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 returned from chassis 51-S4 due to rapid wear of the brushes.
| Identifier | ExFiles\Box 47\4\ Scan218 | |
| Date | 26th January 1925 | |
| To EFC. {E. Fowler Clarke - Electrical Engineer} AC.37. X.4383. DYNAMO RETURNED FROM CHASSIS 51-S4. 20 HP. No.365. This machine was returned on account of the rapid wear of the brushes. It was found that the positive brush was worn so far as to be well past the travel of the spring. The control brush was retarded by 7° or 8° beyond the position obtaining on present production, but the output was not excessive because it was found that the main brushes were advanced from the neutral position by 4° or 5°. Two or three commutator segments seemed slightly burnt, but the armature was found to be OK on the drop test. There was no definite projection of mica from the commutator but the machine is of an earlier production than those having machine undercut commutators and it seems probable that slight pieces of mica may be preventing correct seating of the brush. A continuous running test (with another positive brush) at about 1750 r.p.m. for 80 hours was made, and the brush wear noted, the figures being Positive .035" Negative .0135" Control .0105" No direct comparison of these figures for the standard condition machine is available, but they are judged to be larger than they should be. If the commutator connections be retarded by one segment and the control brush adjusted to suit and the micas undercut by the present method, the machine should be up to good production standard. EFC {E. Fowler Clarke - Electrical Engineer} /RJA. | ||