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 Smith 2D Dynamo, including performance evaluation, specifications, and comparison with alternatives.
| Identifier | WestWitteringFiles\F\April1921\ Scan96 | |
| Date | 1st April 1921 | |
| Contd. -4- EEC4/T21.4.21. Smith 2D Dynamo. For some considerable time now we have been experimenting with type 2D dynamos made by Messrs. Smith, and a number of these have been fitted and run on experimental cars. Apart from the earlier machines, we have to date received two machines incorporating the modifications required by R.R., one of these machines went to U.S.A. on 4-Ex, the only failing of that machine was that it put up a slight amount of noise. In the second machine which we have quite recently received, the singing has been reduced to an absolute minimum so as to be practically non-existent, but at the expense of a slightly later cutting in point which causes the performance not to fall quite within the limits of our specification, although very nearly. (This is the first Smith 2D machine which has not been within our limits). The principle of operation of the Smith machine is different from that of the Lucas and necessitates one conductor less between switchbox and dynamo. The Smith dynamo could not be immediately introduced as standard without at the same time making some change in the switchbox. Messrs. Smith have all along been particularly anxious to meet our requirements, and have done their best in this direction. We are shortly receiving from them yet another machine which they say will meet our specification with complete silence at the same time. The running qualities of the Smith machines have been tried out on experimental cars and so far every satisfaction has been given. Our opinion is that the Smith machine is the nearest approach to the ideal machine which we require for the R.R. car. The numerical particulars are as follows :- Weight 33½ lbs. Carcase dia. and length 5.77" by 3.775". Armature dia. and active length 3.15" by 3.775" Earliest cutting in speed (cold) 450 r.p.m. Quoted quantity price of these machines with all the minor improvements required by R.R. £19.10.0. This is more than Lucas, but then it must be remembered that it is much more nearly what we require. We would also like to mention here that in the case of the cutout a state of affairs similar to that of the dynamo exists. Smith cutouts have done well on experimental cars and the most recently received cutouts embodying the R.R. improvements are in our opinion the best cutouts we know. If the Smith dynamo were standardised no doubt the Smith cutout would be standardised with it. (Contd). | ||