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).
The determination of brush friction and brush-short-circuited currents for four different armatures.
| Identifier | ExFiles\Box 34\3\ Scan121 | |
| Date | 15th February 1916 | |
| H.M. 984 a (HOT) (S.C. 596. 15-2-16) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 1546. -7- Brush Friction and Brush-Short-Circuited Currents. We have determined these for four armatures, two 17 slot and one each of the other two. The mechanical brush friction being a small quantity is difficult to determine accurately, but from our results, we can way that it is represented by .05 to .10 ampere in the driving motor, i.e. from 4 to 8 watts, but in any case, it is unimportant. We have plotted out curves of driving motor armature current which represent the total losses. (m + a + b + c + d), also for comparison on the same sheet, some which represent (m + a + c). The difference ordinates between these two groups represent brush-short-circuited current losses + mechanical brush friction, only the latter is almost negligibly small. The brushes used were C. M.{Mr Moon / Mr Moore} Morganite Brushes. Only one pair of opposite brushes were cross connected in the above tests. | ||