A multi‐row radial air‐cooled aircraft engine, figs. 1 and 2, having in the embodiment shown four radial rows and seven helical banks, has each of its banks supplied by a separate magneto 116 through the ignition harness 117 and a separate induction manifold 224 from the supercharger casing 36. The engine is made up of six main parts, namely the propeller shaft housing 30, magneto drive housing 32, crank‐case 34, supercharger 36, accessory drive housing 38 and auxiliary drive housing 39. The propeller shaft 40, fig. 3, is supported in the housing 30 by a bearing and thrust ball race 48, 50 and bearings 62 and 64 and is connected to the crank‐shaft 58 through sun‐and‐planet gearing 52, 54, 56 and 60. The gear 54 having its teeth cut helically so as to produce a rear‐wardly acting thrust component, has in its rear face a plurality of equi‐spaced pistons 78 which bear against the fixed ring 80 and gear 54 is splined to the casing 30 at 72, 74. Oil from a pump is forced into the cylinders behind the pistons 78 to balance the thrust component, and as the engine torque is directly proportional to the oil pressure in these cylinders, engine torque may be read directly from a pressure gauge connected to said cylinders. The magneto housing 32, no. 9, has seven magneto mountings 115 and seven magneto driving shafts 118 which are geared to the crank‐shaft 58. The crank‐case, figs. 9 and 11, is composed of a number of parts 124, 126, 128, 130 and 132 which are held together by the bolts 134. The valve cam rings 150 which are geared direct to the crank‐shaft 58 by gears 164, 168, 170 to run at one‐sixth engine speed, each carry a three‐lobe inlet and exhaust cam track 154 and 156 respectively which operate the rocker arms 155 and 157 through the tappets 146 and pushrods 81 and 83. The crank‐shaft (see Group XXIV) is carried by five bearings 208, the centre one of which is flanged to locate the shaft axially and transmit thrust to the crank‐case. The two outer bearings are pressed and pinned in the holes 131 of the partitions 163. The centre three bearings are carried in disks 138 which are axially split and have keys 139 inserted between their faces which engage the partitions 162. The disks 138 are made of a material with a higher coefficient of thermal expansion than the crank‐case so that for easy assembly they are made with a sliding fit which tightens to a force fit when the engine warms up. The cylinder liner 214 has a cooling muff 216 and a cylinder head of aluminium alloy shrunk on it and the rocker boxes 218 and 220 are diametrically opposed so that the cylinders may be reversed when the engine parts are to be used as a pusher instead of tractor assembly. As shown in fig. 1, the induction manifolds 224, which are attached to the flanges 75, fig. 9, on the cylinder heads, are located between the rocker boxes and thus keep the diameter of the engine to a minimum. The supercharger 36, fig. 12, with a vaned diffuser 230 has an inducer 274 and impeller 228 driven from the crank‐shaft through a spring drive and hydraulic damper unit 206 (see Group XXIV), a gear 240 attached to said unit, and through cither two low‐speed fluid couplings 234 (one only of which is shown) and gears 244, 250 and 326 or two high‐speed fluid couplings 247 (one only of which is shown) and gears 242, 248 and 326. A fuel feed valve 276 in web or boss 278 discharges fuel, as metered and proportioned to airflow by the carburettor, into the spinner cup 280 which is carried by and rotates with the impeller 228. The fuel passed through nozzles 282 into the airstream and valve 276 shuts when the fuel pressure exceeds a predetermined value. The accessory drive housing 38 contains seven radial shafts and mountings for engine accessories such as oil pumps, tachometers, etc. All the shafts, one of which 346 is shown, are driven from the bevel gear 294 which is splined at 313 to the shaft 308 which runs through the hollow impeller shaft and is splined at 310 to the crank‐shaft 58. The cooling fan 364 which has turbine blades 365 between the ring shrouds 367 and 368 is driven by low‐ or high‐speed fluid couplings 372 or 375 and a series of gears 398, 400 and 382 which drive the gear 380 carried by the spider 378 splined to the shaft 308 at 313. The power take‐off shaft which may be used to drive an auxiliary supercharger, a second propeller or a second fan, etc., is keyed to the shaft 336 which is driven by the sun‐and‐planet gearing 406, 408 and 410.
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