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).
Investigating a 3½ Litre Bentley engine failure, concluding it was caused by an exhaust valve, not the piston.
| Identifier | ExFiles\Box 86\2\ scan0118 | |
| Date | 28th October 1933 | |
| To Wor.{Arthur Wormald - General Works Manager} From Hs.{Lord Ernest Hives - Chair} c. to C. c. to R.{Sir Henry Royce} c. to Ry. c. to Rn.{Mr Robinson} c. to EP.{G. Eric Platford - Chief Quality Engineer} c. to EX. γ 2316 Hs.{Lord Ernest Hives - Chair}1/MJ.28.10.33. X788 Re. 3½ Litre Bentley Piston Failures. We have now had a chance of examining the engine which failed on Brooklands and we find that the piston failure was caused by a failure of the exhaust valve, the head of which came off and jammed under the piston. Owing to the piston being broken up it was not until the engine was dismantled that the real cause of the failure could be ascertained. We are very glad to find that it is not a piston failure because the failure having occurred so quickly we had wondered whether there was some certain set of running conditions on Brooklands which was more severe than we had anticipated. We have examined the pistons out of our open experimental car which has run 13,000 miles including a lot of test work on Brooklands and we find that these are free from flaws. These pistons are identical to those fitted to the first 15 Bentley cars so our confidence is now becoming restored although we still think it would be a wise precaution to examine them after each 5,000 miles. As regards the valve failure. We have had one previous failure on all the test bench running of the Bentley units similar to the one which went on Brooklands. It is easily possible to greatly improve exhaust valves. E.{Mr Elliott - Chief Engineer} is arranging to give us a sketch of this and we hope to have them fitted to the car which will be tested with the strengthened pistons. The exhaust valves are interchangeable with the 25 HP. so that if it is decided to change over any existing valves could be used up for the 25 HP. Hs.{Lord Ernest Hives - Chair} | ||