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).
Bentley valve failures during Le Mans race preparation and proposed solutions.
| Identifier | ExFiles\Box 88\4\ scan0169 | |
| Date | 18th June 1936 | |
| To RHC.{R. H. Coverley - Production Engineer} c. to E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} X254 Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}10/KW.18.6.36. Bentley Valves. During the original 24 hours endurance in preparation for the Le Mans race we had 2. S/SLV inlet valves break off at the ring groove in the stem. In order to overcome this it was decided to use KE-965 inlet valves having a much greater impact strength. After running 9 hours endurance on the latter, the engine began to pop back and it was found that all the inlet valves were cracked and in two cases pieces broken out of the rim of the seat. Inspection of the section by the laboratory shews that these valves have been taken from a much larger forging than necessary, with the result that when machined down to the valve drawing, all the forging strength has gone. A forging suitable to produce this particular type of valve in KE-965 is to E.46092, an aero valve which has been produced in considerable quantities for use in Czecho-Slovakia. If there are none of these forgings available, an Ex drawing should be supplied for producing forgings for inlet valves to EX.20968 in KE-965. Will you please have made a number of such valves. As an alternative we wish to try some S.65 material for the inlet valves, this having a high impact value. 3 off each type to be fitted in the high power head EX.22594 on E-3 for further endurance. The regulations for the T.T. are now at hand and we must use standard dia. valves, that is, 1.6" dia. inlets and 1.4" dia. exhaust valves. At present we are using 1.7" dia. inlet and 1.35" dia. exhaust. Will you instruct if necessary that the 2 castings which are being taken off Ex.22594 cylinder head, be altered to suit the 1.6" dia. inlet valves. These heads are the ones instructed for in the memo. Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}30/KW.16.6.36. with chill casting of the exhaust seats. These heads to be progressed as far as possible with exhaust valves 1.400" dia., otherwise as Rs.{Sir Henry Royce's Secretary}276 which can be fitted. | ||