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 showing Summers torsiograph results for Engine B 80 Unit No 2 without a damper.
| Identifier | ExFiles\Box 124\1\ scan0077 | |
| Date | 22th April 1939 guessed | |
| SUMMERS TORSIOGRAPH RESULTS ON ENGINE B 80 UNIT Nº 2 WITHOUT DAMPER AMPLITUDE DEGREES 1.4 1.2 1.0 .8 .6 .4 .2 0 10½ 9½ 8 6½ 5½ 4½ 4 3½ ENGINE R.P.M 1000 2000 3000 4000 5000 FIG 1 RM{William Robotham - Chief Engineer}/JRS | ||