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).
New engine mounting design to address vibrations and chassis wobbles.
| Identifier | ExFiles\Box 137\4\ scan0232 | |
| Date | 27th February 1931 | |
| R.{Sir Henry Royce} FROM DA{Bernard Day - Chassis Design}/EV.{Ivan Evernden - coachwork} X634 DA{Bernard Day - Chassis Design}/EV{Ivan Evernden - coachwork}1/M27.2.31. C. to SG.{Arthur F. Sidgreaves - MD} HS.{Lord Ernest Hives - Chair} F.{Mr Friese} re. VIBRATIONS. 1634 From deductions and tests it appears that what is known as "diamond engine mounting" will isolate the engine vibrations from the chassis and hence the body, but that with such a mounting the torsional rigidity of the crankchamber having been removed from the front end of the chassis we run into wobbles and jellying as would be expected. It therefore appears that we need an engine mounting that will: (1) permit the engine to oscillate about the crankshaft. (2) prevent the frame twisting out of plane. In other words we need a mounting which is the inverse of that on Silver Ghost. We attach herewith sketches which shew diagrammatically the linkage which lies as close as possible to the frame web. The engine is mounted in trunnions fore and aft and has 4 arms as at present. These arms extend out and on their ends are levers, two a side, being free to move on the tubular arms, and also on the large cantilever bearing on the frame web at "A". The ends of the stiff levers are joined at 'B' by a bolt. Rubber is placed under 2 or 4 feet. The engine can oscillate over a sufficient range due to the arcs of the levers being tangential, and the movement of each lever end being in the same direction. When the frame starts to twist out of plane the lever ends move in opposite directions and rapidly, so calling in the crankcase torsional stiffness. For the sake of the crankcase we might be glad of the slight flexibility of the mechanism. We only need the rigidity provided now by thin rubber feet. This Sch. was suggested when we were dealing with jellying on P. 2. in 1929, but was not tried as we had then no cars with trunnion mounting fore and aft such as we have now. We gave HS.{Lord Ernest Hives - Chair} a sketch when he was at WW. on Wednesday the 25th., and we would like to try it on a car if you do not object. DA{Bernard Day - Chassis Design}/EV.{Ivan Evernden - coachwork} | ||