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).
Experiments with different grades of Morganite brushes and spring pressures for starter motors.
| Identifier | ExFiles\Box 35\1\ scan 014 | |
| Date | 9th September 1919 | |
| X.2656. To R.{Sir Henry Royce} from EFC. c. to CJ. c. to E.{Mr Elliott - Chief Engineer} c. to En. c. to By.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} EFC3/T9.9.19. X.3348 - RE BRUSH GEAR ON STARTER MOTOR X.3082. X.2656. Using the present standard strength of brush spring, viz., F.7180, we had experimented with several grades of Morganite brushes, as the result of which we came very decidedly to the conclusion that the present standard brush containing a large percentage of copper was more satisfactory than either grades which we tried containing more carbon. The trouble we experienced was heating at the contact surface, causing irregular contact between the brushes and the commutator, and finally causing the commutator to get into a very bad condition. This did not occur except on rare occasions with the type which we have at present standardised, which is of C.M. type Morganite. However, it may be that with a yet stronger spring, a brush containing a high percentage of carbon would give a still more satisfactory effect. This we propose to try and we are for this purpose instructing up some springs experimentally which give a still stronger pressure (about 50% more) than the present standard spring F.7180 which was considerably stronger than the original springs G.3900. EFC. | ||