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).
Compression and axle gear ratios for the 40/50 model, distinguishing between open and closed cars.
| Identifier | ExFiles\Box 19\7\ Scan059 | |
| Date | 25th July 1922 | |
| To Hs.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} c. to CJ. BJ. c. to WOr.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} c. to EP.{G. Eric Platford - Chief Quality Engineer} PN.{Mr Northey} X790 R2/M25.7.22. X.790. X.3426 X4299 I think Mr. Hives's memo. regarding the roughness of the present 40/50s is quite in accordance with my views. The 2 points that stand out are :- (1) That it is quite necessary to have a different compression ratios for an open car than for a closed one. Let us therefore decide to still maintain the two compressions, reducing them both slightly, say 5%, so as to follow a safe and medium policy, moving slowly and by small steps in the direction we think is most desirable. (2) The second point which stands out is the axle gear ratio. In this case also I have always recommended that there shall be 2 gear ratios - one for the heavier cars, and one for the lighter ones so as to give approximately the same acceleration for each car and the same hill climbing capacity. What the gear ratio shall be experience will point out but certainly I think we ought not to go lower than 15/52 teeth pinions for the open cars and 14/52 for the closed cars. Experience may shew us that we should have one tooth more in each pinion or that we ought to have 3 gear ratios, so that a very light sports car might have a 16 teeth pinion. Naturally of course there are people who have light open cars but do not drive fast; these would come under the middle-class having 15 teeth pinions. It should be realised that our 40/50 engine is a large one, and to run it at the speeds we do it is extremely contd:- | ||