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).
Half-charge dynamo scheme using a changeable resistance unit to regulate output.
| Identifier | ExFiles\Box 163\6\ img075 | |
| Date | 26th November 1930 | |
| X6016. Wor.{Arthur Wormald - General Works Manager} c - BY.{R.W. Bailey - Chief Engineer} EFCl/W.26-11-30. Re :- Half-Charge Dynamo Scheme. (Sg{Arthur F. Sidgreaves - MD}14/E.25-11-30.) The equipment fitted to 58-GN was one of six sets which had been produced for trials cars in further confirmation of the satisfactoriness of the system, as indicated by the 10,000 mile test on 23-EX. A small, easily removable and changeable resistance unit, something similar to a ballast resistance unit, and located just over the distribution box, is a feature of the system. Electrically this is included in the field winding circuit of the dynamo, at all times except when the head lamp switch is "on", and causes the dynamo output to be less at all speeds than its full output by an amount which is entirely dependent upon the value of the resistance. The object of the arrangement is to make it possible to use a "high" output dynamo to meet the demands of heavy consumption head lamps, but at the same time not to inflict this high output on the battery for long periods when the lights are not required, and thus to minimise battery deterioration. This calls for a rather high value of the resistance and correspondingly low dynamo output, whereas Town running circumstances call for a much lower value of the resistance and a "reduced" output much nearer to the full amount. As a matter of policy, it would be considered better, if possible, to have one value only of this resistance, i.e. a compromise for the average case, and such a value has been tentatively standardised (after 10,000 mile test). We are, however, now forced to the conclusion that three or more different values of this resistance should be available to suit different circumstances of running. In particular, as a result of Sg{Arthur F. Sidgreaves - MD}14/E.25-11-30, we are arranging to have ready to-morrow two resistance units of different, but low value, and I can arrange to go to London as suggested by Sg.{Arthur F. Sidgreaves - MD} in his last paragraph but one on Friday, taking these units with me in order to demonstrate to him the modification of the "reduced" output which they effect. We are well aware of the lateness of the commencement of charge, referred to in Sg{Arthur F. Sidgreaves - MD}'s third paragraph - this is a necessary result, firstly, of the use of a higher output (Contd :- | ||