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Aviation History
1920
1920 - 0884.PDF
The blocks in which these rockers are pivoted'are^cleverly contrived, by hollowing, to serve as water outlets, rubber-hose connected into a single lead, in the same manner as the water- inlets below, which are served for the circulation by an Albany type spur-gear pump. Aft, two six-cylinder magnetos are platformed and driven, through the usual reduction from the crank-shaft extension ; and further aft still, through a flexible sheathing, that extension connects to an A.B.C. starting motor. Unlike some Vee-types this Austin motor is well balanced as AUGUST 12, 1920 as the valves, which are set in transversely and diagonally at the orthodox 15 degrees, are operated, as to the exhausts— ; which are on the outer line—by yoke-like rockers, yoke- pinned to the heads of tubular tappets actuated direct from the single central cam-shaft enclosed in the crank-chamber. But the upper ends of these tubes are slotted to let out the claw-like ends—to engage the inlet-valves—of pull-down rods - within these tubes, which are again slotted below, at the sides, to let in the ends of rockers jointed to the rods, housed and pivoted in bronze castings, and actuated by risers from the cam-shaft, all in a manner somewhat reminiscent of Curtiss practice, but very much neater and actually lighter though more substantial. Actually—how rare in an aeromotor—it is possible to get out either valve without dismounting a cylinder bodily with all its related parts. One has simply in either case to detach first, the exhaust piping from its ring-nut attach- ' ment, and then the induction manifold in which all the inlet Valve gear detail of the 200 h.p. Clerget : Features are the yoke type construction of the rockers, and the concentric tappets ; also the water outlet immediately above the exhaust valve-jacketing a unit with a substantial crank-chamber moulding downwards into a very deep base-chamber, from which the lubrication is understood to be, as it should, force-fed throughout, by way of connecting-rods and all through the usual drilled leads. Normal speed is 1,500 r.p.m. geared down to 1,050 on the propeller; and the consumption is 18 gallons of petrol and 7 of lubricant, which works out at 0.58 pint and 0.22 pint per b.h.p. Of half the size for its 200 h.p. and in practically all points the gem of the collection, is the Clerget V. eight. It is certainly as compact as any monobloc of greater r'eclame ; and its cylinder groups seem to be made in that fashion, until it is seen that the cylinders and their corruga.ted copper water- jackets are mounted as units, but have the jackets moulded so that the intermediates butt flush against the outwardly- rounded end ones, in a construction more certain and no less economical. The valve gear, valve arrangement and all pertaining thereto is quite as simple and accessible, and much cheaper than two overhead cam-shafts and separate drives : Valve-gear detail of the S.P.A. 250 h.p. " Six " :1 Note the manner in which the inner halves of the bell-crank- rockers are disposed within the neat tubular cam- shaft casing. Also the lubrication supply and'return- pipes valves are housed with their volute band-type springs, and- lift out the inlet valve bodily with its seating, after which the faulty exhaust valve can be dropped and drawn through the inlet port. Incidentally, the exhaust valves are heavily waterjacketed, with the water outlets direct above each one. Butted close to each induction bar is a special carburettor with a single jet, delivering a rich mixture which is impover- ished as the drum-throttle opens the second of two gauze- Italy's sole example : The 250 h.p. S.P.A. six- cylindered engine. Apart from the clean- ness of plain modelling, this engine is refined down toia weight of 2\ lbs. per h.p. —' ready to run
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