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).
Technical discussion on dynamo speeds, battery charging characteristics, and output specifications.
| Identifier | WestWitteringFiles\D\March1920\ Scan42 | |
| Date | 13th March 1920 | |
| Contd. -3- Ckl/T13.3.20. It is argued that high dynamo speeds are mostly obtained during running in the open country and in circumstances in which the battery gets sufficient charging in any case, so that the loss of out-put at such speeds is a matter of small moment and may even be desirable from the point of view of the reduced boiling up that the battery may receive. It was, they stated, considered by one of their customers that a drooping characteristic curve was quite a desirable feature. The machine with which they would supply us, would have a similar output curve to this type 2D. It would attain cold a voltage of 12.4 at a speed of 440 R.P.M., and hot it would attain a voltage of 13.6 at a speed of 510 R.P.M. These speeds would correspond respectively to road speeds of 8.5 miles per hour and 9.8 miles per hour, using our present standard speed ratio of 1.56. The use of a pulley giving an exact 1.5 speed ratio would raise these speeds to 8.8 and 10.2 miles per hour respectively and would, therefore, comply with the specification that the dynamo should cut in at 10 miles per hour. It would, however, enable an output of 10 amperes to be easily attained at 14 miles per hour cold and 17 miles per hour hot. Regarding the heating tests, we have not so far been able to get these ready for issue. We hope in the course of a day or two to give you some figures illustrating the actual operation of cutting in and cutting out, both on the Smith and Lucas dynamos in Contd. | ||