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 design, addressing field coil windings, power output, and testing for car and aero engines.
| Identifier | ExFiles\Box 34\3\ Scan165 | |
| Date | 15th December 1920 guessed | |
| Contd. -3- R3/G17418. Contd. there is much more to be considered than the maximum horse power or the maximum efficiency. It was these auxiliary considerations which led us to wind the field coils of our starter motor with apparently too many turnings. The result of your early test was so surprising to me when it was found that our motor was heavier, and yet did not give either efficiency or horse power as good as others, I became anxious to know in what way we had varied, but the matter is much clearer now, and I think we had better concentrate on work more urgently required. Regarding the stock of materials, these could be used up for making starter sets for the car, for which they are evidently suited. I should not attempt to fit them to the "Kondor" which we think will be all right with a Lucas "A" motor or this same motor re-wound in both the armature and field coil for a higher speed. We do not propose to have anything to do with making starter motors for these aero engines, as our hands are so full with other work. If, however, you do make an additional test of the R.R. motor to get the same speed, I should certainly keep the field coils two in series, two in parallel, which seems to make them about correct for a good output. One would expect with increased voltage, to find that the horse power would increase from 1.35 to about 2.25, and the revolutions for maximum horse power from 900 to 1500. The maximum efficiency would probably be a curve shewing a maximum at 2500, slightly higher than the 12 volt one. If these speeds are though too high, then the voltage should not be 20, but something less. R.{Sir Henry Royce} | ||