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).
Performance and wear of various main and control brushes during testing, with a table summarizing the results.
| Identifier | WestWitteringFiles\K\October1923\ Scan75 | |
| Date | 22th October 1923 | |
| Contd. -4- EFC6/T22.10.23. These main brushes were afterwards run with an EG.60 control brush, but during the test, the brush gear broke up, and the brushes were spoiled (the breakage being traced to an initial flaw in one of the stamped brush holder). CG.2 Le Carbone. This set was run with a Z control brush for reasons as above. Both positive and negative ran well and acquired a moderate polish. The commutator was left a fairly uniform light brown. The wear is :- Positive .050" Negative .026". The various brushes used in the tests are sent herewith, duly labelled, for your examination, the pigtail terminals and insulations having been removed and the brushes otherwise marked with their polarity. For convenience the wear on the various brushes tested, besides being previously given, are herewith tabulated. Generally speaking the amount of wear is in inverse ratio to the quality of the running obtained. Brush material. Positive. Negative. Control. Le Carbone Z. .035" .025" .020" EGO Morganite. .011" .009" .040"Light springs. EG2 " .014" .017" .042" HM{Capt. W. Hallam - Head Repairs}6 " .0435" .0375" .0785" LFC3B Le Carbone. .033" .040" --- EG.30 " .055" .026" .0515" CG.2 " " .050" .026" --- | ||