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 report into the failure of a Bentley rocker shaft.
| Identifier | ExFiles\Box 88\4\ scan0208 | |
| Date | 28th May 1937 | |
| RHC.{R. H. Coverley - Production Engineer} c. to RM{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux} Handwritten: 254 Reiles RHC{R. H. Coverley - Production Engineer}/Cy.6/LS.28.5.37. Handwritten: Gry{Shadwell Grylls} where are our tests BENTLEY ROCKER SHAFT FAILURE. ------------------------- Handwritten: Rm{William Robotham - Chief Engineer} On investigation of the failure we find that the nut became loose, which allowed hogging and sagging of the shaft until a fracture occurred through the weakest place of the section around the stud clearance hole. Evidence of this is clearly marked on the shaft. The reason for the nut coming loose are firstly and obviously, insufficient tightening in building, or after possible dismantling by Depot or owner. Looking further, the embracing fit of the pedestal may have been destroyed by unintelligent burring of the bore. The spherical seating of the pedestal and the washer may be unsatisfactory in finish and bedding. Collapse of these surfaces would then follow, reducing the tension in the stud, and slacking back of the nut would occur. In view of the small number of failures from this cause, one hesitates to condemn the present scheme and suggest a locking plate to the nut, as this device could not be of the ordinary flat variety on account of the split feature of the pedestal, but a castellated nut could be fitted. Mainly the spherical scheme is satisfactory, provided normal precautions are taken to fully tighten the nut, and while we will look into our assembly here we do not consider a locking device necessary. RHC{R. H. Coverley - Production Engineer}/Cy. [Signature] | ||