OK, I really want to go Coil-Over, but I have not seen a link-type setup that i have REALLY liked, so i thought of something i have never seen before. This is going on the cruiser, Rockwells and 44's, maybe XML's later. The pic should be explanatory, sorry it is not to scale, or measured accurately, but you get the idea.

http://www3.baylor.edu/~Wes_Hanson/linkdesign.jpg

So has anyone seen this setup before, or tried this setup before?? Any problems with this setup??

Any input is appreciated -

I think W. Evans has something like that , at least he did on his first truck.

Dirtrod, I "believe" Walker used a reverse-triangulated 3-link. The A-arm came back off the front x-member. This was on his S-10 blazer, anyways, i dunno if he had a rig before that. I think this will be a little stronger than his setup. That is important to me because of the heavy axles and bigger tires. If this setup won't work, I will probably go with a setup like Walker's Blazer, but i think this wuold be a little better, even if only marginally so.

Thanks-

how would it move?
if the whole thing went up at the same time wouldn't the axle wrap bar, and the lower links bind?
why not just make the lower links "Y" at the axle and attach at the center and above the tube? wouldn't this alleviate axle wrap?
not to mention I have never heard of axle wrape on coil-overs?, but hey I'm no engineer

i think that that will bind to no end because of your little axle wrap link. as the axle articulates downwards, the red links will move in an arc that is MUCH larger than the green. and besides. with it pointing towards the front like that, as the suspension compresses and extends (like speedbumps) the arcs of the two sets of rods will fight one another and it will BIND.

why not just do it the proven way, and that is with an a-arm or that funky little link coming towards the back?

go ahead and try it, but i wouldnt expect it to work very well. cool idea though.

That could be, I only remember that the top link came off the front, and at a angle to the right ft. corner, but I didn't look very close. I think you will have a conflict between the links if you dont angle the top to work with the panhard

Draw the side view of that at different compression and droop levels, to scale. You will find that the pinion angle/caster changes a ridiculous amount even over a relatively small amount of travel. That is why no one uses that setup. It will not bind, at least not untill the pinion is pointed essentially straight up.

Yup...Bind city. I too am no expert, but I can plainly see that when the axle moves up/down the green link AND the red links will want to travel in opposite arcs. Why not move the wrap bar to the rear and use it as a 3rd link/wrap bar?

--D

I would go straight-up 3-link with all 3 links running rearward.

And make sure you get the panhard as low to the axle and as long as possible.

Squash

Personally, I'd dump the panhard and angle 4 links to the rear, or do a wishbone top link to the rear.

Originally posted by Gordon
Draw the side view of that at different compression and droop levels, to scale. You will find that the pinion angle/caster changes a ridiculous amount even over a relatively small amount of travel. That is why no one uses that setup. It will not bind, at least not untill the pinion is pointed essentially straight up.

Exactly what I was gonna say Gordon. One more question Elf, why? Why not go with the standard track bar, 2 lowers and 1 upper mounted in the NORMAL locations?

Elf,
probably the most tested and easiest is the Y links with a Panhard. go check out the front of a landrover defender. It's easy and it works
try to get the panhard as parallel to the axle tube as possible and also try to get it to match the draglink of your steering, I believe otherwise you will get bump steer
I know the steups without the Panhard work as well, but I believe they are much harder to package as well as Kinda tricky with normal steering
if you are going all hydralic it's not as much of a concern
good luck, It's tricky stuff, but fun as hell to figure out.

Gordon:
Draw the side view of that at different compression and droop levels, to scale. You will find that the pinion angle/caster changes a ridiculous amount even over a relatively small amount of travel. That is why no one uses that setup. It will not bind, at least not untill the pinion is pointed essentially straight up.

You are correct, and i had thought of that, but this will keep the pinion pointed at the tcase most of the time. And i'm not going to be baja racing this thing, its just for rockcrawling, and mall crawling. I am most concerned about articulation, not droop and compression.

Goat Boy:
One more question Elf, why? Why not go with the standard track bar, 2 lowers and 1 upper mounted in the NORMAL locations?

I didn't know there was a Normal???? please explain- are you talking about radius arms???

fcfred:
probably the most tested and easiest is the Y links with a Panhard. go check out the front of a landrover defender. It's easy and it works

The thing i don't like about this setup, is it puts the housing in a bind during articulation, which means you have to use fat rubber bushings at all the mounting points on the lower "Y's". This results in a little more axle-wrap, especially with 44's and low gears. You have to sacrifice control over the axle, in order to get flex.

My setup would not try to twist the housing the way radius arms do. I think the only drawback to the design is the massive change in pinion angle during compression, and extension of the whole axle.

The only reason i don't like Walker's setup is that it puts a lot of pressure on the top of the A-arm. My truck is going to be big and heavy, not as lightweight as his.

I cannot run any links rearward off the front axle inside the framerails, there is just no room. Exhaust on one side, driveshaft on the other.

Thanks for the ideas guys, keep 'em coming!!

Forgot to mention- my front driveshaft sits flat right now, and i have 1410 joints, so it can take around 30 deg. of angle before there is any binding.

I did a 4 link quarter elliptic setup as my Senior Project for my Mechanical Engineering Degree. You need one constraint for each degree of freedom you wish to eliminate. Lets see... the axle can move linearly in X, Y and Z plus rotate about the same. Thats 6 degrees of freedom. You want the axle to go up and down... ha! Minus one degree. And you want the axle to rotate about the axis of the truck. There you go! Four constraints are needed. Angled four link works. Three link with a panhard works... etc etc. I bailed on panhards, they cause the axle to shift right and left as the axle moves up and down... didn't want that. I considered something similar to what you picture... but like others in this string have pointed out, even a little movement of the axle and the pinion angle will change drastically. Like when you drive down a dirt road at moderate speed and hit a bump you could bind and break a driveshaft or u-joint.

