22.5.
Torsion bar
This is a straight bar of circular or square section fixed to the frame at one end, and a lever or wishbone-shaped member connects its other end to the wheel. A torsion bar suspension system used on a car is illustrated in Fig. 22.24. The diameter is increased at each end of the bar and the bar is connected with the levers by serrations. Provision for the adjustment is made at the frame end to ‘level’ the suspension.
Since the coil spring is a form of torsion bar, the rate of both springs depends on the length and diameter. The rate decreases or the spring becomes softer if the length is increased or the diameter is decreased.
Fig. 22.24. Torsion bar spring.
