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 report into a burnt-out sequence starter main and auxiliary switch unit from chassis 24-WJ.
| Identifier | ExFiles\Box 64\4\ scan0310 | |
| Date | 27th October 1930 | |
| X7655 By.{R.W. Bailey - Chief Engineer} from EFC. c. By/RD. c. C/Gn/WFH/EG. EFC2/AD27.10.30. X.7655. SEQUENCE STARTER MAIN AND AUXILIARY SWITCH UNIT EX CHASSIS 24-WJ. This switch was received by us in a very unusual condition for special investigation. The relay switch winding had had the insulation completely burnt away but in no other respect was the unit particularly damaged, in fact the unit would still work normally. It would appear that the current by which the coil was burnt out could only have reached the coil via the push button switch. Quoting from my assistant's report WE.55 we have :- "To burn the insulation to the extent shown the coil would have to be in circuit a long time, much longer than one would ever expect the push button to be held on. As an experiment, a new coil was placed in circuit with a 12 volt battery for 15 mins. but this treatment only blackened the insulation without charring. The voltage was then raised to 17.5 and after three minutes the insulation had badly charred. It therefore appears that this relay coil must have been in circuit when the engine was running and the dynamo charging the battery". It would appear that the only possibility was that the push button switch jammed and did not break the relay circuit when the pressure was released so that this coil became subject to the full voltage (about 17.5) of the dynamo battery system when full rate charge was taking place with the battery fully charged. However, as we have had no opportunity of examining the push button switch or the wiring circuits in question we cannot say definitely what caused the trouble. We cannot see a reason why this fault should be considered R.R. responsibility. The unit has been indiscriminately removed from the chassis without a proper diagnosis of the trouble being made. EFC. | ||