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).
Analysis of speed indication errors at different temperatures and for different tyres.
| Identifier | ExFiles\Box 50\4\ Scan333 | |
| Date | 22th November 1929 | |
| -2- On the chassis the speed errors cold (17.2°C) will be the same as the mileage errors. At 30°C. the speed errors will be 3.4% high for average tyres and 1.15% high for the largest tyres fitted. The speed indications of M89. 765. 11/41 at 600 r.p.m. exactly with the correspondingly correct drive revolutions per mile were found to be :- | Temperature (°C) | Miles per hour indicated at 600 r.p.m. | Corresponding correct revs. per mile | |---|---|---| | 17.0 | 52.1 | 691 | | 20.0 | 51.8 | 695 | | 24.0 | 51.6 | 697 | | 26.0 | 51.4 | 700 | | 28.0 | 51.4 | 701 | | 30.0 | 51.2 | 702 | | 32.0 | 51.0 | 706 | shewing the instrument to be rather badly incorrect in itself at all temperatures. The temperature error between 17 and 30°C. is only 1.8% in this instance. On the chassis the speed error cold (17.0°C) will be 18.5% high for average tyres, and 15.9% high for the largest possible, and at 30°C. these errors will become 16.7% and 14.1% respectively. Is it your wish that this instrument should go to R.{Sir Henry Royce} reading as above? EFC. | ||