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 performance, addressing issues like 'jaggers' and proposing alternative mechanical schemes.
| Identifier | ExFiles\Box 73\2\ scan0294 | |
| Date | 24th March 1924 guessed | |
| contd: -2- slow speed servo) for two reasons :- (1) heating, and wear of servo. (2) Gentle application even at high engine speeds. If we do not keep to this gentle application we shall get 'jaggers' on applying the brakes at high speeds, and if we do use the slow speed application we may get too much lag in shunting before we obtain assistance from the servo. So we still have the difficulty of holding the car at close quarters on steep inclines which to me we must be able to do either by the direct foot pressure or by a promptly acting servo. Owing to the speed limitations given above, to prevent jaggers (and possibly servo wear) we cannot get a promptly acting servo without some ratchet scheme of taking up the slack (or clearance and worn brakes) by the foot pressure. This is not at present done on DES.60 or our modification of it so that as far as I can at present see we are probably not yet quite out of the wood. In addition to the last scheme instructed - DES.60 we have :- (1) My simple way of concentrating all foot energy on the back brakes, and trusting entirely to ordinary back wheel braking as at present for all shunting etc. (If we divide our foot energy into 4 wheels we get little result.) This is RRM. scheme (which might have DES.60 second rod.) This I understand is to be tested out. (2) If we want prompt assistance from the servo then you can have single ratchet as Hispano, or single ratchet between servo clutch and operation, (but this is only assistance one way). Agreed system will shew if this is favoured. (3) Or we can have the scheme proposed by me of double ratchets and divided clutch to DES.60. (4) Or we can have the double ratchet drive scheme where the servo always goes forward, outside the box all appearing simple. In my very limited testing of the car sent to Le CanadelHenry Royce's French residence I thought something further was needed, but I did not test it severely either as a sudden emergency application at high speed for 'jaggers' or much shunting at close quarters on inclines. Also I did not know if the angles, conditions and adjustments were suitable to shew the effect equal to a worn brake. I also thought such tests are better made nearer home in a selected safe place, as the roads here are contd:- | ||