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Aviation History
1928
1928 - 1130.PDF
DECEMBER 6, 1928 THE BRISTOL "JUPITER" FAMILY—(IV) from p. 1005.) Lubrication System REFERENCE was made previously to the drive for the oil pumps, which is in the form of a notched driving plate which engages with two dogs on the tail end of the crank- shaft, the plate being liberally perforated with holes so as to provide a passage for the oil from the pump into the hollow crankshaft. In the present article it is proposed to deal with the pumps themselves, and with the circulation of oil inside the engine. Before going into details, however, it niay be well to state that the general lubrication system of the " Jupiter " is of the " dry sump " type, in which fresh oil is supplied under pressure from one pump, and, after passing through the engine is withdrawn by another known as the scavenger pump, and returned, via a cooler, to the tank. Certain parts are supplied with oil under direct pressure, while others are lubricated by splash. Oil is delivered under pressure to the cam gear, the big end of the master connecting rod, the magneto and oil pump drives, and thence into the hollow crankpin. Two ducts are drilled radially through the crankpin wall, and their outer ends emerge on a flat formed on the outer face of the pin, the oil thus being admitted to the inner surface of the floating bush, which is interposed between the crankpin and the master rod big end. A number of holes in the bush itself pass the oil to the outer surface of the floating bush, and thus to the big end of the master rod. From the ends of the floating bush the oil emerges, and is splashed to the inner surface of the crank-case,'cylinders, pistons and small ends, etc. The main pressure supply leaves the inside of the crankpin through a duct in the front web, and this communicates with a broad shallow oilway formed on the front portion of the shaft. The components situated on the shaft i.e., main bearing, crankshaft sleeve and eccentric of cam mechanism) form a cover over this oilway and form a reservoir from which the cam sleeve is lubricated via a groove and holes in 0(t TWBMOMETtR t« SCJVENCE STSTEM. OIL ftJTEt . rn*KE ELBOW THE BRISTOL "JUPITER VI " : Diagram of lubrication system. c.c.-gun gear drive, and gas-starter distributor drive. Splash lubrication by the oil which has drained from the parts mentioned above is supplied to the pistons, small ends of the connecting rods, wrist pins of articulated rods, main crank- shaft roller bearings and spherical roller bearing, and tappets and cam faces. The valves probably receive a certain amount of lubrication from oil that has passed the pistons. The scavenger pump (which has a capacity of approxi- mately one-third greater than that of the pressure pump) collects oil from the sump unit at the bottom of the crank- case, and returns it by way of an oil cooler, to the main oil tank. From the oil tank the oil runs to the pressure pump under the force of gravity. . The Internal Oil Circulation The oil delivered by the oil pressure pump into the hollow bore of the rear end of the crankshaft passes through the shaft bore to a duct drilled in the rear web of the crank throw. crankshaft sleeve. From the recess between the two halves of the cam sleeve bushes the oil is distributed over the surface of the bushes by spiral grooves. The intermediate bearing, i.e., the roller bearing immediately in front of the front web, is splash lubricated by oil thrown off from there. The eccentric of the cam gear has two recesses formed in its bore, from which holes communicate with the compound pinion. Oil from the pinion and from the cam sleeve lubricates the rest of the cam mechanism and the front main bearing. A spring-loaded brass ring on the crankshaft makes contact with the surface of the thrust bearing housing, and prevents the oil from leaking out through the front. Of the drives, etc., on the back of the engine, the white- metal tearing of the magneto drive sleeve is supplied with oil bypassed direct from the pump chamber, and led by a duct drilled in each magneto drive spindle to its bearing. A duct in the rear cover leads to the plain bearing of the C.C. drive spindle, and from there upwards to the spindle of the gas 1036
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