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 performance, including cut-in speed, belt ratios, and comparisons with other electrical systems.
| Identifier | ExFiles\Box 61\2\ scan0089 | |
| Date | 22th August 1917 | |
| R.R. 235A (500 T) (S.D. 408. 26-4-17.) Bm. 2/156/13. To Mr. Young. R.{Sir Henry Royce} X.3014 FOR "C" RAD. ENGINE Or dynamo not arranged to "cut in" early enough. As far as I can remember the best we have installed for a convenient drive, and probably for not overcharging the battery at high speed and cutting in at a convenient speed, is the Butler 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 12 miles an hour, therefore the "cut in" should not be under 12 m.p.h. on the road. The belt ratio on the dynamo and the engine should not be more than 1 1/2 : 1 if the pulley is too small, otherwise the belt slips or the fuse blows out. If it is under this ratio, (3) we think it is necessary to have a 12 volt plant with a starter motor. If a starter motor is used, it will not be necessary to have a Trembler ignition. We should be pleased to know whether we can supply a satisfactory non-Trembler ignition. A non-Trembler ignition would have sufficient resistance, and should fire the engine up to 2000 revs. i.e. high speed! The battery/coil system has the disadvantage of giving a good spark at slow speed, but is not so reliable and will not run with a fair economy of current. Kindly take this matter up with Mr. Olah. So far as Lucas seem to have failed. Their original dynamo on the TDA could not be driven because the pulley were too small. There was also a particular set fuse on the switch board which was blown on two occasions. When this happened the dynamo still gave current at a much increased speed. This caused the wrong impression i.e. it was thought the belt was slipping. O.T.Q. | ||