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).
Further trials investigating starter motor jam issues by varying voltage and torque.
| Identifier | WestWitteringFiles\P\2July1926-September1926\ Scan057 | |
| Date | 17th August 1926 | |
| EFC2/T17.8.26. -3- Contd. stated, so far that does not appear to have been wrong. Since your note we have made further trials, but this time we have increased the teazer torque by the application of a higher voltage. The method of experimenting was to provide an additional six-volt battery unit and having got the jam on the normal voltage (though this is now very difficult to get and necessitates a lot of trials) step up in additional two volt steps until engine turning can be effected. It was arguable from the fact that the main current would overcome it, that it was not of the nature of a complete jam, but of a partial jam in which friction was sufficient to prevent a small torque getting away with the engine, though a big enough torque would do so. It was a jam in the sense that there was quite sufficient torque to turn the motor definitely on correct entry and slide the pinion into engagement. We found from various trials that in some cases the addition of only two volts extra would effect the get-away whereas in one particular case it was actually necessary for an additional six volts to be applied before this could happen. Then again, going the other way, we found that though we could in the majority of cases get away and start the engine on five cells the occurrence of the jam was more probable, also having produced a jam on five cells this could sometimes be cleared on six. The whole set of observations would appear to prove that failure was dependent upon the exact shape of the teeth at the point of engagement, and it gave one the impression that | ||