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).
Analysis of a crossmember fracture on the Wraith Bumper Chassis due to heavy loads from the roll bar.
| Identifier | ExFiles\Box 119\1\ scan0042 | |
| Date | 8th July 1937 | |
| Rm.{William Robotham - Chief Engineer} --- c.c. Rm{William Robotham - Chief Engineer}/Les.{Ivan A. Leslie} EV.{Ivan Evernden - coachwork} 1024 SECRET. Da.{Bernard Day - Chassis Design}1/HP.8.7.37. Wraith Bumper Chassis. With reference to Rm{William Robotham - Chief Engineer}/Les.1/R.30.6.37, the fracture of the crossmember at this point appears to be due to the heavy load from the roll bar, which, unlike the shock damper reaction is not relieved by the torque member projecting forward from the side plate. The reaction from the roll bar being taken at the far side of the chassis, the lever load from it appears as a nearly vertical up and down load on the attachment of the side plates to the cross member. This load may be 1000 lbs, equally distributed among the 4 bolts. We suggest that the reason why the cross member cracked at the rear right-hand bolt is because this is a very rigid point and the metal has been damaged by the welding. Your backwardly projecting torque member may relieve this concentration of stress to the extent that it can resist bending and torsion. It is not very good in torsion but may be sufficient to protect the cross member flange. It looks as though the state of the cross member at this point wants watching. Da.{Bernard Day - Chassis Design} | ||