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).
Solutions for engine vibration and body boom issues by modifying engine mountings and flywheel design.
| Identifier | ExFiles\Box 12\6\ 06-page038 | |
| Date | 25th March 1931 | |
| HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} (At Le CanadelHenry Royce's French residence.) R4/M25.3.31. X7830 C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} C. to PN.{Mr Northey} BY.{R.W. Bailey - Chief Engineer} E.{Mr Elliott - Chief Engineer} X. 634. X. 7005. X. 7830. P.2. BODY BOOMS. We have removed the rear feet and the vibrations of the engine do not now affect the body so much. There is however too much movement of the frame, bonnet, etc. for this treatment (no rear feet) to be considered satisfactory, so I wired my previous wish to fit the rear feet with thick soft rubber to get some stiffening and damping effect from the engine crankchamber. I want you also to try if it makes much difference to remove the rubber entirely from the front feet. It is just possible that as regards body booms the difference between the thin rubber and none may only be slight. The object of removing the rubber is that if we could bolt the front arms up solid we should get a very stiff cross member well forward. I am very sorry to say that even now after all my telegrams and writing I have not heard of a single car being fitted up as I wished, viz: (1) With an improved flywheel (tested) to remove the whirl above the engine's maximum speed of say 3300 revs. (2) The engine fitted with one third or one half balance weight by the 4 weights at 30º, or by using the 4 weights opposite 1, 5, 7, & 12, webs, and four half units opposite 3, 4, 9, & 10., and a thicker flywheel flange if possible. When we have got the above engine, which should be the best we know, it should very soon be our production engine. We mount it in the frame the way I wished - i.e. either with all 4 feet with softer rubbers, or the rear feet only with soft rubbers (in neutral condition,) and the front feet more or less solid. One would assume that it is very difficult to detect any difference in frame stiffness when using the tube for the front bearing in the diamond mounting. Our engine here is by no means steady when run up to high speed with the car standing. It does not appear to be either the master period of the crankshaft or the variation of kinetic energy in the pistons. If HS.{Lord Ernest Hives - Chair} and RM.{William Robotham - Chief Engineer} are too busy with their work perhaps they will kindly allow Mr. Grils or one of the juniors to reply to my various memos., and explain when my wishes can be carried out, or why they cannot, or should not be. We think the cure of taking away completely the rear feet to be (in our car) worse by far than the trouble, so have coupled them up again after a couple of runs because the bonnet knocks badly, etc. When one runs the engine up with car standing there is much vibration from the engine going through several periods like | ||