I'm currently working on setting up my rear 1/4 eliptic 4-link, but still deciding on how the links are gonna be. I had built a couple scale models of what I liked, I'm leaning towards a double V setup. I've seen this used a lot and it seems to work well, but it is always set up with the with the upper links coming off the top of the pumkin. When I built a model of this, it seems that under articulation, the tire being stuffed moves away from the center of the truck. I was thinking, what if you set it up like this, with the lower links connecting on the bottom of the axle tube, next to the pumkin.

Wouldn't that make the side being stuffed move more toward the center of the truck, kinda pulling the truck over the tire. With my model it seem that the axle pivots off of the point marked by the yellow X. I was just thinking that it might help balance during articulatoin, might be wrong, just looking for your input.

but it is always set up with the with the upper links coming off the top of the pumkin

this is probably because of ground clearance issues.

Brook

That came to mind, I was thinking if you connected the links right under the axle tube, and next to the pumkin, the wouldn't be in the way much at all. Like where the red X's are here:

the uppers are typically placed high on the rear to allow for a flat/minimal angle (on flat surface) to maximize drop (angles at full drop).
It decreases chances of binding.
Dont re-invent the wheel - keep the outers as straight as possible as low as possible and as long as possible.
What do you like bought 1/4 elip?
I'd recommend leafs w/dual shackles and the 4-link!

why keep the outers as straight as possible?????

if you put the links where you suggested with the red x's you wont have much angularity. that = bad. You need as much angularity as possible to limit the leverage the links exert on the mounting points.

Sorry about that reply if it didnt sound right, ive had about 11:beer:'s and am haing a hard time hiiting hte correct keys.

Brook:flipoff2:

Tiriangulate the UCA's and mount them to the top of the pumpkin. IMHO, I would think the last place you would want to mount control arms would be towards the bottom of the pumpkin, since the arm angles would be greater, and would undoubtedly get hung up in the rocks.

I dont see any problems with ground clearance or the angle of the links at all. The links are not going to be put at aby extreme angles on drop, no more than on a standard setup. Pic #1 is the setup I'm talking about and Pic #2 is whats commonly done. I'm just wondering if this setup would make my 4Runner more or less likely to rollover.

you loose angularity when viewed from the top.

I dont think that it would be bad enough to cause a problem. I've seen links done with a lot less angularity then that. Some have only the upper links in a V and the lower links straight, I'm not saying i think that its good idea, but it apparently works OK.

Try it and let us know. I wasnt thinking about having both upper and lower links being angled. I beleive it would work fine. I thought about doing my angled links to the bottom of the axle as you have suggested, but didnt cause I wanted one set of the links to be straight for simplicity.

Brook

I might just give it a shot, I'll let ya know haow it turns out.

I have some cool pictures of the set-up in the picture. It works good for me. I could e-mail them to someone if you want to post them. Bryan.

thats really close to the (SA link)

You mentioned that you had constructed some model mock-ups of the suspension. Would it be possible to find the Instant Center from the model? This may give you some empirical data as to what control arm angles are acceptable, as well as a general idea of stability. At any rate, give it a shot and let us know how it works.

Originally posted by Rock'em Sock'em
You mentioned that you had constructed some model mock-ups of the suspension. Would it be possible to find the Instant Center from the model? This may give you some empirical data as to what control arm angles are acceptable, as well as a general idea of stability. At any rate, give it a shot and let us know how it works.
Do you mean the axis that the axle rotates on? Empirical Data?, dunno what that means, I'm just a highschool kid\

I figure that in this setup, the rotating axis would be like this.

Mine would be like this, grey line

Mine runs the setup you mentioned in the first post, though the angles of the "V"'s formed by the links aren't exactly equal top and bottom.
I don't have any roll steer/ rear steer, whatever you want to call it, but the axle does swing a little bit side to side on flex. It has never caused me any trouble, and sidehills are definitely not a problem.
What I don't like about the double triangulated links is that the lower links, which push forward, don't get the push in a straight line like a standard 4 link, so the forces on the links aren't in a straight line with your bushings or heims. Or are they?

Originally posted by Slagburn
What I don't like about the double triangulated links is that the lower links, which push forward, don't get the push in a straight line like a standard 4 link, so the forces on the links aren't in a straight line with your bushings or heims. Or are they? I imagime you're right, the forces exerted(sp?) on the heims(in my case it will be Johny Joints), aren't going to be in a straight line, but as long as the components are up to the job, everything should be OK. I think the JJ should do alright, and the links, I'll just make 'em real beefy, maybe 1.5 .185 wall DOM, that should do it.

Oh yeah, can any recomend the best JJ to buy? All Pro's look a little week. I was thinking maybe AOR's orbit eyes, they look nice. I also heard that Currie makes some 3" JJ, anybody know about those?

I don't know how heavy your rig is, but I would reccomend at least 1.5" x .250 wall dom for your links. Unfortunately I have no experience with the JJ, but I have heard from many people recently that RUbicon expresses JJ are real nice and beefy.

