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Aviation History
1948
1948 - 1764.PDF
49O FLIGHT Details of crankshaft, showing massive constrOhipn and the Blackburn patent XwnJtotigt thrust bearing. Com- ponents of piston, rings,fudoton and con-rod assembly, and, below, comfmenprof cylinder, head and valye assembly seen stp^frately and in unified form. w CIRRUS BOMBARDIER . . . chamber connects to the downstream extremity of the inlet trunk, so that the pressure differential between the up- and down-stream ends of the trunk induces a flow of induc- tion air in the form of a by-pass return circuit through the capsule chamber. The purpose of this ;is to regulate the output of the in- jector pump according to manifold depression, altitude and ambient air temperature. The integral of these conditions causes the capsule (which is sealed at atmospheric pres- sure) either to expand or contract and so move a servo valve to regulate oil pressure on one side or other of a piston in the pump, in order, in turn, to vary the stroke of the plungers which pump the fuel to the injector nozzles. The injector pump is mounted on the forward side of the wheelcase at the rear of the engine and lies along the star- board side. Immediately behind the airscrew rear cone (a Capasco processed-asbestos unit) on the airscrew shaft, is a Wood- ruff-keyed pinion which, through an idler, gives drive to a hollow shaft running back along the port side of the Detail section through cylinder head showing location of injector nozzle in relation to port passages, valves and sparking plug positions. cylinder skirts in the base of the crankcase. This shaftis the main drive transfer to the wheelcase on and through which the various auxiliaries are mounted and driven; atthe same time, the drive shaft functions as the oil gallery for supply of lubricant to the main crankshaft bearings andbig ends. The main oil supply pump is driven direct from the rear end of the auxiliary drive shaft, and its outputis conducted through passages in the rear cover wheelcase to the rear bearing housing of the auxiliaries' drive shaft,to the constant-speed unit and, via the latter, to the main thrust bearing. The oil supplied to the end bearing of theauxiliary shaft is fed into the interior of the shaft, and each of the split bearing shells in which the shaft runs isgrooved on the outer and inner diameters with unking holes at the split joint. These bearings are housed in thecrankcase webs which also carry the main crankshaft bear- ings, with core passages in the webs communicating be-tween the two. Thus, under normal system pressure plus centrifuge action, the oil is conducted from the shaftinterior out through the grooved bearings and so, via the core passages, to the main bearings. As already described,internal plumbing in the crankshaft distributes oil to the crankpins. For lubrication of the compound front main and thrustbearing, oil from the supply pump is passed through the c.s.u. pump, where the pressure is boosted to a maximumof 400 lb/sq in. From here, dual core passages in the crankcase top cover conduct the oil to the front of theengine, each oil passage serving one thrust bearing trough. This oil is also the supply to the pitch-change mechanismof the airscrew. Radial holes from the peripheries of the thrust flanges down into the shaft core allow transfer ofoil from the thrust bearing troughs into the distributor plug in the shaft interior, whence pressure oil is directedto the airscrew to effect pitch change. Thus, one thrust flange is supplied with '' fine-pitch'' oil whilst the othergets "coarse-pitch" oil, but although when the airscrew is constant-speeding the oil supply is divided rapidly andalternately first to one thrust flange, then the other, even when a large change in r.p.m. is quickly selected, thethrust flange in the '' return'' circuit is still supplied with oil at abundant pressure for its purpose. As readily seen in our main drawing, the arrangement Length - . 41.34m. Height - 3LI4in. Width - I7.2in.
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