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).
The performance and testing of Smith type A and 2D dynamos.
| Identifier | ExFiles\Box 3\5\ 05-page162 | |
| Date | 4th March 1920 | |
| Contd. -3- CK{Mr Clark}2/T4.3.20. For the Smith type A dynamo, these figures will be seen to be about 500 R.P.M. for the cold condition and 585 R.P.M. for the hot condition. We have, however, now received a second machine from Messrs. Smith called type 2D, in which they have lowered the balancing speeds to about 430 and 500 R.P.M. for the cold and hot condition. This they have done at some slight expense of maximum ampere out-put when the machine is hot, namely, 11.4 amperes as against 12.3, but curiously enough the maximum out-put on starting up quite cold seems to have been unaffected. We are, at the moment, making tests of the Smith and Lucas cut-outs, to obtain exactly the effect of temperature, and we hope, in accordance with your various requests, to be able to let you have these results very soon. We further look upon the balancing speed taken in conjunction with the steepness of the out-put curve after the cutting in point, to be of more importance than the exact point at which the cut-out operates, because variations in the latter have a lesser per cent effect on the ampere hours generated by the dynamo at slow and moderate speeds. The speed ratio between engine and dynamo as at present standard for J series, is about 1.56 allowing for a slip of a few per cent; thus the road speeds corres- ponding to the figures given above are as follows:- Contd. | ||