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).
Investigation into a dynamo fault caused by sticking brushes on an experimental Wraith car.
| Identifier | ExFiles\Box 168a\3\ img118 | |
| Date | 7th October 1938 | |
| 6142 To By.{R.W. Bailey - Chief Engineer} c. to By/RD. c. to RMC/FMD. Rm{William Robotham - Chief Engineer}/RC.{R. Childs}1/JH.7.10.38. Dynamo Fault Due to "Ticking" Brushes. An outstanding case of a dynamo ceasing to charge, through the brushes not sliding freely in their holders, has been investigated by us. We were informed that the dynamo, a standard machine, on one of the experimental Wraith cars, would not charge when starting in a cold condition. After running on the road for about ten minutes, however, the fault automatically cleared, and behaviour was quite normal. Preliminary testing of the system, shewed that the fault was in the dynamo, which was consequently isolated and tested by itself. The brushes were thought to be free in their holders, and commutator was cleaned, but in no way could the machine be made to excite. It was then removed for test on the bench. On the bench the procedure was as follows :- First the insulation of the machine was tested, and found to be alright. This involved lifting and replacing the negative brush. The commutator was again cleaned. No effect. The brushes were tested for freedom in the holders, when a slight tendency to stickiness was noticed on the negative brush. Both brushes were removed, examined, and re-placed. No effect. Each brush spring was then drawn back and allowed to snap forward on to the brush, thus hammering at the brush. No effect. | ||