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).
Description of an improved semi-servo four-wheel braking system, detailing its operation and the function of the servo components.
| Identifier | ExFiles\Box 178\1\ img080 | |
| Date | 9th July 1924 | |
| - 2 - various levers - to the rear brakes in a very similar manner to the method employed on the RR. cars with the rear brake only. This braking system is an improved semi-servo system. It is seen that the rear brakes are operated by servo pull plus direct pull from the foot pedal, while the front brakes are operated by servo pull only. The leverage is so proportioned that 40% of the braking effort is taken to the front wheels and the remaining 60% is taken to the rear wheels. OPERATION OF THE RR. FOUR WHEEL BRAKE SYSTEM. See diagram attached. SERVO:- The essential parts of the servo are the rotating drum G.{Mr Griffiths - Chief Accountant / Mr Gnapp} (which is free to float endways) and the two friction plates F.{Mr Friese} and F'. which are keyed together to prevent the rotation of the one without the other but have relative end movement. They are separated by means of a spring so that they do not exert any pressure on the rotating drum. The two operating levers A.{Mr Adams} and B. are not rigidly connected with the friction plates but by means of the cam between them, they are able to draw the two plates together until they press against the rotating drum. The pressure with which they press against the drum will depend upon the pull tending to separate the two levers A.{Mr Adams} and B. and upon this pressure also depends the force required to resist these plates rotating with the drum. As seen from the sketch the tendency for these plates to rotate and carry with them lever E.{Mr Elliott - Chief Engineer} will result in a pull at (contd). | ||