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).
Test report on commutator sparking and brush wear under various conditions.
| Identifier | ExFiles\Box 50\5\ Scan191 | |
| Date | 27th June 1923 | |
| -3- Contd. There was a perceptible improvement in the commutation from the point of view of sparking and wear, though the surface of the commutator again attained approximately the same condition, (it had been cleaned up between the tests). At the end of this 2500 mile run the wear was found to be as follows, and it will be noticed that this is distinctly less than previously:- Positive brush .023" Negative " .008" Control " .008" The average amperes and volts during these two tests were for the first test 6.5 amperes at 14.65 volts, and for the first half of the second test 8.5 amperes at 14.65 volts, and for the second half of the second test 10.5 amperes at 14.9 volts, the output having been increased half way through the test by an alteration to the control brush position, because it was decided to make the test a little more severe than as at first started. Equivalent of 5000 miles at 2500 R.P.M. In this case we did not start again with a clean commutator, but put back the commutator and brushes in the same condition as taken from the previous test. 5000 miles was run without the machine being altered in any way, the output, except during the warming up periods, was 7.5 amperes at 14.5 volts. During this test the commutator became cleaner and the positive brush a little smoother on the rough portion. Sparking was very slight, the wear on the brushes being as follows :- Contd. | ||