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 endurance test report on machine performance, focusing on brush and commutator wear.
| Identifier | ExFiles\Box 168a\3\ img427 | |
| Date | 7th March 1937 | |
| -3- requiring a major overhaul. The small R.K. machine is capable of delivering 14 amperes, at 13.0 volts, at 5,000 r.p.m. with a certain amount of sparking which is considered permissible. Compared on the same basis, the Lucas machine is not as good; the sparking for the same conditions of load and speed being worse. In respect of brush noise also, the Lucas machine is worse. This point, however, will finally be decided on the road test. Endurance. This test provides some indication of the reliability of the machine, and the length of life of the commutator and brushes. Running under the same conditions of high speed, (5,000 r.p.m.) and output, (11 amperes at 13.0 volts) the Lucas machine ran for 306 hours, as against 195 hours for the R.K. machine. In each case the machine was run until it failed, through one of its brushes wearing down to such an extent that it ceased to make contact. The resultant brush wear, measured as the average wear of the two brushes, (positive and negative) in thousandths of an inch per hour, run, was as follows:- | | Hours run | Average wear in thous./hour. | |---|---|---| | Lucas. | 306 | 1.38 | | R.K. | 195 | .36 | The longer running time of the Lucas machine was to some extent due to the greater wearing length of the brushes. Wear of the commutator was proportionally greater than that of the R.K. machine. Summarising these results we find that, in the main, the Lucas machine is lighter than the R.K. machine and has a longer brush life; but that it will probably be found to be noisy. The latest modified R.K. machine, scheme 1072, will compare better with the Lucas machine as regards cost and weight; but in order to compare it in respect of the brush wear, it should be fitted with L.G.3 grade brushes, and perhaps | ||