" GaugeMiniature RailwaysWe supply sets of parts for home construction asfollows:-

Set of parts for Open Wagon, any railway... 2/3

Set of parts for Closed Van, 20 -ton type ... 2/6

Set of parts for Scale Loco, comprising 6 -voltElectric mechanism ready for running, com-plete Body, Buffers, Boiler Fittings, etc. ... 30/6

Send for lists and samples, 3d.

HAMBLINGS, 26 Charing Cross Road, W.C.2

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Over 20,000 testimonials have been certified by Accountant'sCertificate. 700 Doctors and 27 Police Forces use this Course.

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MODEL RAILWAY LAYOUTS

Fig. 1.-A view of the New Elmo Station on the West Midland Railway showing goods bemg backed up a 1 in 90 gradient.

BEFORE the subjects of baseboards andtrack -making are discussed, a fewtypical layout plans will prove interest-

ing. Three designs are given, each onesuited to a different kind of room, but firstof all a few general principles which governthe matter of layout design must be given.

A common mistake is to allow no pro-vision of track for the storage of wagons andcoaches. Many an enthusiast has got holdof a thoroughly good plan to work upon andhas completed the structure, only to findthat he is limited to three coaches and abouta dozen wagons owing to the fact that thereis nowhere to leave them standing. Anotherimportant matter is that of providingplenty of headway clearance where morethan one level of road is provided for.Bridges and tunnel entrances should not,except in special instances, be raised undulyfor the clearance of rolling stock, but thegreatest care must be taken to allow enoughspace to prevent any fouling. If it is simplythe matter of a bridge headway, the stand-ard loading gauge should be adhered to;but if it is a matter of leaving enough roomfor access to trains in case of derailment,there will be need for fully 3 in. or evenslightly more. Where there is any coveredtrackway, it is a decided advantage if thewhole of the upper covering of the tunnelcan be made to lift off bodily. On no

By Edward BealSome Suggested model00 -Gauge Layout Plansfor a Small, Medium,and Large Room.

account should any point or crossing beplaced within a tunnel or covered runway,and, wherever it is possible to do so, pointsshould not be arranged at places difficultof access.

GradientsAvoid anything steeper than 1 in 40, and

make your incline even more gradual thanthat if you can. It is often possible toshorten the length required for an incline,by running one track downwards and theother upwards, thereby reducing thedistance, if necessary, by one half. Thereshould be no curves sharper than 24 -in.radius, 4 -ft. diameter, measured to the outerrail, and, where it is at all possible, gradecrossings should be entirely avoided. Thatis, where one line must directly crossanother, the one should be carried over theother by means of a bridge.

0 1 2 3 9 5 6 7 8 9 10 /1 1210

14 /5 16

Fig. 2.-A plan of an 00 -gauge layout for a room measuring 16ft. x 12 ft.

The layout, Fig. 2, embodies the followinginteresting features. Two stations of theterminal type ; up and down roadsthroughout ; a continuous run so that trainsmay be operated as long as desired betweenthe two stations ; a single -line branch to acoal -mine ; a large model dock basin com-plete with entrance lock, cargo crane, andthree factories (F). These latter arearranged wholly on the background sheet,and may be built up of flat cardboard andbrick -paper, using Merco window sashpapers. An absolute novelty incorporatedis that of the gravity hump marshallingyard which we will discuss later. There isalso a large locomotive depot to accom-modate about a dozen engines. The wholeof this system is included, without over-crowding, in a room 16 ft. by 12 ft., havingan entrance on the north side. There aretwo levels in the layout, most of the forma-tion on the east side being high-level (withrail -level 2i in. above that of the low-levelrail), the opposite west side Being low, andthe .approach to the high-level occupyingthe north and south. The levels of thevarious tracks are clearly shown by thearrows.

A Dock BasinThe dock basin is formed by simply

removing certain of the boards which form

Fig. 3.-A layout plan for a room 20 ft. x 12 ft.


the base, and refitting these underneath thebaseboard proper. The entrance lock, withthe shapes for the dummy gates, will requireto be specially cut out, the narrow jettyarm being laid in. To simulate water, thebest material is heavy sheet glass, in onepiece if possible, though the lock will requirea separate piece. Between the boards andthe glass should be laid thin cardboard orthick brown paper, suitably painted a dark,muddy brown, and sprinkled near the corn-ers with some heather leaves or dyedsawdust.

Trains leave station A, running down-ward by the left-hand track, taking one ofthe tracks nearest the south wall, andjoining the continuous track near thebridge. They pass under the building ofstation B and round the north side, downthe continuous way on the east and thenalong the track marked " low level " be-tween the two inclines on the south. Theycontinue to take this circle as long asdesired, then branch off up the left inclineto the south and to station B. The othertrack, of course, is for the reverse run.Continuing from station B, the trains takethe single inclined track above the coachsidings, and follow it right round the roomto the pithead near station B.

