Posted by Alex J [216.54.94.2] on Friday, August 09, 2013 at 14:35:11 :
In Reply to: Unequal length links? posted by Chris Case [75.36.40.81] on Friday, August 09, 2013 at 13:51:04 :
I've run the numbers on the link suspension throughout the 10" of travel and the axle stays nearly perfectly in plane (0.78 degree change in caster/pinion angle overall. When the travel gets excessive things start to get funky though and the pinion angle jacks up quickly, however the suspension will be limited to never see those values. The primary reason for the unequal length bars is to give some anti-dive to the front under braking. Equal length bars yield a 0% anti-dive and can allow the rear to pass the front in a hard braking situation as the suspension doesn't resist the forward increase in load by distrubiting through the links as a vectorized sum. Obviously the vector will change direction relative to the suspension position but going from static (ride height) to dynamic braking, the suspension is less likely to compress and a compressed suspension means that the rear mass is pushing on the front more and thus unloading the rear. The towers are out 3.5" from the CG of the frame but you are correct that they will induce some torsion to the frame sections. I am planning to box the frame and trangulate across the front crossmember to absorb some of that loading and translate it across. Ideally there would be a full width cross brace but obviously no movement for that. The struts themselves have a built in ability to resist roll but aren't nearly as harsh as the leaf springs are. The rear leafs will still be in place so think of it more like a monobeam suspension like on an old farm tractor. The chassis pitch will be loaded against the stability of the rear springs, not entirely but moreso, and the front will be a touch softer than originally. So now instead of the suspension acting like a "radio flyer wagon" it'll allow some freedom of movement and put less cross torsion through the chassis length wise. The tops of the struts are about at the CG of the truck where the engine should go as well. Wish they could go higher but there are fenders there.
Lots of math, and not just jumping into this blindly and bolting things on with my finger's crossed.
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