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28.) Unfortunately, as mentioned previously, this section is not available for inspection. Six 24-tooth planet pinions are mounted on trunnions pressed into a machined- out split cage. Pinion roots and flanks are Rockwell C 59. Core hardness (including tips) is C 41. Case depth is 0.045 in. Trunnions (Fig. 29) are low-alloy steel carburized on the journal surface only to give Rockwell C 59 on the case, 42 on the core, and a case depth of 0.035 in. Pinions run on pressed-in steel-backed copper-lead lined bushings. The lining is 0.020 in. thick, of coarse structure but otherwise of very good quality and satisfactory for its purpose. The pinion cage is splined to th propeller shaft and retained in place by a large nut. The propeller shaft is the steel mentioned previously as being similar to AMS 6254. It is hardened throughout to Rockwell C 59. The propeller attachment is not common to American standards. Splines are involute type — 22 single and one wide spline cut on the basis of 24 splines. Outside diameter is 3.725 in. and spline depth 0.135 in. Cone seat diameters are 3.735 in. for the large cone, and 3.228 in. for the small. A 1-in. wide undercut is machined between the latter and the spline ends. Propeller nut threads are 2.5- mm. pitch x 80-mm. diameter. A small gear is bolted to the pinion cage to provide some type of drive on the crankcase front section. This

gear forms

the basis




the under

discussion of this section.


  • A gear-driven centrifugal

supercharger turning at 8.48 x crankshaft speed is incorporated in the engine. The drive is accomplished in a manner very similar to that used on an American engine. The main accessory drive and starter shaft, driven through a splined coupling from the rear main bearing journal and running in a bronze bushing in the supercharger rear cover, serves a number of purposes. (See Fig.30.) The hub for a spring-loaded supercharger drive gear is integral with this shaft. The impeller shaft rides on two steel- backed, copper-lead lined bushings on journals of this shaft. The shaft itself is of the material described previously having a core hardness of

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Rockwell C 40 and a case of 55 at wear points. The single-speed supercharger drive is completed by a case-hardened cluster gear and pinion mounted on a shaft fixed in the supercharger rear housing and

piloted in a



in the





intermediate incorporates steel-backed

drive cluster a coper-lead lined,




aluminum-alloy impeller is mounted on square splines on the impeller shaft just mentioned. A steel bushing is incorporated in the impeller. Impeller diameter is 9.62 in. Impeller design is conventional with 12 vanes apparently machined and bent per American practice. A 14-vane supercharger diffuser plate of magnesium alloy (Fig. 30) is mounted by means of 14 screws to a supercharger rear housing flange. Fourteen intake pipes are taken tangentially from the annulus formed between the supercharger front and rear housings, the oil baffle plate and the diffuser plate. The supercharger entrance passage from the carburetor is conventional but appears to be slightly small for an engine of this size. Axial clearance in the entrance is low.

Supercharger oil sealing is accomplished by four cadmium- plated cast-iron piston rings in impeller shaft spacer grooves at either end of the impeller. The rings seal against steel sleeves tightly fitted into the supercharger rear housing and the crankcase oil baffle plate. (See Figs. 31 and 32.) It is interesting to note that a boss for venting the supercharger oil seal is cast into the supercharger rear housing but left undrilled.

ACCESSORY DRIVES — The 50-tooth spring-loaded accessory drive gear mentioned previously also drives all of the accessories except the magnetos through a centrally located 19-tooth idler gear to: (1) a 29-tooth generator drive gear and shaft; (2) a 40-tooth oil- pump drive gear and shaft; (3) a 40- tooth accessory gear box drive gear and shaft. An 8-tooth spiral gear is machined into the oil-pump drive shaft and mates with a 9-tooth spiral gear on the fuel-pump drive on the left side of the engine at 1.11 engine speed. The square shaft and square pad, formerly standard on American engines, are used for the fuel-pump



Magneto drive (Fig. 33) is accomplished from a 30-tooth spur gear integral with the crankshaft extension through an intermediate magneto driveshaft which runs in two bronze bushings in the supercharger rear cover. Machined integral with this shaft are a 24-tooth spur gear and a 14-tooth bevel gear. The bevel gear mates with two 20- tooth bevel geared magneto shafts mounted laterally in bronze-bushed support housings which are, in turn, mounted in the supercharger rear cover. (See Fig. 34.) No oil seals are provided. Three-stud flange mounted magnetos are mounted on either side of the rear housing and are driven through a splined coupling engaging the female splines in the magneto gear shafts.

LUBRICATION SYSTEM — A three-section oil pump comprising a pressure pump and two scavenge pumps is mounted on the rear cover. Oil from the pressure pump is taken through passages in the supercharger rear housing and a disc-type oil strainer to the large bronze bushing in which the anti-propeller end of the crankshaft extension runs. Oil transfer to the drilled crankshaft extension is accomplished through slots in the bushing and drilled holes in the shaft journal. All forward engine lubrication is taken through this journal and on through the drilled passages in the crankshaft. Master connecting-rod bearing lubrication was mentioned previously. Knuckle-pin oil is bled from the master-rod bearing clearance through holes drilled near one end of the bearing. These holes in the shell connect holes drilled in the rod flange and thence to corresponding holes in the hollow knuckle pin. Piston-pin lubrication is by splash. Holes for this purpose are drilled in the articulated rod eye near the shank and in the bottom of each pin boss in the piston.

Propeller reduction-gear oil is taken from the hollow front crankshaft journal and propeller shaft through holes in the splined mount for the pinion cage and on through drilled passages to the hollow pinion trunnions.

Valve-gear lubrication is through a ring-sealed sleeve and a spring- loaded tube to the intermediate cam drive gear bracket, thence through a

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