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).
Performance changes to a dynamo after modifications, comparing it to previous tests and specifications.
| Identifier | WestWitteringFiles\J\March1923\ Scan2 | |
| Date | 1st March 1923 | |
| Contd. -2- EFC/T2.3.23. previous to modification. The early or rising part of the characteristic curve has been, by this change, bodily shifted approximately 100 r.p.m. later (at 62ºC), but above 1600 r.p.m. the output has been considerably increased, the curve being more flat-topped. The field coil resistance has been increased from 2.6 to 3.1 ohms, and the field current at cutting in point (hot condition) reduced from 3.1 to 2.55 amperes. Comparative results of this and previous tests are shown on the accompanying photostat. It will be seen that the curve does not now in the early stage meet our specification of performance. Although some advantage is gained at the higher speeds, this is at the expense of a fair amount of loss of low road speed charging, the point of crossing occurring at about 1600 r.p.m., i.e. at 32.5 m.p.h. with the low gear (13/60 back axle). Thus it is questionable whether the change is desirable, especially in view of the fact that we may be able to effect still further improvement with the machine as at present, without overheating, but still further retarding the control brush. There is, however, a limit to this process due to brush sparking. We have now for comparative test a Goshawk dynamo with a thicker carcase (larger external dia.) and air gap reduced to .012" in place of .015". EFC. | ||