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).
Vehicle electrical systems, including charging currents, lamp voltages, and cutout points.
| Identifier | ExFiles\Box 54\1\ Scan107 | |
| Date | 7th July 1936 guessed | |
| Contd. -2- EFC1/T. In regard to your opinion that the charging current can be further reduced without any fear of the battery running down, we think this may be quite correct, but as pointed out previously, it is very difficult to make such a test on our own experimental cars as they are rarely run in certain circumstances which are conducive to such a test, and I think perhaps we might arrange a machine for you with an exaggeratedly reduced output that you could run for us unofficially throughout next winter, if you cared to and could do so, as your circumstances of running would probably be most satisfactory for the purpose. The curve of ours which you have shewing the output not rising above 12 amperes is correct to the revised arrangements of the dynamos as we are turning them out now, when everything on the chassis is fully warmed up. I think your machine was altered by Mr. Bellringer, and it may not necessarily be correct to our latest production test for reduced output. It has always been my impression that lamps made for 12 volt systems are really 15 volt lamps. In any case they are usually marked 12/14 volts, and I agree with Mr. Lucas that real 12 volt lamps would not be satisfactory, i.e. would burn out quickly on the chassis system. Though I do not know definitely I feel almost certain that lamps for any 12 volt system must actually be made for a higher rate of voltage than ordinarily reckoned. They may still be called 12 volts, because they are used on a nominal 12 volt chassis system. Your experimentally running on five cells only would be very interesting. Currents will be reduced all round, including charging current. You may be able to observe beneficial effects on - (1) The cutout contact points. (2) The ignition contact points. It might be argued that the cutout should be re-adjusted for the lower voltage, but I do not think this is essential. You should, of course, find that at the instant of the cutout coming in the ammeter several amperes of charging current, and that at the time of cutting out, less reverse current will be required, or it even may cut out before the dynamo-battery current has reversed. From the cutout contact points point of view, this should be better, as it is desirable for the cutout to make a little late and switch on several amperes instantaneously, and then to break without a reverse current (practically at zero current | ||