THIS paper deals with one system of designing rubber springs; outlines its advantages; indicates its limitations; and describes the approach to the problem.
This spring is of the torsion type, called “Torsilastic,” and is claimed to present advantages not only in its characteristics as a spring but also in flexibility of application which makes it possible to meet a wide range of requirements by variations in spring design and in the length of the moment arm which applies the torsional load. In general, it consists of an inner shaft surrounded by an annular layer of rubber bonded to the inner shaft and also to an outer metal shell. The outer shell is split into two segments. The spring is stressed in torsion by anchoring either the shaft or outside shell to the chassis and rotating the other member.
When used not only as a spring but also as a mounting, the spring is claimed to offer the following advantages: reduction in harshness of ride; lowered noise level due to insulating properties; elimination of bearings, bearing parts, spring seats, and mountings; reduction of static friction to a minimum due to elimination of bearings; freedom from lubrication, rattles, and squeaks; cleanness and simplicity of design with low weight.
Engineering data and diagrams are presented to assist in the design and application of the rubber torsion springs in various ways to various types of automobile chassis as well as to railroad and streetcar suspensions. Included are methods of calculating angular deformation and considerable data on creep, hysteresis, durometer hardness, and stress-strain relationships.