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).
Experiments and findings regarding valve spring reliability and suppliers.
| Identifier | ExFiles\Box 158\4\ scan0162 | |
| Date | 2nd July 1937 | |
| To E.{Mr Elliott - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} c. to Sg.{Arthur F. Sidgreaves - MD} c. Hs.{Lord Ernest Hives - Chair} c. By.{R.W. Bailey - Chief Engineer} VALVE SPRINGS. The position of our experiments with regard to valve springs is as follows:- (1) That in the uneven coiled form, springs made by the Tempered Spring Co. to Rm.{William Robotham - Chief Engineer}260 are proving very reliable, and of several cars and test bed units fitted with these springs for the last 6 months we have had only 2 failures. These occurred on the test bed. The above are in 'Swedish Wire' and the saving in cost per chassis as compared with S/CV. is 25%. Have run 17,000 miles in France without failure and an S.S. has been issued for incorporating on Bentley. (2) Similar springs to the above in 'Swedish Wire' either bought direct from Sweden or from the Tempered Spring Co. and finally coiled at R.R. are not so good and we have experienced a number of failures. This is not due to any fault in the operation of coiling as microscopic inspection of the fracture reveals nothing in the way of flaws in the wire. We therefore assume that some 'heat treatment' is given in the case of springs made by the Tempered Spring Co. Efforts are being made to find out whether this is so or not. (3) In the meantime we are trying a low stress spring made in "Swedish wire" and coiled at R.R. in an endeavour to be independent of the Tempered Spring Co. as far as springs in "Swedish Wire" are concerned. This particular spring is to RS.{Sir Henry Royce's Secretary}540, has uneven spaced coils and in the choc positions the stress is approximately 90,000 lbs/sq.in. against 115,000 lbs/sq.in. with the Rm.{William Robotham - Chief Engineer}260 springs. We hope to make this a success on Wraith and be able to do without bottom tappet springs, which if incorporated would raise the production cost. (4) The O.H.C. in the early stages on the test bed had broken several valve springs in S/CV. These were then changed over to 'Swedish Wire' springs with uneven coiling as obtained from the Tempered Spring Co. Since then there has not been a failure. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} | ||