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Aviation History
1939
1939 - 0674.PDF
238 FLIGHT. MARCH 9, 1935 Iw**** tain. The Bristol Company met this requirement by the 118 h.p. Lucifer, which was type-tested in 1922 ; and in 1925 a 100-hours type test was completed by the 140 h.p. Lucifer IV. The smallest Bristol aero engine ever built was the two- cylinder horizontally opposed 33 h.p. Cherub, developed in 1922-23 from the Bristol flat-twin stationary unit. The Cherub, which had a capacity of 1.095 litres, passed its type test in 1924 and won six out of seven prizes (including every first award) in the Light Aeroplane Trials at Lympne in September of that year. The next year saw the Cherub again aid in carrying off eight prizes in a similar competi tion at Lympne, including one for the greatest altitude (11,900ft.) and the first five places in the handicap races. An improved version, giving 36 h.p. and known as the Cherub III, appeared in 1925, and after completing its 100-hour type test was put into production for a large variety of light aircraft. Bpth direct-drive and geared versions were made. A few Cherubs are still in existence —in Australia, we believe—and the Bear^more Wee Bee monoplane is still airworthy. The year 1923 saw the introduction by the Bristol Com- Forged cylinder heads characterised the " F " Series of Jupiters which were introduced in 1929. On the left is a typical geared "F "-type Jupiter and above is a close-up of the first forged cylinder head. pany in the Jupiter VI of the two-piece crankshaft and one- piece master rod, giving more robust construction and larger bearing surfaces. By this time the Jupiter was giving 485 h.p., but reliability was certainly not being sacrificed to performance, as was proved when a produc tion unit fitted, incidentally, with a Bristol Triples carburetter, was taken from stock, installed in a Bristol Bloodhound, sealed and flown for 250 hours (representing over 25,000 miles) without the necessity arising for break ing the seals or making any replacements. Later this engine figured in a flight from London to Cairo and back, the time for the 6,000 miles being 60 flying hours. High'Compression Research Two versions of the Jupiter were now developed, one being a Service type with the high compression ratio of 6.3:1, while the other, with a 5:1 compression, was adopted by Imperial Airways for service on the Empire routes. That was in 1926. As far back as 1923, also, it had been realised that there would inevitably be a demand for engines which could maintain their power at altitude. They way in which this could be achieved was known theoretically, but it was clear that much development work would have to be done before the supercharger, the real solution of the problem, could become an accepted and standard engine component. In the meantime, some of the advantages of the supercharge engine could be obtained in a very simple way by increas ing the compression ratio. There were obvious limitations, such as the need for throttling at low altitudes, but that was the price which had to be paid for the better power at height of the high-compression engine One of the two Jupiters developed was, as already stated, of the high-com pression tvpe. While meeting the need for reducing the drop m power with height by sup- Forerunner of a range of nine-cylinder radials which have met witn outstanding suC^," The first Pegasus (««)• • Baffles indicate the use of a ring cowling- The cylinder shown is from a two-spee super charged Pegasus xvi' of to-day s—/--flWWf :
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