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).
Operation and testing of a starter motor engagement and automatic hold-off feature.
| Identifier | ExFiles\Box 168a\2\ img061 | |
| Date | 1st March 1932 | |
| -2- When the engine starts, the motor is thrown out of engagement and spins at a fairly high speed for two or three seconds before coming to rest. With the motor field energised, therefore, as would be the case if the teaser remained on contact, the armature would build up a back voltage which would oppose the battery voltage and prevent the motor field being magnetised sufficiently to draw the armature into gear again. As soon as the motor slowed down sufficiently the armature would tend to move forward again into gear but during this time the engine has been well started and the finger instinctively has left the press button, so that a re-engagement is impossible. Even if the push button is still held down, the starter pinion does not attempt to engage but just rubs against the flywheel gear ring and the resulting noise would be sufficient indication if one absent-mindedly held the button down too long. As a result of this theory we insulated the hold on circuit on one of our experimental chassis and tried one or two engagements entirely satisfactorily, there being ample time for the push button to be released when the engine started. It will be seen, therefore, that we possess inherently an automatic hold off feature for a short time. We are quite willing to demonstrate starting a P.2. engine without the hold off switch operating and should be glad to have your opinion as to the feasibility of the scheme in view of the reduced cost for J.3. and Peregrine. FB/WAT. | ||