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).
Analysis of starter motor gear ratios and spring mechanisms, comparing with a Bosch design.
| Identifier | WestWitteringFiles\T\November1928\ Scan095 | |
| Date | 17th December 1928 | |
| EFC1/T17.12.28. -7- Contd. in much the same way as our own. At the moment we feel that the problem on our own starter is somewhat different, partly on account of the gear ratio which is probably higher than in the Bosch case, resulting in the fact that our motor armature would be spun to a higher peripheral speed before disengaging. In regard to the strength of the pinion or 'jump-back' spring, we have put in hand a spring of low initial pressure but high rating. We had been of the impression that the set of this spring was too great. The longitudinal pull of the pinion Bosch armature was capable of compressing this smaller spring on that unit, whereas our longitudinal pull was not. We have given a considerable amount of thought to the matter of the relative quantities of the spring, longitudinal attraction, brush frictional effect, gradient, ordinary frictional effect and fluid frictional effect, and we cannot see that it is really possible to obtain relief from both end thumps at the same time and in all temperature circumstances unless we introduce some form of fluid friction damper which can absorb the kinetic energy which necessarily results from the use of a sufficiently powerful spring with a sufficiently great longitudinal pull. EFC. | ||