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).
Report comparing the performance and wear rates of different grades of machinery brushes.
| Identifier | WestWitteringFiles\Q\2-July1927-September1927\ 45 | |
| Date | 18th August 1927 | |
| Contd. -2- EFC3/T18.8.27. In the case of (a), my assistant reports as follows :- "The brushes ran reasonably quietly and shewed no abnormal sparking. The contact surfaces attained a fair polish but not more than is obtainable with standard Z brushes. The commutator was left in moderately good condition but with slight signs of burning at the trailing edges of the segments. The wear of the brushes is - Positive .027" Negative .027" Control .024" These amounts are somewhat more than the average obtained with standard Le Carbone Z and Morganite EG2 grades. This test has not shown up any distinct advantage in the EGA brushes over the standard, but further experience might shew an absence of the tendency to screech which sometimes exists on standard machines." In regard to (b) my assistant reports - "They ran without chattering or excessive sparking and attained a good polish, slightly better than the EGA grade and possibly better than Z grade. The commutator was left in fairly good condition similar to what is obtained with standard brushes. Wear was smaller than with the EGA brushes, but is possibly, on the average, slightly more than that of Z brushes, the amounts being :- Positive .0215" Negative .0155" Control .0155" The amounts of wear observed on the most recent similar test with standard Z grade brushes were :- Positive .011" Negative .010" Control .0235" These brushes appear to be worth further test. We were informed by Mr. Lawrence of the Le Carbone Co. that these and EGA brushes had a lower coefficient of friction than Z grade, and as they compare with Z in other features they may offer a solution to the chattering difficulty sometimes experienced. A closer comparison with EG2 Morganite brushes from this point of view might also be beneficial." Contd. | ||