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Aviation History
1931
1931 - 0099.PDF
JANUARY 30, 1931 THE AIRCRAFT ENGINEER SUPPLEMENT TOFLIGHT The 100-b.p. inverted " Chaise " engine. (FLIGHT Photo.) -icond and fourth cylinders, are set at a very smallj vee angle ii one another so as to reduce the overall length of the engine and yet keep the frontal area small. The engine is inverted Hi give a clear view. The crankcase and cylinders are of ast iron, the cylinder heads of aluminium and the pistons of magnesium. The crankshaft is built up to peimit the assembly "f the connecting rods, which are carried on double roller hearings. Windows are fitted on the top of the erankcase >ver so that inspection of the interior may be made. A •ature of this engine is the elimination of all pipe work, • xcept that for the petrol feed to the carburettor. ATo petrol "i' oil pumps are fitted, the lubrication being done by special am throwers rotating in the crankcase and dipping into the nil reservoir. A distance of 2,000 km. is estimated on one I'plenishment of oil. A current of air for cooling the oil is arranged through the crankcase by means of breathers. Water-cooled engines were mostly of the twelve-cylinder ''( type. For very large powers the double vee arrangement "i cylinders was used in three banks, each of four or six Winders for the 12- and 18-cylinder engines respectively, '•' for small powers the single line of four or six cylinders was ••'st common. An engine with a slightly unusual arrangement of cylinders, but at the other end of the scale from the Chaise engine as regards power, is the Hispano Suiza 18-cylinder, 1,000-h.p. engine. In arrangement it resembles the early Sunbeam Viking engine, and has three banks of six cylinders, each forming a very broad arrow, the angle between the banks being 80°. The balance is very good and the engine has an even firing order. The torque curve should be very smooth, due to the large number of cylinders employed. Nitrogen- hardened cylinder liners are used, and, in accordance with the firm's standard practice, three carburettors are fitted on the side of each block of six cylinders. It is stated that the engine gives more than 1,600 h.p. when naturally aspirated at a compression ratio of 10 to 1 and a speed of 2,400 r.p.m. (The Hispano Suiza Company is not yet seriously converted to supercharging, although one of their smaller engines is now fitted with a gear-driven centrifugal compressor.) Recent experimental work in this country and elsewhere has indicated the possibilities of evaporative cooling, and also the use of high temperature coolants to reduce the radiator drag and give consistency of engine operation, but none of the water-cooled engines shown was stated to have been operated under either of these conditions, nor was there any suggestion that development work along these lines was proceeding. Few inverted engines were shown, there being, besides the Hispano-Suiza is of the Type. (FLIGHT Photo.) Broad Arrow' The 500-600 h.p Siemens-Halske S.H.20. (FLIGHT Photo.) Chaise engine already mentioned, only the Farman eight- cylinder vee engine and the 12- and 18-cylindei double vee engines of respectively 350, 550 and 600 nominal horse-power. These engines are fitted with the well-known Farman reduction gear, so that the airscrew shaft is in line with the crankshaft. Inversion, therefore, gives the same freedom from obstructed view when installed in an aircraft, as would be obtained by the same treatment of a direct drive engine. The necessity to ensure a clear view and at the same time to obtain an easilv streamlined engine form is met in another way by the Rolls Royce series of engines. These are of the 12-cylinder water-cooled vee type, in which a straight spur wheel reduction gear is used to bring the airscrew shaft into a position practically central, looking from the front, with the whole engine. As the engine is particularly compact in arrangement, good streamlining can be obtained with no obstruction to the pilot's view and the difficulties attendant on an inverted design of engine are avoid 'd. As regards the choice between geared and ungeared engine^, British constructors in many of their later designs are 96e
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