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).
Comparing the reliability and types of Elliott, Waltham, Watford, and Smith speedometers.
| Identifier | ExFiles\Box 36\1\ scan 082 | |
| Date | 12th September 1921 | |
| X2915 Da.{Bernard Day - Chassis Design} from Hs.{Lord Ernest Hives - Chair} 6 X613 X2915 RE. SPEEDOMETERS. Hs{Lord Ernest Hives - Chair}5/LG12.9.21. The Elliott Speedometer has given a tremendous lot of trouble. It is a very expensive instrument and yet is unreliable. The most satisfactory Speedometer we have had on test is the "Waltham". It is the revolving disc type. It has the advantage of being exceedingly well-made, silent and steady. We are also at present trying the Watford and Smith Speedometers which are the centrifugal type but very much cheaper than the Waltham. Hs.{Lord Ernest Hives - Chair} Da{Bernard Day - Chassis Design}'s memo in X 1809 | ||