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).
Issues with coil spring frequency, wheel flap, and wishbone bearings on a Bentley 111 chassis.
| Identifier | ExFiles\Box 99\2\ scan0106 | |
| Date | 7th January 1938 | |
| LES 497. Dr. C. Rm.{William Robotham - Chief Engineer} C. Rm{William Robotham - Chief Engineer}/EV.{Ivan Evernden - coachwork} BY.11/G.7.1.38. P. BENTLEY 111. CHASSIS. Re: Da.{Bernard Day - Chassis Design}2/G.31.12.37. The above memo was discussed on Tuesday afternoon. It was suggested by Rm.{William Robotham - Chief Engineer} that we had hit the natural period of the coil spring in the suspension - to check this it was arranged to have a variable speed motor coupled to drums to enable varying speed conditions to be produced. We were with this motor drive able to pass through the period and demonstrated it was at 110 bumps at approximately 15 M.P.H. and the natural frequency of spring tried by Rm.{William Robotham - Chief Engineer} was also 110. It was agreed to produce a spring with 8" total free movement - this was ordered yesterday by drawing to particulars supplied by EV{Ivan Evernden - coachwork}/Bastow. No Continuous Wheel Flap. The fact that the running was on a natural frequency speed explained failures and dispelled the idea that the shimmy was at all speeds. We were unfortunate in hitting by accident a running speed on the bumper which coincided with spring frequency - this should have been realized much earlier, by not recognizing this we have lost time and worried unnecessarily about design issues, which did not arise re. frame failures. Re Rubber Bush. (Outer Bearing of wishbone). It was decided to make a spherical all metal joint here, as the rubber joint had a strictly limited life with the onerous duty imposed on it. The axial movement of the bush is the direct resultant of lateral wheel movement due to the inclined axis of the joint. By BY.{R.W. Bailey - Chief Engineer} | ||