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Aviation History
1926
1926 - 0145.PDF
MARCH 4, 1926 Test Runs Among the tests carried out at the Waddon Works of A.D.C. Aircraft Ltd., it may be mentioned that on the two 10-hour runs at normal r.p.m. of 1,450 and 90 per cent, of the rated power (270 b.h.p.), the average petrol consumption was 140 pints (79-5 litres) per b.h.p. per hour, which is equi- valent to 0-52 pint (0-295 litre) per b.h.p./hour The fuel used was Shell aviation spirit with the addition of 20 per cent, of Benzol. As being more representative of actual flying conditions, an endurance test of 35 hours (also officially observed) was completed on the calibrated airscrew, without a mechanical 42 mins. ; " Nimbus," 24 mins. Max. ceiling • " Puma,"15,500 ft.; "Nimbus," 19,500 ft. The speeds obtained with the two engines were :—Groundlevel: " Puma," 115 m.p.h. ; "Nimbus," 134 m.p.h. ; at 10,000 ft. : " Puma," 109-5 m.p.h. ; " Nimbus," 121 m.p.h. ;at 15,000 ft.: "Puma," 102-5 m.p.h.; "Nimbus," 114 m.p.h. It will thus be seen that the extra power which Major Halford has succeeded in getting out of the " Nimbus " has a very marked effect upon performance when the engine is fitted in the D.H.9. A similar gain would undoubtedly be obtained in other machines, and the " Nimbus " is a striking THE A.D.C. " NIMBUS " AERO ENGINE: Some constructional details. 1 shows one of the Duralumin dogs holding down the cylinders, while just below the end of the water jacket may be seen the locking strap device of the watertight joint, details of which are shown in 2, in which the castellated split ring is of phosphor bronze and is threaded internally to engage with the threads on the cylinder barrel. 3 shows an exhaust valve with its rocker, and in 5 is indicated diagrammatically the manner of locking the steel liner to the cylinder head aluminium casting by means of the valve seating. The latter is shown in 6, while in 7 is shown the special tool used for locking the valve seating. failure, at normal r.p.m. and 270 b.h.p. During this test the average petrol consumption worked out at 0-535 pint (*>-303 litre) per b.h.p./hour. Prior to the 20 hours a power curve was officially checked hy Air Ministry officials, the results being given in the table ut end of this article. In order to obtain a basis for comparison, a D.H.9 has been t'-sted with full load, both when fitted with the standard '' Puma " and with the " Nimbus " engine, when the follow- ing results were obtained : Climb to 6,500 ft.1( >-3mins. ; " Nimbus," 7-7 mins. To 10,000ft. 18-8 mins. ; " Nimbus," 12 mins. ; to 15,000 ft. Puma,"Puma," Puma," 125 proof of the opinion advanced by Commander J. Hunsaker during a lecture at the R.Ae.S., when he stated that although there might not be any great gain in reducing the weight of existing engines, there would be an immediate gain in keeping the engine weight and size the same, but increasing the power. In the " Nimbus " the remarkable features are : the low weight per h.p. (under 2 lb.), the low fuel consumption, the relatively low engine speed (1,450 normal, 1,600 maximum), and the very small frontal area, which latter allows of an engine installation offering a small head resistance. As to the scope for an engine of this type and power, and bearing in mind that the engine has been designed to be pro- 0D
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