From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Rear axle crown wheel and reduction ratio specifications for various engines.
| Identifier | ExFiles\Box 114\1\ scan0161 | |
| Date | 13th October 1938 | |
| 1015 Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} BY.7/G.13.10.38. REAR AXLES. It is evident that a crown wheel 8.500 dia. with .650 offset for Hypoid condition will cover the requirements of our 4¼ litre engines, as/represented by our present six or its development for Wraith and Bentley, but for the 5¼ litre engine (8 cyl.) this is inadequate. For the 4.6 reduction ratio I prefer the 8/37 combination. For the 5¼ litre engine Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}'s suggestion to use the Phan.lll seems reasonable, particularly as it is already in use and does not demand development. BY.{R.W. Bailey - Chief Engineer} | ||