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Aviation History
1928
1928 - 0327.PDF
APRIL 26, 1928 THE VICKERS-POTTS OIL COOLER IN modem .high-speed aircraft, with their hi<*h-pOweredengines cowled in as much as possible, the heat which is imparted tojthe lubricating oil during its passage throughthe engine cannot readily be radiated from the crankcase—a system of cooling that gave more or less satisfactory resultsin the past. Today, therefore, it becomes necessary to seek some other means for reducing the temperature of the oilbefore it makes its journey through the engine. The usual method of doing this is to insert a special oil•cooler^ in the pipe line between the engine scavenger pump and the oil tank. Such a device is the Vickers-Potts oilcooler, which forms the subject of the accompanying notes and illustrations, and which is manufactured by Vickers, Ltdof Vicker's House, Broadway, Westminster, S.W.I. The Vickers-Potts oil cooler—which is used extensivelyon machines of the Royal Air Force—is a standardised unit oi comparatively low aerodynamic resistance, and cantherefore be placed in the slipstream of the air screw or other convenient place on practically every type of aircraft. Itconsists of a series of hollow fins threaded on two tubes, through .which the oil passes on its way from the engineto the oil tank. These fins are arranged for series flow, i.e., through each fin or element in turn. A byepass valve isinserted between the inlet and outlet pipes, to provide an alternative path for the oil when starting from cold, and alsoto prevent excessive pressures on the fins. The internal construction of the cooling element is suchthat the oil is exposed in thin layers to the cold surface of the fins, while spacers between the fins break up the flowof oil by eddying, thereby causing a rapid transfer of heat. The external space between the fins—which is increased bythe local flattening of the latter—enables the air to pass freely between them without causing undue drag. These fins are all of standard dimensions, so that anynumber may be employed from 5 to 11 fins, to suit all engines, from 250 h.p. to 800 h.p., and to meet the various require-ments. Standard coolers are made with 5, 7, 9 and 11 fins to cover this range. The cooling surface per fin is approxi-mately 145 sq. in. (930 sq. cm.), and the reduction of tempera- ture of the oil in passing through one fin is from 1° to 6C C,according to the rate of flow and the temperature of the air ; the complete unit should permit oil being returned to theengine at a temperature of 70° C. The Vickers-Potts Oil Cooler, as fitted on an aircraft with a Bristol " Jupiter " engine. The complete weights, and the drag at 100 m.p.h. (air flow along major axis of fins) of the various units areas follows :— 5-fin unit, weight 9-75 lbs. (4-4 kgs.) ; drag, 1 • IB h.p.; 7-fin unit, 11-75 lbs. (5-3 kgs.); 1-46 h.p.; 9-fin unit, 14 lbs. (6-35 kgs.), 1-79 h.p.; 11-frn unit, 16-5 lbs. (7-5 kgs.), 21 h.p. This cooler measures approximately 1 ft. 4 in. in length by 4£ in. wide, and projects from the fuselage, etc., from about 5 in. in the 5-fin unit, to about 9J in. in the 11-fin unit. The Vickers- Potts Oil Cooler. This diagram shows the ar- rangement of the fins, which are made up in units of 5, 7, 9 and 11, according to requirements. 291
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