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 from a consulting engineer regarding the design and clearance of patent tappets and spiral spring washers.
| Identifier | ExFiles\Box 147\1\ scan0035 | |
| Date | 27th March 1935 | |
| COPY A.{Mr Adams} B. BUCKLEY, O.B.E., F.C.G.I., M.Inst.C.E., M.Inst.W.E. Consulting Engineer. 64, Victoria Street, Westminster, S.W.1 27th March, 1935. Lieut. Colonel M.{Mr Moon / Mr Moore} Ormonde Darby, Aero Sales Department, Messrs. Rolls Royce Ltd., 14, Conduit Street, W.1. Dear Sir, Further to my letter of the 23rd inst. and our interview of the 26th when you kindly showed me a report on my patent tappets containing what we may perhaps call the "choc-a-bloc" criticism I would say that it is an essential feature of my design, as illustrated for example by blue print No.62, that the two spiral spring washers should be assembled practically in that condition, that is to say, close coiled. For instance, the designed tappet clearance of that particular unit, when cold, is 0.004 inch. The height of the cotter slot in the valve stem is 0.400 inch. Then we have:- Combined thickness of two cotters, 2 x 0.125.... 0.250 inch. Thickness of outer spring washer when completely close coiled .... 0.145 " Total thickness 0.395 inch In other words the outer spring washer when assembled between the cotters has still only 0.005 inch to go in order to be close coiled and this is only 0.001 inch more than the designed tappet clearance with the engine cold. Turning now to the inner spring washer it is intended that when first assembled it shall be close coiled by means of the adjusting screw. The combined length of the valve, etc., will then be such as to give a tappet clearance of | ||