The Rolls-Royce design team realised that producing a scaled-up version of their GriffonV-12 engine would lead to excessively large combustion chambers and problems with detonation.[2] The team concluded that a larger number of small cylinders would be the answer 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.[2]
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. The new engine followed the layout of the Napier Sabre and similarly used sleeve valves but with a simplified drive system.[2]
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.[2]
(1946-1949) - Increased compression ratio (7:1), 3,500 hp at 3,500 rpm and 28 lb boost.[4] Fifteen engines produced at the Derby Rolls-Royce factory. First flown in a Westland Wyvern on 16 December 1946.
