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).
Armature dimensions, tapering, and air gaps related to grinding punched plates.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 195 | |
| Date | 22th June 1927 | |
| Contd. (2) EFC5/T22.6.27. difficulty with the grinding of punched plates. We feel that the grooves ought in this case certainly to be milled so that the bottom of the groove is parallel to the top, in which case the question arises as to whether 3.100" of armature should be at the middle or at either end. We are of the opinion that the 3.100" should be the maximum armature dia. and that every bit of field winding space should thus be obtained. In regard to the actual taper- if we follow the recommendation of your note HL/M16.5.27 which asks for .050" increase in air gap between the inner and the outer positions, then scaling the travel of the armature on LeC.2425, and finding this to be .850", we find that the difference in dia. of the armature from one end to the other would be no less than .325, or an armature dia. of 2.775" at the small end. We doubt if it is your recommendation to have this large figure of coning of the armature surface. As previously explained, we cannot give any recommendation for the amount of this taper by calculation, but are of the opinion that a suitable amount to try in the first instance would be from 3.100" at one end to 2.900" at the other, i.e. a difference of .200" on the dia. or .100" in the air gap, corresponding to a longitudinal movement through a distance equal to the whole length of the armature. The actual change in air gap between the inner and outer positions would then be .850 / 2.750 x .100" = .031" | ||