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 output, battery charging limitations, and potential improvements.
| Identifier | ExFiles\Box 163\6\ img110 | |
| Date | 24th December 1930 | |
| -2- EFC3/AD24.12.30 contd. different resistances all for 14.0 volts constant and 80°C. of the dynamo carcase. Answering your last paragraph on your first page, we are of the opinion that it would be an improvement to have full charge in the S & T position as well as in the H S & T position. There would be no need in this case to reduce the dynamo output at all for the reason that when the side and tail lamps are being used, the existance of the other circumstances of hot atmosphere (summer and daylight) which we have to guard against in setting the dynamo, is very improbable. If it were not for the fact that a man might remove his lighting fuses for the express purpose of obtaining full battery charge on a summers day, and might forget that he had done so, we could even in the present circumstances set the dynamo say 1 to 2 amperes higher. We are not quite clear regarding the import of your last paragraph in view of the fact of R's non-agreement to the enlargement of the dynamo, as in any case we are at present doing all we know to obtain the last ounce of output generally from the dynamo consistent with the limitations imposed. We have carefully studied the safety margin in various circumstances from the point of view of overheating and we must reasonably maintain this, if however, we could always be sure that the dynamo would be switched off when the voltage rose to a certain limiting value, then the ampere output setting of the dynamo at lower voltages could be considerably increased. This calls rather emphatically for automatic means. It would then be possible (as a rough proximation) to obtain the same output from the present standard 56 coil machine as from the high output machine and at the same time to maintain the earlier cutting in of this present machine. The only other alternative we can see is to improve the cutting in of the high output machine by increasing the length of armature as we have already suggested, and particularly as we now have information from PN{Mr Northey} that the battery will not keep up in Town running conditions with the high output dynamo, simply because the voltage average speed is insufficient to allow the necessary number of ampere hours to be generated. This, of course, is an extreme | ||