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).
The testing of a 20/25 dynamo with doubly tapered pole pieces, concluding there is no advantage.
| Identifier | ExFiles\Box 68\4\ scan0324 | |
| Date | 9th February 1931 | |
| X5663 Ey. from EFC. c. Ey/RD. c. Wor.{Arthur Wormald - General Works Manager} EFC5/AD9.2.31. X.5663. 20/25 DYNAMO WITH DOUBLY TAPERED POLE PIECES. At RD's request we recently received for test from Mr.Brock a 20/25 dynamo with pole pieces tapered off at both the leading and the trailing sides. On a preliminary run performed with the object of determining the temperature setting of the machine, it was found that the control brush angle was such as to lead to too great an output, the dynamo overheating in the course of two hours to the extent of throwing the commutator solder. As we have reported, we have proved that there is no advantage fundamentally in tapering the pole pieces over the simpler method of concentrically increasing the air gap. In the case of any variation of a dynamo with the idea of improving the output characteristic, a process of experimental testing by which suitable positions of the brushes may be found, must be made in every case. We think that any suggestions of this sort should be put to us merely as suggestions owing to the fact that we are well able to say what the value of such suggestions will be in regard to improvement in output characteristics. EFC. | ||