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).
Dynamo testing, focusing on brush positioning to resolve sparking and heating issues.
| Identifier | WestWitteringFiles\J\March1923\ Scan35 | |
| Date | 26th March 1923 | |
| EPC4/T26.3.23. -2- Contd. in partial contact, the contact surfaces sparking badly during the process. If so, this should be overcome by the more exact dimensions now obtained. A case of this sort has just been brought to my notice on a dynamo on one of the experimental cars. No definite complaints of similar failure have recently been received from the Test Dept. Originally, the main brushes were set as nearly as possible, in the time available for experiment, in the exact no load neutral position. (We have now proved that this was correct within .040" on the commutator circumference, the slight error being one of retard). We have lately undertaken a series of tests in which the main brush position is being varied, and in each position of which, the position of the third brush for the maximum output consistent with a given degree of heating is found. Thus a series of curves of performance of the machines is obtained, all for an approximately equal degree of heating, and the commutation also is carefully watched. This is not only being done on a standard machine, but also on the machine with reduced gauge of field winding and also on the machine with increased section of carcase and reduced air gap, and it is hoped to be able from this to give definite recommendations in connection with the E.A.C. dynamo. These tests will cover your requests to test result of the main brushes being given a lead in the direction of rotation. (This we call a retard; actually in our tests in addition to neutral position, four retarded and two advanced positions are being tried). Contd. | ||