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).
Letter to the A.T. Speedometer Co. discussing the performance testing of a modified speedometer under temperature variations.
| Identifier | ExFiles\Box 50\4\ Scan120 | |
| Date | 18th June 1927 | |
| X4308. Expl: Dept: Hs {Lord Ernest Hives - Chair} /RmL/LG. 18th. June. 1927. Messrs. The A.T. Speedometer Co., 20, Avonmore Rd., West Kensington, W.14. A.246. Dear Sirs, We thank you for your letter of the 7th. inst. and for the speedometer No. A.246 modified to overcome the variation due to temperature. We have tested this instrument and find it to be a very definite improvement over your previous model No.18744. The actual decrease in the reading with a temperature rise of from 18°C to 34°C is 4%. While we should, of course, prefer to have an instrument which does not exhibit any variation in this respect, we consider that 4% is permissible. We have carried out some tests on the road which indicate that our instrument boards normally attain a temperature about 8°C -10°C above that of the atmosphere. Therefore for British conditions the mean temperature of the speedometer is 20-25°C and it would be advantageous if all speedometers despatched for our use could be arranged to be correct at this temperature. We should like to know whether you are in a position to incorporate your latest modification on all speedometers for our use immediately, also whether you can modify some of our present stock for experimental use. If so, we will forward three or four to you. Yours faithfully, | ||