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).
Typed memorandum discussing the 'lag' in servo braking systems and the advantage of bidirectional operation.
| Identifier | ExFiles\Box 73\3\ scan0107 | |
| Date | 8th July 1924 | |
| contd :- -2- is depressed, before the assistance from the servo can be felt. This we call the 'lag' of the servo between the time the pedal is pressed and the brakes are effectively applied. As an example of the advantage, let us assume a car to be shunting in a garage, when it becomes necessary for the car to stop in a few inches to avoid hitting some object which may not be visible to the driver but of which he has received warning from an observer, under these conditions no servo will operate so that unless the direct braking is sufficient to hold the car, the car will travel forward until the servo 'lag' has been overcome. By this time it is possible that damage has been done to the car. The R.R. system is at present the only one on which the servo is operative either when the car is going forward or on reverse. It is considered very desirable that the braking should be equal in both directions. On other makes of car in which the servo only works in the forward direction, it may take 6 or 7 times the pedal pressure when going on reverse to obtain the same degree of braking. This may prove very dangerous - as an instance - a lady might drive the car and find that in the forward direction the brake pressure was such that she could hold the car with ease, if, however, she came to a steep hill and xxxxx happened to miss the gear and the car ran backwards, it might be physically impossible for her to apply sufficient pressure to hold the car. Again, with an expert driver, if he is contd: | ||