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 C.A.V. dynamos and motors, including issues with commutators.
| Identifier | WestWitteringFiles\G\September1921\ Scan48 | |
| Date | 13th September 1921 | |
| -2- Contd. of their visit. Since Mr. Glaser's appointment, he has been carefully going over their dynamos. Sometime previously, the C.A.V. had sent us a curve of output of the small dynamo they have in preparation for the Goshawk, which curve readily complies with our specification of output of dynamo for this car. They have evidently been to a lot of experimenting in order to secure the performance for which we have asked. Therefore, it will be particularly interesting to see if we obtain on our bench test the same performance as they have given. They agree that our specification, which gives the kind of curve that is required for this class of work, is very suitable and that up to the present most dynamos have not given a curve of this nature, and therefore they have experimented with a view to seeing what can be done in this respect. The dynamo is of the single field winding third brush control type which naturally gives the curve of output must nearly in accordance with the specification. Mr. Glaser agreed that there were difficulties in connection with the contact of the third brush on the commutator varying the output, but he considered that they could satisfactorily overcome this by so designing the machine that the fringe of flux, in which the conductors in immediate connection with this brush are working, is not too concentrated. It may be remembered that, as stated in our report on the visit to the C.A.V. works, we did not think the C.A.V. work on motors and dynamos was good, but rather that they made the cheapest job consistent with reasonably satisfactory operation. As regards the motors, which Mr. Glaser says he has not yet turned his attention to since his appointment, these are made with low resistance windings to give greater activity for their weight and we are of the opinion from experience with C.A.V. motors that the large currents resulting from this are not sufficiently provided for in brush gear and commutator. We have now made tests of two C.A.V. motors; one of the aero type ZC, some considerable time ago, and we have recently, run an SB{Mr Bull/Mr Bannister} type motor which we obtained a short while ago, to your instructions, with a view to possibly using this on the 40/50 chassis. In each case, however, during the tests the commutator has pitted up and it is on account of this that we say we do not think the commutator and brushes are of sufficient current carrying capacity. On pointing this out to Mr. Glaser, he agreed, | ||