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 of flywheel test results with and without a tail bearing.
| Identifier | ExFiles\Box 181\M13\M13.2\ img025 | |
| Date | 13th January 1931 guessed | |
| IV-G-6 {WW FLYWHEEL} WITHOUT TAIL BEARING 2500 3000 3200 WITH TAIL BEARING (BALL RACE) -> 2900 3100 | ||