The Hump Marshalling YardThe hump marshalling yard will require

elucidation. In planning this feature,which is the most instructive and fascina-ting of all railway models, it is desirable tobranch the yard out of a high-level roadand to run it by its normal down -grade outby a low-level. Fortunately, this is oftenpossible, since these sorting yards are nearlyalways located in actual practice away fromexisting stations, and sometimes link upotherwise divided routes. We will assumethat a goods train, with a main line engineat its head, arrives for marshalling on thetrack marked " ramp " at station B. Thisramp is the well-known Lanal UncouplingRamp, and the engine is uncoupled on pass-ing over it. It then runs on ahead, leavingits train, and taking the loco road just abovethe hump, coming down to the sectionwhich is parallel with the tracks on thewest side. There it waits until required.Meanwhile, a shunting engine which hasbeen waiting near or on the turntable atstation B, gets behind the abandoned goodstrain and begins slowly to push. Thepoints are set for the hump itself, whichconsists of a considerably raised length oftrack having a quite sudden fall on theoff -side, and fitted with another ramp. As

the wagons pass over this hump they areautomatically uncoupled, one at a time,and each runs quickly down the 1 in 12gradient, taking the siding which is set forit, continuing to run more slowly down the1 in 18, and coming to a pause before reach-ing the grid. The whole train is split upand arranged in this manner, each siding inthe yard taking wagons for a certain district

STATION D

lade.medium 10.1

his baseboard

R-Lstererrest

Os

Seale, of Feet0, 1. 1 3 4

that the doorway entrance is provided witha hinge flap in the baseboard for ingress ;the hump yard has been so arranged that onthis flap those tracks occur which do notrequire an outside conductor rail, thoughthe main lines will require conductors.

A Layout for a Large RoomIn Fig. 2 is shown a somewhat more

Loop

1T5 I01 C

Public Highway median level

Exposed . *slower for hone

eo°AM

LP YARD ova -rowel

R." 1 In 12 115 18

I

Re.

1_ 1 9 10 11 1'2 11 la 1.5 10 if 18 1,11 tp 2,1

Fig. 4.-A layout plan for a room measuring 24 ft. x 12 ft.

or factory. The main line engine whichhas been waiting at the foot then gathers upthe train again by backing in and out of thesidings and proceeds on its journey with itstrain correctly sorted. The hump itself isarranged to stand out well above the yardformation level, and the track upon it mustbe laid with some care and precision, allirregularities being avoided, yet the fall ingradient being definite and adequate. Muchwill depend upon the type of wheel bearingsemployed. The new " pin -point " bearingswould require a slopeas the common bearings. The buildershould experiment with a batten beforedefinitely settling upon the percentage to beadopted. The track marked " brake vans "serves the purpose indicated ; several vansare stored at this point, so that if needs bethe train can be broken up into more thanone unit, the brake vans being, of course,sent down the hump last.

Reference letters will make clear thevarious buildings and other features. Fmeans factory, ES engine shed, C goodsshed, LB lifting bridge, CC conservancycottages, DO dock offices. It will be noted

Fig. 5.-An 00 -gauge auto steam train.

ambitious scheme for a large room, 20 ft. by12 ft.-an unused garage being the idealsite. This plan, designed by the writer,has been in use in the south of England forsome years, and appears to give every satis-faction to its enthusiastic owner. Hereagain there are two levels, with threestations and a dock. A large space near thecorner is given over to the entrance, andthere is a lift -bridge at this point. Startingfrom station A, the track being double allthe way, trains take the double junction tothe main down -gradientover the bridge. Here station B is reached,where the main headquarters of the systemare located. Tracks then pass beneathstation A to the up -gradient on the northside, the trains running through ruralscenery over the lift bridge and around thecontinuous run-a desirable feature for asmall room-and thence finally to station Cby the dock. There are a number of in-dustries-two factories, a coal -mine, and apetroleum store. The locomotive depot atstation B is very extensive. There is noturnable at station C, but one might readilybe arranged near the tankery. In all in-

January! 1936 NEWNES PRACTICAL MECHANICS 263

stances, crossovers for the escapement ofengines arriving on trains at platforms, havebeen excluded from these plans, since theneeds of these can be entirely eliminated bysimply arranging a dead -alive section ofconductor near the inner ends of suchtracks. Arrived engines can thus beswitched out and departure engines run onthe other end of the trains, the arrival engine

The room is 24 ft. by 12 ft., and one purposein including it is to show what rarely isshown-the beautiful amount of detail andthe elaborate arrangement of roads whichcan be arranged within a fair-sized space in00 -Gauge. Nevertheless, the space is notreally extraordinary ; many an 0 -Gauge orlarge system occupies a much larger site tofar less advantage. It is one of the common

Fig. 6.-The bascule end of a new lift bridge on the West Midland Railway.

leaving after the train is out. An un-coupling ramp will, of course, also be re-quired for uncoupling the arrived engine.Main line engines of considerable haulingpower will be needed for this layout, asunfortunately there is a minimum gradientover the bridge to station B. The inclineon the north side is not so severe.

A Further DesignThe plan in Fig. 4 will be found a most

interesting arrangement, though the space itrequires is a little beyond the reach of many.

errors to assume that because there is agood-sized room at one's disposal, one willgo in for a large gauge. For this reason,00 -Gauge never gets a fair trial, being nearlyalways confined to very restricted spaces.To lay this system would cost about onethird the money involved in laying down avery limited 0 -Gauge system, notwith-standing the amount of track there appearsto be.

