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).
Investigation into the causes and extent of excessive brake pedal travel on the EAC-VII model car.
| Identifier | WestWitteringFiles\Q\December1926-January1927\ 122 | |
| Date | 28th January 1927 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to BJ. Wor.{Arthur Wormald - General Works Manager} c. to RGJ. E.{Mr Elliott - Chief Engineer} c. to BY.{R.W. Bailey - Chief Engineer} DA{Bernard Day - Chassis Design} Hs{Lord Ernest Hives - Chair}/RmS/LG28.1.27. LOST PEDAL MOVEMENT - EAC-VII. X7470 M X7420 We have been rather concerned on this car because when braking with any severity, the foot pedal can practically be pushed to the floorboards, even when little or no wear has taken place on the rear brake shoes. We consider that in an emergency a load of 300 lbs. might be thrown on the rear axle lever extremities (P). With a servo torque multiplication of 2, this only represents a pedal pressure of about 160 lbs. which we know can easily be exceeded. We therefore carried out tests, taking this load as a basis for a maximum, to ascertain how much pedal movement we should expect to lose due to elasticity in the system. We divided these tests up into three parts :- (a) Lost movement due to flexibility in the drum and back axle levers, shafts etc. (b) Lost movement due to the twisting of the rear springs under braking torque. (c) Lost movement due to elasticity in the system between the pedal and rear axle. The results shewed us that the main point where distortion is greater than on the EAC.lll. cars is the rear brake drums. There is also a loss of .400" pedal travel due to the rear springs twisting which does not occur on EAC.ll. The total amount of 4.03" lost pedal movement with 160 lbs. pressure due to elasticity and shoe clearance is somewhat contd :- | ||