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).
Brake servo adjustments, pedal pressure calculations, and the effects of unequal braking on steering.
| Identifier | ExFiles\Box 73\2\ scan0202 | |
| Date | 19th January 1924 | |
| X9940 To R.{Sir Henry Royce} from DA.{Bernard Day - Chassis Design} c. to RS.{Sir Henry Royce's Secretary} Dal/M19.1.24. BRAKES. X.9940. X.9770. Referring to Hs{Lord Ernest Hives - Chair}4/LG17.1.24. We should like to say that we went into the question of pulling up the rear brakes by the pedal through the servo shortly after you went away, and came to the same conclusion as Mr. Hives, viz - that as the mechanism stood it would not be possible to do it, though we did not get such high pressures as Mr. Hives does. But it was always part of the scheme to alter the windoff on servo (angularity of pull rod referred to by Mr. Hives) which has since been done under your instructions, (and which seems should be an advantage in any case), to reduce slightly the force of the pull off springs on the back axle, and to increase slightly the leverage which the servo has over these springs. In this way the figure which Mr. Hives gives as 143 lbs. pedal pressure we made to be 59 lbs. (allowing 75% efficiency through out.) this is the pedal pressure before the back brakes are pulled by the servo, and though it is still high it did not seem to us to be unreasonable. The front brakes are of course pulled on first which may possibly be an advantage as we know it is advised by some makers. We propose as soon as we have completed our promise on EAC.2. which we expect to do today, to scheme the suggested dashpot. UNEQUAL BRAKES Referring to the point about unequal braking affecting the steering it seems that the effect of unequal brakes on the front should be more pronounced than on the rear, because the arm of the couple tends to increase in the former case and to decrease in the latter. DA.{Bernard Day - Chassis Design} see original for sketch. | ||