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).
Scheme for taking up clearance in rear brakes by rotating the servo with foot pressure.
| Identifier | ExFiles\Box 30\6\ Scan141 | |
| Date | 12th July 1923 | |
| R.R. 403A (40 H) (EL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. Expl. No. 9940 REF:Hs{Lord Ernest Hives - Chair}/ACL1/LG3_1. 24. DA.{Bernard Day - Chassis Design} from Hs{Lord Ernest Hives - Chair}/ACL. RE. SCHEME FOR TAKING UP CLEARANCE IN REAR BRAKES BY MEANS OF ROTATING THE SERVO BY FOOT PRESSURE BEFORE SERVO SHOES COME INTO OPERATION. It would be difficult to get this scheme to operate satisfactorily owing to the following conditions. (1) With the standard leverage as on the 40/50 four wheel brake system, the pull in the rod operating the servo toggle amounts to .56 pedal pressure. The pull required to rotate the servo (with shoes not in contact with drum) to take up the rear brake clearance is found by experiment to amount to approx. 80 lbs. at 3.35 rad. which is the rad. to which the pull rod is attached. If the pull rod could be so arranged that it rotated the servo at this radius it would require a pedal pressure of 80 / .56 = 143 lbs. The servo shoes would have to be separated by a spring of sufficient stiffness to prevent the shoes pressing on drum below a pull of 143 lbs. This also would result in an appreciable amount of front braking before rear brakes came into operation. The pressure on each font brake shoe with standard arrangement is approx. 11 X pedal pressure. We should therefore expect to get 1573 lbs. at front shoes when the rear shoes just came into contact with drum. This again would result in having to alter the pressure distribution in the system and it would be contd:- | ||