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).
Page 6 of a document detailing motor load and brush distress testing procedures.
| Identifier | ExFiles\Box 168a\2\ img037 | |
| Date | 20th March 1931 guessed | |
| -6- With S₂ switched on a brake load shall be applied to the wheel and when S₁ is switched on to obtain engagement the brake torque shall be suitably adjusted until the main motor current (indicated by A) is 150 ± 1 amperes in which condition the motor shall be run for 5 minutes. Switch off S₁ when engagement has been effected. During the last minute of the test the torque shall be at least 900 lb-inches. The speed shall not be less than 90 times the motor terminal voltage which shall be 9.0 ± .1. On this load test, the specification that the ratio of the speed to the terminal voltages must exceed a certain figure ensures that the magnetic and electrical circuits are good. That is to say, that no undue amount of electrical resistance is introduced in the shape of bad connections or brush contacts, and that the air gap and concentricity of the armature are O.K. (10) BRUSH DISTRESS TEST. With the motor running under the same load conditions as in the load test, each side by side pair of brushes should be lifted off the commutator in turn, in which circumstances the other pair of brushes diametrically opposite have to carry the full current. If they do this without showing signs of distress, which would be indicated by a jumping of the ammeter needle, they may be considered O.K. The others in turn may be proved to be O.K. in a similar manner. | ||