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).
Analysis of competitor vehicle body and engine mounting techniques and their effects on noise and vibration.
| Identifier | ExFiles\Box 170\2\ img160 | |
| Date | 17th June 1933 guessed | |
| -2- As a recent convert to the rigid frame and body school. The subframe on P.11. was a mistake, and a heavy and costly one. The solid mounted bodies, Chrysler & Packard, make better motor cars. My guess is that the P.11 cross-member was just stiff enough for bad resonance, and without assistance of a rigid body mount, not stiff enough to get past the resonance peak on the upward side. We have produced shimmy on drums running 50 M.P.H. max. speed just by loosening up the two forward body bolts. A rigid body mount is very noisy. Chrysler uses a rubberised material rather softer than brake lining which with a frame that follows the contour of the body still gives sufficient rigidity without too much trouble. They are not immune from noise trouble. Even with a floated engine they have trouble with shock absorber noise and tyre noise. The new spoked tin wheels which threaten to replace wire, are full of road noises. Rubber-mounted shackles cut down noise and vibration close to the source. All the cars which have gone to very soft motor mounts this year have trouble with a soft and sloppy feeling about the nose of the car, even when fender shake is kept down either by the pivotted mount of Chevrolet etc., or by similar means. The most successful is the Packard Super-8, which with a full float for the engine almost as spongy as Chrysler's, at still obtains a fairly solid feel by a solid mounted radiator with very stiff diagonal braces to a heavily reinforced dash, the radiator tied to headlamps and fenders by means of which are practically solid though rubberised to prevent cracking. That is, the whole front end is "triangulated" like the Hupmobile but using the radiator itself as the front triangle. The soft mounted Chevrolet engine, while it immensely improves the cruising speed of the car, has resulted in an inferior road car because of the sloppy nose. One of the worst cars is the Auburn 12 which has a terrific lateral shake at the windshield, in spite of an x-member frame and apparently because of the massive engine. Since these are all resonance problems it stands to reason that one man's meat is another man's poison and that overdoing the thing which gives worst results will generally effect a cure. Parasite wind resistance is being held down. See this year's Studebaker with the slot between fender and hood almost eliminated. Air speeds here we find 30% above travelling speed. Built in horns and a similar lamp treatment to Pierce Arrow seen on the way. Forward grills like Pontiac if not unduly obstructed and if carried well | ||