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Aviation History
1929
1929 - 0525.PDF
FLIGHT, MARCH 14, 1929 piping, flexible connections between the engine and thebulkhead are essential, in order to relieve the engine union of any vibrational movements tending to unscrew it. Thisis particularly important with the large diameter oil-feed pipe. Rubber connections are suitable, provided they are wrapped with metallic gauze, wire or asbestos, to comply with the requirements of the Fire Prevention Committee. To check oil temperature, especially on new types of machines, the use of oil thermometers is essential. These should preferably be of the Mercury Invar type ; one should be fitted in the oil scavenge pipe line, between engine sump and oil-heated elbow, and another in the oil feed pipe line from tank to engine. The installation should be carefully carried out to ensure that the thermometer is actually in the oil stream, and also that a local restriction is not caused. Pressure gauges should read up to 60 lbs. sq. in. for " Jupiter " VI and VII, where the normal oil pressure is 40 lbs. per sq. in., and up to 80 lbs. sq. in. for the " Jupiter " VIII, IX and XI, where the normal oil pressure is 60 lbs. per sq. in. Gauges should be of the overload type, to allow for high pressures generated when starting with cold oil. Oil Coolers.—On all " Jupiter "-engined machines, provi- high pressures generated when starting up under cold condi- tions. Oil System The Amyot Pressure Relay.—With this system, the engine lubricating oil is not used to transmit the operating pressure from the engine to the gauge in the cockpit; instead, a special bellows mechanism is fitted to the engine pressure gauge connection, and a flexible pipe, filled with a special transmitting fluid, relays the pressure to the cockpit gauge. The outstanding advantages of the system are :— (1) That rupture of the relay pipe does not permit the engine lubricating oil to escape ; and (2) The transmitting fluid, unlike lubricating oil, remains of approximately constant and low viscosity over the whole range of operating temperatures, therefore the time lag customary without the Amyot system when starting from cold is obviated. These advantages are particularly apparent on multi- engine installations, or those operating in cold climates. The transmitting tube is obtainable in lengths to suit different installations. Bristol Oil Centrifuger (Carter Patents).—This centrifuger is intended to be installed in the oil return from engine, and is supplementary to the standard engine filter, being intended GAS FEED TO DISTRIBUTOR. TYRE INFLATORUNION. PRIMING PUMP PISTON. STARTING COCK PETROL SUCTION PIPE PETROLPRIMING PIPE. '3-WAY COCK. PIPE TOAIR TANK Diagram of Viet Starter. sion must be made for cooling the lubricating oil after it leaves the engine. The most suitable method is by means of an auxiliary oil cooler, which should be fitted between the scavenge pump and oil tank, care being taken that the position selected allows a good air flow through the cooler, both when climbing and flying level. The size of the cooler will depend upon the operating conditions, but it must be sufficiently large to prevent the temperature of the oil feed to the engine exceeding 70° C, and the oil output from the engine exceeding 100 to 105^ C. These figures, 100 to 105 C, are only permissible under exceptional circumstances, and 85° C. should be considered a maximum working figure. These allowable temperatures are for Castrol R, or pure-treated pharmaceutical castor oil. To prevent damage to the oil system when starting up under very cold conditions, some form of bye-pass or short- < ircuiting arrangement must be included, automatically cutting out the oil cooler until the oil warms up. The standard Bristol coolers arc of the tubular type, and 'in- made in three sizes :—The small, or 10-tube type, suitable tor fast and lightly-loaded machines. The medium, or 12- tube type, suitable for medium-speed machines, and the large, or 11-tube annular type, suitable for heavily loaded, slow-speed machines, or those operating in tropical climates A spring-loaded bye-pass relief valve is incorporated in each type, safeguarding the cooler against damage from to trap the extremely fine particles of foreign matter which the standard filters cannot cope with. The centrifuger is operated by the oil circulation, and a bye-pass is incorporated, permitting the oil to discharge freely in case of the centrifuger being temporarily out of action. STARTER SYSTEMS On the ungeared " Jupiter " engines, provision is made for priming the induction system, to be used in conjunction with propeller swinging by means of a Hucks Starter, and a hand starter magneto connected to the centre terminal on the mam magnetos. A suitable primer for general use is the Ki Gass, while for cold climates, a somewhat different arrangement is recommended. On all engines, provision is made for using a pressure starter, such as the Bristol Gas Starter, or the hand-operated Viet Starter. For the latter, a special distributor valve is required. On the geared engines, a hand-turning gear is- fitted. The reduction ratio is 30 to 1. and provision is made for operating handles to be fitted to the port and starboard sides, and either or both can be used. The hand turning gear should be used in conjunction with a suitable priming system and hand-starter magneto. For details of the installation, equipment, etc., application should be made to the Bristol Company direct. Metal Propellers as Skids IT will probably be remembered that when the late Mr. Larry Carter crashed on a racing aeroplane, the Fairey metal propeller bent under the fuselage, and formed a sort of skid, on which the machine slithered along without overturning At the time it was thought that this was something of a. " freak " occurrence. There have, however, more recently been several cases where the same sort of thing has hap- pened, and always when the undercarriage has given way th§ Fairey metal propeller has doubled under the fuselage and formed a skid on which the machine slided along. Thus may a metal propeller definitely serve to save lives in a crash. 213
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