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).
Exhaust valve spring failures, testing methods, and potential solutions.
| Identifier | ExFiles\Box 88\4\ scan0051 | |
| Date | 26th April 1934 | |
| [Handwritten] Smith Should like your Comments on paragraph marked. Rm{William Robotham - Chief Engineer} To WGR. from E.{Mr Elliott - Chief Engineer} x254 E.6/HP.26.4.34. c. Hs.{Lord Ernest Hives - Chair} By.{R.W. Bailey - Chief Engineer} Sft.{Mr Swift} [Text crossed out] Mx.{John H Maddocks - Chief Proving Officer} EP.{G. Eric Platford - Chief Quality Engineer} [/Text crossed out] Chassis No. B.54-AH. Referring to memo Mx.{John H Maddocks - Chief Proving Officer}5/T.26.4.34, the exhaust valve spring which has broken appears to have fractured as the result of a fault in the wire. Valve springs were originally chalk tested for faults in the unenamelled state but this was found to be ineffective and it is understood that all production valve springs are now run on the rig for four hours at a suitable speed and that this has been very successful in showing up any bad places in the wire, but we are bound to assume that no eliminating test can be made infallible and we are therefore trying out a scheme to Lec.3873 in which a spring ring is used to prevent the valve dropping. It has been suggested that the use of double valve springs would prevent the engine being wrecked in the case of a valve spring failure and it somewhat follows that when one spring is broken there is a chance of locating the failure before the remaining spring breaks. This however is not of much use if no notice is taken of the noise set up, and this is a point which depends entirely on the driver. We have had two cases we find from the Repair Department of valves falling in on the 20/25 and damaging pistons and heads. || There is very little difference between the springs of the Bentley and the 20/25. They have the same number of coils of the same diameter wire and one is stressed just a little more than the other. If a valve spring fails the car can be driven several miles if handled carefully, but if no notice is taken of the failure it is inevitable that the valve will fall in, and we think this applies to both single and double | ||