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 results for two speedometers, measuring M.P.H. and revolutions per mile at various temperatures.
| Identifier | ExFiles\Box 50\4\ Scan202 | |
| Date | 13th June 1928 | |
| X.4308 13.6.28. B (1) TEST ON SPEEDOMETER NO. 247.D.730.15/52. TESTED IN NEW BOX WITH FAN IN, AND HEATER IN CENTRE. THERMOMETER ON LEFT OF BOX. Temp. (°C) M.P.H. at 800 rpm. Revs. per mile. 16.3 49.8 723 20.1 49.2 732 22.1 49.0 734 25.0 48.7 739 28.1 48.3 745 30.3 48.1 748 Points O (2) TEST ON SPEEDOMETER NO. B247. D730 15/52 HEATER IN LEFT HAND SIDE OF BOX ALSO FAN IN BOX. THERMOMETER ON LEFT Temp. (°C) M.P.H. at 800 R.P.M. Revs per mile. 16.3 49.5 727 20.1 49.0 735 22.0 48.8 738 25.0 48.6 739 27.0 48.3 745 30.0 48.1 748 Points ⌻ | ||