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).
Technical discussion on vehicle frame stiffness for sedan and soft-top models, comparing different construction methods and their effects.
| Identifier | ExFiles\Box 170\2\ img280 | |
| Date | 2nd July 1935 guessed | |
| -4- ties of the job are clear. The picture we get from all this is:- (1) Sedan jobs. (Metal frame and roofs). It is desirable and entirely practical to eliminate the frame entirely. We should have no more than a rudimentary frame for ease of assembly. Benefits in weight, cost, and floor height are considerable. (2) Soft Top Jobs There is no way of getting torsional stiffness out of these. So they must have higher floors than the sedans and must have stiff frames. In some of them the body is not stiff enough to hold itself together even if mounted on an infinitely rigid frame. Therefore the best practice seems to be Chrysler's in which a 4" X-member in the body is bolted at many points to a 5" X-member in the frame. This gives a virtual X-member 9" deep and at the same time offers a good foundation to the lower ends of the pillars. (3) Increased stiffness does not mean increased weight. For instance several divisions this year have increased stiffness 2 1/2 times as compared with last year, with a saving of 15% to 20% in frame weight. This by repeated tests and attention to frame detail. From watching Park Ward's operations I have the idea that none of your bodies have appreciable torsional stiffness. Therefore it would seem to me that your task is to produce a frame which will give 3000 lbs feet per degree between wheel centers. For this reason I am sending you this stuff, hoping to get useful comments in return and perhaps some idea of what stiffnesses you actually get on English coach-work. We think that independent suspension only affects the problem to a minor degree. In other words, to get a good frame one has to have a certain stiffness whatever the suspension, but with an inadequate frame the independent will be more noticeably bad than the front axle. One other comment. If the frame stiffness is of a certain inadequacy and is progressively improved, the first stages of improvement will almost always make it worse. This is certainly where the P II X-member fell down and where numerous other manufacturers have fallen down simply because they have not realized that they are dealing with a resonance curve and not with a simple mechanical shake. Attached sketch is intended to illustrate this. | ||