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).
Technical memo discussing potential causes of lag and sticking in a servo mechanism, with suggestions for improvement.
| Identifier | ExFiles\Box 73\1\ scan0139 | |
| Date | 7th April 1924 | |
| To R.{Sir Henry Royce} from DA.{Bernard Day - Chassis Design} c. to HS.{Lord Ernest Hives - Chair} S E C R E T. 499/D DA{Bernard Day - Chassis Design}2/M7.4.24. E.A.C. SERVO. X.1559 X.1013. Referring to Mr. Hives' report on the servo of the agreed scheme - HS{Lord Ernest Hives - Chair}5/LG4424 - we suggest that the slight lag in pulling on the brakes which is noticed, and which was also noticed on the Renault scheme, may be due to air trapped be- tween the plates which takes a short time before it is squeez- ed{J. L. Edwards} out. We suggest that if this is so it would be possible to reduce it by putting a number of radial grooves across the face of the ferodo plates. When we saw the Renault car at the Show the servo was inside the gearbox. It is possible that it is an oil servo, in which case the lag then would probably be due to the time taken for the oil to be squeezed out. As regards the servo sticking in we suggest that the angle of thread has only a small amount to do with it, the principal cause of sticking in being the pressure between the jaws tying the 2 plates together. This sticking together would become more apparent as the angle of the thread was dropped, because the torque transmitted is greater and might give the impression that it is the thread itself sticking. From some figures Mr. Hives sent us with a 45° angle of thread we gathered that the clutch was sticking in then. It is true that lowering the angle of thread loses more motion in applying the servo but it seems likely we can do with very little clear- ance. One thing we notice is that the pressure per sq.in. on the RR. servo is much less - (about 1/3) than that on the Hispano. (DA{Bernard Day - Chassis Design}) | ||