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).
Bench rig test of polished Z brushes on Dynamo B, detailing performance and wear.
| Identifier | ExFiles\Box 50\5\ Scan348 | |
| Date | 10th September 1924 | |
| EFC. AC.23. X.4333. 10th Sept. 1924. X.4333. X.4610. POLISHED Z BRUSHES ON DYNAMO B WITH TWO COILS PER SLOT (ALTERNATE POLARITY). These brushes have run three periods on the bench rig with reversed, normal and reversed polarity respectively; each comprising one night each of constant speed running at 1740, 2500, 3500 r.p.m. and about 24 hours intermittent daytime running. Each period represents a little over 2500 miles, making 7500 in all. Throughout the running, there was very little sparking with either polarity the commutator maintained a good surface and the brushes were always well polished, except for a narrow line along the trailing edge of the control brush, with the reversed polarity. Only the main brushes were polished, there being no polished controls. There is no definite advantage apparent in the use of the polished brushes. The brush wear (total) was:- Common .015", Main .0095", Field .0135". EFC/FJA. | ||