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 of a servo star spring on a Wraith, its effects, and the planned investigation.
| Identifier | ExFiles\Box 109\5\ scan0149 | |
| Date | 28th November 1939 | |
| 664 To Sg.{Arthur F. Sidgreaves - MD} from Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} c. Hd.{Mr Hayward/Mr Huddy} Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}9/MH.{M. Huckerby}28.11.39. FAILURE OF SERVO STAR SPRING. We have been endeavouring to find out why the servo springs failed on your car. It is the first failure we have had on a Wraith and Hd.{Mr Hayward/Mr Huddy} knows of only one failure on a 20/25. The effects you noticed when driving the car after the loss of one spring are what we should expect. On Wraith the servo levers have stops so that in the event of the travel of the servo becoming excessive due to any reason, the driver will always have direct braking to the rear even though the front brakes have become nearly or completely inoperative. Of the four springs on your car two were broken and one cracked. The Laboratory's report on the cracked spring is that the material and hardness are correct but that the surface could be improved. The difference between the servo star spring on Wraith and 20/25 is very small and we do not think will account for a failure. As soon as we can we are starting up a rig to get accelerated fatigue failures on both types of spring, and also on Wraith springs with a better surface finish. Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} | ||