Leaf Spring
This type of springs is widely used in light and heavy commercial vehicles.
Construction
A leaf spring is built with number of leaves. The leaves are placed one over the other, and are held together by clamps and a bolt at the center. The leaves are usually given an initial curvature or cambered, so that they will tend to straighten under load. The spring is clamped to the housing
by means of U – bolt. The longest leaf known as the main leaf or master leaf has its ends formed in the shape of an eye.One end of the leaf spring is
attached to the frame through shackle as movable. Another end is attached
with anchor pin as non movable.
Working Principle
When the vehicle travel over a road undulation, the force from the road act on the leaf spring and the spring gets straightened. This variation in length is accommodated by the oscillation movement of the shackle. Thus, the road force makes the deflection of the leaf spring and absorb the vibration.During deflection, the energy is stored in the leaf spring and the stored energy is dissipated when the leaf spring retains its original position. Thus the road shocks are reduced and the ride comfort is increased.In light commercial vehicles spring rubber or hard plastic bush are used.Phosphorus bronze bushes are used in heav y commercial vehicles. The lubricating oil with graphite is used in the bushes for lubrication.
Material chromium vanadium steel,
Chromium- Nickel- Molybdenum steel,Silicon- manganese steel, are the typical materials that are used in the manufacturing of leaf springs.
Type of Leaf Spring
(a) Quarter Elliptic Leaf Spring
(b) Semi Elliptic Leaf Spring
(c) Three Quarter Elliptic Leaf Spring
(d) Full Elliptic Leaf Spring. (e) Transverse Leaf Spring
Quarter Elliptic Leaf Spring
The figure shows the simple arrangement. The one end is fixed
on the side member of the frame by means of U Clamp or I Bolt while the other end is freely connected to the front axle. In such springs the camber is provided on the upward side so that the leaves tend to straighten when the front axle beam is subjected to shock load. The cost and the weight of this type spring is low. This is also known as the cantilever type leaf spring and it was used in olden days.n
Semi-elliptical leaf spring
The simple construction is shown
in the figure. This type ofarrangement is mostly used in automobile and it resembles the semi. ellipse in shape. The leaf spring is made-up of a
number of steel leaves. Each leaf is of a different length, but with equal width and thickness. The uppermost longest leaf having bushes at its two ends, is called the master leaf. The one end of the spring is rigidly fixed
to the vehicle frame while the other end is attached with the help of shackle. The shackle accommodates the variation in the length while vehicle driving on rough terrains. This type of spring arrangement
is requires less maintenance, easy to repair and it has long life.
Three quarter elliptic leaf spring
The figure shows the arrangement. The three quarter elliptical spring is the combination of quarter elliptical spring and semi elliptical spring. One end of the semi elliptical spring is
attached to the frame through shackle and the other end of the semi elliptical spring is attached to the quarter elliptical spring by means of the shackle. The other end is bolted to the frames and being rigidly
held by I – bolt. This type of arrangement was more popular in olden days and not used now-a-days
Full Elliptic Leaf Spring
The simple construction of this
type is shown in figure. In
this type, two semi elliptical springs are connected in opposite manner to form an elliptical shape. The full elliptical spring is attached rigidly to both the axle and the frame. Spring shackles are not necessary, since both the top and bottom members will elongate by the same amount when compressed. This arrangement was used in olden cars and not used now-a-days
Transversely mounted semi- elliptical inverted leaf spring
The figure shows the
arrangement. In this arrangement, a semi- elliptical leaf spring is mounted transversely along the width of the vehicle. The springs are placed, so inverted that the longest leaf
is located at the bottom. The mid portion is fixed to the frame by means of U-bolt. The specialty of this arrangement is the use of
two shackles. The rolling tendency of this type leads to its unsuitability for vehicles.
