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).
Failure analysis report on a broken 'Make & Break' spring from a Phantom III, identifying under-tempering as the cause.
| Identifier | ExFiles\Box 131\2\ scan0041 | |
| Date | 30th August 1937 | |
| 1113 BY: H1/EJW.1/JN.30.8.37. M 1,395 c. to Rm.{William Robotham - Chief Engineer} c. to Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux} c. to Rm{William Robotham - Chief Engineer}/Wst. c. to Mx.{John H Maddocks - Chief Proving Officer} Laboratory PHANTOM III - MAKE & BREAK SPRING. Ref. Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux}2/N.24.8.37. The broken spring from chassis 3-BT{Capt. J. S. Burt - Engineer}-37 - Mr.Lloyd, mileage 1800 - has been examined. The hardness is 657 V.P.N. We have already issued two reports - M 1,224 - H1.4/AG.10.11.36 and M 1,248 - H1.1/AG.9.1.37 - dealing with similar failures. These were submitted by Rm{William Robotham - Chief Engineer}/Wst, and it was found that high hardness figures of the order of 644 - 649 V.P.N. were obtained on the broken springs, whereas an unbroken spring which had run 300 hours gave 540 V.P.N. It was concluded that the faulty springs had been undertempered, and it was pointed out that springs taken from production at that time were giving hardness figures varying from 609 - 653. It was also suggested that some more satisfactory springs should be obtained, so that we could confirm that the normal hardness was in the neighbourhood of 540. These however were not supplied. There is little doubt that under-tempering is the cause of the trouble, and in any case it is unsatisfactory to have the springs in such a hard condition. It would be a simple matter to correct any stock which may be in this condition by retempering at 375°C to 385°C. H1/E.J.W. | ||