The railhead is station A, and the routeis not difficult to follow. Passenger trainsfirst circle the room and take the concealed

tunnel loop in the north-west. Here theypass over the lengthy viaduct and run intothe junction C. Here there is a double -track connection to station E, which we willdiscuss later. Continuing from station Cthe next halt is through the tunnel at thelarge station B. Then through anothertunnel and underneath station E, aroundthe room, to the north side, where D is atlength reached. In the reverse direction,trains travel by way of the lift bridge nearthe doorway, under A and E to B andjunction C. Here the downgrade may betaken instead of the road to the railhead A,and the route is by way of the lift bridge,along the south side, and up to the central,medium level station E.

Three LevelsOn this layout there are three levels, but

all gradients are extremely lenient, spacebeing ample. The hump yard has anexcellent situation between the medium andthe low-level lines on the south side. Itsarrangement is exactly as before. The is-land baseboard in the centre is divided by amedium (2b in.) level public highway along-side of which are the station buildings for B,complete with baggage depot and threeshops. There is no direct relation betweenthis highway and station E, though theformer serves to isolate the one side of thebaseboard distinctly from the other. Notethe exposed crossover for the hump yard.This enables goods trains after having beenmarshalled to pass from the up to the downtrack. There are generous locomotivefacilities throughout ; the main depot is atA where there is a mechanical coaling stageof the modern type, the running shed havingapproaches both by a grid and the turnable.There is a similar coaling stage at B, andhere there are ample coach storing sidings.Here also there is a turntable, as will befound at the terminals E and D. The flyingjunction on the north side is of the oppositetype to that in Fig. 1. There is a smallengine shed at the hump yard, where theyard engine is kept. Note that the cross-over for station E is situated on the eastside of the layout, on the short straightsection within the low-level loop.

Operating a Sun -Ray LampMANY readers have shown a con-

siderable amount of interest in thesun -ray lamp described in our last

issue, and have asked for further detailsregarding the best method of operating it.The lamp can best be fed from a 200- to250 -volt supply of A.C. and should beconnected only to a power point rated tosupply not less than 10 amp. The reasonfor this is that the current is high when thearc is first " struck " by touching togetherthe points of the carbons.

Additionally, it is necessary to connecta fixed resistance in series with the lamp to

TERMINAL

WIRE WOUND ROUNDASBESTOS STRIP

WOODBLOCK

The Particulars Given Below AreEspecially Applicable to the LampDescribed on page 185 last month

prevent too great a current surge when thearc is first " struck." Such a resistancecan be made very simply by using lb.of 20 -gauge Eureka resistance wire ; thishas a resistance of slightly under 28 ohms.The resistance of the carbons is about 2ohms, so that the total resistance of thecircuit is approximately 30 ohms. This

*'\WOODBLOCK

means that the maximum current whichcan flow when the lamp is first started isslightly over or under 8 amps.

A suitable form of construction for theresistance is shown below, where it will beseen that the wire is first made into a longspiral-about in. in diameter-afterwhich it is wound round a strip of asbestossheet, to which a pair of terminals is fitted.The simplest method of forming the spiralis to wind the resistance wire round a pieceof iron rod ; this should be about Ile in.diameter, because the turns will spring outslightly, due to the springy nature of the wire.

L-11111j111111RESISTANCE

CARBONS

These two illustrations show the simple form of construction adopted for theseries resistance, and also show how it is wired in series with the supply andthe carbons. Provided that the correct length, gauge, and kind of wire is usedit is not necessary that the exact form of construction shown should rigidly be

adhered to.


Newnes

HOME

MECHANICBOOKS

ILLUSTRATED

Your interest isbound to be here

THE HOMEWOODWORKER

MODEL BOATBUILDING

THE HANDYMAN'SENQUIRE WITHIN

TOY MAKING FORAMATEURS

25 SIMPLEWORKING MODELS

MOTOR CARUPKEEP ANDOVERHAUL

ACCUMULATORS- CAR ANDWIRELESS

MODELAEROPLANES AND

AIRSHIPS

POWER DRIVENMODEL AIRCRAFT

SIMPLEELECTRICALAPPARATUS

LATHE WORKFOR AMATEURS

OnlyIf- net

From all Eooksellera

NEWNES

r .lecirw Pinning ame

There are several Ways of Playingthis Simple Game, thus addingExcitement and Variety

Fig. 1.-Sketch showingthe complete game.

THIS game, which works from a pocketbattery, costs little more than ashilling, and will provide endless amuse-

ment during the winter months.For a baseboard use a sheet of three-

ply wood about 10 in. by 6 in., although youmay make the model any size to suit your-self. Draw a circle of about 24 in. radiuson your baseboard, and another of If in.from the same centre. Divide these circlesinto six parts by marking off the radiusround the edge of each circle and cut out sixpieces of tin to the shape shown in Fig. 1.These must be nailed or screwed to the baseso as to leave a small gap between eachpiece. When cutting tin, it is always agood plan to make a paper pattern first.The pattern in this case is made by drawingthe circles and dividing them as explainedabove. It will improve the appearance ofthe model if you make sure that the edges

Figs. 2 to 4.-Details ofthe arrow, axle bracket,

and lampholderconnections.

