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).
Polar diagram comparing the crankshaft oscillations of the 20-HP and Phantom models at the speed of resonance.
| Identifier | ExFiles\Box 25\3\ Scan171 | |
| Date | 9th November 1926 guessed | |
| 20.H.P VIBRATION PHANTOM VIBRATION POLAR DIAGRAMS OF 20-H.P. & PHANTOM CRANKSHAFT OSCILLATIONS AT THE SPEED OF RESONANCE. | ||