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).
Tests conducted on servo star springs to resolve judder issues, with a recommendation for the Wraith model.
| Identifier | ExFiles\Box 108\3\ scan0120 | |
| Date | 3rd March 1938 | |
| -3- Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale}8/WH.3.3.38. The four points of the star springs on our servos are now made to register on all 4 springs by means of a keyway in the servo shaft into which project keys on the star springs. When the keyway becomes damaged due to repeated adjustment of the servo, the keys can stick in the keyway and prevent the normal action of the star springs. A better method of keeping the 4 star springs registered is a small steel clip, which does away with the necessity for keys, and which cannot bind, and this is our recommendation for Wraith. The following is a list of tests we have made :- (1) Removal of Star Springs. Makes judders easy to obtain, and maintain. (2) Star springs sticking in groove. Judders of short duration can be obtained, intermittently. (3) Star springs free in groove. Under very sudden pedal applications, at 70-80 m.p.h. there is a suspicion of a judder. (4) 35° Servo cams, low µ linings. No change. (5) Slotted links replaced by fixed jaws. No improvement. (6) Slight flexibility in servo pick-up rod. Slight improvement, not very definite. (7) Extra "sponge" in servo pick-up rod, obtained by spring washer. Extremely harmful: anything approaching slack here is very detrimental. (8) "Pull "on" spring attached to servo pick up rod. If strong enough will stop judders, but necessitates extra strong "pull off" springs to balance. Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} | ||