The Rubicon Express JJ, those are the ones that have that thread together, I'll have to look into them some more. Theyr'e spendy though.

I just wanted to insert some of my observations on suspensions. Most people on this board angle the upper links into the pumpkin because it places the roll center closer to the center of gravity. This will cause the body to roll less when the rig is off camber. You can make the lower links angle into the pumpkin and it will still work just fine. You will get more body roll when you are off camber, but you will have a smaller moment trying to lift the rear tire.

For the links that don't V you can make them parallel and this allows them to carry the forward load more easily, but they can cause some binding problems when you flex the vehicle. If you built a model you can test to see if you will have a binding problem, if you don't then I would go with straight links. I hope this makes sense.

Mine is dual triangulated upper and lower. Without the springs connected,I can articulate the axle freely throughout its range. I mounted the uppers on top of the 3rd member and the lowers on top of the axle tubes to get the correct ride height without sacrifising the angles on the arms. You want to try to keep the arms as parallel to the ground as possible, but not pointing down. If the arms point up too much it will lift the vehicle during acceleration (anti-squat). Also, with the lower arms going from the outside of the axle to the center, under the t-case output, it will push on the center of the chassis when articlulated, thus pushing the vehicle foreward. On a standard 4-link, when articulated, the lower arm that is drooping is at an angle pointing upward. When you try to go foreward, the link arm is pushing up on the outside of the chassis where it connects and it tends to push you over on your side. This is a proven fact. Move the lower arms in at the front and it will work better.

I choice the dual triangulated rear as well for my CJ project. After fabbing the arms(1.5" .500 wall DOM) I turned the frame upside down and worked the suspension through every possible twist and turn. The pumkin stays well centered and pinion angle stays consistently pointed at the t-case even at 30" inches of droop.

Regards
MT


http://www.jeepcj.homestead.com/files/pinionshot.jpg
http://www.jeepcj.homestead.com/files/rearrolling.jpg
http://www.jeepcj.homestead.com/files/rear4Links.jpg

We did a similar setup on my friend's CJ-8. Check out the thread from the build-up http://www.pirate4x4.com/forum/showthread.php?s=&threadid=59312 for more info and pictures.

The axle seems to stay centered under the vehicle and displays very little (if any) rear steer. With it's parallel arms it doesn't hop, it just puts the power to the ground.

Our biggest issue was before we limit strapped the rear. Since the front is still SOA it didn't want to flex and forced the rear to do all the work. This caused the stuffed side to slide across its bumpstop as the body twisted more and more because of the uneveness of the flex between front and rear. I'm sure that if we were to go with something flexier in the front that it would even it out and the issue would not be there.

Originally posted by jesselt
Mine would be like this, grey line

How do you figure that your roll axis will be the grey line in your drawing when the uppers will mount below the axle housing? Like someone else said, don't try and reinvent the wheel here.

Originally posted by PIG


How do you figure that your roll axis will be the grey line in your drawing when the uppers will mount below the axle housing? Like someone else said, don't try and reinvent the wheel here.
I'm not mounting the upper links on the bottom of the housing, I'm just takeing the standard double V setup and fliping it over. So th lower links angle into the bottom of the housing, and the upper links angle from the outside of the axle to the top of the t/c.

Originally posted by jesselt

I'm not mounting the upper links on the bottom of the housing, I'm just takeing the standard double V setup and fliping it over. So th lower links angle into the bottom of the housing, and the upper links angle from the outside of the axle to the top of the t/c.

Your roll axis WILL be fuct. Also, why are you doing this...........?

Originally posted by PIG


Your roll axis WILL be fuct. Also, why are you doing this...........?

Thats what I was wondering, would the roll axis change be a problem or not, thanks for the input guys, I'll probably just run them like normal.

Thanks,
Jesse

One thing that I forgot to mention;
When I first designed mine, the distance between the upper and lower arms at the axle housing was approx. 4 inches. After wheeling it one trip I found out that this was not enough distance because it was pulling its-self apart. It bent a 2x2x.250 wall x-member and it started ripping my bracketry apart on the housing. I increased the distance of the rear links to 7.5 inches and that solved my problems.

Originally posted by jesselt

I'll probably just run them like normal.

Thanks,
Jesse

You just answered your own question.

Originally posted by desertoy
One thing that I forgot to mention;
When I first designed mine, the distance between the upper and lower arms at the axle housing was approx. 4 inches. After wheeling it one trip I found out that this was not enough distance because it was pulling its-self apart. It bent a 2x2x.250 wall x-member and it started ripping my bracketry apart on the housing. I increased the distance of the rear links to 7.5 inches and that solved my problems.

Thanks, I figured that is was good to keep distance between the links at the houseing as high as possible, you figured 7.5" is good, thanks man.

Originally posted by PIG


You just answered your own question.
No, you answered it and I responded by agreeing with you. I was just throwing around some ideas, ya don't gotta be rude about, although it's much more fun taht way:flipoff2: :flipoff2: