Comparison photograph of two different flywheel designs, one solid and one with lightening holes.
| Identifier | ExFiles\Box 98\5\ scan0035 | |
| Date | 1st August 1939 guessed | |
| EB 3955-6. Rm. {William Robotham - Chief Engineer} 619. | ||
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).