WIX Archives

Re: Merlins and Griffons

Posted by Christer on Mon Oct 28, 2002 11:50:12 AM

In reply top Merlins and Griffons posted by Ron Henry on Mon Oct 28, 2002 10:02:40 AM

Ron,
I think that You?re spot on. I actually have one of the books from RRHT "Rolls-Royce Piston Aero Engines". Quite detailed for such a small book with such a huge topic. You get a good overview of pinpointed technical difficulties and development.
The Griffon and the R have the same ancestor, the Buzzard (H-engine) which was a scaled up Kestrel.
The Griffon was a derated R tested as early as 1933 but not continued at that time. Shortly before the war it was taken off the shelf and experimental runs started in 1939 and the first production variant flew in a Firefly in 1942.

I have a feeling that the lower developement level of the Griffon focus on the RPM, 3,000 for the Merlin and 2,750 for the Griffon, an illusory difference.

What really is important is the maximum piston speed which dictates the load on the bearings, crankshaft, con-rods etc.
The stroke for the Merlin is 152 mm which at 3,000 rpm gives 15,2 m/s.
The stroke for the Griffon is 168 mm which at 2,750 rpm gives 15,4 m/s.
If you add the higher component weights in the Griffon to the equation the difference is bigger than what is indicated by the piston speeds.

I don?t believe that there was any significant difference regarding developement level, do You?

Christer

Follow Ups: