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, showing readings at various temperatures after 10,000 miles.
| Identifier | ExFiles\Box 59\2\ Scan046 | |
| Date | 9th July 1930 | |
| A.T. SPEEDOMETER TEST RECORD. Date :- 9-7-30 Speedometer :- A.T. No A677. N800. 14/32 Remarks :- Taken off 23 EX after 10000 miles. Counter revolutions per mile 800.8 (found by actual trial). 45.0 Miles per hour indicated at 600 r.p.m. exactly :- Temperature (°C) | M.P.H. indicated. | Revs. per mile. of drive for correct speed reading. 20.0 | 51.1 | 704 22.0 | 50.7 | 710 24.0 | 50.3 | 716 26.0 | 50.0 | 720 28.0 | 49.8 | 723 30.0 | 49.6 | 726 32.0 | 49.4 | 729 35.0 | 49.1 | 733 Percent fall of reading between 20°C. and 30°C. 2.9...... 8.7.30. | ||