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).
Hand-drawn diagram illustrating the geometry of two meshing gears on graph paper.
| Identifier | ExFiles\Box 136\1\ scan0319 | |
| Date | 13th April 1940 guessed | |
| O1 r1 r1+a1 Add. Circle Add. Circle L M N P O2 r2 cos φ φ r2+a2 r2 r1, r2 PITCH RADIUS OF GEARS a1, a2 ADDENDUM | ||