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).
Proposed reduction in axle ratio for the 20 HP car, considering engine crankshaft limitations.
| Identifier | Morton\M2.7\ img025 | |
| Date | 2nd February 1927 | |
| X5840b To PM; from HS.{Lord Ernest Hives - Chair} c. to Sg.{Arthur F. Sidgreaves - MD} CWB. EP.{G. Eric Platford - Chief Quality Engineer} 20 HP. CAR. X5350 HS{Lord Ernest Hives - Chair}/LSR.2.27. With reference to PM4/BHS.2.27. It is agreed that the new axle which is going on the 20 HP. car for 10,000 miles is equivalent to approximately half a tooth less than the standard. At the moment we have no designs for any further reduction in gear ratio. We have got to go very slowly in the matter of gear reduction on the 20 HP. car because of the critical period of our crankshaft which occurs at 3300 revs. We know that if we happen to run on this period it will produce a most disastrous effect. On the high compression 20 HP. car which we are running, we can reach this period on top gear under favourable road conditions. Considering therefore that we have this very definite limit to the engine revs. on the 20 HP., we consider that the proposed reduction in axle ratio is all that it is safe to do at the moment. Hs.{Lord Ernest Hives - Chair} | ||