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Aviation History
1924
1924 - 0339.PDF
MAY 29, 1924 filGHf ™ N—*rttsi¥ir>* ^ litre) per horse-power per hour, and the oil consumption 0-03 pint (0-017 litre) per horse-power per hour. This engine has direct drive. No figures are available yet relating to power and speed. THE BRISTOL " CHERUB " WE have been fortunate enough to secure from the Bristol Aeroplane Co. the accompanying photographs of the new Bristol " Cherub " light 'plane engine. These photographs have not been published before, and show the engine as it will appear in the 1924 light 'plane- trials. Unfortunately, space does not permit a detailed description of this engine in the present issue of FLIGHT, and such description must be reserved for a future occasion. The following brief par- r " 1 ' 120 110 100 90 6b 34- 32 30 28 26 24 22 20 18 16 14- r ' es -60 •55 50 1600 2000 2400 2800 3200' R.P.M. 3600 4O00 4400 Power and petrol consumption curves of the Bristol "Cherub." ticulars should, however, give a fair idea of the " Cherub." which, it should be noted, has been specially designed for use in light aeroplanes. The bore and stroke of the " Cherub " are 85 mm. and 96 • 5 mm. respectively, giving a total capacity of 1,095 c.c. The compression ratio is 5-5 to 1, and the engine- develops 22 b.h.p. at a normal speed of 2,500 r.p.m. The maximum per missible speed is 4,000 r.p.m. when the engine develops 34 b.h.p. At normal revolutions and power the " Cherub " consumes 1 -4 gallons (6-38 litres) of petrol per hour, and 0-5 pint (0-28 litre) of oil. The weight of the "Cherub" is 81 lbs. (36-8 kgs.). It is of interest to mention that the older type of " Cherub has some extraordinarily good performances to its credit. Thus, for one thing, it was the first small engine to pass the Air Ministry type tests, which are of a very searching charac ter. Also, fitted in a racing car on Brooklands race track, the " Cherub " engine had a gruelling test in the 200 miles (320 km.) race, when it was kept running at full power for three hours. In connection with the type tests, it should be pointed out that during these the " Cherub " completed a 50 hours' non-stop run at 90 per cent, of the full power. Few large aero engines, and certainly no engine of such low power, have ever accomplished a similar performance, which is one of which the Bristol Aeroplane Co. may justly be proud. The new "Cherub" has not, as far as we are aware, been put through such strenuous officially observed tests, but there is little doubt that the new " Cherub " will worthily uphold the Bristol reputation. It is expected that the new engine will be seen in several of the two-seater light 'planes being entered for the September competitions at Lympne. In addition to the direct-drive model, the Bristol Aeroplane Company are marketing a geared type in which the propeller is driven at half the engine speed This engine is slightly heavier than the ungeared model, weighing 105 lbs. (47-7 kgs.). In certain machines, however, where it is desired to have very good propeller efficiency, it may be worth while fitting the slightly heavier geared model. A feature not usually found on aeroplanes has been incor porated in the Bristol " Cherub." This is in the form of an impulse starter, by means of which the pilot will be able to start his machine without requiring outride assistance. THE COVENTRY VICTOR " GNAT." BLOW we give a photograph of the Coventry Victor " Gnat " light 'plane engine. We have been unable to obtain from the makers any data relating to this engine, beyond the fact that it is stated to be rated at 10-38 h.p. This would appear to indicate that the horse-power, according to the R.A.C. rating, is 10 h.p., while the engine actually develops 38 b.h.p. It will be seen that overhead valves are employed, and that the valve gear is of somewhat unusual type, or, at any rate, the cages surrounding the valve gear. The engine looks very neat, and is stated to be of very simple construction capable of hard work for long periods." Further information will be awaited with interest. The Coventry-Victor " Gnat " light 'plane engine. 339
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