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).
Specification card for a driving spring detailing wire diameter, coil count, helix diameter and length.
| Identifier | ExFiles\Box 103\3\ scan0128 | |
| Date | 7th November 1931 guessed | |
| Hs{Lord Ernest Hives - Chair} 461 DIA OF WIRE .092 4 WORKING COILS AND AN EXTRA COIL GROUND SQUARE EACH END) MAKING A TOTAL OF 6 COILS OUTSIDE DIA OF HELIX .632 - 10 FREE LENGTH .800 8 OFF DRIVING SPRING LcC 2547 | ||