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).
Experiments with narrower brushes in machines, detailing performance, heating, and testing results.
| Identifier | WestWitteringFiles\O\2April1926-June1926\ Scan086 | |
| Date | 13th May 1926 | |
| Contd. -2- EFCL/T13.5.26. It therefore does not appear at all unreasonable for the brushes to be reduced in circumferential width, and this we have done to the extent, as indicated on the diagram, of taking them down from .375" to .280" in the case of the main brushes, and from .275" to .187" in the case of the control brushes. It has been consistently the case in our experiments that the output for a given degree of heating (the output being varied by moving the control brush) has been more in the case of the narrower brush machines, than in the case of the standard. Or conversely, that the maximum heating for the given output to which we set the machines for service is definitely less by about 10° to 15°C. Further to this, the commutation of the machine has been uniformly excellent with the standard, and we have not so far arrived at any feature in which these narrower brush machines may be said to be inferior to the standard. Up to the present, we have three of these machines made experimentally, and two further are in the course of experimental production. On these three machines we have completed our bench tests, and two have now been placed respectively on chassis 10-EX and 12-EX, though so far only about 1000 miles have been run. The third machine is at present undergoing more complete tests and this will be run on our continuous running rig for observations of Contd. | ||