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Aviation History
1920
1920 - 0764.PDF
twelve-cylinder Sikh,^which has its cylinders—180 mm. bore and 210 mm. stroke—mounted as ring-connected units in two banks at 6o° and secured to the crank chamber by the usual foot-bolts, supplemented by dog yokes carried upon the sus- pension bolts of the eight crank-shaft bearers. As a departure —both in this and the 400 h.p. six-cylinder vertical Sikh— from the Sunbeam construction of aluminium with steel liners in other models, each cylinder unit is of steel, with steel waterjackets welded on, and moulded to a rectangular shape at the heads, thus providing space for three exhaust valves on the outer side and three inlets on the inner side : each valve-set being operated by three-finger overhead rockers, with a single thumb piece to tappet rods actuated from an encased cam-shaft at the bottom of the V. As with all makes exhibited except the Beardmore, the cylinders are dismounted, unit or block, and all adjacent parts freed or dismounted to dismount any valve. The rockers are mounted on steel bracket forgings, perforated to lessen weight, and their tubular pivotal parts are interconnected by rubber-jointed metal-tube sections, inserted so as to form a continuous oil-lead, with a U connection at the forward end : one end at the rear uniting with the supply lead from the crank-chamber through the rearmost breather, JULY 15, 1920 At the Aero Show : Close view of the Sikh cylinder head and valve-gear de- tail ; showing the manner of the single-stream high velocity water flow—the only water connection— along the exhaust valve- line ; the line lubrication of the valve-gear through the long tubular pivots of the bell - crank - rockers, with their inserted metal and rubber connections ; and the location of the four spark-plugs in the cylinder head. On the right three-quarter rear view of the 800 h.p. 12- cylinder Sikh engine. Chiefly displaying ignition detail and controls ; the petrol tank air-pump ; and behind it the cover plate facilitating the withdrawal of the camshaft whileXthe other end unites with the return lead into the distribution gear. Known practice is followed in the Sikh induction, which runs from a water-jacketed carburettor located high at each bank end, with direct flow round one bend into omnibus type mainfolds— there being four carburettors in all—and in the water-circulation system. This latter, from large-output centrifugal pumps located beneath the base chamber, and skew gear driven direct from the crank-shaft, delivers the water through the rearward carburettor waterjacketing, and onward in a high-velocity flush along the exhaust valve line only, in one direct lead constituted by the unions between the cylinder heads. The constructive design, with the number of valves—two more for each unit than any other—and the quadrupled ignition to all units from four twelve-point magnetos, rear- wardly platformed and driven from that end of the cam- shaft—where this shaft can be withdrawn by removing an end plate—first by a bevel and then by helical gearing to their spindle-couplings from the main central driven spindle, from which also an air-pump drive is taken—may be perhaps regarded as the chief external features. The firing order is IA, iB, 5A, 5B, 3A, 3B, 6A, 6B, 2A, 2B, 4A, 4B. Internally, AT THE AERO SHOW : Three-quarter views of thejexhaust and induction sides of the 400 h.p. 6-cylinder Sikh. These display the water-inlet on the same principle as in ;the 800 h.p. jmodel, but from a pump located aft, and driven from the distribution gear. Also the induction in the Maybach manner from a water-jacketed carburettor at each end. The quadruple ignition is also fitted 764 , >: '
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