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 design, comparing internal vs external wheel cylinders and outlining reasons against a hydraulic system.
| Identifier | ExFiles\Box 110\1\ scan0003 | |
| Date | 28th December 1935 | |
| -2- "Sufficient for the day", however and we can deal with this problem later. But design for 2 1/4 wide, the narrower one will easily go in. What I mean about surface temperature is that we have established that "fade" and deterioration of linings and fierceness is not due to temp. of drum above atmosphere, but temp. of surface of lining above drum. This is the greater factor. The only way to keep this down is to have a wide brake. The drum can have one rib only to start with, but make it tough. Internal wheel cylinder. Our external wheel cyl. as B.V. gets just as hot as an internal one. The reason why we use it is to get the leverage. It is equivalent to 1 3/8" internal cylinder. But when using a brake with 2.5 times K factor less push is needed and I think 1 1/4" dia. will do. I have no slide rule here. Be prepared to fit a 1 1/4" cylinder if necessary. The drop in drum diam. is almost the same as drop in weight of car, as regards leverage etc. 10/12 ÷ 28 / 35 We must try to use a law out of centre point inspite of the internal cylinder. There was a difficulty on B.V. I think that with a new brake set up that this can be done. Everyone else does it. The big reason for the internal cyl. is that it makes possible a reduction in pull off spring poundage. This will be quite a trouble, to make the brakes feel right. The simplification of the system (no servo) will enable us to reduce rear pull off springs. The B.V. front wedge necessitates heavy pull off springs. This is only possible because of the servo. Linkage. I am not in favour of a hydraulic cylinder or pedal for the original design. Reasons :- (1) Clumsy, difficult to get in when pedal is depressed into engine compartment. Our stems are curved. Big Reason (2) There are big problems connected with cross binding. (3) The diam. of the cylinder is absolutely bound up with the leverage to front and diam. of wheel cylinders. The diam. has to be 0.6 approx. nobody can make such a small size, where you can get it I don't know, and when you have one the experimental dept. will want to alter it to 0.6125" to give more front braking. | ||