113
« on: 21 January 2014, 10:54:21 »
In short.....
The wishbone length and inclination defines virtually everything about how a car handles. According to the geometry chosen, the wheels angle to the road can be controlled ( or not ) so that its at 90 degrees to give the best grip. Or indeed to give diminishing grip at certain points.
The concept is the Roll Centre. The geometry of the wishbone leads to an imaginary point called the roll centre, which is the point about which that end of the car rolls around in cornering. The roll centre is the "god" principle of suspensions.
The designer really needs to contrive the roll centre so that it remains in the same place through the whole suspension travel and usually that the front one is lower than the rear one, leading to controllable understeer. the handling is then adjusted through the anti-roll bar strength.
getting technical, on a macpherson strut car the roll centre is found by extrapolating inboard the plane through the outer wishbone ball joint and the wishbone fulcrum until it meets the plane perpendicular to the strut. But to simplify, you can imagine a long broom handle attached to the wheel, pointing inboard. The length of the broom handle is the wishbone effective length and the roll centre is the height at which the end is being held. As an exampkle, if your roll centre is eight feet above ground, then the tyre will fall out onto its outer shoulder very quickly.
hope this helps
