Ok 4-Link Guru's, Take A Look At My Rig...

[RANOVRU]

Alright, I triangulated the upper rear like everyone suggested and that did elminate the possibility of any side to side movement. You can see here from a top view...






And from the side the links look parrallel like they're supposd to be, here...







Now here's the problem; after I got my front shocks on last night and wired everything up I drove it around the living room just to make sure everything was working correctly. The front, which has triangulation AND "traction bars" (see pic)




worked perfect. But the rear has horrible axle wrap at the moment. I mean horrible.

Now, what I'm wondering is why there is so much axle wrap if it's set up like it's supposed to be. I took suggestions from many different people on here and did some reading and the jist of what I came up with was from a top view links should have a fair amount of triangulation; from a side view links should be as parrallel as possible.

To remedy this I plan on doing to the rear what I did to the front, add "traction bar/s". While I'm sure this will fix the problem just like it did for the front, I'd like some info/explanation as to why this is happening to my rear. Is it something I did? Is it not set up right?? Or is everyone clueless???

[TwistedXT]

from what i am seeing is this.. on the front, your links seem to be the same length top and bottom , where as on the rear the links on th bottom are longer causing the axle to roll under torque/ compresion... make the bottom links the same length and that should solve your problem (or to better describe it, your front axle upper and lower have the same rotation points, making it an even compresion, do this to the rear)... now, the "traction bars"... dont really do anything. you should'nt need them. The triangulation of the bars will keep the axle put, but one thing to keep in mind is that on top of your axle where they triangulate from, that bolt is to long and will end up bending when you are under power on a climb... move the mounting brackets in closer to make that point stronger... Looks pretty good so far... keep us up to date...

[RANOVRU]

Thanks for the insight.

Actually, the front links are different lengths (uppers are longer than the lowers) and the rear links are the same length. Sorry if the pics look deceving.

Now, just to give you some background, I tried running the front without the "traction bars" and it did the same thing. The traction bars DID help believe it or not. I guess it makes sense to me because I'm actually seeing what's going on, but they completely eliminated the axle wrap. Without them the axle was all over the place, with everything else the same as you see in the pic minus the tracion bars.


I understand what you're saying about how I "shouldn't" need them, but that's why I'm asking this. But then how come I get all of this axle wrap without them??

[scout21972]

I'm not a 4 link expert, but from what I have been told and what I have tried the chassis end of the links should be closer together than the axle end. Meaning that the vertical difference should be about 1/4" to 1/2" min. difference, with yours I would say 1/2" at least. If you did this and tried to make the links the as close to the same length as possible it should eliminate axle wrap and prevent the axle from moving side to side. I hope this helps.

[TwistedXT]

Ok.. .I'm trying to think how to word this so bear with me if it makes no sense whatsoever....

If you were to take a cross-section of your rig, and the points of rotation for both upper and lowers... on the front, they seem to be rotating on the same plain, or with suspension compresion, your axle does not rotate, you get a smooth up and down travel, now, on the rear, it looks like the lower links have a longer throw then the top which under compresion would cause the axle to actually rotate clockwise/backwards which is what your axle is trying to do under foward movement anyway so your rig may want to squat under acceleration. One thing you could try is to place an angle finder ontop of the axle fully extended downward and then take a reading, then compress the suspension and take a reading... these numbers should be the same... so if it starts out level... it should end up level no matter where is sits throughout the entire rotation of the suspension.

If the track bars are actually doing something then you must have a little bit of play in your links... if so then they would deffinatly help keep thing in place... one thing you can try is to triangulate both uppers and lowers... or just bring you lower mounts on the chassis in to meet at the middle, that would hold everything in place and it would also keep the axle centered during articulation.


did i confuse you yet?

[RANOVRU]

If anyone cares to try and explain what they think is the best way to set this up, feel free to modify these cheesy paint drawings. I just made them to show basically what the rear look like now from a top and side view-


TOP-






SIDE-








And here's a pic of my current set-up with me trying to describe exactly what's happening. The arrow over the axle pointing back to the motor is the direction in which the axle twistes when trying to crawl. This intern triggers the following- the arrow over the bottom link shows te direction that the lower link goes when it's pulled up and back; then the shocks compress (arrow compressing shocks) and the chasis ends up going down or squating.







Any suggestions as to placement of the current links in order to fix this would be appreciated. Otherwise I'll be adding another link/s to the rear.

[RANOVRU]

Originally Posted by TwistedXT

Ok.. .I'm trying to think how to word this so bear with me if it makes no sense whatsoever....

