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 periodic nature of wobble in chassis, detailing tests with different engine and radiator mountings.
| Identifier | ExFiles\Box 15\1\ Scan086 | |
| Date | 12th March 1929 guessed | |
| contd :- -2- revaluation of the earlier tried systems, in particular the first strip rubber mounting which was found to be appreciably below the required standard, and was 'written down' from 80% to 60%. It was also said that once a car had been vigorously wobbled it is more prone to wobble afterwards. The policy therefore adopted was to apply the ultimate cure to the chassis known to be the worst for this defect. PERIODIC NATURE OF WOBBLE. A chassis with the original diabolo rubber mounting was exhibited on a bump test with alternate bumps on the drums, and it was clearly shewn that the radiator wobble came on at a critical speed. PROGRESS OF RESULTS. After the shoe scheme with .225 rubbers was found to violently wobble on the test road it was re-built with new front feet having max. area possible and thin rubber linings fore and aft to obtain the max. possible stiffness. Another chassis was also prepared with the original SS.{S. Smith} mounting having flexible diabolo rubbers so that we had two chassis each with the cross in the frame, but one with the most rigid engine mounting and the other the most flexible. Both of these cars experienced violent and equally unpleasant radiator wobbles on the test road, the former of quick periodicity at the higher road speeds, and the latter of slower periodicity and greater amplitude at somewhat lower road speeds - about 5 to 10 m.p.h. less. In these two examples we had the engine acting as a rigid cross and also as a flexible cross with a small amount of damping in each case. (1) The first conclusion formed from this test was that it is not possible to alter the flexibility of the frame either up or down enough merely by altering the engine mounting to escape from the wave band in which periodic radiator wobble occurs. (2) The second conclusion formed was that to proceed in any case in the direction of still further increased stiffness was out of the question, as the engine would have to be used to the max. extent as a rigid cross, and the booming and roughness produced thereby would be quite unacceptable. The ideal in this direction would be an infinitely rigid frame with an engine mounted on soft rubbers unfortunately beyond practical achievement at the moment. contd:- | ||