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Aviation History
1928
1928 - 0618.PDF
JULY 5, 1928 BRISTOL " JUPITER " SERIES VII Cylinders.—Composite construction, the barrels beingmachined from alloy steel forgings, with an integral com- bustion head, of cast aluminium alloy, carrying the valves,valve guides and rocker mechanism, and valve ports. Head secured to barrel by studs and set screws. Cooling finsturned from solid. Pistons.—Cast aluminium alloy, slipper type, fitted withtwo gas and one scraper ring. The gudgeon pin floats in both piston and connecting rod, secured against end motionby circlips. Valves.—Overhead, two inlet and two exhaust per cylinder,of special heat-resisting steel with hardened steel caps to take the thrust of rocker screws. Fitted with triple concentricsprings. Operated—through tappets, push rods and overhead rocker gear—by large two-row, four-lobed cam, runningconcentric with the crankshaft and driven from latter by eccentric epicyclic gearing at one-eighth engine speed. Connecting Rods.—One master and eight articulated rodsmachined from 65-ton nickel-chrome steel stampings. Master rod has a solid big-end lined with hardened steel sleeve,bearing directly upon bronze-backed white-metal-lined bush floating on the crankpin. Crankshaft.—Built-up from hardened and tempered60-ton nickel-chrome steel stampings. The shaft spigots in the maneton, being registered by a taper key formedintegral with the eye of the maneton. The complete shaft is carried on two main roller bearings, located immediatelybehind each crank web, with a special Skefko double-purpose roller bearing at the air-screw end and a small white-metalsteady bearing at the tail end. Drilled throughout for lightness and oil passages. Crankcase.—In two main portions, front and rear halves,of stout well-ribbed section, machined from duralumin stampings. A face joint is made on the centre line ofcylinders by nine collar bolts, the rear projections of which are utilised for attaching the engine to the aeroplane mounting.A rear cover carries the magnetos and magneto drive, petrol and oil pumps, and other auxiliary units. Lubrication.—Engine-driven duplex-gear pump, the feedpump supplying oil at 60 lbs./sq. in. through hollow crank- shaft to tail bearings, big-end, cam gear, etc. Oil returnedfrom sump to tank by scavenge pump. Carburettors and Induction System.—The Bristol "Triplex"carburettor, consisting of three variable-jet type carburettors formed in one body and operated by one set of controls,mounted at the rear and lower end of the crankcase on the intake side of the supercharger blower. The carburettoris heated by the hot oil drawn from the engine by the scavenge pump, the oil also circulating through the air intake elbowand the induction elbow. This ensures complete vaporisation of the mixture and prevents the possibility of the freezing-upof the carburettor at low temperatures. Additional heating is also provided by a forward type air intake drawing thecarburettor intake air over the lower cylinders. Ignition.—Dual by two H.T. magnetos mounted on therear end cover of the crankcase and driven by bevel gearing from the tail end of the crankshaft. The ignition control isfixed. Petrol Pump.—Gear wheel type on rear end cover, givingnon-fluctuating flow direct to the carburettor. Positively driven from the gun-gear drive shaft through a ball-endedvertical shaft enclosed in a telescopic tubular duralumin shaft. Bearing surfaces automatically lubricated by thepetrol circulating through the pump. Supercharger.—An integral gear-driven supercharger isincorporated in place of the spiral induction system used on standard " Jupiters." mounted immediately behind the rearwall of the crankcase, concentric with and driven from the tail end of the crankshaft, around which it revolves. Asystem of slipping clutches ensures the impeller against shock loads. The mixture is drawn axially into the impeller anddischarged radially via a fixed diffuser into an annular induction chamber, thence to the cylinders via nine radialpipes. Number and arrangement of cylinders.—9, in single rowradially. Cooling.—Air. Bore.—5-75 in. (146 mm.).Stroke.—7-5 in. (190 mm.). • / Compression ratio.—5 to 3.Power.—Normal, 420 b.h.p. at 1,755 r.p.m. and 12,000 ft. maximum, 440 b.h.p. at 1,950 r.p.m. and 15,000 ft.Airscrew.—Clockwise (airscrew end). Direct. Carburettor.—Bristol " Triplex " oil heated.Ignition.—Dual, 2 H.T. magnetos. Weight.—760 lbs., bare (39 -8 kg.). Length o.a.—4 ft. 8 in. (apx.) (1 -4 m.). • . - - - Width o.a.—4 ft. 8 in. (apx.) (1 -4 m.).Height o.a.—4 ft. (apx.) (1 -I m.). Fuel consumption.—27-5 gallons/hour (123 -75 lit./h.).Oil consumption.—5-2 pints/hour (2-9 lit./h.). 566
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