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 performance and wear of different grades of brushes and their effect on the commutator.
| Identifier | WestWitteringFiles\Q\2-July1927-September1927\ 47 | |
| Date | 18th August 1927 | |
| Contd. -4- EFC3/T18.8.27. The main brushes ran quietly but the Z control brush made a certain amount of chattering noise. The wear of the brushes is :- Positive .014" Negative .013" Control .0375" The result obtained with these brushes is much inferior to that obtained in Oct. 1924 (AC.28) with LFC2, a very similar soft grade, which polished well and wore less. The wear is not as large as that obtained with EGA and EG3417 grades however. The commutator has been left clean but with slight roughness on many of the segments, by the LFC3AB8 brushes. Apparently they do not supply enough excess lubrication to prevent chattering of the control brush." It is difficult to show that brushes of these soft grades are superior to those of the more usual hard graphitic type as represented by our standard and the Morganite EG2, though it has been observed that soft brushes have been used on a number of continental machines, e.g. Scintilla and Bosch. In the latest type Bosch machine, however, it has been observed that the grade has been changed to a type more like our standard. Altogether, as regards the 20 HP. at any rate, we think it is fairly well proved that little if any improvement over the standard Z grade is possible, though it is certainly the case that the grade EG3417 reported above, gives indication of having some little advantage in certain directions. We refer more particularly to reduction of brush screech, which, as reported, occasionally occurs. Contd. | ||