ALONG with larger tires, independent wheel suspensions, higher speeds, and the dynamic and vibrational problems associated with these innovations, came the need for chassis frames having a high resistance to torsional movements. The X-member-type frame has been the most generally adopted means for obtaining increases in this direction.
However, the past few years have seen the need for torsional rigidity in the chassis frame to be intensified. Although considerable gains have been made, in general, these gains have been accomplished not by major improvements in the design of the structure but by the addition of material. Consequently, the weight of the chassis frame has become a serious problem, so much so that in many cases special heavy frames are being used for the open-body types where the need for a stiff frame is acute.
The purpose of this paper is to present certain experimental data pointing the way toward greatly increased chassis-frame stiffness without the weight penalty heretofore associated with such increases. As an example:
In a standard 1935 car, a closed model having a steel top and a trunk, the torsional-resistance value approximated 10,000 ft. lb. torque to twist the structure through an angularity of 1 deg. The chassis frame's resistance alone (the frame being a conventional X-member-type weighing 265 lb.) equaled 1700 ft. lb. For the same weight it has been possible to replace the standard frame with one having, by itself, a torsional resistance equivalent to the stiffness of the complete standard car.