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).
Continued report on speedometer testing, discussing errors related to temperature and control spring weakening.
| Identifier | ExFiles\Box 59\2\ Scan057 | |
| Date | 9th August 1930 | |
| -6- EFCL/ADL9.8.30 contd. assurance that the instruments have not been touched we can only put this down to a weakening of the control spring. Any effect which may have been due to loss of magnetism would have been quite swamped by this effect. In the particular case of the speedometer referred to in Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/ADL4.8.30 our bench test showed this instrument to be in error in itself (compared with our requirements) in that its self correctness occurred at a temperature of 28°C. in place of 35°C. the result of this was that the speed readings were 1% low relatively. The last paragraph of Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/ADL4.8.30 would appear to suggest that we should make the speed indications still higher in relation to the counter miles to an extent which corresponds to making the instrument correct in its self relation at a temperature considerably higher than 35°C. This would result in the self error of the cold instrument becoming considerable. EFC. | ||