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).
Laboratory check and temperature performance analysis of an A.T. Speedometer for the 20/25 HP model.
| Identifier | ExFiles\Box 59\2\ Scan029 | |
| Date | 20th May 1930 | |
| By.{R.W. Bailey - Chief Engineer} from EFC. c. Hs.{Lord Ernest Hives - Chair} c. Wor.{Arthur Wormald - General Works Manager} X4308 X.4308. A.T. SPEEDOMETER (20/25 H.P.) No.D.999 A further 20/25 HP. A.T. production speedometer 720. 11/50 has been checked in our laboratory. The instrument was found to be correct in regard to its 720 spindle revolutions per counter mile. It was our impression however, that in accordance with our recommendations and Hs{Lord Ernest Hives - Chair}/RM{William Robotham - Chief Engineer}2/MJ30.1.30, the revolutions per mile of these instruments were to be altered to 735 in order that the mileage readings should not read so much higher as the present 4.1% which results from the drive revolutions per mile being 750. The speed indications of the instrument at 600 R.P.M. exactly were found at various temperatures to be in accordance with the following table, from which it will be seen that the temperature error is quite small and well within the limit we have demanded. Temperature (°C) | Miles per hour indicated at 600 R.P.M. exactly. -----------------|------------------------------------------------ 15.0 | 51.9 20.0 | 51.4 22.0 | 51.1 25.0 | 50.6 28.0 | 50.4 30.0 | 50.4 35.0 | 50.3 The temperature at which the instrument is correct in itself is somewhat above 35°C. so that all speed readings within | ||