If you were to take a cross-section of your rig, and the points of rotation for both upper and lowers... on the front, they seem to be rotating on the same plain, or with suspension compresion, your axle does not rotate, you get a smooth up and down travel, now, on the rear, it looks like the lower links have a longer throw then the top which under compresion would cause the axle to actually rotate clockwise/backwards which is what your axle is trying to do under foward movement anyway so your rig may want to squat under acceleration. One thing you could try is to place an angle finder ontop of the axle fully extended downward and then take a reading, then compress the suspension and take a reading... these numbers should be the same... so if it starts out level... it should end up level no matter where is sits throughout the entire rotation of the suspension.

If the track bars are actually doing something then you must have a little bit of play in your links... if so then they would deffinatly help keep thing in place... one thing you can try is to triangulate both uppers and lowers... or just bring you lower mounts on the chassis in to meet at the middle, that would hold everything in place and it would also keep the axle centered during articulation.



did i confuse you yet?

I liked that last idea you mentioned and had thought about that. Any idea's for the shocks if I did that??

As for the first part of your post, we must have been typing at the same time...

[Trailerguy]

Ok, this is how I would set it up. Measure the height of the tires. For an example lets say the tires are 5" tall. Take that number and multiply it by .25. This will give you 25% of that number. In this case you would get 1.25". That is the vertical distance needed between the links on the axle end. This gets rid of axle wrap. Now take that 1.25" and divide it in half. This would give you 5/8". Set you vertical distance of your links at the chassis side at that. Adjusting the vertical distance at the chassis end will change the anti-squat. From what I see, your links would never converge, causing you to have an extremely high anit-squat %. I think what you have is an axle that is trying to push the chassis around through the links and the springs are the only things keeping this from happening. So the springs countering the anti-squat effect give it the look of having axle wrap. By adding the other links, you are binding the suspension and keeping it from working freely, which is what drag racers do. I would suggest checking your vertical distance of your links at both the axle and chassis. Correct those first, then you can start to correct the anit-squat %. By changing the verticle distances, that should the % enough to help. Let me know, I could always run your numbers on the computer and see what the problem is. Changing the link lengths will change more of the roll angle than anything else. Don't be worried about that right now.

[Squid121]

I think the lower links should be mounted lower on the axle. That way the bottom of the axle won't be able to rotate, instead it will just push the chassis. If you mount the lower links lower, then you should not need traction bars because the lowers at that point will in fact be traction bars as well as the bottom links. Same thing with the front. This is how my full size truck was and it worked perfectly. Hope this helps.

[f0cker]

I'd lower the upper link mounts at the chassis to make the links parallel or maybe even a little bit below parallel. This will give the axle less distance to distort the link geometry when it rotates.

[RANOVRU]

Originally Posted by Trailerguy

Ok, this is how I would set it up. Measure the height of the tires. For an example lets say the tires are 5" tall. Take that number and multiply it by .25. This will give you 25% of that number. In this case you would get 1.25". That is the vertical distance needed between the links on the axle end. This gets rid of axle wrap. Now take that 1.25" and divide it in half. This would give you 5/8". Set you vertical distance of your links at the chassis side at that. Adjusting the vertical distance at the chassis end will change the anti-squat. From what I see, your links would never converge, causing you to have an extremely high anit-squat %. I think what you have is an axle that is trying to push the chassis around through the links and the springs are the only things keeping this from happening. So the springs countering the anti-squat effect give it the look of having axle wrap. By adding the other links, you are binding the suspension and keeping it from working freely, which is what drag racers do. I would suggest checking your vertical distance of your links at both the axle and chassis. Correct those first, then you can start to correct the anit-squat %. By changing the verticle distances, that should the % enough to help. Let me know, I could always run your numbers on the computer and see what the problem is. Changing the link lengths will change more of the roll angle than anything else. Don't be worried about that right now.

My tires measure about 6.25". If you want to try and run some #'s and let me know basically how far (vertically) to space the links on the chasis and the axle I'd be willing to try that...


Thanks



EDIT: I tried it and got basically about 1.5" on the axle end and .75" on the chasis end. That sound right?

[Wrecker]

From what I can see it looks like your lowwer links are mounted at the farthest radius from your axel centerline. Which in turn is causeing the axel to rotate about the top link. If this makes any sense, by having your links parallel and the lowwer link mont on the axel farther forward than the top link mount, the lower link has no lever arm on the rear axel. When the suspension compresses instead of the axel trying to push the lowwer link forward it is actually pulling it back, then rotating about the top link mount.
Anyways, since that probly made no sense at all I would try mounting the links the correct distance apart to see if that helps. If not try moving the lowwer link mount on the axel farther back, closer to the same horizontal point that the upper link is mounted.
Sorry if this makes no sense.