Good luck with the homebrew, but what you need to do is find a good suspension book and READ IT. It will educate you about roll centers, anti-squat characteristics, oversteer and understeer control and a bunch of other stuff you need to know before you start trying to design a suspension system. Suspension is a fairly complex system and needs to be properly designed to be functional and SAFE.

Sorry to preach a little, but really, an improper design can be very unsafe. If you crack up on the trail that's one thing, but if you're ever going to drive it on the road there is the poor guy driving next to you to think of.:nuke:

Originally posted by elf_cruiser
I cannot run any links rearward off the front axle inside the framerails, there is just no room. Exhaust on one side, driveshaft on the other.

Thanks for the ideas guys, keep 'em coming!! [/B]

What are the constraints of your truck? Can you run a link on the outside of the frame up to the front axle?

Squash

umm one of the fabtech kits use that style linkages on one of there rear suspention kits. it works real well in the rear cause the pinion moves up as the axle drops. for the front tho it wouldnt work as well because you couldnt get the green link long enought to work properly.

its my opinion that panhard bars suck and should be avoided where long wheel travel is desired.

Realsquash:
Can you run a link on the outside of the frame up to the front axle?

That's how the lower links are, in red. I cannot run an upper A-arm, or a splayed 4 link from the center of the rig forwards, because there is no room underneath. I have seen a U-shaped upper arm that fits around the oil pan, but that won't work because of my extremely high driveshaft, and exhaust on 1 side of the straight-6.

Rolled79:

You're right, i prolly should get a good book and read it, but i have a feeling that most books are not going to approach things from the perspective of slow speed rockcrawling. So, do ya'll really think taht the pinion angle will change enough to snap a 1410 joint, just by going over a speedbump at 30 or so??

I think that Walker's setup would cause the same pinion rotation, and it has worked for him. Am i wrong??

Thanks again for bringing up some good points...

walkers truck did indeed use somthing like this but it was a triangulated bar in the front so no panhard bar. I imagine it will work but the big problem I see is your forward link is too short, it may limit overall travel. probably no biggie for articulation though

Originally posted by elf_cruiser



I didn't know there was a Normal???? please explain- are you talking about radius arms???


Thanks for the ideas guys, keep 'em coming!!

Not radius arms. 1 upper 2 lowers and a trackbar. Look at GOAT1's. A also think that the tan TJ from S &N is set up like this. Look MOM no shitty radius arms....
http://www.polyperformance.com/heep01.jpg

Also check out www.offroaddesign.com and look at the new pix of Stephen's blazer. He has a 3-link w/panhard up front.

Squash

When it comes to this link suspension stuff, you got three choices.

1 do lots of research and think you understand it, rebuild it once or twice because you were wrong.

2 Copy one that works from someone that already did #1

3 just fab something wacky up keep redoing it untill you get it to work or revert to numbers 1 or 2.

People who think they are smart pick options 1 and 3 people who are smart pick option 2.

Look MOM no shitty radius arms....

OK, i see and that is a cool idea. but i'm afraid i can't get a link to run from the center of the frame to the carrier like that, because my pinion is sooo high. Maybe if i fabed a xmember under the tranny, and ran it off of that to the center of the axle, but that would mean losing some ground clearance. Hmmm.

I just don't know...

[QUOTE]Originally posted by elf_cruiser
:


I think that Walker's setup would cause the same pinion rotation, and it has worked for him. Am i wrong??

YES you are wrong, Walker evans truck has the upper and lower
control arms coming from the front of the frame rearward to the front axle. Not some from the front of the axle, and some from the rear.
I dont think you would need to wory about hitting a speed bump at 30 mph and breaking a u-joint, with a setup like that you would
never see 30! Even with big rig u-joint you will break something
with the extreme amount of change in pinion angle, and binding in the drivline.
Do like rolled79, and others have said do your research.

Originally posted by elf_cruiser


OK, i see and that is a cool idea. but i'm afraid i can't get a link to run from the center of the frame to the carrier like that, because my pinion is sooo high. Maybe if i fabed a xmember under the tranny, and ran it off of that to the center of the axle, but that would mean losing some ground clearance. Hmmm.

I just don't know...

Elf,

It does not neccessarily have to be on top of the diff like that. Don't be afraid. And yes Gordon, #2 is key. Its called benchmarking.

Yeah Gordon, i hear you, i have been looking at what other people have done for a long time... I just haven't seen what i'm looking for, i guess. And i can't fit the traditional A-arm or 4 link up front like what most people do, not without a few more inches of lift, anyways...

What about making the lower arms shorter, say 20% longer than the green arm. Would that help, or hurt??

Also Rock Hugger - I could swear that his lower links came from the center of the rig, at least on his Blazer, i've seen it in mags and on video. I don't know as much about the S-10 pickup he drives now. Anybody else know for sure??

Some people do the lower links just like you described and then add 1 upper link on one side outside the frame rail, If the upper link is close to the same length as the lower links this works pretty good from what I have seen, there are rarely clearance problems with that setup, it works similar to a wristed radius arm that lots of EB guys use, but you can get things up higher and put the instant center farther back so the front squats less on the slickrock.