Sway Bar Caluclations - Asymmetrical End Lengths

[SMRacer]

I am interested in the forces resulting from asymmmetrical end link adjustments on a sway bar.

Specifically what equation governs the forces applied to the A arms due to the sway bar when the adjustable links between the sway bar and the A arm are different lengths?

 

[bentheswift]

Force = torque/radius

 

[NormPeterson]

If you know the rate of the bar (lb/in @ the endlink connections) the force is [rate]*[amount of endlink preload displacement]. Note that preloading the bar(s) will normally change the spring forces and cornerweights slightly at all four corners.


Norm

 

[Yawing]

The ARB has to see the same torque on one side to the other. regardless of the MR. So if you work out the ARB is trying to twist x degrees per G of sprung mass roll, then you know the loads at each wishbone, then you know the loads at each wheel, hence the roll resisting moment.

The effect is a variation in the roll stiffness, it wont make the car assymetric.

 

[NormPeterson]

Preloading the bar by adjusting endlink lengths does not affect the rate of the bar. The cross-weight change does cause an asymmetrical effect.

Norm

 

[Yawing]

I dont think he is talking about preloading the bar, more so running different motion ratios side to side

 

[NormPeterson]

The description of the link being adjusted and how it is being adjusted seems clear enough.

I suppose that it would be possible to adjust the pickup points laterally along the control arms to change the MR (and also the endlink force directions and hence the overall bar loading), but I don't think that's what the OP is asking about.

If it's unequal bar arm lengths that you're thinking of, there will be some coupling between 'heave' and 'roll'. There's more to sta-bar stiffness and deflections/loads at the endlink connections than the effects of a torsionally loaded shaft alone.


Norm

 

[evelrod]

Obviously, you both have a grasp of the problems, but from a practical point...read that as what I do on my race cars...there is a great deal of compromise when attempting to set up an "asymmetrical" cornering load.
First, it's a difficult task, at best. Pre loading an anti roll bar is just not, or at least not normally done. It really throws a monkey wrench into roll calcs. and is just 'so non linear'!
Secondly, altering the dimensions of the connector lengths, location on the bar and, location on the suspension link can and do have some positive results. Not huge on my 'door slammers', but significant. Roll characteristics can, therefore, be changed left turns v right turns. I tried several combinations (my rear bar is infinitely (well...sorta) adjustable so I have tried several combinations. All I can say is that everything is now symmetrically adjusted. Asymmetrical settings just opened a cans of worms for me as a vintage racer...My two cars, a Mini Cooper and a Lotus Cortina are just not sophisticated enough to warrant the added effort...Perhaps there is a 'pro' engineer that can elaborate further. I'm just too far out of the loop after so many years.

Rod