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).
Cause of noise in the Goshawk dynamo.
| Identifier | ExFiles\Box 51\1\ Scan314 | |
| Date | 30th November 1923 | |
| To EY. from EFC. {E. Fowler Clarke - Electrical Engineer} To EP. {G. Eric Platford - Chief Quality Engineer} c. Sft. {Mr Swift} for Mr. Brock. X.4383 EFC {E. Fowler Clarke - Electrical Engineer} 5/T30.11.23. X.4383 - GOSHAWKAero EngineCodename for 20HP Car / Aero Engine after KestrelAero Engine DYNAMO NOISE. Though perhaps we cannot up to the present consider this definitely substantiated, we have a good deal of evidence pointing to the following conclusion - that the amount of irregularity in the magnetic drag on the armature, when the brushes are lifted and the field winding excited independently, is a measure of the noise which the dynamo will produce. The dynamo is of course arranged, so that with an ideal degree of accuracy of workmanship there would be no irregularity in the magnetic drag on carefully turning the armature round in the field produced as described. Because there are four poles and 29 teeth, even if the armature slots were straight, any irregularity should occur uniformly 4 x 29 times per revolution. As a matter of fact we have now tried a machine with straight slots on the bench and we find the noise to be the worst ever experienced. With the slots skewed as they are, then in the ideal case there should be no irregularity in the magnetic drag when the armature is turned round, but the law of magnetic traction is such that it can hardly be expected that the workmanship can be so fine that no irregularity would be experienced in any cases. Eontd. | ||