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).
Inclining a brush surface in its holder to counteract commutator friction by creating an opposing tangential force.
| Identifier | ExFiles\Box 50\5\ Scan228 | |
| Date | 1st October 1923 | |
| Contd. -5- EFC1/T1.10.23. holder the top of the brush will be. It will be agreed that the remedy for this will be, so to incline the surface of the brush at the bottom of the spring slot, that the spring in bearing upon this surface normally, produces a force which has a tangential component of sufficient magnitude to produce an opposite moment in excess of the moment due to the friction at the commutator already referred to. The amount of inclination should be sufficient that any variations, as mentioned, due to the frictional effect between the spring and the brush, should be more than accommodated. We find by experiment this deviation from the horizontal to be a minimum of 15°. The result is then that under all conditions of running one side of the brush is, as far as possible entirely in contact with one side of the brush holder and entirely clear of the other side, and it should then be really a matter of indifference as to what the amount of slack of the brush in the holder (at any rate as regards the thickness) might be. This idea was first suggested to us at the Works by the brush gear on the Canning dynamo which was recently installed for starter motor tests in the Production Dept., in which this is done. The side of the brush holder against which the brush is not in contact is entirely dispensed with. When the spring is lifted, the brush is entirely free with the exception of its pigtail. Contd. | ||