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).
Comparative tests of Goshawk dynamo brushes made from various materials.
| Identifier | ExFiles\Box 50\5\ Scan243 | |
| Date | 22th October 1923 | |
| To R & E from EFC. c. CJ. & BJ. c. BY.{R.W. Bailey - Chief Engineer} EP.{G. Eric Platford - Chief Quality Engineer} DA.{Bernard Day - Chassis Design} Mr Brock X4333 EFC6/T22.10.23. X.4333 - GOSHAWK DYNAMO BRUSHES IN VARIOUS MATERIALS. Comparative tests of Goshawk dynamo brushes of various materials have now been completed, but before reporting further it is desired that it should be understood that this comparison has been effected on a commutator with the old method of undercutting, and with the brushes not bevelled on the brush spring pressure surfaces. (The new improved method of undercutting is now in use, which ensures the complete removal of the mica, the result being similar to that observed on the Bosch and Scintilla dynamos commutators. Also it is now instructed as standard that the tops of the brushes be bevelled to 15° slant, to take the spring pressure, in the manner described in our previous report EFC1/T1.10.23). The dynamo was run with each set of brushes continuously overnights at each of three speeds viz. 1750 r.p.m. 2500 r.p.m. and 3500 r.p.m. in rotation, until the equivalent (total) of 2500 miles was covered. In addition the machine was run intermittently during the day times for a total period of about 50 hours in each case, the test of each set of brushes thus covering a working week. The total running in each case would be the approximate equivalent of 3,700 miles. (On the intermittent running the machine, by means of a mechanically operated switch and variable resistance, Contd. | ||