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).
Technical explanation of the operation and silent release mechanism for a servo brake system.
| Identifier | ExFiles\Box 16\3\ Scan060 | |
| Date | 19th August 1929 guessed | |
| - 2 - Quite apart from the use of fibre-faced stops or additional stops, I want to make it clear that we claim to have silenced servo release entirely on a car with metal stops by the following:- (1) Ball thrust cam levers which apply and release the servo effect more smoothly. (2) A Tee lever with suspension center moved upwards about 2". (3) Adequate friction in T lever suspension equal to 35 - 40 lbs. at the pivot or 18 - 20 lbs. in front brake pull rod. (This I believe is your own figure, but we appear to have been trying to get by with less.) May I ask your patience with following explanation referring to SK-362 attached. On applying brakes, rod A through cams B, pulls rod C, opens gap D on our rear stop and applies rear brakes first. As cams B feel resistance, they apply servo and stop pin E lifts lever F.{Mr Friese} The rear brakes, having the resistance of rear pull off springs overcome by direct foot action, come on first suspension arm G swinging away forward to position H.{Arthur M. Hanbury - Head Complaints} When rear brakes are "well on" the front brakes are applied by the T lever swinging about position J and therefore moving the suspension arm center back from H to K.{Mr Kilner} If K is ahead of the original position L(and suspension arm friction adequate) the brakes will come off quietly. Because, when brakes are released, K being ahead of L, stop M will close ahead of stop D.{John DeLooze - Company Secretary} If stop D closes ahead of stop M further movement backwards of the brake pedal causes the servo action to "collapse" and stop M closes violently. If friction of suspension arm is inadequate stop M (especially in reverse) closes violently while stop D is still open thus:- First slackening of pull in rod A causes servo action to decrease sufficiently to allow T lever to rotate clockwise opening a small gap at N. (Particularly with the ineffective pull rod angle of reverse motion.) @continued- | ||