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, recording indicated speed and drive revolutions per mile at various temperatures.
| Identifier | ExFiles\Box 50\4\ Scan334 | |
| Date | 29th November 1929 | |
| X4308. 29/11/29 X.4308. A.T. SPEEDOMETER TEST. Speedometer No. D500. TRO 1/50 Speedometer type 20HP Speedometer Other particulars taken from stock Temperature (°C) Miles per hour indicated at 600 R.P.M. exactly. Revs. per mile of drive for correct speed reading. 20.0 | 51.3 | 702 22.0 | 50.9 | 707 24.0 | 50.4 | 714 26.0 | 50.2 | 716 28.0 | 50.0 | 720 30.0 | 49.9 | 721 32.0 | 49.7 | 724 Miles per hour at 1200 R.P.M. 3.6.29. EFC. | ||