LEAF SPRING SUSPENSION SYSTEM IN AUTOMOBILES

Leaf springs are made up of a number of curved bands of spring steel called leaves sticking together in order from shortest to longest. This stack of leaves is fastened together at the center with a center bolt or U- bolt to prevent the longitudinal movement. Similarly sometimes the leaves are made with pips or projections at the bottom and recess at the top surface. The leaves are arranged in such a way that the projection of the upper spring should mesh in the recess of the lower spring. Also to keep the leaves from slipping out of place, they are held at several places with the clips. Both ends of the longest or main leaves are bent to form spring eyes, used to attach the spring to the frame. To adjust the variations in length of the master leaf while the vehicle move across the road irregularities, one end of the spring is connected to the fame through a shackle and the other end is mounted directly on the frame with a pin. For the front suspension, it is a usual practice to provide the shackle in the front side of the spring to reduce the wheel wobble.

Generally, the longer a leaf spring, the softer it will be. Also the more leaves in a leaf spring, the greater the load they will withstand. But on the other hand as the spring will become firmer, the riding comfort will suffer.

The curvature of each leaf is called a nip. As the nip of the leaf is greater, shorter the leaf will be. Each leaf curves sharply than the one above the stack. When the center bolt is tightened, the leaves flatten somewhat and causing the ends of the leaves to press very lightly against one other.

The suitable steels that have been used for the manufacture of leaf springs are chrome-vanadium steel        (C-0.46%, Cr-1.4%, Va-0.18%), silico-manganese steel (C-0.52%, Si-1.95%, Mn-1.05%) and carbon steel (C-0.55%, Mn-0.6%, Si-0.2%).