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Aviation History
1927
1927 - 0660.PDF
SEPTEMBER 1, 1927 By far the most interesting exhibit on the French stand was the new Farman inverted engine, which made its first public appearance on this occasion. This engine is believed to mark a distinct step forward in the history of French aeronautics, and consequently it is intended to give a fairly full description of it here, although sufficient information was not available for us to be in a position to give all the details that might be of interest. Doubtless when the engine has been through its preliminary development period, the Farman firm will supply us with further information, which we shall then be pleased to place before our readers. In the meantime it might be pointed out that for most of the data published below we are indebted to an article reprinted from our excellent French contemporary L'Aifonautique, and handed to us on the Farman stand at Copenhagen. considerable interest not only in France but throughout the aviation world. The immediate result of this attempt is a new engine, the Farman type 18 "\Y-1, which develops 550 h.p. at 2,800 r.p.m., and a propeller speed of 1,100 r.p.m., while giving a maximum output, at 3,400 r.p.m., of 730 h.p., for a total weight, in running order, and including all equipment, but without cooling water, of 421 -8 kg. (927 lbs.). By choosing the inverted type of engine, the Farman works believe to have achieved certain other advantages, such as large propeller clearance, allowing of a propeller of greater diameter, or conversely permitting a lower undercarriage. Also, it is claimed that the induction system is simplified, since shorter pipes can be used, while the low position of the carburettors permits of using direct gravity feed. The THE NEW FARMAN INVERTED ENGINE : Of the 18-cylinder " broad arrow " type, this engine develops. 700 h.p. at 3,200 r.p.m. for a total weight in flying order, but without water, of 421-8 kg. (927 lbs.). The Farman planet reduction gear permits of this high speed without sacrifice of propeller efficiency. In designing their new engine the Farman engineers were encouraged to go for higher powers by increasing the speed rather than by adopting larger cylinder dimensions. It was thought that this course was justified by the success attained with the Farman planetary reduction gear, which has given excellent results on older types of Farman engines, and has won recognition abroad to the extent of being adopted, among others, by the Bavarian Motor Works for their new B.M.W. engines. Starting with the supposition that their reduction gear (supplied in several standardised ratios) is now such that reasonably good propeller efficiencies can be maintained even with relatively high engine speeds, the Farman works proceeded to develop their new inverted engine, holding the view that the advantages of increasing the power by speed and not by dimensions would justify such a course. Among these advantages are claimed the following: small and light moving parts, good "^induction arrangements, small bores and strokes, the possibility of using fairly high compression, moderate piston speeds absence of vibration, and last, but not least, good reliability. Whether these advantages have been fully realised only the future can show, but at any rate the attempt is one of very valves are very accessible while the engine is in a machine, since they can in most cases be reached without the use "I ladders. When the top of the crank-case is removed, the crank-shaft is readily reached for inspection, etc., and a water header tank can be placed inside the engine cowling, thus avoiding one more projecting accessory. The objection usually raised against the inverted engine, that the sparking plugs of the " hanging " cylinders are apt to become oiled-up, is claimed already to have been solved in the case of the lower cylinders of a radial engine, so that there does not appear to be any reason why the inverted water-cooled should be any worse off in this respect. . The 18 cylinders of the new Farman engine are arranged lij three banks of six each, as in previous " right way up ^ Farman engines, and have a bore of 110 mm. and a stroke cu 125 mm., which compare with 130 mm. and 160 mm. respec- tively of the previous type of 500-h.p. engine. One result of the small cylinder capacity has been that a high compressi >:i ratio can be used (about 6 to 1). In spite of the high spee", of revolution, the piston speeds are no higher than those of tn earlier 500-h.p. engine, i.e., about 11-7 metres (38-4 ft.) P« second. The cylinder blocks are Alpax castings, with ST 606
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