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).
Technical memorandum discussing methods for achieving a silent dynamo by adjusting the number of teeth and pole span.
| Identifier | WestWitteringFiles\F\April1921\ Scan48 | |
| Date | 1st April 1921 | |
| To EFC. from R.{Sir Henry Royce} Copy to GJ ORIGINAL. X294 RE SINGING DYNAMOS. X1005 X4383 R9/G27/4/21. It is interesting to hear that my anticipations of an even number of teeth and even span of poles results in a silent dynamo. When I said it was advisable that the span should be such that the same number of teeth are always under a pole, it was intended that this should apply to an odd number of teeth. It is my suggestion for getting a silent machine with an odd number of teeth, which is always used on a four-pole machine with a coil grouping of three. It would, of course, conduce to extra silence with the even number of teeth, and also the constant number of teeth under the pole should both be adopted, and also the gradual approach of the coming and leaving teeth. All of these precautions might be taken with very little, or no extra cost. You will remember that I particularly favoured the Rotax dynamo because it was reported that this was extremely well made, it was a light machine, and owing to it only having three brushes and one field circuit, it was the simplest, both in itself and in the wiring and switch arrangement. Moreover, it promised to be no heavier than the more complicated schemes, and promised to give us an equally good performance curve. I should therefore persevere with this system, in conjunction with the Rotax people, and also on our own, to learn the possibilities. You will remember that for "Goshawk II" the car is geared for a much lower speed. The enclosed cars for town work will be geared for 20 miles per hour at 1,000 of the engine, and as the dynamo would be going at 1 1/2 engine speed it would permit of a small and light dynamo of a much higher speed than our 40/50 (Contd.) E'K' 529V (100 L)(2'H 199' 11-9-20)C' 3200 | ||