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).
Specification table comparing two different armature designs.
| Identifier | ExFiles\Box 39\2\ Scan031 | |
| Date | 6th December 1920 guessed | |
| .2. ARMATURE. | | | | |---|---|---| | Slots. | 31 | 27 | | Conductors. | 496. | 432 | | " per slot. | 16 | 16 | | Coils " " | 1 | 1 | | Comm. Bars. | 31 | 27 | | Turns per coil. | 8 | 8 | | Virtual Conductors. | 62 | 54 | | Pitch. | 15 | 13 | | Step. | 7<br>1 to 8 | 6<br>1 to 7 | | Slot. | .101 x .360 | .117 x .423 | | Dia. at bottom. | 2.03 | 1.90 | | Pitch " " | .206 | .221 | | Tooth Sec. " " | .105 | ..104 | | Gauge S.W.G. | 22 | 20 | | ||