Migrating scrub radius and trail

[CHagen]

I do not understand this concept physically. Susprog3d and optimum G website both suggest that the scrub radius and mech trail change with steering angle. and I am incredibly confused as to how this happens. Can someone elaborate as to what is going on?

 

[GregLocock]

Castor and KPI.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[CHagen]

hmmmm. The COP is a theoretical point so to make things simple lets just call it a point. A point some distance from the kingpin axis scribes a circle as it rotates about the axis. When you add KPI and castor that circle becomes inclined inward and to the rear respectively. Viewed from above this makes the circle ovate to varying degrees and directions depending on the amount of KPI and castor. As the wheel steers the point changes distance from the axis as it travels around this oval. I realize calling the COP a point some fixed distance from the kingpin axis is a gross simplification, but do I have this concept correct?

 

[GregLocock]

That sounds right. I'm assuming this is a simple suspension type with no compliances?


I'm more used to double ball joint suspensions with soft arm bushes - the location of the king pin is then a matter of conjecture.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[CHagen]

Yes it is a simple two ball joint thing but very laterally stiff with some yet to be determined longitudinal stiffness.