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).
Dynamo design, 'cutting in' points, resistance values, and various charging schemes.
| Identifier | ExFiles\Box 163\6\ img076 | |
| Date | 26th November 1930 | |
| (Contd :- - 2 - dynamo, and secondly of the use in conjunction with this of a resistance in the field winding. The use of one of a much lower resistance value, however, would improve the "cutting in" as well as the reduced output and to provide for Town running. It will be realised that this same value would not be suitable for the other extreme of touring mostly in daylight. Referring to Sg{Arthur F. Sidgreaves - MD}'s paragraph commencing "our dynamos": it has been the case until the advent of the "high output" that our "cutting in" point has been good (low speed) It has, as previously explained, with the size and weight of the machine available, not been possible to maintain this good "cutting in" at the same time as increasing the full output. This has been realised by R.{Sir Henry Royce} and he has in his memos sometimes remarked upon "the unnecessarily early cutting in". Personally, we have always been against a very high output in view of the loss of output on low speeds occasioned and the danger, even with the ordinary system, without the half-charge scheme of running into trouble of insufficient output in Town running conditions. The half-charge scheme was the outcome, the dynamo used with it having been specially evolved to give the very best "cutting in" point consistent with the high output. We still hope to effect some further improvement. When there was a suggestion of having two different dynamos (apart from special cases) R.{Sir Henry Royce} viewed this with disfavour, saying that the wrong man would get the wrong machine. In the case, however, of these resistance units which are so easily changed, perhaps it may be said that the argument does not equally apply and that the two or three different values suggested might all be standardised. If this is not done there is almost sure to be some amount of trouble in both extreme cases. We should like to take this opportunity of referring again to the scheme of auto charge control scheme, a suitably high output machine is intended to be used but the charge is automatically controlled by being switched on and off so as on the average to give an amper-hour output to the battery, which is demanded in every case. This is a system that automatically adjusts itself to the requirements of different circumstances of running and it has shown great promise during the relatively small amount of experimental (Contd:- | ||