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).
Requirements and specifications for a dynamo system on a 4½ inch car engine.
| Identifier | ExFiles\Box 183\M22\ img022 | |
| Date | 11th November 1918 | |
| From R.{Sir Henry Royce} copy to G.{Mr Griffiths - Chief Accountant / Mr Gnapp} W. EH. X.794 X.3014 ORIGINAL 11th November, 1918. R6/G111118.F 7CA RE DYNAMO FOR 4½" CAR ENGINE. As far as I can remember, the best we have installed for a convenient speed, and probably a convenient drive for cutting in at low speed and for not over-charging the battery, is the Bijur system, similar to the one you have sent for the Drawing Office lights at West WitteringHenry Royce's home town. (1) We cannot do with a heavy dynamo. (2) We do not think it is necessary to charge under 15 miles an hour, therefore the "cut in" should act at about 750 on the dynamo, and the belt ratio should not be more than 1½ to 1, otherwise the pulley is too small. (3) We think with a starter motor it is necessary to have a 12 volt plant. We should be pleased to know whether we can supply a satisfactory 12 volt non-trembler ignition. With a starting motor, it will not be necessary to have a trembler ignition system. The battery ignition coil should have sufficient resistance to run with a fair economy of current at slow speed, but capable of firing the engine up to 2,000 revs., i.e. high percentage of non-inductive resistance. Kindly take this matter up with Mr. Clark. So far Lucas seem to have failed, their original dynamo on 7 CA could not be driven because the pulleys were too small. There was also a particular fuse on the switch board which was blown on two occasions. When this happened dynamo still gave current at a much increased speed. This caused wrong impression, i.e. it was thought belt was slipping, or dynamo not arranged to "cut in" early enough. R.{Sir Henry Royce} | ||