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).
Comparative analysis of various dynamo models and their suitability for use in cars.
| Identifier | ExFiles\Box 36\4\ scan 202 | |
| Date | 21th April 1921 | |
| Contd. -2- EFC4/T21.4.21. The balancing speed above mentioned corresponds, with a suitable belt drive ratio of 1.56, to an R.P.M. of the dynamo of 540. The corresponding figure for the cold condition would then come out at about 440 r.p.m. as against 610 as at present. A performance such as described is more universally suitable for R.R. cars, some of which are in use in town and some in the country, because at the low road speeds a larger amount of current is being delivered to the battery to accommod- ate the more frequent starts, and at high speeds a comparatively small amount of charging being done, thus favouring the life of the battery by reducing overcharging. The Lucas E.575 dynamo has also the failing of being to some extent a singer, and this feature has been a source of continual trouble both to Messrs. Lucas's and ourselves. The reason the E.575 Lucas dynamo was used in the first instance was that, of dynamos available at the time, this was the most suitable machine. The only alternative was the C.A.V. N.G.R.R. type whose performance characteristics were somewhat better than those of the Lucas E.575, but which in other respects, e.g. workmanship, finish, and judged reliability, did not satisfy our demands. It will be understood that the time available for prolonged experimental comparative tests on cars was insufficient. The question may be asked, Why has not every endeavour been made to substitute as standard a machine other than the Lucas E.575 ? The answer to this is that from that time onwards we have left no stone unturned to bring this about, but we have failed, not on account of our own short- comings, but because dynamo makers have so far failed to give us a machine which is exactly right for the purpose. We have from time to time had various makes and types of dynamo in view, but not one of these entirely satisfied our requirements, in every direction. Some have satisfied us in some ways and others in others. Details of the various machines will be found set out below :- Lucas A.400 Dynamo. WE have had from Messrs. Lucas several samples of this dynamo which is a much larger machine of the 4-pole type. Carcase dia. 6.775" Armature dia. 4.55" Weight 40 lbs. This dynamo has output characteristics which as regards earliness of cutting in and quantity of charge at low Contd. | ||