Roll Center Migration
Roll Center Migration
(OP)
What are the effects of lateral roll center migration? From what I have read, I generally understand that significant lateral migration of the roll centers is a bad thing. Is this true? Why? I can't seem to find much information on the effects of roll center migration. Does it matter if the rear moves farther than the front, or the front farther than the rear? Thanks for any insight!





RE: Roll Center Migration
First you have to figure out how to calculate it, and then you have to consider what its migration by your defintion would affect.
The method I prefer to use to establish RCH,
d(Fz)/dFy*semitrack
in a lateral force at the contact patch test, gives a RCH only.
However people who like geometrical constructions can find a lateral position for it.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Roll Center Migration
RE: Roll Center Migration
Goran
RE: Roll Center Migration
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Roll Center Migration
If you defined the roll center to be the intersection of the force lines from each tire and defined the roll axis to be the axis about which the car rolls, then what sort of effects would its lateral migration result in?
RE: Roll Center Migration
Then the angles of the FL determines how much geometric weight transfer we will get for suspension of each individual wheel. This is quite independent from the previously described movement of roll.
We have now four FL where the force goes straight into the ground without affecting the suspension system. The greater the angle of a single FL are, the more power goes geometrically through the suspension in question.
If we now go back to the place where the FL intersect, but do not call it Rc, so we'll see what significance this has.
If the FL intersecting the middle between the wheels all FL will get the same angle. In a curve the load of the outside wheel FL will produce a lift of the car, while the FL of the inside wheel will press the car down. Since in this case, the intersection of FL is located in the cente of car (the same slope on all fours) so would these forces become equal. But now the outer wheel receives more load and the result is that we get a greater lifting force than lowering. So by altering the FL angle, and thereby altering the spot of FL intersection, during suspension movements we may be able to lessen the lifting (jacking) effect produced by the outside wheel. This is done by creating a geometry that moves the intersection of the FL to the inside wheel during roll.
Of course, there are a number of other things that happen if altering the FL angle, like camber effect during roll and car balance, but this is a to big an issue to bring up here.
Goran
RE: Roll Center Migration