Typically each arm has a spherical joint (ball joint) or rubber bush at each end. Consequently they react loads along their own length, in tension and compression, but not in bending. Some multi-links do use a swing arm or wishbone, which has two bushes at one end.
On a front suspension one of the lateral arms is replaced by the tie-rod, which connects the rack or steering box to the wheel hub.
In order to simplify understanding it is usual to consider the function of the arms in each of three orthogonal planes.
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2 Front view 3 Side view 4 Advantages of multi-link suspension 5 Disadvantages of multi-links 6 Related Pages |
The arms have to control toe/steer and lateral compliance. This needs a pair of arms longitudinally separated.
The arms have to control camber, particularly the way that the camber changes as the wheel moves up (into jounce, or bump) and down into rebound or droop.
The arms have to react traction and braking loads, usually accomplished via a longitudinal link. They also have to control castor. Note that brake torques also have to be reacted - either by a second longitudinal link, or by rotating the hub, which forces the lateral arms out of plane, so allowing them to react 'spin' forces, or by rigidly fixing the longitudial link to the hub.
In its simplest form the multi-link suspension is orthogonal - that is, it is possible to alter one parameter in the suspension at a time, without affecting anything else.
This is in direct contrast to say a double wishbone suspension where moving a hardpoint or changing a bush compliance will affect two or more parameters.
It is very hard to optimise the geometry without a full 3d analysis, and compliance effects are important.
Vehicles
Automotive engineering
Automotive suspension designPlan view
Front view
Side view
Advantages of multi-link suspension
Disadvantages of multi-links
Related Pages