14-08-2012, 04:19 PM
MULTI-LEAF SPRINGS
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Multi-leaf springs are widely used for automobile and rail road suspensions. It consists
of a series of flat plates, usually of semi- elliptical shape as shown in fig. 4.20. The
leaves are held together by means of two U-bolts and a centre clip. Rebound clips are
provided to keep the leaves in alignment and prevent lateral shifting of the plates during
the operation. The longest leaf, called the master leaf, is bent at both ends to form the
spring eye. At the center, the spring is fixed to the axle of the car. Multi- leaf springs are
provided with one or two extra full length leaves in addition to the master leaf. These
extra full-length leaves are stacked between the master leaf and the graduated-length
leaves. The extra full-length are provided to support the transverse shear force.
Nipping Of Leaf Springs
As discussed in the previous section, the stresses in extra full length leaves are 50%
more than the stresses in graduated –length leaves. One of the methods of equalizing
the stresses in different leaves is to pre-stress the spring. The pre-stressing is achieved
by bending the leaves to different radii of curvature, before they are assembled with the
centre clip. As shown in Figure the full-length leaf is given a greater radius of curvature
than the adjacent leaf.