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).
Investigation into the cause and remedy for broken Phantom III valve springs.
| Identifier | ExFiles\Box 96\2\ scan0124 | |
| Date | 30th July 1936 | |
| X354 Sg.{Arthur F. Sidgreaves - MD} o.E. c.Hs.{Lord Ernest Hives - Chair} o.Hy.{Tom Haldenby - Plant Engineer} o.Mx.{John H Maddocks - Chief Proving Officer} BY/Cgh.{W Clough}1/MC.30.7.36. Re: Phantom III Valve Springs. Further to BY/Cgh.{W Clough}11/MC.27.7.36., we have had the broken valve springs taken from 34EX. carefully examined and find that the material and heat treatment are perfectly satisfactory and that the fractures have started from the inside of the coils also in each case the starting point was a small pit or depression in the surface of the wire. These depressions are undoubtedly due to the guide rollers of our spring coiling machine picking up material from the spring wire. We have also examined some of the springs taken from 32.EX which have stood up throughout the 15000 miles test and find that they are quite free from the above defect, so that we can safely say that if the defect is eliminated the springs will stand up, therefore suggest we send to Lilliehall two sets of springs which have been carefully inspected so that they can be fitted on 34.EX and Lord Portarlington's car. We are of the opinion that the defect will only be in the first few sets of springs which were rushed through the works after the breakages occured in the first place, but we are having springs taken from some of the chassis in the Test Dept. also some springs from the erecting bay and having them examined so that we can then decide whether any further action should be taken in regard to chassis which have been built and not left the Works. In regard to chassis which are at Coachbuilders, we suggest that it would be advisable to remove the springs from one or two of the early ones and return them to us for examination in order to obtain a lead as to how far the springs should be changed retrospectively. In order to avoid the trouble arising in future, steps are being taken to prevent the spring coiling machine "picking up" but in view of the fact that the small depressions referred to above represent the difference between springs standing up and breaking, we suggest that the design of the springs and stresses in same should be re-considered. With reference to the tappet adjusting screws we will report on these immediately we have completed our investigations. BY/Cgh.{W Clough} | ||