Relative Height of the 2 roll centres

[gryphon]

FEW DOUBTS
1.When we place roll centre close to ground there is a huge lateral migration of the roll centre. http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif Can someone please enlighten me how this migration of roll centre will effect handling.
2.how do we decide relative height of front and rear roll centre. http://fsae.com/groupee_common/emoticons/icon_confused.gif I ve read that front roll centre is lower.Why?how do we decide this difference of height?
Is there some way to decide cog height at different transverse planes?

Thanking everybody http://fsae.com/groupee_common/emoticons/icon_smile.gif

[gryphon]

FEW DOUBTS
1.When we place roll centre close to ground there is a huge lateral migration of the roll centre. http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif Can someone please enlighten me how this migration of roll centre will effect handling.
2.how do we decide relative height of front and rear roll centre. http://fsae.com/groupee_common/emoticons/icon_confused.gif I ve read that front roll centre is lower.Why?how do we decide this difference of height?
Is there some way to decide cog height at different transverse planes?

Thanking everybody http://fsae.com/groupee_common/emoticons/icon_smile.gif

[gryphon]

http://img151.imageshack.us/img151/3922/87797594.th.png (http://img151.imageshack.us/i/87797594.png/)

[gryphon]

http://img151.imageshack.us/img151/3922/87797594.png (http://img151.imageshack.us/i/87797594.png/)

[Tom W]

Is that really a huge lateral migration?

You're working in degrees of roll there, so assuming that you are running somewhere in the region of 1 degree of roll /g and that your maximum lateral acceleration will be somewhere between 1.5 and 2g then you will be looking at a maximum lateral migration of ~25mm. We run a front track of 1200mm, so presumably you are not hugely dissimilar. I would say that the migration isn't going to make any major difference to anything in the grand scheme of things.

Claude will tell you that you get a stiffening/softening effect on opposite wheels as the RC moves laterally. He will also tell you that it is a particularly bad thing to have your roll centre move outside your wheels. I've never bothered to crunch numbers as to the effect of this, but with 25-30mm of movement I would be prepared to take a stab that it is pretty minimal.