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).
The results of verifying different front engine mounting configurations to address clutch jaggers and vibrations.
| Identifier | ExFiles\Box 14\5\ Scan305 | |
| Date | 25th September 1934 | |
| COPY. To Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} From G.W.H. Hotel de France, Chateauroux, Indre, France. September 25th, 1934. 26-EX. We have been verifying the results obtained by the front engine mounting. First of all, we reverted back to the front flexible mounting and brought into prominence all the faults, boom period 25 to 35 MPH, with the exception that the clutch jaggers were not so pronounced, and it took some time before we could reproduce a slight jagger. Upon further investigation we found we had omitted to replace the tie rod between the pedals and the engine case. This was fitted, and clutch jaggers were almost as bad as when the car first came out. Taking the tie rod off again reduced the jaggers to practically nil. After having settled that point, we fitted up the engine front solid, that is, we took the rubbers out of the front engine feet and replaced them by steel packing pieces, making the engine feet solid with the frame, and no tie rod. The result was, bad shaking of the front of the car during the torque reaction period up to approximately 12 MPH, from that speeds upwards, one could feel the vibrations throughout the body. Wing and head lamp movement was not appreciably reduced. There was a bad period of boom from 25 up to approximately 38 MPH. There was no sign of clutch jagger. Steering did not appear to be as selective. The next test was with the front central mounting only. This brought us back again to where clutch jaggers could only be obtained under abnormal conditions. The torque reaction period slightly shakes the front, above this the engine was as smooth as with the flexible mounting, and boom period no more pronounced. The torque reaction dampers were then fitted and set to 35 lbs, on long lever (3").. No clutch jaggers could be obtained under any condition that we could test. Head lamp and wing movement steadier. The soft rubbers in the front engine feet are only useful to prevent the excessive rocking over of the engine, but hard rubbers must not be used. We have therefore again come to the conclusion that for the best all round purposes, the central front mounting with torque reaction dampers and soft rubbers in the front engine feet, as designed for flexible mounting, should be used. P.T.O. | ||