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 and battery performance in relation to headlamp current and output curves.
| Identifier | WestWitteringFiles\V\2January1931-April1931\ Scan073 | |
| Date | 27th March 1931 | |
| EFC2/AD27.3.31 contd. -3- With regard to the last paragraph of RL/M 9.3.31 we see the matter as follows :- So long as head lamps demanding only moderate current in relation to dynamo and battery size were in use, a dynamo of moderate output only was necessary. Without any charge control, either hand or automatic, a sufficiently good compromise was obtainable by utilising the simple field winding third brush controlled machine with a moderate fall of output with speed. In the average case at least, the output was sufficient for the lights, aided slightly by the battery at high speeds and was not excessive for the battery when the lights were not in use. The use of larger head lamps demanded a jump up in the output, when it immediately became necessary, or at least highly desirable, for the sake of the battery to have some means of controlling the output depending upon whether the lights were in use or not. Once that is done the reason for a falling characteristic entirely vanishes and we are left with the struggle to maintain the output at speed, while we are still using the simple arrangement of machine. There are ways and means of not having such a rapid fall as we have usually used and all the possibilities are being explored. It will never be possible, however, to make a flat or even nearly flat curve of output with speed so long as the simple arrangement of dynamo is retained. Any modification which increases the peak output and increases the speed of cutting in appears to make a flatter curve because the proportional reduction shown by the output curve on the usual speed base is less in relation to the peak output. Some results for the Lucas dynamo as standard on the Vauxhall car are now available and will shortly be reported upon. EFC. | ||