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).
Continued discussion on the performance of E.575 and C.575 dynamos, detailing factors that affect out-put curves.
| Identifier | WestWitteringFiles\D\May1920\ Scan76 | |
| Date | 29th May 1920 | |
| Contd. -2- EFC1/T29.5.20. the amount of such increase not being objected to by us. This again would be approximately what would have happened to the machine had Messrs. Lucas adopted Mr. Royce's suggestion of lengthening the E.575 machine, without otherwise making an alteration. The present C.575 machine, although giving the earlier cutting in which we require, nevertheless is disappointingly low in normal out-put in the hot condition, as reference to our curves will show. We attach a copy of comparison curves of the E.575 and C.575 dynamos in each case for both the cold and hot conditions. These curves are very nicely representative of the performances of the two machines. In passing we might mention that an out-put curve taken without due regard to certain conditions may not be comparatively representative of the performance of a dynamo. The out-put curve is, for instance, considerably affected by the following conditions :- (1) The exact temperature of the dynamo at the time of test. (2) The exact opposition E.M.F. of the battery at the time of test. (Note:- The out-put is higher for a higher battery E.M.F.). (3) The exact position of the control brush. In regard to (1), our standard method is to take the cold out-put curve with the dynamo as nearly as possible at 18°C. Sufficient points only are taken to give a Contd. | ||