Thanks for the replies and help. As for the formulas I was just going to guess on the initial force, and then do the calculations for min and max angles and a few in throughout the suspension cycle. I figured this would help me to see a pattern, if any, in relation to the angle beween the arm and the link. But now I am starting to think I should just focus on the motion ratio. I don't really care about the forces applied as from an engineering stand point, but rather I was thinking that it would help me to be able to understand the relationship between the rotation and angle change vs motion ratio.
Anyway, here is a basic graph of the wheel travel vs shock travel. This one is set up for 24" of wheel travel and has an inside bellcrank angle of 90*. Also the bellcrank is mounted behind the axle in this graph. I have one of it in front of the axle but have not measured or graphed it yet, and honestly may not be able to make it fit between the axle and the truck cab. Still need to do a rough measurement of space avaliable. So like all suspensions, compromises must be made.
What do you think?
I was surprised at how linear the line is, but then again this is my first run at it. And if I did go ahead and build it I would be using the dual rate coils, shock bump zone, and hydraulic bumps as the progression in my suspension.
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Can i ask how you actually got that graph? Did you actually model it with a moving axle (with either links or leaves)? Or did you just model straight up movement on the cantilever link and see what the shock did? Those are two VERY different things.
Your graph is shock travel VS wheel travel. A motion ratio graph would be (shock travel divided by wheel travel) VS wheel travel (at least i like it vs wheel travel). Your graph shows that your motion ratio goes from around 0.58 to 0.46 motion ratio which is pretty much just constant. With links this MIGHT be possible.....
Reason i ask about your graph is this photo below was a graph of a cantilever setup on the back of a leaf spring truck (behind the axle). Not mine, but i was able to ACTUALLY measure the shock vs wheel travel (at every one inch of wheel travel with main leaves on). We were going to see if it was worth the time and hassle to redesign it, but with the leaf springs doing funky things and his graph for the most part moving towards a 1/1 motion ratio at bump we decided to leave it. The last 2 inches of travel drop off on the motion ratio due to the axle rotating at full bump. We decided that there wasnt much chance to eliminate the drop off on motion ratio without reducing bump travel, remounting the springs, shackles, and redoing the whole rear so just tossing in a hydaulic bumpstop would add more benefit then remaking everything. To be clear, 1/1 means the shocks and wheel travel are the same, so a .5 motion ratio in the graph would mean .5 inch of shock for 1 inch of wheel travel. The uneven graph is due to changing angles between the link and cantilever, shock angle, axle movement, and axle rotation.
Attached photo's of a "cantilever shock" set up, in the bed of Walker Evans Dodge class 8, circa 1983. I too, copied this set-up in my old class 8, but apparently never took a photo of it.
Can i ask how you actually got that graph? Did you actually model it with a moving axle (with either links or leaves)? Or did you just model straight up movement on the cantilever link and see what the shock did? Those are two VERY different things.
Your graph is shock travel VS wheel travel. A motion ratio graph would be (shock travel divided by wheel travel) VS wheel travel (at least i like it vs wheel travel). Your graph shows that your motion ratio goes from around 0.58 to 0.46 motion ratio which is pretty much just constant. With links this MIGHT be possible.....
I got the info for my graph the old fashioned way. I made a funtional scale model of the rear suspension (shock, bellcrank, bellcrank to axle link, axle, and 4 link) out of paper and thumb tacks! And so far it is just cycling in side view only. Ended up looking like some sort of suspension "pop up book", but I loved it.
Next I was going to make a full scale model in side veiw and double check the numbers. I have all my stuff just need to find the time to do it.
This is for a linked rear suspension, and I want to redo the graph so that it is in the correct format.
And thanks for all the tips and the cool pictures!
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Originally Posted by socalmoto
