suspension understanding problems

[reece146]

Ok, as an attempt to get everyone on the same page here is a diagram that shows a rough idea of where the instant centre (IC) for a few suspension types end up. Where the lines converge is the IC.


Race and Rally Car Source Book, Allan Staniforth, Haynes Publishing, pp 50

This is the location of the hinge point in the frontal plane.

Now, the wheel is located at the center of the hub of course, this is the length of the lever arm from the hinge or more commonly the front view swing arm (fvsa). I don't know the specifics of how the VAMOS code locates this - is it where the wheel centerline crosses the king pin inclination axis (KPI)?, is it the wheel's contact patch, something else?

To drill down on a SLA setup like the XS uses in real life:


Chassis Engineering, Herb Adams, HPBooks, 1993, pp 47

This is only considering the frontal plane view. The percentage of anti-dive or anti-squat is also related as the geometry of the suspension defines these qualities. This makes the side view of the car also come into play with respect to the location of the hinge point. I believe that in the case of VAMOS the antis are just a number dialed into the .car file and not directly extrapolated from the suspension geometry.

To see what I mean:


Race Car Vehicle Dynamics, Millike & Milliken, SAE Press, 1995, pp 632

The big problem with this model as I see it is that it is only close to realistic values within small suspension deflections. Not a big deal and arguable that it makes the sim more playable as there is only so much feedback you can get from the console even with working force feed controls.

We haven't really touched scrub radius or KPI at this point.

Btw, I have a MY2000 "XS" in my workshop. I can try to get real world numbers off it but being put away for the winter there is a lot of crap in the way. I can try to get at it over the next few weeks.