Introduction

A leaf spring is made of many rectangular steel strips of different lengths (called leaves) stacked one over the other. The length, cross section, and number of strips depend on the load to be supported. The leaves are bent in elliptical shape and, hence, the leaf spring is also known as elliptical spring. Helical spring cannot take any lateral force, while a leaf spring can take lateral force also, hence, is widely used in the suspension of automobiles, railway carriages, etc.

The longest leaf, called the master leaf, is at the top and the other leaves of calculated length, called graduated leaves, are placed below the master leaf. The topmost leaf is provided with a circular eye at each end for fixing (Figure 23.1). The ends of the master leaf can also be straight for some applications. The smallest leaf is at the bottom. The leaves are clamped together with U-shaped clamps to keep them aligned. Sometimes, one or two extra full-length leaves are provided below the master leaf to take transverse shear force. Leaves are kept in their position by a center clamp or U bolts.

Each leaf of the spring is made circular with radius of curvature R. Vertical distance from the center of the upper-most leaf to the line joining the bottom of eye is called camber y. There is a difference between the terms spring arch and spring camber. Each is measured when the spring is without any external load.

Arch is measured from the center of the line joining center of eyes, to center of the upper surface of top leaf.