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).
Performance tests for A.T. Speedometers concerning temperature variation and mileage durability.
| Identifier | WestWitteringFiles\S\June1928-August1928\ Scan137 | |
| Date | 29th August 1928 | |
| To R.{Sir Henry Royce} from EFC. c. DJ. E.{Mr Elliott - Chief Engineer} Ds. c. Wor.{Arthur Wormald - General Works Manager} Ey. c. CMB. EFC/T29.8.28. ORIGINAL A.T. SPEEDOMETERS. X4308 According to tests we have made with one or two recent production instruments, the drop of reading between the temperatures 18°C. and 30°C. does not now exceed 3%, which we consider satisfactory. The temperature at which the instrument reads correctly varies a little but may be said to lie between 25°C. and 35°C., which also we consider satisfactory. In regard to change of magnetism with time, so far we have only had one repeat test of an instrument after a mileage of 4175, and in this one case there was no change of reading. We have other instruments whose performances have been carefully noted and will be re-observed after a suitable mileage. In regard to the small type dial instrument, the first sample of this showed a similar degree of satisfaction in regard to reading and change of reading with temperature, but had to be returned for correction as the trip counter was not working correctly. It has now passed through our laboratory O.K. and been placed on an experimental car. In the meanwhile we are obtaining another instrument with a suitable axle ratio for another car. Owing to the fact that in these instruments the mechanism has to be got into a smaller space, we are of the opinion that some amount of running is necessary on an experimental chassis before we can standardise. The prospects, however, are very satisfactory. We do not think more than a few thousand miles in each of two cases would be necessary. EFC | ||