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).
Issues with armature taper, engagement thump, and potential solutions involving stronger springs.
| Identifier | WestWitteringFiles\S\September1928-October1928\ Scan149 | |
| Date | 27th July 1928 guessed | |
| -2- Contd. able to return the armature so as to give a second chance of engagement. As we shall further refer to below, we infer that the present armature taper of 3.100 to 2.900 is too large and we have accordingly instructed for further armatures to be built with a taper of half this amount. It also should be contributory to the improvement of the motor in other respects, to which we also refer below, e.g. power and efficiency. We are of the opinion that this change of armature taper is likely to overcome this difficulty. In regard to (II) the difficulties are :- (1) Armature end thump on engagement, which is considerable with the weak spring, but has been materially reduced by the insertion of a stronger spring. This occurs even when working on teazer circuit only without allowing the main current to come on. The stronger spring was arranged to give the same tension in the uncompressed position, but to have a higher rating. It therefore would (a) Return the armature to its initial position when the end-on fault occurred, and give it another chance of engagement, (b) Absorb more energy and relieve the outward thump on engagement, even to the extent of this appearing sometimes to be altogether absent. (2) The end thump on disengagement. This appears to offer the biggest problem, for instance as to how to absorb the energy of the motion of the armature without shock or rebound. This was slightly improved by putting in a fibre washer, an improvement which was annulled by the insertion of the stronger spring. (3) Gear noise in turning the engine on main current is not too bad. Contd. | ||