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Aviation History
1929
1929 - 0524.PDF
FLIGHT, MARCH 14, 1929 a definite amount, but that at all other throttle openings the normal mixture is provided. To prevent the possibility of a flat spot when opening up for taking off, etc., the control lever is connected up to a cockpit control, and can be kept out of action when desired. The throttle position at which the weakening device comes into operation can be arranged to suit the desired cruising setting ; the amount of weakening obtained is fixed as determined by bench tests and prevents any possi- bility of damage to the engine through running on too weak a mixture, while the automatic action relieves the pilot of all provision must be made for priming the pnmp when starting. Although the pump will function up to a greater head, it should be remembered that the maximum permissible head for the carburettor feed is approximately 12 ft. The installation must provide for petrol to'be circulating through the pump at all times when the engine is running The relief valve supplied as a separate unit for mounting on the bulkhead or other convenient position is intended for use when the pump feeds the carburettors direct, petrol delivered in excess of the engine requirements being bye-passed back to the main tank or suction side of the petrol "pump i L I EXHAUST RING AND \ / DEFLECTOR SUP- > i PORTED FROM / REDUCTION GEAR ===•=.4 CASING. DEFLECTOR RING BOLTED TO EXHAUST RING. OOLINGAIR INLET. COOLING AIR OUTLET. MAIN OUTLETPIPES " Jupiter " VII, IX and XI [exhaust system diagram. worry from this source. For long endurance flights a special development is used, owing to the progressive closing of the throttle as the flight proceeds. The Bristol Engine-Driven Petrol Pump The Bristol engine-driven petrol pump is of the well- known gear wheel type, as developed by the British Royal Aircraft Establishment. The pump gives a non-fluctuating flow, and all bearing surfaces are automatically lubricated by the petrol circulating through the pump, leakage along the driving shaft being prevented by a spring-loaded, cork- packed gland. Lubrication System On all " Jupiter " engines the oil tank should be located so that the bottom of the oil tank is not lower than 20 in. below the engine centre line when the machine is in the tail down position ; the positive head is unlimited. All oil pipes are f-in. diameter, except the feed pipe from tank, which must be 1-in. diameter, to ensure a free flow to the engine when starting up under cold conditions. Unless the oil level with full tanks is below the engine feed connection a 1-in. shut-off cock must be included in the feed pipe from tank to engine to prevent oil leaking through the pump on a long stand by, and flooding the lower cylinders. " Jupiter VI A " oil- ing system diagram. zFEED SYSTEM• SCAVENGE SYSTEM RUBBER JOINTSCOVERED WITH GAUZE OR COPPERWIRE. -fr" SCAVENGE FILTER.- to' ERNEGA£E I : COVER FEED SYSTEMTHERMOMETER RETURN PIPETO TANK SCAVENGE. SYSTEMTHERMOMETER. This pump iS standardised on the "Jupiter"' Series VII, VIII and IX engines, being positively driven from the gun gear drive shaft, the pump being mounted on the induction elbow in a conveniently low position. The pump runs at half engine speed and delivers approximatelv 100 per cent, in excess of the engine requirements. The delivery under varying heads is sensibly constant, and the pump will maintain its output under a combined suction and delivery head up to 30 ft. The suction lift should not exceed 20 ft., and as the pump is not self-priming in aD cases where the pump operates with a suction lift' As a safeguard against the possibility of the engine being run with the oil turned off, the oil cock should either be interconnected with the petrol cock controlling the feed to the carburettors, so that the oil is automatically turned on with the fuel supply, or connected up with the magnetos, so that when the oil cock is shut the magnetos are earthed. Where the oil is interconnected with the petrol, instructions should be placed in the cockpit against shutting off the petrol while taxying in, as in this case the engine might be running for several minutes with the oil shut off. Owing to the shortness and comparative rigidity of the 212
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