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).
Comparison of performance curves for various dynamo modifications, including different coil counts and pole piece designs.
| Identifier | WestWitteringFiles\V\December1930-February1931\ Scan164 | |
| Date | 26th January 1931 | |
| -2- EFC4/AD26.1.31 contd. Curves I and II correspond exactly with curves I and III on 1. in the 40/50 case. Curve III however, is for a dynamo otherwise similar to I but with the pole piece modification i.e. it is for a 56 coil machine with pole piece modification whereas in the 40/50 case II was a 48 coil machine without pole piece modification. The object of giving curve III in the present instance is in connection with some dynamos on 20/25 chassis in America and the desirability of giving U.S.A. particulars of a modification by which the output can be suitably altered in accordance with their demands and as indicated in Hs{Lord Ernest Hives - Chair}5/MJ16.1.31 and Sg{Arthur F. Sidgreaves - MD}4/E19.1.31 It will be seen that both curves I and III for the machine unmodified and modified respectively are for the same temperature rise setting and they are therefore comparable in every respect. Curve II on the other hand, is for a 48 coil high output machine and the temperature rise setting allowed has been 7° more owing to the fact that such a machine is intended to be used with the two-rate charge scheme. In spite of some repetition we think it worth while to put down the following :- Curve I. is for the 20/25 56 coil present standard dynamo. " III. is for the same dynamo with the pole piece modification such as is made to increase the peak output and output at speed but with some loss of cutting in. whereas Curve II. is for the recent experimental 48 coil high output machine with polar modification. The curves we have so far given this year are, of course, for various modifications of machine with which modifications we are already familiar. The value of giving these curves at the present moment is that they are given on our new and very definite basis so that curves for further developments of machines as they are from time to time issued, will be strictly comparable with the curves already issued this year and the resulting improvements can therefore very definitely be appreciated. | ||