WIRE TO T2of any pieces of tin that you may use areperfectly straight and smooth. If youdo not possess a file, rub the tin on a stone toget a smooth edge. It is well worth yourwhile to take a little trouble in order tomake a model which will look neat and wellfinished.

The ArrowThe arrow is made from tin or sheet brass.

An old pair of scissors will cut tin, but youmay need special shears for sheet brass un-less it is very thin. Make the arrow accord-ing to the size of your circle ; 44 in. by f in.is a suitable size. Cut it to the shape shownin Fig. 2 and punch a hole in the centre.

The axle consists of a nail knockedthrough the baseboard from below. Inorder to make the arrow turn freely and tomake a good contact, cut a piece of tin3 in. by f in. and bend it into a bracket asshown in Fig. 3. Punch a hole in thecentre, slip it over the axle and nail or screwit to the board.

Illuminated Score BoardFirst obtain six small lampholders to take

an ordinary 3.5 -volt pocket bulb and screw

A WIRE CONNECTS Ti TOCENTRE BRACKET

A WIRE CONNECTS -12ID BASES OF LAMPS.

them in position. These can be bought fora few pence, but if you prefer to make themyourself, fix to the base a strip of tin about5 in. by 4 in. Then cut six pieces of tin14 in. by I in. and bend as shown in Fig. 4.Make a hole into which your lamp will fittightly. This may be done by punching ahole with a nail and enlarging it. Nowscrew the six brackets in position so thatthe bottom contact of each lamp will reston the strip of tin. Make sure that eachbracket is separated from the next by asmall gap.

Connecting the PartsSolder, or fix by screws, a wire to each

piece of tin in the circle, and to the centrebracket. The wires are shown by brokenlines in Fig. 1, whilst Fig. 4 makes it quite

WIRE FROMPLATE.

clear how the wires must be connected tothe lampholders. Each wire from thecircle goes to a lampholder, and the wirefrom the centre bracket must be connectedto the battery. Another wire goes from thetin strip under the lamps to the battery. Ifyou have bought your lampholders, connectthe bottom screw of each one to a piece ofwire, which must go to the battery. Thiswire takes the place of the tin strip in thehome-made lampholders.

Connect the wires from the tin plates tothe lampholders, by passing them throughholes and carrying them underneath theboard so that they are out of sight. Remem-ber that in all electrical models, the contactsmust be tight and clean if you want goodresults.

A Sliding ContactYou can make a sliding contact between

the arrow head and the circle by means ofa short piece of copper fie*. The arrowmay be weighted by clipping a pieceof tin round it. This will keep thewire in contact with the tin plates as thearrow turns.

Now make a box by nailing a suitablepiece of wood on each side of the row oflamps and put a cardboard partition be-tween each lamp. For the top of the box,glue a piece of tissue paper firmly in placeand paint suitable numbers over each lamp.


AN ILLUMINATED DOG COLLAR

"WOULD an illuminated dog -collar be

a fit subject for a patent, and doyou think it would have any market value ?

" I have designed some for my own dogs,using different coloured lights to distinguishbetween them, and wondered if the idea wasworth patenting." (E. P., Hants.)

THE broad idea of illuminating a dogcollar is not patentable, but it may be

possible to obtain a Patent for a specificmethod of carrying out such an idea. As noparticulars are given of the method em-ployed, it is not possible to advise furtheras to patentability of the proposed con-struction. The commercial value of suchan invention will depend not only upon thecost at which the article can be sold, butalso and principally upon the way it ismarketed.

AN ELECTRIC GAS -LIGHTER" M Y idea relates to an electric gas -

lighter which ignites the gas by aspark, produced by pressure on a lever.

" The spark is produced by electro-magnets which are worked horizontally alongthe inside of the handle by means of thelever-one pull on the lever making onespark.

" I should like to know if the idea is a novelone, and if I could get a patent on same."(H. C., Forest Gate.)

THE improved electric gas -lighter, ifnovel, would form fit subject for Patent.

One of the earliest electric gas -lighters,some fifty years ago, employed a small in-fluence machine in the handle which wasoperated by gearing set in motion by press-ing a stud.

The case of the handle was of ebonite,which was rubbed to generate an initialcharge and the spark was produced at theend of a tube, forming an extension of thehandle, as in a Wimshurst InfluenceMachine. A more recent invention, sometwenty years ago, for use as a hand -lamp,comprised a small magneto within a casing,similar to a pocket -battery lamp, themagneto was operated by a rack mechan-ism set in motion on operating a pivotedhandle against the action of a spring.

It may be possible to obtain a Patentfor a specific construction of lighter, butas no constructional particulars are givenof the invention, no further useful advicecan be given.

AN AUTOMATIC GEAR -BOX" I HAVE just devised an idea for an

automatic gear -box for a car. It isfriction -driven, and the gear ratio is con-trolled by a governor.

" When on a hill too steep to be taken intop gear, a small lever is moved, which actsagainst the governor, thus causing a lowerratio to be selected." (F. S., Sussex.)

Advice by our Patent Expert.

THE proposed automatic gear -box formotor road vehicles is not broadly novel.

One of the earliest change speed gears em-ployed a pair of coned drums, with eithera belt or a movable disc between them.

