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 production, specifically exhaust valve failures due to leaded fuels and the subsequent modifications.
| Identifier | ExFiles\Box 3\6\ 06-page096 | |
| Date | 6th December 1933 | |
| X41553 To WCR. from E.{Mr Elliott - Chief Engineer} E.1/HP.6.12.33. c. Hs.{Lord Ernest Hives - Chair} Hy.{Tom Haldenby - Plant Engineer} uft. re Bentley Production. There are two points on the Bentley chassis in connection with which failures occurred at the last minute and it was thought advisable to make alterations, and incorporate them in the 10,000 mile car before it left for France. These are as follows: Modified Exhaust Valve. Experience with leaded fuels showed that these were accelerating exhaust valve failure, and we have had two cases of the exhaust valve head pulling completely off the stem. A change of material was clearly indicated as well as some improvement in valve form. Some test running which was done over here also seemed to show that the original troubles associated with using austenitic steel for car valves had been overcome, and it was therefore thought advisable to equip the 10,000 miles car with an improved exhaust valve in this material and to the form shown on the right hand side of blueprint Lec.3680 attached. The original design of valve is shown in section on this same blueprint and is labelled KM.165. This shape we consider unsatisfactory owing to the radius between the stem and the head not running through as originally intended but meeting the head with somewhat of a sharp corner, as shown by the pencilled arrow head on the print. It was at this corner that the head parted from the stem in the failures experienced when running on leaded fuels and the change in section arose due to the deletion of the recess on the back of the head which would have carried the radius through. We think, however, in any case the stiffer section shown in the right hand design was called for and these valves have now run over 7000 miles on Hancock's car. modified | ||