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).
Technical discussion on the accuracy of A.T. speedometers and proposed testing arrangements.
| Identifier | ExFiles\Box 59\2\ Scan111 | |
| Date | 3rd March 1931 | |
| X. 6051. S/W...EFC e.{Mr Elliott - Chief Engineer} to BY.{R.W. Bailey - Chief Engineer} X. 6051. Re A.T.SPEEDOMETER. With reference to your EFC3/AD12.3.31, it seems to me that we ought not to take part in technical discussions as to the gear that should be supplied by us for speedometers. We must, of course, leave that entirely to the Works. What Sales have been endeavouring to establish is the result the speedometer gives to the customer. This matter arose originally because by some means or other our speedometers were registering fast and this was quite noticeable on the mileage recorder part of the instrument. It was pointed out to us by a number of customers who knew exactly the mileage from one particular point to another. We therefore asked that the speedometer should be arranged as follows:- (1) That the mileage recorder should be as accurate as it is possible to make it. (2) The speedometer part of it, which we know varies under various conditions, should be never slow and not more than 5% fast. I understand that at the present time we do not definitely test speedometers on complete cars from the point of view of speed, but depend upon the speed as coinciding with the mileage recorder, and accordingly test them on a measured mile and accept speedometers which are up to 6% fast on the mileage recorder. I shall be glad if this matter can be given your early attention and the necessary arrangements made between ourselves so far as certain gears are concerned and the Speedometer people as regards the calibration and the instruments, so that instructions may be given to our Final Testers as to what they are to expect. The matter has again been raised by Commander Glen Kidston, who is apparently doubting the accuracy of our speedometers. C. | ||