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).
Endurance test report on Bentley unit exhaust valves with and without chromium plating.
| Identifier | ExFiles\Box 96\2\ scan0131 | |
| Date | 1st September 1936 | |
| (2) Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}14/JH.1.9.36. We have recently carried out an endurance on the Bentley unit with S/SLV exhaust valves both with and without chromium plated stems. The endurance was carried out at the usual speeds, each hour as follows 30 mins. at 4000 R.P.M. 25 mins. at 4250 " 5 mins. at 4500 " and continued for 20 hrs. running on Ethyl petrol. At the end of this time the valves were in as good condition as the KE.965 valves. The valve clearance in the guides was .001"-.0015" with the S/SLV valves and .0025"-.0035" with the KE.965. In the above condition the S/SLV valves with the chromium plated stems were unmarked and no signs of sticking on the stems, the normal unplated S/SLV stems showed slight signs of sticking and plucking at the stems, as did the KE.965 valves. In the case of the latter material we know from experience that the guide clearance cannot be reduced below .003" in safety, as this metal seems very susceptible to plucking and consequent seizing. If we can use S/SLV valves in conjunction with the latest strengthened type of heads as we now have, Lec.5097 for 25/30. Lec.5141 for Bentley. Lec.5219 for Ph.III. which will of course have to be proved by further running, we are definitely better off in the following respects. | ||