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 plotting amplitude against crankshaft RPM for a Wraith spring drive without a slipper or balance weights.
| Identifier | ExFiles\Box 124\2\ scan0134 | |
| Date | 29th March 1940 | |
| B.60. No 2. WRAITH SPRING DRIVE WITHOUT SLIPPER WITHOUT BALANCE WEIGHTS AMPLITUDE DEGREES CRANK SHAFT R.P.M. 1000 2000 3000 2 4 6 9TH 6TH RM{William Robotham - Chief Engineer} / J.R.S. 29·3·40 | ||