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).
Methods to reduce frame 'jellying' by modifying engine mounts and frame stiffness.
| Identifier | Morton\M19\ img141 | |
| Date | 2nd April 1931 | |
| (3) Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}7/KT.2.4.31 cont. (b) with front rubber mounted engine feet to assist. That this can be accomplished we believe because at the Berlin Show we noticed that the Maybach was almost entirely free from jellying of any sort and yet the mounting of the engine was such that it could not possibly have contributed materially to the frame torsional stiffness. The most noticeable feature of the Maybach was the great size of its frame members. We have fitted at Hs{Lord Ernest Hives - Chair}' suggestion, an experimental car with front side channels double the thickness of our standard members, these were made in the same dies. So far, with the engine stiffness removed, this frame has given encouraging results, and we are now putting all the stiffness into it we can, forward of the engine. With the front apron this should be possible without the result being too unsightly. The other line of investigation is to determine why P.II jellies when P.I. did not, though we agree that P.I. steering is not so selective as P.II and therefore that though we eliminate jellying, the results may not be quite desirable. With reference to your suggestion re. fitting soft rubbers at the rear. We have tried diabolo rubbers in the rear and sandwich in the front but even so the diabolo's were sufficient to cause booms unless they were made so soft and with so little set up that one cannot visualise them adding any stiffness to the frame. With regard to your request re-fitting up the front feet with no rubber in the sandwich. This has been done a number of times in the past and reports show that though it did benefit jellying, the resultant engine vibrations passing to the frame were such as could not be tolerated. We are fitting such feet to a car again which will be available on your return for your inspection at West WitteringHenry Royce's home town. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||