Engine mounting solutions to address frame flexibility and vibration issues in 'SS' & 20HP cars.
| Identifier | WestWitteringFiles\T\January1929-February1929\ Scan021 | |
| Date | 18th January 1929 | |
| HS. {Lord Ernest Hives - Chair} E. {Mr Elliott - Chief Engineer} ) FROM R. {Sir Henry Royce} DA {Bernard Day - Chassis Design} BY ) (At Le Canadel(Henry Royce's French residence).) SECRET ORIGINAL R1/M14.1.29. REC'D AT WW. 18.1.29. 'SS {S. Smith} ' & 20HP. CARS. X7005 X7380 ENGINE MOUNTING ETC. X5005 Apparently there was truth in the idea that the frame (radiator) movements were of large amplitude, and the engine vibrations of small amplitude, and that we might find an engine mounting that would prevent the former, and not transmit the latter, by reducing the flexibility. One gathers that our mounting was about 100 times too flexible, but we did not know that we needed it to stiffen the frame, and if we had not it would have been excellent for engine vibrations. Now we cannot alter (to any extent) the tramping speed of the front axle at any given tyre pressure, but we now conclude that the axle modifications, the stiffened frame and effective shock dampers, give us a combination which prevents this axle tramping building up into a high speed wobble: (this at one time seemed an unsurmountable task.) To make the permanent mounting it is probably most economical to use the frame as one of the surfaces because we seem to require a large area so that we can use thicker rubber and make a more robust arrangement. There are 2 simple schemes naturally come to mind - i.e. something like you have, and as that shewn here: The tubular feet (Phantom standard) seem suitable, and as we have these ready I propose we use them as far as possible. The flange which is bolted to the frame can be be riveted or bolted to the angle plate that rests on the rubber. It would seem that this flange has a base at the correct angle to the bore to suit the frame. [Diagram Annotations] This is the plate to which the engine foot is riveted or welded. Most of the holes are clearance but some are slotted vertically but fit the ferrules so as to locate the engine fore and aft - i.e. the back feet only. 6 bolts in all preferred- see larger sketch. Bolts tightened hard up to ferrules: rubber is compressed as arranged by experiment. Area of rubber upward less than area downward seems good. (1) | ||
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).