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).
Blueprint graph of the Wraith spring drive, comparing performance in 3rd gear with and without a flexible coupling in the prop-shaft.
| Identifier | ExFiles\Box 124\2\ scan0064 | |
| Date | 12th March 1940 guessed | |
| B 60 NO 2 WRAITH SPRING DRIVE --- 3RD. GEAR (DIRECT) WITH FLEXIBLE COUPLING IN PROP - SHAFT — " " " WITHOUT " " 1ST ORDER 1/2 ORDER -1 1/2 ORDER ENGINE R P M AMPLITUDE DEGREES .2 .4 .6 .8 1000 2000 3000 4000 FIG. 1 RM{William Robotham - Chief Engineer} / JRS | ||