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Aviation History
1929
1929-1 - 0382.PDF
FLIGHT, JULY 18, 1929 fiach rocker spindle carries one inlet and one exhaustk; r, each push rod having therefore to operate two rockers, lone on each spindle. The inner arms of the two rockers oper- latinc similar valves are fitted one above the other, the end of lone being in contact with the rod on its under side and with Ithe end of the other rocker arm above. The rocker spindles [have their rear ends anchored by links to the cylinder head Ibut are supported at their forward ends by a steel bracket, Jthe iower ends of which are secured at the lowest point of the [head The brackets are of special material, having a very flow coefficient of expansion. This arrangement provides I for temperature compensation in a simple manner and iconsiderably reduces the effect of cylinder expansion on the Itappet clearances. The cam and tappet arrangement is f similar to that employed in the Jaguar engines, the cam drum (having three inlet and three exhaust cams, the drum being rotated at one-sixth crankshaft speed in the reverse direction. [The pistons arc machined from Y alloy forgings and are also (similar in design to those of the Jaguar, having two compres- sion rings and one scraper ring situated above the gudgeon [pin, the latter being of the fully floating type. The Armstrong Siddeley Genet. The crankcase arrangement is similar to that of the geardriven Jaguar, the cylinders being secured in their sockets by the arrangement previously described. The crankshaft isalso similar, but the connecting rod arrangement although similar to that of the Jaguar differs in that the auxiliaryrods are of H section instead of tubular. The rear end of the crankshaft drives the characteristic mixture distributingfan through gearing instead of directly. The Claudel-Hobson type A.V.T. 100 carburettor deliversthe mixture to the centre of the induction fan housing, the carburettor being bolted to the usual hot oil jacketed induc-tion elbow. Seven branched induction pipes lead from the induction casing, each pipe being further divided near thecylinder heads to connect with the twin inlet ports of each cylinder. A gear-type petrol pump is fitted at the rear of thisengine, a revolution indicator drive being fitted above this pump. Provision for priming is made, the priming ringbeing fitted at the rear of the engine ; each branch priming Ppe is connected to a small atomizing jet fitted in the induc-tion pipes. Provision is also made for gas starting, the distributor being fitted vertically at the top of the forePart of the timing gear housing. The magnetos are fitted at [ *le rear, where they are bevel-driven by the crankshaft, onej°n each side as on the Jaguar. The ignition timing is fixed. The Lynx may best be considered as being " half a Jaguar."Apart from the crankcase body, which is reduced in length • sit has only to accommodate a single group of seven cylinders™d the single throw crankshaft, practically all the other pnts of the Lynx are interchangeable with those ofe Jaguar. The induction fan casing is modified to accom- odate the different induction pipes, these being fitteduially one at the rear of each cylinder. Each pipe is .. ,1^ ,«;:P 1 ted The Armstrong Siddeley Mongoose. made in two separate portions coupled by a sliding joint to allow for cylinder expansion. The arrangement of the auxiliary drives and the location of the oil pumps, magnetos, etc., is as in the Jaguar. Ignition is provided by two B.T.H. seven terminal magnetos. The ungeared Lynx is being shown at Olympia, this engine developing 218 b.h.p. at a normal crankshaft speed of 1,900 r.p.m. and having a maximum output of 230 b.h.p. at a crankshaft speed of 2,090 r.p.m. This engine is also available with a reduction gear of the type described with reference to the geared Jaguar. Also it may be fitted with a gear driven supercharger. The compression ratio is the same as that of the Jaguar, namely 5:1. The Mongoose comprises five Lynx or Jaguar cylinders mounted on a common crankcase of considerably smaller size than that of the Lynx, the front cover of which is of entirely different design as in addition to the oil pumps the magnetos are in this engine mounted at the front, one at either side, with the distributors facing outwards. The The Armstrong Siddeley Genet Major is of quiterecent production. 705
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