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).
Test report on brushes, comparing their performance, wear, and cost against the standard.
| Identifier | ExFiles\Box 166\1\ img002 | |
| Date | 2nd September 1932 | |
| Hs{Lord Ernest Hives - Chair}/Wst.5/ADL2.9.32 contd. -2- The finish of the bevel of the particular brushes received was not, however, as good as Morganite. Only two main and two control brushes were received so that the complete set for running was made up with Z. grade Le Carbone brushes which were used as negatives. Bench tests were made for heating, noise and commutation and in each case these brushes were equal to the standard. These bench tests were followed by prolonged chassis tests during which the brushes ran a total of 17,280 miles. Throughout the running, commutation appeared to have been quite up to standard. The wear of the brushes however, was considerably more than that which occurs with the standard type. This wear on the average was at the rate of .0023" per thousand miles as compared with .009" for the standardbut even at this rate of wear the life of the brush should exceed 50,000 miles. In addition, the commutator was perceptibly worn, a very slight ridge being formed between the two brush tracks. This again is not serious but is certainly worse than standard. Generally, from a running point of view, the brushes appeared to be as good as our present standard but they wear quicker and have a tendency to wear the commutator more. As these brushes are sufficiently close to our standard we recommend that further tests be carried out and we are obtaining a list of brushes from the British Carbon Co. with a view to obtaining further brushes of perhaps a better grade for test. It might be worth while, however, to put on production a sample patch of the British Carbon Grade B. brushes in order to gain further experience with these. The special feature about these brushes is their cost, this being approximately half that which we are paying at the moment to the Morganite Co. Hs{Lord Ernest Hives - Chair}/Wst. | ||