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).
The operation of the brake pedal and servo assistance mechanism.
| Identifier | ExFiles\Box 22\1\ Scan160 | |
| Date | 28th April 1924 | |
| R.R. 453A (20H) (D.A. 652 20-3-24) J.H.D. -3- EXPERIMENTAL REPORT. Expl. No. 9940 4214 REF: Hs{Lord Ernest Hives - Chair}1/LG28.4.24. brake pedal - the first effect is caused by the resistance of the brake pull off springs and operating mechanism. With the pedal connected to all four brakes, when the car is standing, considerable pressure is required to overcome the resistance of the pull off springs etc. This has been reduced as much as possible. When the car is moving, as soon as the servo comes into operation it assists in taking up the pull of the springs, so that the pressure required is very light. When, however, the car is being driven slowly and the brake pedal is operated quickly so that it is in front of the servo, there is no assistance and then one notices that considerable pressure is required compared with when the servo is assisting. The other effect is that with the car proceeding slowly, it is possible to operate the foot pedal so quickly that the brake shoes are pushed on to the drums and offer a resistance to the brake pedal before the servo catches up, the servo then comes on with a thump which brings the car to a stand-still with a jerk. We drove the car with the 'Agreed' scheme with the lid{A. J. Lidsey} off the gearbox so that we could watch the ratchet teeth. We found that as long as the pressure was on the ratchet teeth the brake could be operated smoothly, but whenever the ratchet showed that the pedal had over-taken the servo, it was difficult to get smooth braking. If a driver gets used to applying light pedal pressure for braking and then finds a condition where he can push hard with no braking effect, he pushes still harder, by this time the servo comes on and the contd:- | ||