The invention at present is extremelycrude, and the object sought to be obtainedhas already been much more efficientlyobtained by means of the " Hayes "friction -gear fitted to certain types of cars.

AN IMPROVED CIGARETTE PACKET" I SHOULD be grateful for your criticism

of my improved design of cigarettepacket, details of which are enclosed, andshould be glad of information on the follow-ing points:

" (1) Do you consider the design suitablefor the requirements of mass production andfit subject matter for protection by patent ?

" (2) If so, would you advise me how toobtain a patent with a provisional specifica-tion.

" (3) What do you consider would be thecommercial value of the idea ? " (W. A.,Kent.)

THEproposed cigarette packing is in-

genious and in reply to the specificquestions :

(1) The packing is fit subject matter forprotection by letters patent. As to thecost of mass production, this is not a matteron which an opinion can be usefully given.There does not seem to be any great diffi-culty in production, but it would possiblybe more expensive than the more usualpackings. Further information as to costshould be obtained from manufacturersmaking this class of goods.

(2) The least expensive way of protectingthe invention would be by filing an applica-tion for patent with a provisional specifica-tion which will give protection for twelvemonths, during, which time it should bepossible to ascertain the value of theinvention.

(3) Provided the production costs are notgreatly in excess of present packings andthe idea is novel it should have a distinctcommercial value, since cigarette manu-facturers are always anxious to obtain aselling advantage over their competitors.

A DIRECT -CURRENT GENERATOR"

lPROPOSE constructing a homopolar

or acyclic generator with the whole ofthe magnetic ironwork laminated, and tosupply the field coil with a suitable speechcurrent, superimposed upon a steady directcurrent. By running the generator up to asuitable speed by means of a prime -mover,I maintain that the armature current col-lected by the two brushes will be a steadyD.C. current, with the speech current, similarto that in the field coil, superimposed uponit, but enormously magnified. The D.C.component could be suitably eliminated,and the remaining speech current passedinto the primary of a transformer to bestepped up or down to the voltage required.

" This, therefore, would be a means ofamplifying a speech current without the use

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of thermionic valves and its associated com-plicated circuits.

" The initial speech current from amicrophone, gramo or radio would then beamplified, by a preliminary valve amplifier,the output of which would be utilised as thefield excitation for the proposed machine.The value of the above device to radio relayconcerns, public address amplifier people,and as repeater apparatus for the GeneralPost Office would be enormous.

" I wish to impress upon you the fact thatthe machine is not the usual commutatortype of direct -current generator but theobsolete one -pole machine which was usedmany years ago as a plating and weldingcurrent generator, the output of which isan absolutely ripple -less direct current andyet does not make use of a commutator.Should you consider the above practical Ishould be obliged if you will give me thenecessary advice on patenting same." (J. G.,Carmarthen.)

THE proposed direct -current generatormodified for the object in view, is thought

to be novel and forms fit subject matter forprotection by Patent.

It would probably be best to have a searchmade for novelty unless the inventor is fullycognizant with the subject matter of theinvention. The invention appears to havegreat possibilities, and if the result ofexperiments prove the correctness of thetheory, it should be a valuable commercialproposition.

CRAZY BUILDINGS(Continued from page 232)

of corridors, halls, rooms, and passages,120 miles of them, to say nothing of 1,200doors and 2,673 windows. The cost wassixteen and a half million pesetas, perhapsequal to six and a half millions sterling to-day, but we could forgive it all if only itwere beautiful. But, alas, it is as ugly asDartmoor prison, which it closely resembles-I have seen both from outside. It is theworld's most striking example of how littlemere money and power can accomplishwhen brains and taste are lacking.

The Empire State BuildingAmerica has some modern white ele-

phants, but-unlike El Escorial-they willbe useful presently, and should pay hand-somely when " Old Man Depression " haspassed away. These are the biggest andlatest skyscrapers, which-owing to thecrisis-stand almost empty. The loftiestof all is the famous Empire State Building,now facetiously called the " Empty StateBuilding," 1,250 ft. high, with 102 stories.It is so high that the top often pierces theclouds and stands in almost perpetual sun-shine. It cost about ten and a half millionpounds in our money, has 6,400 windows,and can provide room for 25,000 officeworkers, to say nothing of their businesscallers.

A NEW HANDBOOK !

Power -Driven ModelAircraft.

65 WattsI 25Watts 22 6240 Watts 37 6

The Solon ElectricSoldering Iron has thestrongest heating elementobtainable. Clamped incontact with the bit, itconcentrates all heat.None is wasted. The Solonsimplifies soldering. It isquicker, easier, moreeconomical and more effi-cient. Plug in-solder inthree minutes.

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RUN YOURMODELS

FROM THE MAINS!!To obtain the utmost satisfaction with miniature Lows.or similar working models, it is essential that the sourceof supply is constant. The Heayberd TRAIN TRANS-FORMER has been designed to give constant power withlow running costs. A variable control is incorporated, enab-ling the model to be stopped, started, or speed increasedor decreased. THESE MODEL TRANSFORMERSCAN BE HANDLED WITH PERFECT SAFETY.

Model T101. Price 27/6Output Maximum 22 volts 3 amps.