[Trailerguy]

Originally Posted by RANOVRU

My tires measure about 6.25". If you want to try and run some #'s and let me know basically how far (vertically) to space the links on the chasis and the axle I'd be willing to try that...


Thanks



EDIT: I tried it and got basically about 1.5" on the axle end and .75" on the chasis end. That sound right?

Yes, that's close enough. Try that and let me know what happens. If that doesn't work, you can give me all the measurements for the horiz. and vert. distances and the link lengths, chassis height off the ground that you want, and I'll plug the numbers in and see what we can come up with.

[RANOVRU]

Originally Posted by Trailerguy

Yes, that's close enough. Try that and let me know what happens. If that doesn't work, you can give me all the measurements for the horiz. and vert. distances and the link lengths, chassis height off the ground that you want, and I'll plug the numbers in and see what we can come up with.

Thanks.

Also, like Wrecker mentioned above, doesn't it make a difference on horizontal positioning?? Like whether or not the upper link is farther away from the chasis (in relation to the axle) than the lower one or vis versa?

And how will this affect my chasis height? Before I took it off the blocks it was 5.75" from the ground to the underside. Now that the shocks have settled it's around 5.5". I'd like to keep that clearnace if possible...

[Trailerguy]

Originally Posted by RANOVRU

Thanks.

Also, like Wrecker mentioned above, doesn't it make a difference on horizontal positioning?? Like whether or not the upper link is farther away from the chasis (in relation to the axle) than the lower one or vis versa?

And how will this affect my chasis height? Before I took it off the blocks it was 5.75" from the ground to the underside. Now that the shocks have settled it's around 5.5". I'd like to keep that clearnace if possible...

It will only affect the chassis height if you have to move a lower link. You should be able to adjust where the shock mounts to the lower link to adjust you height. The closer the lower links are to the tires the less flex the axle assembly will have. But really, that should have nothing to do with axle wrap if your links and link mounts all fit together good and are nice and tight. True axle wrap and anit-squat have mainly everything to do with vertical postion and not horiz. Your link length and horiz. distances will have more to do with your roll axis than anything else. Don't get me wrong though, it all goes together and works together, just certain things will change the numbers more than others.

[RANOVRU]

Originally Posted by Trailerguy

It will only affect the chassis height if you have to move a lower link. You should be able to adjust where the shock mounts to the lower link to adjust you height. The closer the lower links are to the tires the less flex the axle assembly will have. But really, that should have nothing to do with axle wrap if your links and link mounts all fit together good and are nice and tight. True axle wrap and anit-squat have mainly everything to do with vertical postion and not horiz. Your link length and horiz. distances will have more to do with your roll axis than anything else. Don't get me wrong though, it all goes together and works together, just certain things will change the numbers more than others.

Well I moved the upper chasis links down in the rear to 3/4" like this...





..and it completely eliminated the problem. The axle mounting points were already close enough to 1.5", so I just moved the uppers down and then drove it around the living room and it worked flawlessly.

I'm gonna try and do the front the same way and get rid of those "traction bars" but I think it might be a little more difficult.

Trailerguy- you'll notice that my links in the rear kind of angle down towards the axle, well the fronts are basically straight across from the axle to the chasis. I think this is gonna have an exffect on what I'm trying to do. Any ideas???


Thanks a BUNCH for the help...

[Wrecker]

that looks much better, good to see you got it all working.

[run2jeepn]

Man I told you these same things a few weeks ago. I even posted links. Anyway's it's coming together good. It just takes time on 4 links. Can't rush and just guess where they need to go.

[RANOVRU]

Originally Posted by run2jeepn

Man I told you these same things a few weeks ago. I even posted links. Anyway's it's coming together good. It just takes time on 4 links. Can't rush and just guess where they need to go.

From what I gathered you were mainly stressing the importance of having some triangulation in the set-up, which I ended up doing. I don't remember you saying anything about vertical positioning of the links on the chasis/axle??

Yea, it does take time and I'm getting restless.

Thanks for the help & compliments...

[Trailerguy]

Originally Posted by RANOVRU

Well I moved the upper chasis links down in the rear to 3/4" like this...

..and it completely eliminated the problem. The axle mounting points were already close enough to 1.5", so I just moved the uppers down and then drove it around the living room and it worked flawlessly.

I'm gonna try and do the front the same way and get rid of those "traction bars" but I think it might be a little more difficult.

Trailerguy- you'll notice that my links in the rear kind of angle down towards the axle, well the fronts are basically straight across from the axle to the chasis. I think this is gonna have an exffect on what I'm trying to do. Any ideas???


Thanks a BUNCH for the help...

Don't worry so much about how the links look from the side. Just do the math for now. Once you know it works, you can fix the way it looks down the road.