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).
Using an epicyclic gearbox, limiting it to four speeds instead of the possible six.
| Identifier | ExFiles\Box 15\5\ Scan177 | |
| Date | 11th November 1930 | |
| - 2 - as to use the epicyclic in all combinations except direct, and R.{Sir Henry Royce} therefore has produced an orderly and natural sequence by limiting himself to four speeds only out of the possible six. BY.{R.W. Bailey - Chief Engineer} | ||