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).
Review of design tolerances and manufacturing methods for valve and stabiliser components.
| Identifier | ExFiles\Box 99\3\ scan0060 | |
| Date | 19th January 1938 | |
| -7- HPS{Horace Percy Smith - Experimental Factory Mgr}/WB.{Mr Brazier/Mr Bell}1/EP.{G. Eric Platford - Chief Quality Engineer}19.1.38. The Valve cap FB.3460 had an interference fit of .002" to .003" on the Valve stem FB.3459 diameter, and with the upper limit this was not considered practical, and the interference was reduced from 0 to .002". Also the inner chamfer was deleted, since when the cap was pressed on to the valve stem, up to the shoulder, the face of the cap went past the shoulder, consequently the valve would not seat. Again the necessity for the adjusting washer is justified to rectify accumulative limits, for, with a valve set correct to drawing from the valve seating to the sleeve face, the valve would not seat, and the distance had to be increased. The method of locking the valve cap to the stem - by punching out the end of the stem - was simple and effective providing a jig was used to prevent damage to the stem. The limits imposed on the various diameters of the valve stem, sleeve and adaptor are close at the present stage, since previous experience has shown this to be necessary. It will be worth while reviewing this position however with a view to facilitating manufacture, since the dimensions and materials of the components have been altered since those tests were performed. Stabiliser, FB.3455/6/7/8. This assembly entails the correct alignment of three small fine limit diameters, and since the Plug FB.3458 is pressed into position there is every possibility of the piston being tightened up, especially after working into the cartridge - two of the four assembled to date have done so - and a slight clearance in the plug bore is required - .003" minimum. Too large a clearance however is not desirable, since it becomes not only a source of oil leakage on the rebound stroke, but also an air inlet during the bump stroke, although the latter could be overcome by drilling the connection to the reservoir well below the oil level. [The following paragraph is struck through with a diagonal line and an 'X' mark in the margin] It is proposed to experiment with larger limits on the piston and guide diameters. The interference limit between the piston FB.3455 and the Cap FB.3456 could be increased to 0/.002" instead of .001"/.002" to assist production. continued | ||