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 rocker clearance, plunger tolerances, and experiments with self-adjusting valve gear.
| Identifier | ExFiles\Box 88\4\ scan0111 | |
| Date | 6th September 1934 | |
| - 2 - Messrs. Rolls-Royce Ltd.. 6th September, 1934. As far as I can determine, the proposed rocker easily clears your modified top-cover Ex.14177 and, if used in conjunction with the push-rod return spring indicated by Sk.4394, will permit of crankshaft speeds in excess of 5300 RPM. Regarding your enquiry as to the maintainance of a diametral plunger clearance of the order of .0004", I understand with the latest machines that plain cylindrical objects such as the plug we employ can be lapped easily in quantities to + .00005". This leaves the tolerance on the ground hole in the thimble as the only serious consideration, and I imagine this could be held at a total figure of .00025". Thus, with one size of plug, the fit could be maintained at .0002"/.00055", or, with two sizes of plug (differing in nominal size by .0001-1/4") the resultant fit would vary between .0002" and .0004". I do not think this variation should lead to trouble in practice and it can be obtained without resorting to selective assembly. I shall be glad to have your comments on the proposed rocker and to hear further of your experiments with the self-adjusting valve gear. Yours faithfully, Frank B. Halford | ||