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 air gap for the Smith 2D dynamo.
| Identifier | ExFiles\Box 3\5\ 05-page218 | |
| Date | 16th April 1920 | |
| X.095 16.4.20 Mr. Clark. --------- X.295. - SMITH DYNAMO. ---------- The air gap of the smith 2D dynamo was included in the list of "Air Gaps of Dynamos", dated 23/3/20, being .015". LF. | ||