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).
Page of a report discussing torsional stiffness in car design, comparing various models and addressing vehicle weight.
| Identifier | ExFiles\Box 178\2\ img088 | |
| Date | 11th January 1940 guessed | |
| - 2 - There are two ways of getting this torsional stiffness. One, which is the lighter, is to use the sloping windshield pillars and the roof rails as the main torsional structure. The other, used by Opel because of their preference for cabriolets, is to build the maximum amount of torsional stiffness into the underbody (meaning the frame and floor structure.) Satisfactory cabriolets cannot be produced with torsional stiffness below 2500 pounds feet per degree; or such is the result of all our investigations on cars, some of which have front axles, but the majority of which have front independents and therefore require more torsional stiffness. The Opel Kapitan Cabriolet finally developed a torsional stiffness of somewhere around this figure, and a development on an export model Chevrolet of 117" wheelbase was unsatisfactory until we obtained torsional stiffness of around 3000 pounds feet per degree. The above figures are only rough, of course, because obviously the stiffness must be fairly uniformly distributed along the length of the body-frame structure if shake is to be avoided. Furthermore, some forms of shake may not be avoided even on cars with very high torsional stiffnesses because they may be excited by such matters as a rear axle with a low plane of support against lateral motion, etc. Bob Schilling has done the most constructive work along these lines of rear axle control including the setting of optimum frequencies for vibration in the six degrees of freedom of a rear axle. Your item No.3: This brings up the very question that was going to occupy my undivided attention for the next five years when the Hs.{Lord Ernest Hives - Chair} cable arrived, calling me back to R.R. work. I had approached O.E.Hunt on the obvious fact that American cars were between 15 and 20% over weight for their size -- that is, a car which weighs 3600 pounds kerb weight should not weigh more than 3000 pounds. I found, furthermore, that Packard had produced a 3800 pound car and were close to production on it in 1938. The matter is, therefore, considered urgent and critical by other organizations than General Motors. (continued)....... | ||