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Rolls-Royce Eagle II / H-24

rr-eagle-2

 

This was the last of the line of reciprocating, liquid-cooled units. The initial design project was conceived toward the end of 1942 as the necessity for a higher-powered engine was foreseen. The Rolls-Royce design team realised that producing a scaled-up version of their Griffon V-12 engine would lead to excessively large combustion chambers and problems with detonation.

Considerations of aspiration and flame travel set a more or less effective limit of about 6 inches to bore size, and with cylinders of this order it has been established that 12 pistons per crankshaft is about the practical limit and considered an X-24 design. This layout had previously caused unreliability with the Rolls-Royce Vulture due to the need to fasten four connecting rods in a complicated arrangement to a common big end bearing.

The designers finally settled on an 'H' layout with two crankshafts and 'blade and fork' connecting rod attachments, the crankshafts being connected through the propeller speed reduction unit. Sleeve valves were decided upon in view of the fact that they offer advantages over poppet valves from the aspect of maintenance and obviation of adjustment.

The case is split vertically into port and starboard halves of cast light alloy, the front wall carrying the tail bearings for the timing gears uniting the crankshafts. Cylinder blocks are also examples of sandcasting technique in light alloy, the upper and lower rows of cylinders on each side being formed in one casting. Each cylinder is ventilated with three inlet and two exhaust ports, the latter ports of each vertical pair of cylinders discharging to a common pair of ejector stacks.

Sleeve drive is by a worm shaft on each side commonly serving top and bottom rows of sleeves, each shaft running in six split plain bearings.

A two-speed, two-stage supercharger and intercooler were used to compress then cool the air-fuel mixture, following Griffon and Merlin practice. Starting was by Coffman starter. An auxiliary shaft driven by the lower crankshaft operated the main coolant pump, intercooler coolant pump, pressure and scavenge oil pumps and a fuel injection pump. Piston ring failures and cylinder head sealing problems were experienced during early flight testing.

 

RR-Eagle22
Rolls-Royce Eagle 22

 

It was designed and built in the early-1940s and first ran in March 1944. The Eagle was never fitted to a production front-line fighter, as it was overshadowed by a new wave of turbojet engines, such as the Rolls-Royce Derwent and turboprops such as the Dart and Armstrong Siddeley Python. Fifteen Eagle 22s were produced to power the prototypes of the Westland Wyvern fighter / torpedo bomber as its intended powerplant, the AS Python was late in development.
 
Early Eagles (I and II) drove a single airscrew, but the Eagle 22 was arranged for contraprops in view of its application to the Westland Wyvern T.F.1 deck-landing strike fighter. In M. S. gear the Eagle delivered 3,415 h.p. at 3,500 r.p.m. for take-off. The maximum power rating in M. S. gear was 3,500 h.p. at 3,250 ft, and in F. S. gear, 3,020 h.p. at 15,250 ft.

 

Variants:
46H Eagle I
(1944) - Compression ratio 6.5:1

46H Eagle II
(1944) - Modified Eagle I

46H Eagle (20 srs) 22
(1946-1949) - Increased compression ratio (7:1), Fifteen engines produced at the Derby Rolls-Royce factory. First flown in a Westland Wyvern on 16 December 1946.

 

Specifications:
Eagle 22
Type: 24-cylinder liquid-cooled H-type aircraft piston engine
Bore: 5.4 in (137 mm)
Stroke: 5.125 in (130 mm)
Displacement: 2,807 in³ (46 L)
Length: 135.5 in (3442 mm)
Width: 43.4 in (1,102 mm)
Height: 50.0 in (1,270 mm)
Dry weight: 3,900 lbs (1,769 kg)
Valvetrain: Sleeve valves
Supercharger: Two-speed, two-stage supercharger, maximum boost +18 lb
Fuel type: 115/150 Octane petrol, DERD 2476
Cooling system: Liquid-cooled, 70% water, 30% ethylene glycol
Reduction gear: Geared spur, 0.2985:1 reduction ratio. contra-rotating right-hand/left-hand tractor
Power output: 3,200 hp (2,387 kW) at 18 lb (124.1 kPa) of boost at 3,500 rpm
Specific power: 1.13 hp/in³ (51.7 kW/L)
Compression ratio: 7:1
Power-to-weight ratio: 0.82 hp/lb

 

 

 

 

 

 


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