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 testing of polished versus unpolished Goshawk Dynamo Brushes, finding no advantage in their use.
| Identifier | ExFiles\Box 50\5\ Scan347 | |
| Date | 10th September 1924 | |
| X4333 To EY/RD. from EFC. {E. Fowler Clarke - Electrical Engineer} c. Wd. {Mr Wood / Mr Whitehead} By EFC {E. Fowler Clarke - Electrical Engineer} 3/T10.9.24. X.4333. GOSHAWK DYNAMO BRUSHES. Referring to your EY/RD9/ML2.9.24 and Wd {Mr Wood / Mr Whitehead} 9/U27.8.24 regarding the proposal for polished brushes, we have carried through a test, the equivalent of 7500 miles, with these brushes with a two coil per slot armature. These tests have not indicated any definite advantage in polished brushes over the standard ones unpolished, so that at the moment we do not recommend their use. It is to be remembered that the commutation generally with two coil per slot armature has been definitely improved and is so good that there seems really to be very little room for any further improvement. On the old single coil per slot armature it might possibly have been a slight advantage, but it is hardly worth while to change over for the few armatures which are still to be produced to the old pattern. Should any definite advantage turn up from our experiments we will report. It may be remarked that the cause of sluggishness of brushes is invariably due either to jamming or presence of oil or grease. We have not observed that the straight forward frictional effect of the brush on the side of the holder has anything to do with this. EFC. {E. Fowler Clarke - Electrical Engineer} | ||