formulas used for canti setup?

I was just wondering what math formulas you used when designing your rear suspension setups. I am about to balk half the ol' mazda and was planning on doing a cantilever/ bell crank style setup. Thanks!

The theory to lever is ratio's. For example if you have a lever thats 3 feet long a connection on one end, than the pivot 1 foot in, the lever would be 2:1. Using my example if the bag was placed on the 1 foot side of the lever the 2 foot side would move 2"s for every inch the bag moves.  Another example is the set up I am doing know for my truck is a parallel 4-link. I am putting the bag in the center of the bar, same thing applies to that to. Easiest way is to either use a drafting program, or draw a scale model and use a compass. If you need help pm, I normally have a little time every day I can screw with autocad at work.

Thanks alot. your example really cleared alot up. I just wasnt sure on how you all were figuring it out. once my parts com in I may hit up you up for a little more advice!

Edited: 6/16/2010 11:42:48 AM by AVTekk

Just to clarify on levers, when you put the bag in the middle of the bar, your pivot is on the end instead of somewhere in the bar, so you wouldn't use the same formula, but its still quite easy. If you put the bag 1/2 way up the bar, then you would flip the fraction and that gives you a 2:1 ratio. If you put the bag 1/3 of the way up the bar, thats a 3:1 ratio. Another formula is to divide the total bar length by the distance from the pivot to the bag center, which we can also express as a fraction. So if we have a bar 24" long, and place the bag at 10" from pivot, then we have a fraction of 24/10. We can simplify this to 12/5, but thats not a convenient ratio to deal with. Instead we'll divide the two together to come up with 2.4:1, or the axle will lift 2.4" for every 1" of the bag.  If you need to convert decimal measurements to the closest inch, you'll need to divide the decimal by the standard ruler scale then round it off. So .4 divided by 1/8 (.125) is 3.2, round to 3, that gives us 3/8ths. You can solve for a smaller dimension if you need to be super accurate.. .4/.0625 (1/16) =  6.4, rounded to 6/16ths, which is the same as 3/8ths, no difference. .4/.03125 (1/32) = 12.8, rounded to 13/32s, slightly largerect..

Awesome! keep the math coming guys! I think knowing the actual math behing suspension setups would really help alot of us to design a properly functioning suspension. What about 4 links, wish bones and all that jazz? what angles to mount bars and so on. thanks again! 

40-45° is the preferred amount of triangulation but improbable on many trucks, I try not to go any lower than 35°. Typically the trucks we build use long bars for more travel, and the longer the bar, the harder it is to get enough triangulation; the frame simply isn't wide enough. On the flip side, a longer bar will typically provide much less roll steer when set up properly giving a more stable ride (another topic all together). Wishbones allow a tighter mounting area (1 vrs 2 on a tri 4link) so you are able to get more triangulation out of a wishbone setup and still run long bars. People get crazy over the length of bars but its not needed, most of the setups I do rarely go near 24", it depends on the application.