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 of amplitude in degrees versus crankshaft RPM for a Wraith spring drive without slipper, with a balance weight.
| Identifier | ExFiles\Box 124\2\ scan0135 | |
| Date | 1st April 1940 | |
| B. 60. No. 2 WRAITH SPRING DRIVE WITHOUT SLIPPER WITH BALANCE WEIGHT AMPLITUDE DEGREES CRANKSHAFT R.P.M 1000 2000 3000 9TH 6TH R.M / URS 1.4.40 | ||