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).
Inherent disadvantages of fitting a new 4-wheel brake design to existing 40/50 HP cars.
| Identifier | ExFiles\Box 73\2\ scan0145 | |
| Date | 12th December 1923 | |
| PN{Mr Northey} x9940 Hs{Lord Ernest Hives - Chair}3/LG12.12.23. 4-WHEEL BRAKES ON EXISTING 40/50 CARS. The inherent disadvantages in the latest design of 4-wheel brakes which it is intended to fit to existing 40/50 HP. cars are as follows :- (1) The servo runs at propeller shaft speed. On the latest design of brakes for EAC-11 and EAC-1, the servo will run at 1/20th. propeller shaft speed. On the Hispano car the servo runs at 1/30th. propeller shaft speed. (2) It is proposed that there will be very little braking on the front compared with the rear. This proportion will be maintained throughout the whole range which means that on a greasy road we shall not get anything like the full advantage of 4-wheel brakes. We shall not be as good as Hispano. The disadvantage of a high speed servo is that if we run our servo 30 times as fast as the Hispano it will generate 30 times as much heat for the same output from the servo. With the servo on the 40/50 cars, if we use the brakes continuously for three or four miles, the servo brake becomes blue with heat. The Hispano under similar conditions only becomes warm and it can be handled. Owing to the speed of our servo, when it is applied the slack in the brake ropes and clearance in the brakes is taken up at such a speed that a nasty thump is felt by the passengers. It would be possible to avoid this by friction or oil damping to prevent the servo operating so quickly. contd:- | ||