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).
Starter motor engagement failures, discussing spring strength, longitudinal pull, and winding specifications.
| Identifier | ExFiles\Box 64\4\ scan0132 | |
| Date | 17th December 1928 | |
| EFC1/T17.12.28. -3- Contd. already explained, the first failure resulting from the use of too strong a spring is that the motor simply comes into engagement, turns the engine, and then drops out quite of itself. It appears a little extraordinary how much the longitudinal pull is reduced by the main current when the speed of the motor increases, this being also illustrated by the rapidity with which the motor gets out of gear, even with straight teeth. In the motors as arranged we have not got the armature in its fully engaging position right opposite the poles, but short of this by an amount .175". Perhaps this could be less On these motors we reduced the gauge of the teazer winding on from 17 S.W.G. back to 18 S.W.G. ( your originally suggested gauge) on account of the absence of the actuator box in series (as in No.1 scheme). We do not think this is wrong, but if it does turn out that we have insufficient longitudinal pull, we can revert to the 17 S.W.G. winding. We wish to avoid excessive current through the teazer contacts. Our tests show that the end pull (on teazer current) is amply vigorous enough at the full engagement end. The question is whether it is vigorous enogh at the start and at just engaging to prevent the faults of possibly not starting to engage and not returning from corner jamming, because of insufficient strength of return spring at this point. We feel that it might be worth while trying a still further reduced taper. Contd | ||