Send Now for Free de-scriptive lists, of HeayberdTrain Transformers, RectifierUnits, etc.

F.C.HEAYBERD&CO 10 FINSBURY ST., LONDON E.C.2.

January I 93S NEWNES PRACTICAL MECHANICS 267

A Picture ProjectorKNOWN as the " K.W." Episkop the

device shown on this page will befound suitable for projecting small photo-graphs, cigarette cards, post cards, andviews of small objects, etc., not larger than31 in. x 31 in. Based on the principle ofreflected light projection instead of the old-fashioned translucent method of the magiclantern, this projector can enlarge objects upto 15-18 times their original size. It canalso project leaves, postage stamps, etc.,in their original colours. The " K.W."Episkop is well ventilated and the sides areasbestos lined. Focusing is accomplishedby means of a rack and pinion, and a silver -surfaced mirror projects the picture theright way up. The projector is arranged

The " K.W." Episkop, which projects small objectssuch as leaves, cigarette cards, stamps, etc., in their

original colours.

to take two pictures at once, so that whilstone is being shown, the one that has beenshown may be removed and the next oneinserted, thus avoiding delay. The picturesare held flat and kept in place by metalmasks. Clear glass lamps of 100 watts(4 -watt type) are recommended for use inthe projector. It weighs about 41 lb. andmeasures 71 in. x 4 in. x 91 in. Theprice of the projector, including cable withswitch and plug, picture carrier, and twometal masks is £5 158. [162.]

A neat and attractive thermometer which is similarin appearance to a clock.

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

Quote number at endof paragraph.

A Neat " Thermoclock "THE thermometer shown herewith, which

is not unlike a clock in appearance, isattractively designed in bakelite, and ispractically indestructible. It can be usedeither as a room or bath thermometer. Itsells at the very moderate price of 7s. 6d.[163.]

A m'dget mouthorgan, the size of which can be gatheredby comparison with the matchbox shown.

A Midget MouthorganAGLANCE at the inset sketch will show

the relation in size between a standardmatchbox and this amazing little instru-ment. Although of such midget dimen-sions (it measures 14 in. x 4 in. x it in.) itis possible to play a full octave, and thevolume is quite surprising. Costing la.post free, it is supplied 'in a box but thering shown in the sketch allows the instru-ment to be attached to the watch -chain.[164.]

An ingenious light tester.

An Ingenious Light TesterTHIS extremely useful instrument

measures the intensity of light without thenecessity for auxiliary apparatus of anykind. It consists of a sensitive moving -coil indicator, calibrated in conjunction

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from 3.- to 42THE WILCO " LOW VOLTAGE TRANSFORMERwith speed control, reduces 200;260 vt. A.C. to 2-8 Pricevolts. Capacity 3 amperes. Will drive small 1C/6motors perfectly; also lights bulbs for models, etc. ria,Send for 40,page Electrical Catalogue "P.M." of other Models

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BALLARD, 71Craces Rd., London, S.E.5

with a photo -electric cell. The two arefitted in a polished black moulded case ofhandy size for carrying in the pocket. Asmall three-way switch at the front selectsthe range and, in addition, provides an" off " position. The cell is of the photo-voltaic type, which gives a potential be-tween its plates when light falls on thefront sensitised plate. The instrument hastwo ranges, enabling good reading to betaken of any light intensity from 1 to 250foot-candles, and since direct values aregiven on the scales the instrument may beused by even an unskilled person.It costs £5 15s. Od. [165.]A Glareless LampESPECIALLY designed to abolish glare,

the glass bulb of this lamp is of novelformation. In the first place the bulb is

An electric light bulb specially designed to abolish glare.

moulded and not blown, as is the standardtype of bulb, and thus greater strength isobtained. The moulding is carried out insuch a way that the bulb is studded withtiny crystal -like incrustations, each of whichis shaped to give perfect refraction of light,and it is claimed that these not only diffusebut also magnify the light from within thelamp. They may be obtained in sizesvarying from 15 to 300 watts. [166.]

The Silent "Bell."'NOWN as the " Sordoviso," the device

illustrated hereunder will interesteither those who are deaf or those who dis-like noise. The device is connected withthe electric bell system of the house andthe electric lighting system, so that thebell push operates the lights. A switch

A novel type of " bell."

enables the device to be set for either dayor night operation ; that is, when the bell -push is pressed during the day the lightswill automatically come on for a momentand at night they will flicker in an un-mistakable way.Priced at 4 guineas, it is fully guaranteedand may be installed in a few minutes.[167.]

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WHEN REPLYING TO ADVERTISERSPLEASE BE SURE TO MENTION

"PRACTICAL MECHANICS."


A Review of the Latest Devices for the AmateurMechanic. The address of the Makers of the Itemsmentioned can be had on application to the EditorPlease quote the number at the end of the paragraph.

A Flashlight ScrewdriverTHE advantages of a flashlight screw-

driver are immediately apparent, andits applications so numerous that it shouldhave a place in every tool kit. It puts adefinite spot of light on to the screw beingdriven, yet permits the operator to useboth hands effectively on his work. Thebit is securely anchored in the handle, whichis specially designed for a firm grip. Theinsulated handle is made of the best quality

A combined torchand screwdriver.

fibre, and can safely be re-commended for 110-, 220-,and 440 -volt work. It issimple in operation. To switchon, turn the fibre screw in thebottom cap. It costs 4s. 6d.,including battery. [145.]

