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).
Graph comparing torsional vibration amplitudes of the Goshawk and Phantom engines at critical speed without external damping.
| Identifier | ExFiles\Box 6\1\ 01-page041 | |
| Date | 9th November 1926 guessed | |
| TORSIONAL VIBRATIONS COMPARISON OF VIBRATION AMPLITUDES AT THE CRITICAL SPEED ON PHANTOM & 20 H.P. WITHOUT ANY EXTERNAL DAMPING PLAIN LINE GOSHAWK DOTTED LINE PHANTOM AMPLITUDE OF VIBRATION DEGREES CRANK ANGLE DEGREES | ||