Quote:
Originally Posted by DCM
the longer arm, has a lower ratio of torsional twist to the upstroke of the suspension arm.
eg.
Short link, 15mm of suspension travel = 47' of torsional twist (stiff action)
long link, 15mm of suspension tavel = 30' torsions twist (soft action)
Running an ARB can allow for slightly softer springing and damping on your suspension, to cope with a rough track, with the ARB controlling pitch into and out of a corner.
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If we were to assume that the bar was perfect (ie no actual twist, just complete transmission of the forces), 47 degrees or 30 degrees would not matter as the opposite side of the cars suspension would need be lifted by an identical amount, as the linkages are identical on both sides of the car.
If we assume that the levers are perfect but the centre section twists at a uniform rate (say, 50%), the lift on the opposite side would also be constant (certainly as you approach zero the relationship would be linear). An input of 20deg from a short link that lifted the other side 10deg would be effectively the same as a long link, deflecting 10 degrees, and lifting the other side 5deg.
But obviously the levers are not perfect, they flex, and this takes up more of the input energy before it gets transferred to the centre section of the bar, and more again as it is transferred back to the opposite side. The longer the lever, the greater the energy loss. And the softer the effect of the bar.
I'm fairly certain that it is the "spring" nature of the lever rather than the leverage itself that causes the bar to be stiffer with a shorter lever. But in all honesty it is not that relevant now as after 5 minutes with the car I have seen the lever effect in action. I probably shouldn't have bothered posting the thread in the first place!