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).
Dynamo improvements including magnetic humming reduction, insulating materials, and output performance.
| Identifier | WestWitteringFiles\D\March1920\ Scan41 | |
| Date | 13th March 1920 | |
| Contd. -2- Ckl/T13.3.20. (1) The provision of an armature with skewed slots and any other little alterations to pole pieces, etc., which they consider would reduce the magnetic humming noise of the dynamo to a minimum. They were quite confident that they could entirely eliminate this. (2) The use of special insulating material which they said was pres-phan impregnated with formite varnish and of which we send you a sample which was handed to us. This material, they considered, would be excellent to depend upon for the electrical contacts although they stated that they had not had any trouble from this source. When the two first machines arrive, we will despatch one of these to you for your consideration. This machine will represent their present standard production and we shall be interested to have your remarks as to how this might be improved in detail to suit our requirements. We have now taken output curves of the Smith type 2D machine, the second machine submitted to us, and are attaching small photostat copy of curves upon which two curves have been added for the cold and hot condition of this dynamo. You will see from these, that they have effected an improvement in the cutting in or balancing speeds, as compared with the previous type A machine, but that this has been attained at a loss of output at high speeds. It is considered by them, and we are inclined to agree, that in spite of the gain of area in the early stages being considerably less than the loss at the higher speeds, there is on the whole an advantage, as it is essential to have all the ampere hour out-put possible at low speeds. Contd. | ||