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 record for an A.T. Speedometer, detailing its performance and accuracy at various temperatures.
| Identifier | ExFiles\Box 59\2\ Scan079 | |
| Date | 9th October 1930 | |
| X.4308. A.T. SPEEDOMETER TEST RECORD. Date :- 9-10-30 Speedometer :- No E.185.785. 11/41 Remarks :- Fitted on 2REX 11.10.30. Drive counter Counter revolutions per mile 785.0 (found by actual trial) . Correct miles per hour reading when driven at 600 r.p.m. :- 45.8 Temperature (°C) M.P.H. indicated at 600 r.p.m. exactly. 17.0 | 47.9 20.0 | 47.5 22.0 | 47.3 24.0 | 47.1 26.0 | 46.9 28.0 | 46.8 30.0 | 46.8 32.0 | 46.6 Percent fall of reading between 20°C. and 30°C. 1.5..... 9.10.30. | ||