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 detailing the investigation and preliminary test results of a British Jaeger Magnetic and a Chrometric speedometer.
| Identifier | ExFiles\Box 165\2\ img127 | |
| Date | 2nd November 1937 | |
| C.A.P. 6065 Rm{William Robotham - Chief Engineer}/RC.{R. Childs}3/JH. 2nd. November, 1937. S.Smith & Sons Ltd., Cricklewood Works, LONDON.N.W.2. For the attention of Mr.Buckland. Dear Sirs, A short time ago, we had passed on to us, for investigation two speed indicators, one of which we understood was a British Jaeger Magnetic speedometer, and the other a British Jaeger Chrometric speedometer. No information accompanied these instruments apart from a statement that "the Flex speed for these instruments must be 1,600 revs. per mile". From this we understand that the indications of both instruments were based on a calibration of 1,600 revolutions per mile. Both instruments were given a preliminary run our observations on which are as follows :- 1. This instrument, presumably the Chrometric speedometer had the characteristic of the pointer taking up its indicating position on the scale, in a series of jerks. It was found that the driving speed corresponding to an indicated speed of 60 miles an hour was 1,480 revs. per minute. When stopped instead of returning to zero, the pointer came to rest at about 12 m.p.h. and only went to zero on starting up again. 2. This instrument is presumably the Magnetic speedometer, as the movements of the pointer are continuous. It was found to have a driving speed corresponding to an indicated 60 miles per hour of 765 r.p. minute. | ||