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).
Specifications for two different clutch drive springs.
| Identifier | ExFiles\Box 169\4\ img235 | |
| Date | 5th January 1933 guessed | |
| Hs{Lord Ernest Hives - Chair} 799 DIA OF WIRE .072 MEAN DIA OF HELIX .350 10 WORKING COILS WITH 3/4 COIL (GROUND) SQUARE EACH END) - SEMI OPEN ENDS) FREE LENGTH 1.350 + .25 LOAD AT 1.100 = 24 LBS (APPROX) SPRING - CLUTCH DRIVE PER II RR CN.{Mr Chamberain} 299 12 OFF Hs{Lord Ernest Hives - Chair} 800 DIA OF WIRE .064 MEAN DIA OF HELIX .320 13 WORKING COILS WITH 3/4 COIL GROUND) SQUARE EACH END) - SEMI OPEN ENDS) FREE LENGTH 1.350 + .25 LOAD AT 1.100 = 15 1/2 LBS (APPROX) SPRING CLUTCH DRIVE PER II RR P.H. 299 12 OFF | ||