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).
Comparison table of pipe and fish tail area inside diameters for 40/50 HP and 20 HP models.
| Identifier | ExFiles\Box 6\7\ 07-page117 | |
| Date | 9th March 1931 | |
| - 2 - Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}2/RT.9.3.31.contd. | | 40/50.HP. | 20 HP. | |---|---|---| | Down Pipe | 2.750. | 1.625. | | Fish Tail Pipe | 1.812. | 1.375 | | Fish Tail Area | 2.25 sq". | 1.3 sq". | All figures inside diameters. 20 HP. Arrgt. E.{Mr Elliott - Chief Engineer} 55794. 40/50. R.32070. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||