Inclined interleaf rectangular sandwich mounting

(Fig. l.l8(c)) These rectangular blocks are la) Double shear pa ¡red sandwich mounting la) Double shear pa ¡red sandwich mounting

(c> Inclined interleaf rectangular sandwich mounting

Fig. 1.18(a-h) Types of rubber flexible mountings

(c> Inclined interleaf rectangular sandwich mounting

Fig. 1.18(a-h) Types of rubber flexible mountings

(e) Mstaxéntríc bush mounting

Fig. 1.18 contd

Fig. 1.18 contd designed to be used with convergent 'V' formation engine suspension system where the blocks are inclined on either side of the engine. This configuration enables the rubber to be loaded in both shear and compression with the majority of engine rotational flexibility being carried out in shear. Vertical deflection due to body pitch when accelerating or braking is absorbed mostly in compression. Vertical elastic stiffness may be increased without greatly effecting engine roll flexibility by having metal spacer interleafs bonded into the rubber.

Double inclined wedge with longitudinal control mounting (Fig. 1.18(d)) Where heavy vertical loads and large rotational reactions are to be absorbed, double inclined wedge mounts positioned on either side of the power unit's bell housing at principal axis level may be used. Longitudinal movement is restricted by the double 'V' formed between the inner and two outer members seen in a plan view. This 'V' and wedge configuration provides a combined shear and compressive strain to the rubber when there is a relative fore and aft movement between the engine and chassis, in addition to that created by the vertical loading of the mount.

This mounting's major application is for the rear mountings forming part of a four point suspension for heavy diesel engines.

Metaxentric bush mounting (Fig. 1.18(e)) When the bush is in the unloaded state, the steel inner sleeve is eccentric relative to the outer one so that there is more rubber on one side of it than on the other. Precompression is applied to the rubber expanding the inner sleeve. The bush is set so that the greatest thickness of rubber is in compression in the laden condition. A slot is incorporated in the rubber on either side where the rubber is at its minimum in such a position as to avoid stressing any part of it in tension.

When installed, its stiffness in the fore and aft direction is greater than in the vertical direction, the ratio being about 2.5: 1. This type of bush provides a large amount of vertical deflection with very little fore and aft movement which makes it suitable for rear gearbox mounts using three point power unit suspension and leaf spring eye shackle pin bushes.

Metacone sleeve mountings (Fig. 1.18(f and g)) These mounts are formed from male and female conical sleeves, the inner male member being centrally positioned by rubber occupying the space between both surfaces (Fig. 1.18(f)). During vertical vibrational deflection, the rubber between the sleeves is subjected to a combined shear and compression which progressively increases the stiffness of the rubber as it moves towards full distortion. The exposed rubber at either end overlaps the flanged outer sleeve and there is an upper and lower plate bolted rigidly to the ends of the inner sleeve. These plates act as both overload (bump) and rebound stops, so that when the inner member deflects up or down towards the end of its movement it rapidly stiffens due to the surplus rubber being squeezed in between. Mounts of this kind are used where stiffness is needed in the horizontal direction with comparative freedom of movement for vertical deflection.

An alternative version of the Metacone mount uses a solid aluminium central cone with a flanged pedestal conical outer steel sleeve which can be bolted directly onto the chassis side member, see Fig. 1.18(g). An overload plate is clamped between the inner cone and mount support arm, but no rebound plate is considered necessary.

These mountings are used for suspension applications such as engine to chassis, cab to chassis, bus body and tanker tanks to chassis.

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