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).
Alterations to the Wraith spring drive damper to overcome crankshaft periods.
| Identifier | ExFiles\Box 8\5\ 05-page15 | |
| Date | 15th December 1937 | |
| To HPS.{Horace Percy Smith - Experimental Factory Mgr} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} c. Rm{William Robotham - Chief Engineer}/Wym.{G. Harold Whyman - Experimental Manager} WRAITH SPRING DRIVE DAMPER. It has been found necessary to increase the damper load from 17 lbs. to 22 lbs. at 1 1/2 radius in order to overcome crankshaft periods. With the present springs that have to be almost choc-a-bloc before this load is obtained and is not a production job to obtain consistently, also the springs in this position are over stressed. No satisfactory alteration to the existing springs would give correct loading without overstressing or high rating which is not desired. Our alternative, of which we would like you to make two sets for trial, are inner springs to go inside the existing. These should be opposite hand winding, give 12 lbs. loading in the working position and as low a rate as possible. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} | ||