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 rule for armature polarity.
| Identifier | ExFiles\Box 68\4\ scan0242 | |
| Date | 23th March 1928 | |
| X1640 23.3.28. RULE FOR ARMATURE POLARITY. In a R etrogressive winding with L eft hand rotation we get a M inus brush under the N orth field pole. Rule. R.{Sir Henry Royce} LMN. Any twoe of the above can be changed together, to form a new statement which is true. EFC. | ||