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).
Examination of a starter motor failure caused by grease from the bearing affecting the brush mechanism.
| Identifier | ExFiles\Box 35\1\ scan 040 | |
| Date | 6th November 1919 | |
| X 2656 To Bn.{W.O. Bentley / Mr Barrington} from EFC. c. to By.{R.W. Bailey - Chief Engineer} c. to EP.{G. Eric Platford - Chief Quality Engineer} EFC1/AT6.11.19. X.3348 X.3644. BRUSHES & BRUSH SPRINGS FOR STARTER MOTOR. X.2656 X.3647. X.3082. With reference to EP{G. Eric Platford - Chief Quality Engineer}14/F5.11.19, and our conversation of this afternoon, we have now examined the particular motor in question and have found the failure not to be primarily due to want of brush pressure. What has happened has apparently been this :- The grease from the bearing has worked its way through and got on and around the lower brush without, apparently, getting on the surface of the commutator, but in such a manner as to prevent the brush having freedom of movement when the motor had cooled down, and the grease congealed. On starting the motor in a cold condition the bedding of this lower brush would be impaired and nearly the whole load would be thrown on to its companion brush at the top. Although it is quite possible that the strongest spring might have prevented this occurrence, nevertheless, weakness of spring does not appear to be, in this instance at any rate, the root cause of the trouble. As to how the grease should get out of the bearing in this manner we do not understand. We have never had this happen under normal load running conditions on the bench but only signs of it under extra heavy load conditions, and we wonder if this motor had been misused in some way because there appears on the carcase a dark-ened patch, rather pointing to the fact of considerable overheating Contd. | ||