A Practical SawTHE difficulty experienced when cutting

large surfaces of corrugated iron,asbestos, ebonite, etc., with an ordinaryhack -saw will be appreciated by those whohave attempted the task. The saw, illu-strated on this page, has been speciallydesigned for this job. The motion ofoperation, as will be seen from the insetsketch, is parallel to the work and thismakes it possible to handle large surfaces.Two sizes are available. The 12 -in. model,with 31 in. depth of cut, is sold at 88. 3d.,whilst the 16 -in. model, with 7i in. depthof cut, costs 138. 3d. Extra blades areobtainable at 48. 3d. per doz. for the smallerand 118. 2d. per doz. for the larger model.All the prices quoted are post free. [146.]

A specially designedsaw for cutting cor-rugated iron, asbestos, etc.

A One -hole PunchUSEFUL for a variety of purposes in

most offices this one -hole perforatorshould also " earn its keep " in the workshop,where it will be found very handy for punch-ing holes in metal foil. Of exceptionallysturdy construction it is designed to punchholes through twenty-five sheets of paperand the solid steel plunger makes a hole

A one -hole punch that will be found suitable fora number of jobs.

is in. in diameter. Two other models for1 -in. and irk -in. holes are available. Theprice is 38. 6d. each, and the carriage is paid.[147.]

Handy Pocket TorchesA SMALL pocket torch is always a handy"thing to carry about. The " Snaplite "is very compact, being flat and measuringonly 3 in. high and about 11 in. wide.There is no external switch, the light beingswitched on by the " snap " lid which alsoforms the reflector for the light. It maybe carried in the pocket, tool -box, anywhere,and will always be ready for use. A choiceof six colourful designs is available. Theprice is 18. 6d., and replacement batteriescost 6d. each.

Another interesting little device whichincorporates the " Snaplite " is the " KeeLite." This is a small fancy -leather casefor carrying keys. The illumination pro-vided by the torch enables one to select theright key on dark nights. Its size is suchthat it takes up very little room in thepocket or handbag. It is made in twogrades at 38. 6d. and 48. 6d. in a variety ofcolours. [148.]

A Midget Electric GrinderSTURDILY constructed, the little electric

grinder illustrated is easily clamped tothe work bench and should prove "a popular

A midget electric grinder.

accessory to the practical mechanic'sworkshop. Operating from A C. mainsit is supplied with 2 yds. of stout rubber -covered cable. The two detachable grind-stones (coarse and fine) are 2 in. in diameterand the switch, neatly mounted on themotor casing is a noteworthy feature.The price is 148. 6d. carriage paid. [149.]

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THERMO-COUPLES" (1) I N connection with your reply to my

earlier letter with regard to thermo-couples. I wonder whether you could letme know the voltage rise per couple perdegree centigrade for the copper-constantonand the brass thermalloy couples.

" By very rough experiment, I found thefigure for copper and iron to be 1/45,000 voltper degree centigrade. Is this correct?

" (2) Would you mind telling me themelting -point of constanton and therm -alloy, as I cannot find them in tables.

"(3) Can the above metals be obtainedin the form of insulated wire? I expectnot, but it would be far simpler thanfixing on loose sleeving.

" (4) Is it correct that soft solder melts at188° C. and bismuth 272° C.? " (K. B.,Winchmore Hill, N.21.)

(1)THE voltage rise per degree centigrade

of a copper-constantanthermo-coupleis of the order of approximately 13,500 micro-volts ( .013500 volt) and for the brass-thermalloy couple about 11,000 microvolts( -01100 volt), the latter figure being subjectto considerable variation in accordance withthe composition of the brass used. Yourfigure of 1/45,000 volt per degree Centi-grade for the copper -iron couple is somewhathigh.

(2) Constantan melts at approximately1,200° C., thermalloy melting slightly abovethis temperature. Such thermo-couples,however, should not be used for tempera-tures above 500° C., since they oxidise orchange in composition at higher tempera-tures. For temperatures above 500° C.thermo-couples of the platinum -iridiumtype are the most successful, although theygive a third less current per degree rise intemperature than does a good copper-constanton couple.

(3) We doubt whether thermalloy can beobtained in the form of insulated wire,but we think that it is possible to obtainconstantan in such form. Enquire at anylarge electrical wholesalers or wirecompanies.

(4) The melting -point of bismuth is 269°C ,Ordinary soft solder melts at approximately180° C., its exact melting -point beinggoverned by the relative proportions of tinand lead present in the solder.

THE THEORY OF BROWNIAN MOTION" (1) COULD you explain the Browning

Theory ? I believe it says that ifyou pour milk and then tea into a cup, themilk and tea will mix much better, than ifyou pour tea and then milk into a cup. Iam not sure that I have got the name right,but I think the principle is correct. Ibelieve it is something to do with the mole-cules of the liquid.

" (2) Is it true that if you pour boilingmilk and boiling coffee into a cup, they willcurdle ?

