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).
Design and mechanics of a vehicle's braking system, including leverage, servo, and pedal movement.
| Identifier | ExFiles\Box 73\1\ scan0124 | |
| Date | 25th March 1924 guessed | |
| -2- or the same lever could be hung up further forward, and the servo arm reduced, or both if necessary. So that in RRM. and -- other this should be promptly done. The foot pedal used to carry the back brakes a certain distance. This should be maintained, or a little more. The front brakes should have the same equivalent clearance, counting the movement of the shoes and the same allowance for wear as before otherwise our direct foot pressure will have little or no effect, and our servo will also be weak, so we cannot depart from this. In the agreed scheme and all those where the foot goes to all the brakes the leverage will be half, because the 5" pedal movement must take up all the slacks and give allowance for wear, whereas in RRM. the pedal only takes up the rear slack and allowance for wear, so the relative leverage can be twice in this case. It should not be necessary for me to go into all this but I feel we are not right by the results. RRM. should be say 10% to 20% less leverage to the back brakes than ordinary 40/50. The rod could be adjustable as in Goshawk. This RRM. scheme should excel over all others in all direct foot braking which I believe is so very necessary for controleven at close quarters. If it does this I believe it may prove to be the best for the moment but it must be rightly proportioned with a powerful servo to give equal braking to all four wheels, at which time the direct braking is only a small proportion. N. sch. 1769. To make this right it appears that the levers closing the servo should be longer. They are shewn 1 3/4". Probably 3" would be better with 30º thread. End pressure = 2 (for 30º) X 3" lever .5 radius of screw = 12 X 2 plates = 24 times rod pull to pedal. The second rod could have limited adjustment and the rear end of this rod is carried by a lever which might experimentally have holes to give 3" lengths, or be long enough to give 85% of present brake pressure for foot pressure. contd:- | ||