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).
Failure report comparing three different dipper switches by cause of failure and number of operations.
| Identifier | ExFiles\Box 168a\2\ img393 | |
| Date | 20th September 1938 | |
| R.R. Dipper Switch to DB.{Donald Bastow - Suspensions}11-1. Operations Cause of failure. 13,690 Breakage of the rocker arm return spring to DB.{Donald Bastow - Suspensions}1-44. 23,986 Breakage of toggle spring to DB.{Donald Bastow - Suspensions}118/. 29,594 Breakage of Tufnol bush DB.{Donald Bastow - Suspensions}664. 32,181 Breakage of Rocker arm return spring to DB.{Donald Bastow - Suspensions}1-44 (second spring). After each failure switch repaired. Lucas FC.22N Specially Developed for R.R. 49,060 Breakage of drum operating steel spring. Lucas Standard. 3,570 Phosphor bronze drum operating spring fatigued, causing it to take a permanent set and so be incapable of turning the contact drums. ............ RM{William Robotham - Chief Engineer}/RC.{R. Childs} | ||