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).
The failure analysis of two Lucas starter motors, serial numbers 58 and 76.
| Identifier | ExFiles\Box 165\7\ img040 | |
| Date | 20th January 1950 | |
| -6- Serial No. 58. This motor was obtained from Lucas as a replacement for No. 62 which we had worn out on the starting test. The motor was fitted to B.40. MK.I. No.3 engine for a further 15,000 starts. After 400 engagements the new motor refused to engage. We found that one of the armature coil end connections had lifted from the commutator and fouled the field coils. The insulation had been rubbed through on all four coils. This motor was taken to Messrs. Lucas by Rm{William Robotham - Chief Engineer}/RC{R. Childs}/JRJ and the fault pointed out to their engineers. The appearance indicated that only one of the end connections had been overheated, and we assumed that this was due to local heating caused by a poor joint. It was pointed out that the slots in the commutator riser were very wide, for the size of the conductor used. Serial No. 76. A further motor was obtained from Lucas on 19.10.49., for the starting test. Clutch slip developed at an early stage and gradually got worse. After 4000 starts excessive sparking developed at the main contacts. The test was stopped at 4400, and the motor stripped for examination. We found that the armature core had been fouling the pole pieces and field connections, and that the main switch contacts were very badly burnt. We also noted that the soldered joints in the commutator risers were poor. As mentioned previously, the slots in the risers are too wide for the size of the conductor, and we think that due to this the solder tends to run out after the dip soldering operation. The motor was taken to the Lucas Works by Rm{William Robotham - Chief Engineer}/RC{R. Childs}/JRJ, and the faults examined in the Lucas starter laboratory. Great concern was expressed over the armature fouling, which appears to be a general fault with this type of motor. Regarding the main switch contacts it was stated that during the early development stages, a similar failure occurred, in which, a sticking solenoid plunger excessively reduced the contact pressure of the main switch. Cont'd..... | ||