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 termination of a 15,000-mile test on a Large Bore 20/25 model due to engine failure after 10,000 miles.
| Identifier | ExFiles\Box 101\1\ scan0195 | |
| Date | 16th April 1936 | |
| X500a To Sg.{Arthur F. Sidgreaves - MD} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Wcr. c. to E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} c. to Mx.{John H Maddocks - Chief Proving Officer} 15,000 miles test - Large Bore 20/25. After 10,000 miles' running in England this test was terminated by an exhaust valve head dropping into the cylinder and wrecking the engine. This exhaust valve had previously done over 100 hours test bed running without giving trouble. It is also similar to the valve on the standard 20/25 which has been in service for a number of years. It is possible that due to the increased top speed performance we are running into valve bounce under favourable road conditions on top gear, and that this caused the valve to fall. There is, however, a new design of valve available which gives a better section at the point at which failure took place. We hope to have the car on the road again by the beginning of next week, to continue the running with these new valves. The engine was unfortunately completely wrecked off, but the bearings, clutch etc. were in excellent condition. A full report by G.W.H. will follow in due course. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||