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 weights of two different types of clutches.
| Identifier | ExFiles\Box 3\3\ 03-page035 | |
| Date | 22th November 1911 | |
| H.R. 1st ideas (Wise. sketch C size) X200 22/11/11 1900 Weights of clutches Standard clutch cone with leather, clutch shaft & clutch brake ring. 124 lbs. Davis clutch, brass hub, shaft & plates 22½ lbs E404 | ||