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Aviation History
1934
1934 - 0085.PDF
FLIGHT, JANUARY 25. 1934 THE CRANKCASE AND ITSCOVER : The crankcase is • carried on eight steel-backedwhite-metalled bearings. Like the crankcase, the top cover isof Electron, and carries the magnetos, distributors and their•driving shaft. (FLIGHT Photos.) than the " Gipsy Major "instead of being two cylinders longer. The new drive forauxiliaries introduced fresh problems. To guard against freezing,a novel and very ingenious scheme was evolved. Theflame trap in the induction system is provided with a flapvalve so arranged that at full throttle the valve cuts off com-munication with the flame trap and joins the carburettorto a duct facing into the air- screw slipstream. Thus at fullthrottle the engine is supplied with cold air and the loss ofpower from the flame trap and warm air is avoided. Atcruising speed, or when throttled down, the enginedraws warm air from inside the engine cowling throughthe flame trap, and all risk of freezing is avoided. Thecontrol is linked to and operated by the throttle. It will be realised that therewere many other problems to solve, and that it was not justa matter of making the crank- case a little longer and puttingexisting " Gipsy Major " parts on it, but sufficient has beensaid to indicate that to produce the new engine in soshort a time was something of an achievement. A detailed specification of the " Gipsy Six " will befound below, but the main features may be summarised as follows: The engine is a six-cylinder inverted air-cooled,with a bore of 118 mm. (4.646 in.), a stroke of 140 mm. (5.512 in.), and a capacity of 9,186 cc. (560.6 cu. in.).The normal power is 184 b.h.p. at 2,100 r.p.m., and the maximum power 205 b.h.p. at 2,350 r.p.m. The com-pression ratio is 5.25:1, and the weight of the engine, complete with airscrew boss, fuel pumps, and cylindercowling, but without starter or generator, is 432 lb. The fuel consumption at full throttle at 2,350 r.p.m.is 15 gallons per hour, and the specific petrol consump- tion at cruising power is 0.55 pints per h.p. per hour. At normal r.p.m. the oil consump-tion is 3-4 pints per hour. Compared with a specificweight of 2.3 lb./h.p. max. of the " Gipsy Major," the" Gipsy Six " weighs but 2.11 lb./h.p. max. Thefrontal area is to all intents and purposes the same as thatof the four-cylinder engine, while the balance is, of course,better and the torque more even, a fact which is obviouswhen one sees these engines running in the D.H.86, wherefour of them are mounted on the leading edge of the lowerwing. GENERAL DESCRIPTION The (iipsy Six is a six-cylinder, in-! verted, in-line type of air-cooled engine. Cylinders.—The cylinder barrels aremachined all over from carhon steel forcings. Special attention has beendirected to the graduation of wall thick- ness and depth of finning in order thatdistortion may be avoided and an even cooling effect obtained. The ends ofthe barrels project deeply into the interior of the crankcase and so providean ample capacity for oil drainage with- out danger of flooding the pistons. Anoil-tight joint is assured by the use of a dermatine ring which is trapped ina recess between the cylinder flange and the crankcase face. The exposed sur-faces of the cylinders are specially treated against corrosion. Cylinder Heads.—Detachable heads cast in aluminium bronze are heldto the cylinder barrels by long high-tensile steel studs extending from the crankcase. A gas-tight joint is maintained between the head and barrel by theinterposition of a copper and asbestos washer located in a recess in the; cylinder head. The two valves for each cylinder are arranged vertically and have,seatings machined directly in the material of the cylinder head. Dual ignition is provided for each cylinder by two 12 mm. sparking plugs, whichare located on" on each side of a compact combustion chamber. The excellent form of the cylinder head permits of smooth but rapid combustion,and all standard Gipsy engines will operate successfully on good grade automobile fuel. The finning has been carefully arranged so that, with theadequate area provided, effective cooling is a straightforward matter on any aircraft. Pistons.—Slipper type, cast in heat-treated aluminium alloy (Hiduminium)to D.T.D. specification 131. The piston is so designed that the thrust from the crown is taken-direct to the gudgeon pin bosses and is not transmittedvia the skirt. Fully floating gudgeon pins are located at each end by external CRANKSHAFT AND CAMSHAFT : The latter is driven from the front end of the former. 85 (FLIGHT Photo.)
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