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).
The properties of High Silicon Chromium Steel for valves and the need to reconsider valve design for aero and chassis applications.
| Identifier | ExFiles\Box 154a\1\ scan0038 | |
| Date | 3rd March 1925 | |
| X1474 R.{Sir Henry Royce} Rr Hs.{Lord Ernest Hives - Chair} BY7/H.{Arthur M. Hanbury - Head Complaints} 3. 3. 25. --------------- VALVES. ------- The High Silicon Chromium Steel we are now using as standard and any other steel with similar characteristics, i.e. the absence of ~~normal~~ recalescence effects, is as a result, softer and less resistant to fatigue effects than ~~the~~ Stainless or Quickstep type of steels. This being so, it is necessary to carefully reconsider the design of the tappet end of the valve, and the scheme for securing the valve spring washer to the valve stem. We have carried out a large number of experiments to obtain the ~~best possible fatigue~~ results from the new steel, but these, whilst very considerably better than ~~those shewn by American made Silchrome~~, are distinctly worse than ~~Quickstep or Stainless~~, hence the need to thoroughly reconsider our tappet end designs, to eliminate any reduction in area or change of shape which can be avoided. ~~It would appear that there are two principle causes of stress on the valve end:-~~ a/- Force along axis of Valve to open valve against spring and exhaust gas pressure, Valve bouncing, or rather the action by which Valve is forced off the cam entirely by too high acceleration is in this class. b/- A tendency for end of Valve stem to wear concave and thereby cause rocker to exert undue lateral force on stem. Our Aero design is good for a/-, but poor for b/-. Our chassis practice is, or could be, good for both a/- and b/-. One does not see why we have one scheme for aero engine and another for chassis. [Handwritten initials: RH{R. Hollingworth} in a circle] BY.{R.W. Bailey - Chief Engineer} | ||