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).
Secret internal memorandum discussing an experiment to double the leverage between the servo and the rear brakes.
| Identifier | WestWitteringFiles\L\Jan1924-March1924\ Scan5 | |
| Date | 1st January 1924 | |
| TO R.{Sir Henry Royce} FROM DA.{Bernard Day - Chassis Design} C O P Y. S E C R E T. E.{Mr Elliott - Chief Engineer} A.{Mr Adams} C. BRAKES. We suggest that an experiment worth trying would be to say, double the leverage between the servo and the rear brakes. The effect of this would be to cause the servo to run through its angle of action (due to wear on the rear brakes) twice as quickly as now but that the work done by the servo itself would be reduced by half which should reduce, one supposes, the wear on the servo by an approximately similar amount. We think we should be justified in using this increased leverage for the following reasons:- (1) Assuming that the total braking done on the car is little more than is done on a standard car with rear brakes only, the rear brakes will be doing little more than half their present work. Consequently with doubled leverage the work done should be about the same as now, and adjustment needed about the same. (2) From Mr. Hives' report we estimate that the servo requires adjustment about once in 1330 miles which we think is too frequent. By halving the work we should increase this distance to 2700 miles or even more, since the effect of heat on the lining may be to cause the wear to be more rapid than is represented by the change of work. While one was adjusting the servo at this period one could operate a quick adjustment between the servo and the rear brake differential if necessary restoring the servo to its initial position with reference to rear brake operation. The position we suggest for this quick adjustment is on the pull rod between the servo cross shaft and the rear brake differential and the adjustment we suggest might be similar to that now used on the servo shoes, and would act the same as the existing quick adjustment for foot brakes. Both adjustments are accessible from underneath, and from the same position of the operator. We should propose to obtain the increased leverage by halving the length of the lever on the servo cross shaft to which the adjustment would be attached. We have ascertained that this can be done. (3) This scheme involves reducing the leverage to the servo itself by half, and we suggest doing this by altering the long lever on the servo shoes. (4) With this doubled leverage to the rear brakes we think there is no doubt at all that we should be able to pull the rear brakes into engagement through the servo, with a moderate pull off spring on the latter, reasonable pedal pressure and reasonable preliminary front braking, thus overcoming the 'chunking' at the same time. DA.{Bernard Day - Chassis Design} | ||