Sorry for delay, the VATman took precedence!
Mike
The only pictures I’ve got of bare “R” engines quite clearly show spur reduction gears.
With a prop of the size used on the S6 and S6B I don’t believe direct drive could have been used.
VERY abbreviated summary of RR piston engines.
I think the RRHT may have been a bit wrong with their explanation regarding epicyclic and spur reduction. In one of their own publications, the Condor 1A has epicyclic but from the Condor III on they had spur reduction. This was in 1923 which is well pre-Kestrel. The Condor was developed from the Eagle which were all epicyclic.
The reason for changing to a spur reduction was to bring the propellor shaft to the centre of the engine.
The next stage was the “F” engine which later became the Kestrel. This was influenced by the Curtiss D12 with it’s aluminium block and steel liners. Prior to this, all RR aero engines had separate steel cylinders with welded-on jackets. The original “F” engine didn’t have a reduction gear but one was added early on. This infers that all Kestrels had a reduction gear.
The Goshawk and Peregrine were developments of the Kestrel. The Goshawk with evaporative cooling and the Peregrine specifically designed for the Westland Whirlwind with a downdraught carburettor and air intake between the cylinder banks to reduce drag, and handed. The handing doesn’t appear to be as simple as it first seems. Many internal drives incorporated a “spring drive” apparently for reasons of backlash. It would seem that these had to be handed as well.
The “H” which became the Buzzard was a scaled up Kestrel and development proceeded at the same time. As is well-known, the “R” was a development of the Buzzard.
The Merlin appears to be a “clean sheet of paper” design, based on Kestrel and Buzzard experience, rather than another variation in size.
The original design called for the cylinders and crankcase to be cast in one piece, like a car engine. When anything broke it caused so much damage they abandoned the idea.
The original head design (ramp head) was also unsuccessful and as a stopgap, a scaled up Kestrel type one-piece head and block was used. Later versions, from the 60 series onwards, used a separate head and block.
A derated version of the “R” known as the Griffon first ran in 1933. When RR realised a more powerful engine was needed, they completely redesigned the Griffon, using the “R” bore and stroke. The intention was to make it as small as possible. Comparing pictures of the original Griffon and the redesigned production version they succeeded brilliantly. The camshaft drives were moved to the front of the engine, and on the early ones, the first part of the supercharger drive.
There’s no mention of when they decided to make it run backwards. 🙂
Sign In
