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).
Speedometer requirements, calibration, verbal specification, and ordering for different car models.
| Identifier | ExFiles\Box 59\2\ Scan160 | |
| Date | 8th June 1932 | |
| X6051 To Mx.{John H Maddocks - Chief Proving Officer} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}1/AD8.6.32. With reference to Mx{John H Maddocks - Chief Proving Officer}15/T7.6.32. we had already appreciated the state of affairs which you mention in your above memo. We decided that our speedometer requirements were almost impossible to put on paper to the manufacturers and we therefore discussed the matter verbally with Mr. Manwaring. As a result of the conversation he agreed to supply us with a speedometer which should conform to our verbal specification. We attach the very careful calibration we have made of this speedometer head and as far as we are concerned we think this is exactly what we require i.e. the mileage recorder is correct and the M.P.H. reads 3.4% fast with new tyres or probably 5% fast with worn tyres. We hand you herewith the instrument head A.T. C.278 and should be glad if you would form your opinion of it on the standard 11/41 tooth axle 40/50 or 12/50 tooth axle 25 HP. and then let us know if you agree with our results. If so, the matter can be settled by ordering all further speedometers for both 20/25 and 40/50 to this specification as the revs. per mile for the synchro mesh 20/25 and 40/50 with the standard axles are both approximately the same. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Attached - Speedometer calibration sheet. | ||