" (3) I have made an arc lamp from theinside of a battery. I took the carbonrods out, and connected them up to themains, with a heating filament in the circuitin series as a resistance. I find, however,that the carbon rods have to be continuallypushed nearer, as they are eaten away.Could you tell me the cause of this, and howit can be rectified ? Should I use specialcarbon rods ?

" (4) Could you explain how to make asimple apparatus for controlling a boat bywireless, having for preference an inductioncoil in the sending station ?

" (5) What would be the best liquid fuelfor a small rocket, and how could I purchaseit, and what would be it's cost ? " (F. J.,Surrey).

(1)YOU probably refer to the Theory of

Brownian Motion, so-called afterRobert Brown, a botanist, who first drewattention to the phenomena. If a veryfine suspension of solid particles is made inwater or in any other liquid and is examinedunder a high-powered microscope, theindividual particles of solid matter sus-pended in the liquid will be seen to be ina state of continual motion and vibration.Similarly, if a cloud of tobacco smoke ispassed into a glass cell and examined underthe microscope, the individual smokegrains will be seen to be in a state of con-tinual movement. Many theories havebeen suggested to account for these andsimilar phenomena, but the theory nowuniversally accepted is that the solid par-ticles suspended in a liquid or in a gas (air)are maintained in a state of haphazardmovement owing to the motions of theactual molecules of the liquid or gas. Theyare, as it were, tossed about here and thereby the moving molecules.

The Theory of Brownian Motion is alliedto the Kinetic Theory of matter whichpostulates that all matter is in a state ofperpetual motion and vibration. If twoliquids are mixed, the particles or moleculesof each liquid intermingle with those of theother liquid. It is easier for this inter-mingling of molecules to take place betweensome liquids than between others, but wethink that in the example of the mixtureof tea and milk which you refer to the easieradmixture (if any) of tea infusion added tomilk is due not to molecular influences butto the physical nature of the particles ofmilk -substance coagulated by the teatannins.

(2) If boiling milk and boiling coffeeinfusion are mixed, true curdling of themilk will not take place. The mixedliquids, however, will form a surface skindue to the coagulation of the milk albuminsby the heat and by the coffee tannins.

(3) When an electric arc is struck betweentwo carbon rods, the ends of the rods in-variably wear away, one forming a de-pression or crate and the other a point.


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This effect is due to the volatilisation of thecarbon by the intense heat produced. Also,some of the carbon is actually burned awayto carbon dioxide gas. There is no meansof avoiding the wearing away of the carbonelectrodes. Professionally made arc lampscontain devices whereby the carbon elec-trodes are continually kept at the samedistance apart, one carbon being fed for-ward as it wears. Such devices may behand -operated or controlled by electro-magnetic means or by mechanicalarrangements. The commonest carbon rodadjustment is, of course, by means of ahand -operated screw, as used in opticallantern arc lamps.

(4) There is no simple apparatus forcontrolling a boat by means of wireless. Itis, of course, quite possible to accomplishsuch a feat, but the apparatus required iscomplicated and it is obviously impossiblefor us to describe here the working detailsfor the construction of such radio apparatus.

(5) You cannot use a liquid fuel in a smallhome-made rocket. Some experimentalrockets, designed and constructed on afairly large scale have used liquid fuelsconsisting of petrol and liquid oxygen.Such fuels, however, require very specialprecautions and it is quite impossible forany ordinary amateur constructor to makeuse of them.

REPLIES in BRIEFD. 0. B. (Saltburn).-The formula re-

quired for determining the exact number ofturns of wire per volt is an involved one anddepends upon the user having knowledgeof the structure of the particular type ofiron employed, the length of the magneticcircuit, the weight of metal, and so on. Forthis reason, we consider that it would not

you the completeformula and suggest that you adhere tothe " rule of thumb " method outlinedin the article to which you refer, i.e. withcore 1 in. cross-section use eight turns pervolt at 50 cycles.

Stalloy stampings are obtainable fromthe Lumen Electric Co., 19 ScarisbrickAvenue, Litherland, Seaforth, Lancs.

F. H. (Sheringham).-It is impossible totell you how to attach the plywood withoutdetails of the construction. Why not adoptthe methods used in connection with the" Flying Flea ? "

E. W. J. (Northfleet).-The discs areprobably obtainable from C. Baker Ltd.,244, High Holborn, W.C.1.

F. McV. (Manchester).-We cannot traceany publishers of blue prints or booksgiving the information you require.

F. E. P. (Birmingham).-Without know-ing the make of headphones, it is impossibleto advise you. It is extremely probablethat the letter " P " is merely a typenumber.

H. F. (Dublin).-Details of how to build the" Flying Flea ' have appeared in our issuesdated October,November, and December.Back issues ill be sent to you for 70.each, post free. You can easily convert thedimensions by remembering that there are2.54 centimetres to an inch and 25.4 milli-metres to an inch.

H. C. 0. (Watford).-Plans of the " Petrolfrom Coal ' model are not available.

B. J. (Welwyn).-The converted motor-cycle engine will be unsuitable for the" Flying Flea." We do not recommend youto use an engine below 15 h.p. Unfor-tunately, we cannot undertake to modifythe design to suit individual materials andequipment.

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Obtainable from Stores, ToyDealers, Stationers, etc., orin case of difficulty from the

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