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).
Comparison of a Lucas machine's features and performance against an existing standard model, focusing on the armature and winding.
| Identifier | WestWitteringFiles\V\2January1931-April1931\ Scan076 | |
| Date | 1st May 1931 | |
| -3- EFCL/ADNO.5.31 contd. This, however, has been altered by us to 117° (i.e. 63° span) for the purposes of comparison on the same heating basis as further described below. It will have been noticed that :- (1) The Lucas machine has a larger air gap than the R.R. (2) The Lucas machine has a finer field winding. (3) The Lucas machine has a bigger control brush span. The arrangement of the armature stampings and winding of the Lucas machine is different from ours in a fundamental respect namely that the stampings have parallel teeth and tapered slots instead of parallel slots and tapered teeth and that the winding is a hand winding. An impression of a sample stamping obtained from Messrs. Lucas is given on a half sheet herewith. The slots are partly enclosed by widening the teeth at the top. In this way the winding area is made considerably greater for the same magnetic permeance through the armature than in the case of our own standard. In this respect, of utilising partly enclosed non-parallel slots together with hand winding, the Lucas machine is similar to the R.{Sir Henry Royce} Bosch. It provides the machine with a definite advantage as regards performance but, at the same time, a definite disadvantage as regards symmetry and want of balance. On test the Lucas machine shows a very poorly balanced armature. The slight superiority of performance, which we report below, of this Lucas machine compared with our 20/25 machine, may be considered to be due mainly to the type of armature stamping and winding (better copper space factor in the slot) and possibly in some degree to the fact that its armature is both slightly larger in diameter and has a somewhat longer active length than our own. The Lucas machine is arranged for operation with a two stage field resistance, thus constituting a three-rate charge scheme, the largest output corresponding to no field resistance in circuit is only permitted when the head lamps are in use. | ||