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Rolls-Royce Vulture

rr-vulture
 

First run in May 1937, the Rolls-Royce Vulture liquid-cooled engine had its 24 cylinders arranged in four banks of six, in the form of an X, and may be considered as two Kestrel-size units with a common crankshaft. It was test flown in a modified Hawker Henley and was used on operations in Avro Manchester bombers, though various troubles, and the desirability of concentrating on the Merlin and Griffon, led to discontinuance of development. (The basic Manchester airframe, with four Merlins in place of two Vultures, became the splendidly successful Lancaster.) The Vulture was also installed in the Hawker Tornado fighter and Vickers-Armstrongs Warwick bomber.

Although the Vulture used cylinders of the same bore and stroke of the Kestrel, the redesigned cylinder blocks had increased cylinder spacing to accommodate a longer crankshaft, necessary for extra main bearings and wider crankpins.

Few details of the engine were ever released, but when it was first described in Flight, in June 1942, it was noted that the capacity was 2,592 cu in. Maximum power ratings were 1,845 h.p. at 3,000 r.p.m. at 5,000 ft in low gear, and 1,710 h.p. at 3,000 r.p.m. at 15,000 ft in high gear. Detail construction followed previous practice in that light-alloy cylinder blocks, head and coolant jacket were employed, with "wet" cylinder liners of steel. The crankshaft was carried in seven bearings. Each cylinder had four valves, operated by overhead camshaft, and two sparking plugs; there were two independent screened magnetos. Variabledatum automatic boost control, with two-position mixture control, was used in conjunction with an S.U. twin-choke, down draught carburettor, and there were two vertical air intakes, coupled by a single entry. The two-speed supercharger delivered mixture to two trunk pipes, each feeding two blocks of cylinders.

The engine was originally designed to produce around 1,750 horsepower (1,300 kW), but continuing problems with the Vulture design meant that the engines were derated to around 1,450-1,550 hp in service by limiting the maximum rpm.

The Vulture had been intended to power the Hawker Tornado interceptor, but with the cancellation of Vulture development, Hawker abandoned the Tornado and concentrated on the Hawker Typhoon, which was powered by the Napier Sabre. Likewise, the same cancellation caused the abandonment of the Vulture-engined version of the Vickers Warwick bomber.

The only aircraft type designed for the Vulture to actually go into production was the twin-engined Avro Manchester. When the engine reliability problems became clear, the Avro team persuaded the Air Ministry that switching to a four-Merlin version of the Manchester, which had been in development as a contingency plan, was preferable to retooling Avro's factories to make the Handley Page Halifax. The resulting aircraft was initially called the Manchester Mark III and then renamed Avro Lancaster, going on to great success as the RAF's leading heavy bomber.

The engine suffered from an abbreviated development period and the reliability of the Vulture was very poor. Apart from delivering significantly less than the designed power, the Vulture suffered from frequent failures of the big end connecting rod bearings, which was found to be caused by a breakdown in lubrication, and also from heat dissipation problems. Rolls-Royce were initially confident that they could solve the problems, but the company's much smaller Merlin was already nearing the same power level as the Vulture's original specification, and so production of the Vulture was discontinued in 1943 after only 538 had been built.

 

Applications:
Avro Manchester
Blackburn B-20
Hawker Henley
Hawker Tornado
Vickers Warwick

 

Specifications:
Vulture V
Type: X-24 supercharged liquid-cooled piston engine
Bore: 5 inches (127 mm)
Stroke: 5.5 inches (139.7 mm)
Displacement: 2,592 in³ (42.47 L)
Valvetrain: Overhead camshaft
Supercharger: Gear-driven centrifugal type supercharger, two-speed, single-stage
Fuel system: Downdraught S.U. carburettor
Fuel type: 100/130 Octane petrol
Cooling system: Liquid-cooled, 70% water/30% Ethylene glycol
Reduction gear: Spur geared via layshaft, 0.35:1 reduction ratio, left-hand tractor
Power output: 1,780 hp at 2,850 rpm, +6 psi boost
Compression ratio: 6:1

 

 

 

 

 

 

 


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