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Aviation History
1931
1931 - 1065.PDF
FLIGHT, OCTOBER 2, 1931 Those who helped to make It possible ALTHOUGH the bulk of the credit for securing theSchneider Trophy permanently for Great Britainmust naturally go to the makers of the enginesand machines, neither would have been possible of realisationvvithout the very wonderful materials, accessories and equip-ment which went into machines and engines. Before these couldbe built, and even before they could be designed, the aircraftand engine designers had to have the knowledge, not only thatthey were available, but that when they were delivered to them,be they raw materials or finished articles, they would be up to thespecifications that had been given them. No smallest piece ofmetal might be the least fraction under strength, and no instru-ment or accessory fail in the slightest degree. It is, therefore,fit and proper that some refer- ence should be made here to thevarious British products which, when formed and assembled,gave the world that beautiful entity the Supermarine Rolls-Royce S.6B, which has raised the prestige of British aviationand engineering throughout the world. Beginning with structuralmaterials, Thos. Firth and John Brown, Ltd., of Sheffield, were responsible for the specialalloy steels used in the reduction gears, connecting rods, cam- shafts and gudgeon pins of the Rolls-Royce " R " engines,as well as for the H.R. Crown steel from which the valves were made. All these are highly-stressed parts, and onlythe best materials were good enough for them. The crankshafts which had to transmit the power im-pulses from the pistons were called upon to deal with enormous torque loads and to convert recipro-cating into rotary movement at speeds as high as 3,200 r.p.m., and at a power output of2,300 b.h.p. Yet minimum weight was to be aimed at. Made of English Steel Corporationhigh-tensile alloy steels, and forged by the English Steel Corporation, the crankshafts ofthe " R " engines stood up to their task man- fully. Of other metal parts used in the Rolls-Royce' K " engines it may be mentioned that the i ll l k B.T.H. Magneto, type SC.12-7C.2, as fitted in the Rolls-Royce "R" Engine. K Magnesium alloy valve rocker covers and waterjacket elbows were supplied by British Maxium, Ltd., while hot brass pressings weresupplied by Wilcox & Lines, Ltd., and Eatonia " bronzes by Yorkshire EngineeringSupplies, Ltd. Ball and roller bearings were necessarily subjected to extremely heavy loadsm an engine of such high power, running at what is a very high speed for an aero engine,flie Hoffmann Manufacturing Co., Ltd., sup- plied the bearings for this year's machines,which was natural in view of the fact that that company had already supplied the ballant; roller bearings for the 1922, 1927 and 1929 Schneider engines, and they had given everysatisfaction. That they did so again this year is wident from the trouble-free running ofttit engines both in the Schneider Contest and m t'ie flights over the 3 km. straight-line speed coi-rse. Vl ith fuel being consumed at such a very high rate, aj!i with high stresses imposed by the sharp turns at high j? , f> the fuel supply becomes a very serious problem.fu"i had to be lifted, in the S.6B machines, from the floats 0 - pressure tank in the fuselage, and the resulting length " NO TROUBLE OFANY KIND : One of the Lodge X 170 plugsfitted in the Rolls- Royce " R " Engines. of fuel pipe line was necessarily long. " Petroflex " tubingsupplied by Hobdell, Way & Co., Ltd., once more stood up to the work admirably, the " unbreakable " qualities claimed for it by the makersbeing fully realised. While on the subject of fuel,reference should be made to the use once more of Pratts' EthylPetrol. It must be remembered that in racing engines such asthe Rolls-Royce " R " type, a very high compression ratio isused in order to get a maximum of power out of an engine ofminimum weight. Ordinary " straight " fuel would not havebeen usable with such high com- pression ratios, and detonationwould have set in before the machines could get into the air.By a special mixture of fuel in which tetraethyl lead was an in-gredient, the rate of combustion could be controlled, and detona-tion avoided. " Ethyl " has now become world-famous andquite familiar to every motorist, but never has its combustion-controlling qualities played a greater part in any success thanit did in the Schneider machines. The conditions under which aracing engine like the Rolls- Royce " R " worked in theSchneider Contest and over the straight-line course are obviously extremely severe, and theignition system must be up to the same high standard as the rest of the equipment. In the actual machines used, B.T.H.magnetos were fitted. These were of the SC. 12-7C.2 type, of that distinctive class of high-tension magneto known asthe " polar inductor " type. This magneto is provided with a stationary armature in which the current is gene-The two magnets are of cobalt steel, having extremely high magnetic characteristics.Before being fitted to the Rolls-Royce engines the B.T.H. magnetos were subjected to severetests. They were run up to 7,000 r.p.m., at which speed they were producing sparks at therate of 28,000 per min. This test was, of course, far in excess of what was actuallyrequired in the engines. If the magnetos had a strenuous time of it,the sparking plugs had possibly an even more difficult task. The Lodge plugs, type X 170,used in the Rolls-Royce " R " engines were specially designed for the engines, but thedesign was based upon the normal Lodge air- craft plugs. In the notes released for publica-tion by the Rolls-Royce firm, a high tribute is paid to the Lodge plugs, which, it is stated,gave no trouble at any time. To design airscrews to absorb efficiently suchnigh power as that developed by the Rolls- Royce " R " engines is a serious problem, butthe Fairey Aviation Company's propeller department was equal to the task, and theFairey metal airscrews produced a good com- promise between the conflicting requirementsof good efficiency at full speed and sufficient thrust at low speeds to get the aircraft overthe " hump." More recently the Fairey com- pany has produced the metal airscrew whichwas fitted to the specially " boosted " engine in the S.6B on which Stainforth established a new world'sspeed record of 408 m.p.h. For this flight something like 2,600 h.p. was taken from the engine, and the Fairey metalairscrew designed for this flight must have absorbed a greater power than was ever before absorbed by a singleairscrew. rated. 995
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