TORSION BAR SPRINGS

A torsion bar spring, usually called as a torsion bar is a spring steel rod that uses its torsional elasticity to resist twisting and takes only the shear stresses. One end of the torsion bar is anchored to the frame or other structural member of the body and the other end to a component that is subjected to torsional load.

The amount of energy stored per unit weight of material is nearly the same as that of the coil spring. Torsion bar is oftenly used with the independent suspension. As shown in the figure, the bar is fixed at one end to the frame, while the other end is fixed to the end of the wheel arm and supported in the bearing. The other end of the wheel arm is connected to the wheel hub. When the wheel strikes a bump, it start vibrating up and down, thus exerting torque on the torsion bar, which acts as a spring.

Torsion bar is lighter as compared to the leaf springs and so it occupies less space. As the torsion tubes are much stiffer than the bars, it is preferred. The main disadvantage of the torsion bar is that it does not take the braking or driving thrust so that additional linkages has to be provided for this purposes. The second disadvantage is that the absence of friction force to damp out the vibrations and hence additional dampers are to be provided.