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).
Letter discussing the design, testing, and manufacturing costs of brake ball thrust cam levers.
| Identifier | ExFiles\Box 41\1\ Scan109 | |
| Date | 3rd June 1929 | |
| OY-1 June 3rd, 1929. Mr. A.{Mr Adams} F.{Mr Friese} Sidgreaves, Rolls Royce Limited, London, England. cc - Mr. Royce Mr. Hives Mr. Bailey Dear Mr. Sidgreaves: BRAKES With further reference to OY-4, May 6th, we attach a photograph of the ball thrust cam levers which we think will interest Mr. Royce, Mr. Bailey, and Mr. Hives. The levers shown are machined with true helical cam faces which are radial at any section normal to the axis of the lever. We now realize that this is a mistake as the radial faces cause the balls to be forced outward and to "spin" slightly against the retaining ring when the levers are operated, which introduces unnecessary friction. We have therefore made another set of levers in which the cam faces are offset 1/8" each side of center. They are also milled with a small cutter so that the faces are slightly hollow, tending to retain the balls in place. These operate satisfactorily, but are still considered unnecessarily expensive. We are next proposing to try a set of levers on which the cam faces are not truly helical but are milled straight across with a cutter having the desired mean helical angle of 61°48'. These would not work as plain levers but we believe they will operate satisfactorily with the point-contact of the four balls, and the ball thrust levers would then be certainly no more expensive to produce than the present plain levers with true ground helical faces. Confirming our earlier letter, we find that the ball-thrust levers give an increase in servo multiplication approximating 80%, and at the same time are the only form of cam levers which we have found that give consistent servo operation on all occasions. -continued- | ||