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).
Table comparing the dimensions and ratios for various dynamo and motor sizes.
| Identifier | ExFiles\Box 64\1\ scan0112 | |
| Date | 18th April 1923 | |
| x9620 18.4.23. X.294. Y.543. R.R. DYNAMO & MOTOR SIZES. X.9620 X.9660 Ratio | | Carcase dia. | Armature dia. | | Air Gap. | Carcase thickness. | |---|---|---|---|---|---| | Dynamo for large car. | 5.5" | 3.5 | '64 | .015 | .312. | | Dynamo for small car. | 5.00 | 3.10" | '62 | .015" | .275" | | Motor for large car. | 5.00" | 3.10" | '62 | .015" | .275" | | Motor for small car. | 4.50" | 2.85" | '63 | .015" | .250" | FPC. [Watermark: BOND EXTRA] [Side note: X9620] | ||