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Aviation History
1942
1942 - 0974.PDF
45o FLIGHT MAY 7TH, 1942 POWER UNITS OF THE FUTURE tion achieved with reverse-flow cooling speaks louder than words for Halford's dictum. The H-24-cylinder Naprt?r Sabre engine of 2,350 h.p. is likely to go into action soon and its performance will be watched with great interest on this side of the Channel and probably a great deal of consternation on the other. No particulars of any new Bristol engines are yet available for publication, but we may rest assured .that Sir Roy Fedden has not been idle. The Bristol Hercules has been in existence now for many years and is giving excellent service in many types of aircraft. Since the Stirling mounts either Hercules or Cyclone 14 engines of the same power, a definite appjjrfsal of the relative merits of sleeve and poppet valves under similar condi tions is now possible. Before the fall of France, it was known that the French had a number of new engines in preparation, including a liquid-cooled 24-cyUnder multi-bank (6 banks of 4 cylinders). There was also the opposed 16-cylinder liquid-cooled Bugatti engine reputedly suitable for wing- submerged installations. Recently, the design of the Hispano-Suiza V-12 engine has been brought up to date and the power stepped up to 1,500 h.p. ; a further in crease of power to 2,000 h.p, is anti cipated for this engine, wjrtfch has a displacement of 36.07 litres. . The H-24-cylinder liquid-cooled His- pano of 72.14 litres originally rated at 2,400 h.p., may be increased to nearly 4,000 h.p. within the next few years. A prominent Frenchman once said, " War is the National Industry of German -." I do not think that there are many among us who are likely to. quarrel with that statement. So it is that when the Germans de sign engines they design war engines pure and simple. Although the French developed the first moteur canon in 1918, a V-8 Hispano, the Germans got hold of the.^idea and I suppose that 95 per cent, of their first-line engines are of this class. Again, with war in mind, they developed petrol in jection so that their engines would operate in any atti tude and would not cut out under the influence of negative g. Owing to their lack of alkylate, a vital ingredient of the higher-octane fuels obtained from natural gas or by-products of petroleum cracking, they concentrated on large engines with copious swept volumes which would tend to obstruct the pilot's view if mounted upright; the engines^were therefore inverted. Finally, they standardised o/ra bore dimension of 150 mm-, and cut out all "spit and polish." German Claims Germany now claims to be producing in large numbers the most powerful engine in the world, for which they also claim a vtry low specific fuel consumption ; they further claim to be producing an entirely satisfactory exhaust turbo engine. The new German engine is almost certainly a Mercedes-Benz, possibly an H-24 of about 70 litres, developing perhaps 3,200 h.p. The Heinkel 177 heavy bomber was until very recently thought to mount four Mercedes engines in two tandems, but the latest information suggests that the 177 actualjiy Wright Double Row Cyclone GR.2600-A5B. A 14-cylinder air-cooled radial with two-speed supercharger. Take-off power 1,600 h.p. and 1,275 h.p. at 11,500ft. Later models have increased the take-off to 1,700 h.p. Hispano-Suiza 90. An H - type 24 - cylinder iquid-cooled engine with two superchargers and 12 carburettors. From a capacity of 72 the power output is 2,000 h.p. at 2,400 r.p.m. mounts two "Unitwin" H-24-cylinder engines, which may or may not drive contraprops. The overwhelming-. merits of such an installation should surely now be apparent to all designers. One of the most interesting of the new Italian engines is the air-cooled inverted V-12 Isotta Fraschini Gamma. The take-off power of this engine has been given at 1,700 h.p. at 2,200 r.p.m. To develop such a high out put at such moderate r.p.m. it is suggested that the swept volume of this engine exceeds 50 litres. In the past, the Italians have used a bore dimension of as high as 175 mm. ; with the most widely used bore/stj*fKe ratio, the cylinder dimensions might, well be: bore, 175 mm. ; stroke, 192.5 mm. ; displacement, 55.562 litres. • As previously mentioned, there arc many advantages gained by designing an inverted V-12 engine ; even with a displacement of 55J litres, the Gamma engine appears eminently suitable for single-seat fighter installations or light attack bombers. Both Russia and Japan are producing excellent engines from all reports. It is possible that Russia may shortly cease altogether from building foreign engines under licence, due to their now inadequate performance, and concentrate entirely on engines of Russian design-;
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