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).
Pros and cons of belt-driven versus gear-driven dynamos for various car engines.
Identifier | ExFiles\Box 133\2\ scan0179 | |
Date | 5th November 1935 | |
Sg.{Arthur F. Sidgreaves - MD} from E.{Mr Elliott - Chief Engineer} SECRET E.1/HP.5.11.35. c.Wor.{Arthur Wormald - General Works Manager}Hs.{Lord Ernest Hives - Chair} By.{R.W. Bailey - Chief Engineer} Mx.{John H Maddocks - Chief Proving Officer} RE ENGINES. Replying to your memo Sg.{Arthur F. Sidgreaves - MD}10/E.4.11.35, the belt driven dynamo as used today is a modern development very different from the pre-War belt drives, of which we have such unpleasant memories. This is mainly because of the tremendous improvement that has taken place in the manufacture of belts developed mostly on the motor-cycles before the era of chain drives. I feel personally that we have got to keep an open mind, and we have got to keep moving with the times, and although a little while ago the idea of belt driven dynamo filled me with a certain amount of misgiving I believe today that the very small amount of horse-power taken by the dynamo, about 3/4 can be very reliably supplied by a belt drive of the right type. Our present gear drive on the 20/25 is very reliable, but far from trouble free, being a prolific source of gear noise and rattles. I have made careful enquiries, and I understand that if we could do away with the dynamo pinion and its drive on the 20/25 we should also do away with 99% of our timing gear troubles. No engine has as many timing gears in front of it as our 20/25. We have succeeded on Phantom 3 in reducing this number by driving the dynamo and water pump in tandem. This scheme is also possible on the 20/25 engine and there is no doubt that putting the water pump on to the back end of the dynamo would be beneficial to a certain extent in silencing the drive. Such a scheme, however, does not provide a ready means of doing away with the other gears as there is still the oil pump and ignition tower to drive, and also it would not do away with very much of the 99% of trouble with gear quietening. Another advantage of the belt driven dynamo is that it can be stood away more from the crankcase, in fact the drive usually demands this, and the cooling of the machine is thereby improved. | ||