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).
Test report for an A.T. Speedometer from chassis 18-GIV after a 10,000-mile test.
| Identifier | ExFiles\Box 59\2\ Scan081 | |
| Date | 3rd October 1930 | |
| Ms/AJL. from EFC. c. Hs.{Lord Ernest Hives - Chair} X4308. EFCl/AD1 3.10.30. X.4308. A.T. SPEEDOMETER D.231. 740. 11/50. EX CHASSIS 18-GIV for 10,000 MILE TEST. This instrument has been duly tested on our bench in the usual manner. The counter revolutions per mile were found to be 742.5. The correct miles per hour reading corresponding to this figure when the instrument is driven at 600 R.P.M. should be 48.5. A table of the actually indicated miles per hour at 600 R.P.M. at various temperatures is given below, the percentage fall of reading between 20°C. and 30°C. being 2.1 :- Temperature (°C) M.P.H. indicated at 600 R.P.M. exactly. 16.0 47.2 20.0 46.8 22.0 46.6 24.0 46.4 26.0 46.2 28.0 46.0 30.0 45.8 32.0 45.6 It will be seen that the instrument is reading low in itself at all times, though the fact that the revolutions per mile at which it is driven are more nearly 750 than 742.5 would seem to correct this error. The probability is that the speed readings will be considered to be, and will actually be rather lower than would be desirable on a customers car. EFC. | ||