roll axis and cog

[KnifeEdge_2K1]

if the cog is below the roll axis will the car roll into the inside of the corner ??

if it does then the outside tires will lift, but since the outside tires are still more heavily loaded then the insides, how can this happen??

[SIMPLETON]

umm, the outsides cant lift. Unless theres a ramp or something stupd for them to roll overr.

[hightower99]

If the CoG for a car is lower than the roll axis then yes as you turn the body will lean into a corner. However your outside wheel will not come off the ground because as you roll into the corner you increase load on the inside tires but because the outside tyres are still the fulcrum of the lever they will not come off the ground.

[KnifeEdge_2K1]

i dont mean come off the ground as in lift completely off the ground, i mean that they would be less compressed then the inner wheels, but since the cog is still above the ground, the outside tires should still be more heavily loaded then the insides

[johnnyperl]

Roll axis has to do with suspension geometry, CoG has to do with weight distribution. If the CoG is bellow the roll center the roll moment will affect the load transfered into the wheels. BUT, the car is still going to act "normal", it will still pitch outward since the CoG is above ground (above the contact patch of the outter wheel).

Basically, the reason it will always transfer load to the outter wheel is because the CoG is always above the contact patch of the outter wheel. Or, more specifically, the lateral acceleration is acting on a point above the contact patch.

[KnifeEdge_2K1]

i know that the outer tires will always be more heavily loaded, but roll has little to do with this

roll is affected by the CoG's placement in relation to the roll centre, if the CoG is below the roll axis then the roll will be to the inside of the turn

the thing is, the roll add's vertical force to the inside tires while removes some from the outside tires, but centripetal force causes the outside tires to gain load in relation to the inside tires, these two process work in opposite directions so theoretically a COG below the roll axis will keep L/R weight distribution equal

i was just wondering if this was possible

[hightower99]

It is possible for some cornering but not all as body roll contributes very little to any weight transfer. However this would be beneficial to tall narrow vehicles like busses and such and would allow them to take corners without fear of rolling over.

[KnifeEdge_2K1]

it's not the roll itself that makes weight transfer but the torque from the force acting on the COG about the roll center

[KnifeEdge_2K1]

im really bad at explaining these things but put it like this
the roll itself doesnt cause much weight transfer because the COG is only moving by a small amount and weight distribution because of this is minimal

but the roll is being resisted by the suspension components since the wheels must stay on the ground, and this is the load transfer i'm refering to

imagine a car sitting on the ground at rest, in order for the body to roll to the left, the suspension components on the left must be compressed

in a car where the cog lies above the roll axis, the load transfer caused by inertia and roll couple is in the same direction, but in my example the forces act in opposite directions, if you were able to somehow make each of these forces equal in magnitude but opposite in direction, you would have 50/50 weight distribution in a corner optimizing grip

now this is next to impossible, you could set it up for one corner but the next it wouldnt be the same, however there would be a net benefit and I'm trying to see if this has ever been done before

[RacingManiac]

One definite benifit is that if your car rolls into the corner, the tire camber won't "degrade" as it would normally, as in losing camber as you roll. Which in itself should help cornering.

At any rate, load transfer is affected by CoG height off the ground, not its distance from roll center/axis. So the benefit of a car rolling into the corner should come purely from the tire camber...

Now to build a car with that low of the CoG is unlikely, but you can raise the roll center in your kinematic, but high roll center has its own problem with jacking force....

[wheresgeorge]

its not how much you put into the car its how much fun you have while working and adding new things to your car. thats why a lot of people like rice burners and imort cars. there is a lot of shit you can do to those cars. yeah i would take an american muscle over anything put i would love to see what i could do to a civic or eclipse.

[SIMPLETON]

There is one car that does roll into the corner, the Kolbe "Curve-bank" car. It did it through linkage though and not through impossible physics.

[RacingManiac]

There is one car that does roll into the corner, the Kolbe "Curve-bank" car. It did it through linkage though and not through impossible physics.

Its not impossible, as I said you can quite easily design the suspension kinematic to have a high roll center....

[KnifeEdge_2K1]

One definite benifit is that if your car rolls into the corner, the tire camber won't "degrade" as it would normally, as in losing camber as you roll. Which in itself should help cornering.

At any rate, load transfer is affected by CoG height off the ground, not its distance from roll center/axis. So the benefit of a car rolling into the corner should come purely from the tire camber...

Now to build a car with that low of the CoG is unlikely, but you can raise the roll center in your kinematic, but high roll center has its own problem with jacking force....

load transfer is affected by both these variables

in a car with no suspension then yes cog height and wheelbase is all that matters

but as a car tries to roll, the suspension components (which remain flat relative to the ground) try to resist the roll, which adds to load transfer

[RacingManiac]

but as a car tries to roll, the suspension components (which remain flat relative to the ground) try to resist the roll, which adds to load transfer

Between individual wheels of the car yes, overall total amount no. Assume if the car can generate the same amount of cornering force with a high roll resistance setup as a low roll resistance one, then the total load transfer between the 2 setup will be the same provided that the track and CoG height are equal. But that is unlikely as a car with more roll will likely degrades other handling traits as well, thus reduces the overall cornering force.