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 failure of valve springs, attributing the cause to vibration and material variation.
| Identifier | ExFiles\Box 80\3\ scan0124 | |
| Date | 20th June 1912 guessed | |
| (2) out enquiries to two other makers for further batches of raw springs. With reference to the reason for the failure of our valve springs, I think it is important to note that we have a very great number of inlet valve springs break on the rig in addition to those of the exhaust valve, and it can be observed on the rig that the vibration of nearly all the springs is very great indeed; and I think this is one of the important reasons for a spring break-ing although the calculated stress is comparatively low. The result of this vibration is that some of the coils are nearly always compressed choc-a-block when the valve is lifted, and consequently, in the event of a coil being slightly irregular, the stress will be localized at such a point. The epidemic of broken valve springs seems to some extent to have died out and consequently it would appear that the real cause was due to variation in material or treatment by the makers. The failures on the test rig however point to the fact that we are very near the limit and that it is necessary to make some improvement. The chief point I wish to draw your attention to is the fact that the inlet valve springs fail as well as the exhaust, which proves rather conclusively that the recent addition to the lift of the exhaust valve is not | ||