Front A-arm force vectors question

Just thinking about a few things while I'm getting stuff ready so I can sandblast my frame. The force vectors in the front A-arms keeps popping into my head. I know the front spreader bar is a popular addition to stiffen up the frame in small block cars, but that's not an easy option for those of us with big blocks. I'm looking at a two piece type bar that will not be affected by the fan/water pump area. Just so I'm not doing anything stupid, correct me if I'm misunderstanding the vectors here. It appears to me that during cornering, the outside wheel/tire obviously is doing more work than the inside wheel/tire. With that, it appears that with the tire gripping on the ground, there will be a couple of force moments in the arms above that footprint patch. So, under cornering, is the lower A-arm under compression, and the upper A-arm under tension?
Just trying to make sure I'm not waaaaaaayyyy off base here.

thanks,
Mike

Mike, the way I understand your question, it would seem to me, the lower arm is under more vertical loading from the obvious weight transfer and the lower arm is forced to the center of the car....and conversely the upper arm is forced to the outside of the car....but not nearly so much because of the difference from tire patch to lower balljoing center, and that distance to the upper arm is much greater, so it has the leverage.....

the way I think you asking....:bonkers:

mrvette said:

Mike, the way I understand your question, it would seem to me, the lower arm is under more vertical loading from the obvious weight transfer and the lower arm is forced to the center of the car compression....and conversely the upper arm is forced to the outside of the car tension....but not nearly so much because of the difference from tire patch to lower balljoing center, and that distance to the upper arm is much greater, so it has the leverage.....

the way I think you asking....:bonkers:

Click to expand...

I believe we're on the same track here. Thanks.

Yes, when going around a corner the cornering forces work inboard on the tire and they operate in the contact patch of the tire with the ground so this means that the lwoer arm is pushed inboard and the otuer is pulled outboard. This is also what bushing deflection shows. THIS is also the reason why a rear steering setup will give OVERSTEER under this bushing deflection.

Twin_Turbo said:

Yes, when going around a corner the cornering forces work inboard on the tire and they operate in the contact patch of the tire with the ground so this means that the lwoer arm is pushed inboard and the otuer is pulled outboard. This is also what bushing deflection shows. THIS is also the reason why a rear steering setup will give OVERSTEER under this bushing deflection.

Click to expand...

BUT if the bushings were urethane or other really stiff material...grease fitting/metal.....that affect would be greatly reduced or eliminated....NO??

:hunter: and if it was rubber bushings with front steer, that lower A arm being pushed toward the car centerline would make the turn less agressive, effectively turning the car LESS rather than more....NO??

IF what I said above is correct, with the metal/urethane bushings...it would/should? not matter if the car was front or rear stear as there is no deflection from the control arms....NO?? or other factors in there...??

:gurney:

Yes, that's why stiffer bushings there are better. Even then it would still matter, there's always some deflection, and the frame deflects too.