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).
Conclusions from tests on brush gear, outlining specifications for its components and comparing standard vs experimental machines.
| Identifier | ExFiles\Box 168a\3\ img435 | |
| Date | 30th January 1937 | |
| RM{William Robotham - Chief Engineer}/RC.{R. Childs}3/MH.{M. Huckerby}30.1.37. Brush Gear. From tests carried out on the bench, and observations of machines on cars, we arrived at the following conclusions:- (1) Brush holders should be made of brass. Aluminium surfaces produce a sluggishness in brush movement, which causes sparking, and a tendency for brushes to stick. (2) The wall of the holder, forming the bearing surface of the brush, should be dead flat. These points were submitted to the Morgan Crucible Coy., who are experts on brush gear, and who offered to investigate the matter, with a view to supplying the most suitable grade of brush. They were in agreement with us, and added the following points:- (3) The bearing surface wall should be machined flat: broaching is not good enough. (4) The pressure arm should be rigid with a separate control spring. A flexible arm like our standard, where the control spring and pressure arm are one, allows the brush to chatter, and so cause sparking. (5) Pressure arms on all holders, should be acting in the same direction round the commutator. These points formed the specification, to which the brush gear, on RR.scheme 911 machine was made. Therefore, apart from the fact that the winding still includes a lap coil, this experimental dynamo incorporated the best armature and brush gear that we could devise. Bench Test. Test. Standard machine. Xpl. machine. Heating test. max. output at lowest speed 22 amperes at --./ at for temperature rise 1510 R.P.M. 1650 R.P.M. of 55°C. Continued | ||