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).
Brush wear and commutator condition after a 2500-mile test run, noting issues with mica.
| Identifier | WestWitteringFiles\K\June1923\ Scan85 | |
| Date | 1st June 1923 | |
| Contd. -2- EFC1/TUT.6.23. fair but there was slight sparking. The commutator blackened somewhat, but uniformly, i.e. not more particularly pronounced on some parts of the segments than on others. At the end of this 2500 miles, an examination revealed the wear to be as follows:- Positive brush .038" Negative " .0105" Control " .0085" The negative and control brush surfaces at the end of the run presented a well bedded and polished appearance. The positive brush gave the appearance of being well bedded and polished over a short distance from the leading edge but rough over the rest of the surface, although bedding was taking place all over. This feature is a characteristic of the positive brush in nearly every case, and makes it appear at first sight as if it were only bedding on the polished portion. It was noticed at this point that there were traces of mica not properly cut away from the edges of the slots, so that some portion of mica remained in contact with the brushes. At this point the main brushes were moved to the new standard position and steps were taken to completely remove any traces of mica standing up above the undercutting. Running at 1750 r.p.m. was again started. (N.B. The machine was driven through a flexible drive coupling from an experimental Smith dynamo, used as a motor, and supplied at suitable armature and field voltages for the purpose). Contd. | ||