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).
Continued report on brush bedding, sticking issues, and machine maintenance.
| Identifier | WestWitteringFiles\V\2January1931-April1931\ Scan035 | |
| Date | 3rd February 1931 | |
| EFC/ATL3.2.31 contd. -4- whilst there might be a very slight temporary effect, it appears on examination most improbable that a few revolutions in the backward direction can upset for any length of time the bedding acquired by long periods of continuous running in the forward direction. Always when running forward the resultant forces of spring pressure and commutator drag hold a brush flat against the trailing side of the holder. The actual effect on the brush due to a few revolutions of backward running is to remove only a minutely small quantity of material. Summarising the matter of (2b) and (3) it may be said that once proper bedding is secured on brush holders with no production inaccuracies, no variation of output, apart from that due to brush sticking (see below), will subsequently occur. What constitutes correct brush bedding however, may, in the case of the control brush, vary from machine to machine from a completely polished surface to a partly polished and partly dull surface as previously described. This amounts to the fact that the only effect recognised is an initial fall in output due to the change in the control brush surface condition. In regard to sticking, brushes are liable to become sluggish if (a) The machine is over-oiled. (b) The brush clearances in the holders are below the amount specified on the production test specification. Reasonably normal clearances and our recommendation of cleaning periodically with petrol, will guard against this to a reasonable degree. Even a small amount of surface stickiness of the brush is catered for by the clearances given. EFC. | ||