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).
Comparison of the effect of 15 and 16 tooth axles on a car's maximum speed based on tests at Brooklands.
| Identifier | ExFiles\Box 49\1\ Scan298 | |
| Date | 4th April 1921 | |
| x3457 To F.N. from Hs.{Lord Ernest Hives - Chair} c. to E.P. c. to E.J. Hs{Lord Ernest Hives - Chair}1/LG14.4.21. X3457 X3545 COMPARISON OF 15 & 16 TOOTH AXLES. We are quite satisfied that there should be no reduction in the maximum speed of a car when fitted with a 15 tooth axle in place of the 16 tooth. This was proved by tests taken on Brooklands. It is also confirmed if one compares the power curves and gear ratios. The only reason one can give why there should be less maximum speed with the 15 tooth axle, is that owing to the increased engine speed, the power curve falls off. If we take the speed of 75 M.P.H. the engine revs. with a 16 tooth axle is approximately 2330. If we fit a 15 tooth axle the engine revs. at that speed would be approximately 2500. If we compare these speeds on the power curve with the engine running with cut-out open, we find that the curve is practically flat. If the horse power is the same at these two speeds at the road wheels, then there can be no difference at the maximum speed. If the car was run with cut-out closed, then the maximum speed with the 15 tooth axle might be slightly less because with the cut-out closed the power curve drops off very much more rapidly. We consider that it would be a waste of time and money to repeat the tests on these two axles, at least, until some argument has been put forward why it should be done. Hs.{Lord Ernest Hives - Chair} | ||