10111 Multileaf spring eye support

Axle location by multi-leaf springs relies on the spring eyes having sufficient strength and support to cope with the vehicle's laden weight driving and braking thrust and lateral forces. Springs designed

(a) Unwrapped

(b) Halfwrapped

(ct FulSv imilitaryl wrapped

Fig. 10.75 Spring eye protection

(a) Unwrapped

(b) Halfwrapped

(ct FulSv imilitaryl wrapped

Fig. 10.75 Spring eye protection for cars and light vans generally need only a single main leaf (Fig. 10.75(a)) wrapped around the bush and shackle pin alone, but for heavy duty conditions it is desirable to have the second leaf wrapped around the main leaf to give it additional support.

If a second leaf were to be wrapped tightly around the main leaf eye, then there could not be any interleaf sliding which is essential for multi-leaf spring flexing to take place. As a compromise for medium duty applications, a partial or half-wrapped second leaf may be used (Fig. 10.75(b)) to support the main leaf of the spring. This arrangement permits a small amount of relative lengthwise movement to occur when the spring deflects between bump and rebound. For heavy duty working conditions, the second leaf may be wrapped loosely in an elongated form around the main lead eye (Fig. 10.75(c)). This allows a degree of relative movement to occur, but at the same time it provides backup for the main leaf eye. If the main leaf should fracture at some point, the second leaf is able to substitute and provide adequate support; it therefore prevents the axle becoming out of line and possibly causing the vehicle to steer out of control.

10.11.2 Transverse and longitudinal spring, axle and chassis attachments (Figs 10.76-10.83) For small amounts of transverse axle twist, rubber bushes supporting the spring eye-pins and shackle plates are adequate to absorb linkage misalignment, and in extreme situations the spring leaves

Fig. 10.76(a and b) Main spring to chassis hinged cross-pin anchorage themselves can be made to distort and accommodate axle transverse swivel relative to the chassis frame. In certain situations where the vehicle is expected to operate over rough ground additional measures may have to be taken to cope with very large degrees of axle vertical deflection and transverse axle tilt.

The semi-elliptic spring may be attached to the chassis and to the axle casing in a number of ways to accommodate both longitudinal spring leaf camber (bow) change due to the vehicle's laden weight and transverse axle tilt caused by one or other wheel rising or falling as they follow the contour of the ground.

Spring leaf end joint attachments may be of the following kinds;

a) cross-pin anchorage (Fig. 10.76), b) pin and fork swivel anchorage (Fig. 10.77), c) bolt and fork swivel anchorage (Fig. 10.78), d) pin and ball swivel anchorage (Fig. 10.79), e) ball and cap swivel anchorage (Fig. 10.80).

Alternatively, the spring leaf attachment to the axle casing in the mid-span region may not be a direct clamping arrangement, but instead may be through some sort of pivoting device to enable a relatively large amount of transverse axle tilt to be

Fig. 10.77 Main spring to chassis pin and fork swivel anchorage

Fig. 10.78 Main spring to chassis bolt and fork swivel anchorage

Fig. 10.76(a and b) Main spring to chassis hinged cross-pin anchorage

Fig. 10.78 Main spring to chassis bolt and fork swivel anchorage

)bl Planview

Fig. 10.82 Axle to spring spherical seat mounting

Fig. 10.79 (a-c) Main spring to chassis pin and spherical swivel anchorage

Fig. 10.79 (a-c) Main spring to chassis pin and spherical swivel anchorage

(bl Planview

Fig. 10.80 (a-c) Main spring to chassis spherical swivel anchorage

Fig. 10.80 (a-c) Main spring to chassis spherical swivel anchorage

la) Endview (b) Sideview

Fig. 10.81(aand b) Axle to spring pivot pin seat mounting la) Endview (b) Sideview

Fig. 10.81(aand b) Axle to spring pivot pin seat mounting accommodated. Thus transverse axle casing to spring relative movement can be achieved by either a pivot pin (Fig. 10.81) or a spherical axle saddle joint (Fig. 10.82) arrangement. Likewise for reactive balance beam shackle plate attachments the

Fig. 10.83 Tandem axle balance beam to shackle plate spherical joint

joints may also be of the spherical ball and cap type joint (Fig. 10.83).

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