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 for standard dynamo and motor sizes for large and small cars.
| Identifier | ExFiles\Box 61b\3\ scan0134 | |
| Date | 5th July 1921 | |
| X.294. X.543. STANDARD R.R. DYNAMO & MOTOR SIZES. 5.7.21. | | Carcase dia. | Armature dia. | Air Gap | Carcase thickness. | |---|---|---|---|---| | Dynamo for large car. | 6.00" | 3.625 | .020" | .312" | | Dynamo for small car. | 5.00" | 3.10" | .015" | .275" | | Motor for large car. | 5.00" | 3.10" | .020" | .275" | | Motor for small car. | 4.50" | 2.85" | .015" | .250" | EFC. Handwritten (right margin): X543 L209 | ||