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).
Valve spring failures in various engines from 1935 and 1936.
| Identifier | ExFiles\Box 126\2\ scan0039 | |
| Date | 30th June 1936 | |
| 30th June, 1936. VALVE SPRING FAILURES Valve spring failures which have occurred during the last eight or nine months come under two headings. (1) 1935 C.V.Engine, Spring P.35762 Very few cases of faulty material were found on this spring. It appeared to suffer badly from surge when checked with stroboscope, and practically all failures were of the surge type, about 1 1/2" coils from static end of spring. The spring surged most at just over 1900 camshaft r.p.m., which coincides with one of the calculated speeds. Various single springs were tried and a fair measure of success was obtained with SK.21652, although some breakages were experienced both in Aero wire and D.T.D.5.A. - piano wire lt treated 1% Carbon As will be seen the mean stress and stress range were reduced slightly in this spring. The use of double springs SK.21822/3, the inner being a sliding fit in the outer, with a nominal clearance of .004" finally cured the trouble. The double springs have a fairly low mean stress and the range is very moderate, also due to the telescopic fit of the two they are damped against surge. Only two cases of failure have come to our notice on these springs and we attribute one of these, at least, to corrosion. (2) 1936 6-Cylinder Engines. Failures on spring P.39567, which had passed through vigorous experimental test, are attributed to faulty material. Our first failures were due to a peculiar surface defect on the wire, which was apparently covered by a thin Cont'd... | ||