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3 link front...

Ghost

Ghost

Member Number 257
NAXJA Member
Location
Hartsville, South Carolina
I have been laying under the heep lately trying to figure out what to do. I was thinking of a 3 link and did some searching but did not find much here. What happened to the URF I think it was 3 link build up thread? I was measuring where I could put the lower nad upper links and discovered that with my 203/205 setup I could run lower links about 40" long. Do I want this? Is longer better or should I shoot for a 30" or so lower link. The plan was puting the upper 3rd link on the passanger side. I know I need about 8"-9" of seperation at the axle end but what about the frame end? Can they be closer or do they need a lot of seperation too? This is all new to me and the plan was to do some reading on what everyone has. Unfortunately I cannot seem to find any of the threads. Any build threads you guys have would be greatly appreciated. Maybe we can get them in one thread with the right title for easeyer searching.
 
My radius arms are 40" long and work fine. Just try to mount them up nice and high at the frame because they'll stick back so far.

Or you could just "ramp" the mounts, some people seem happy with that method.
 
Here's how mine ended up.

3link.JPG


sub5.JPG


DSC01778.JPG


DSC01774.JPG


I've been extremely happy with it so far. Very predictable handling on road & off, and it has much less unloading during climbs than my old radius arm setup did.

Converging the links towards the frame side (having less separation there vs. the axle) is usually desirable; mine's got about an inch and a half less at the frame. I can adjust it about an inch either way:

DSC01894.JPG


but so far I haven't had a reason to want to try and tweak it.
 
what do you hope to accomplish with a 3 link?

what dont you like about your current front suspention?
 
XJ_ranger said:
what do you hope to accomplish with a 3 link?

what dont you like about your current front suspension?
Click to expand...
I actually learned why longer link are better at Tellico this year. I was climbing a rock and the front looked like it was being pushed under the jeep and the front was rising just not the axle. Talked to Sean and some others and this is what I am kicking around. I am running the factory UCA at 17.5" and the LCA at around 18.5" and about 9" of lift. The CA angles on the bottom are steep and there isn't a lot of room on the drivers side for long upper and lowers. Flex is not an issue ATM I have plenty.
 
Here is a link to Jes's photo albums. Tech and Tech2 have a number of pics of his and crashes hidden long arm 3 links.

http://www.fototime.com/ftweb/bin/ft.dll/home?userid={0641A5A9-DB40-46BE-9569-B61D5BC8B151}&tio=0

Here is a link to a thread of my hidden 3 link long arm build:

http://www.naxja.org/forum/showthread.php?t=56420&highlight=Hidden+3+link

A number of the pic links are not working though. I'll post up some current links to my stuff below:

Frame mods.
http://share.shutterfly.com/action/welcome?sid=8IbtGzVo3bMvi

Long arm prep.
http://share.shutterfly.com/action/welcome?sid=8IbtGzVo3bMtq

4wd shifter mods.
http://share.shutterfly.com/action/welcome?sid=8IbtGzVo3bMvA

Long Arm part 1
http://share.shutterfly.com/action/welcome?sid=8IbtGzVo3bMuE

Long Arm part 2
http://share.shutterfly.com/action/welcome?sid=8IbtGzVo3bMum

Jeff
 
This is the exact reason why I'm now building longs arms as well! Vettboy gave me some good advise (thanks) & have the 3rd link setup done on the pass side(well mocked up) & cycles sweet, only 1 deg change in caster @ full bump-droop. May need a little tweek here & there but it's close enough for goverment work.. Now i have to remove the wishbone & add a tracbar & build mounts on the Waggy 44. My XJ has a Vortec V6 with NP241 T-case so I have other problems getting everything tucked up inside the frame rails, dang tcase hangs 4 inches below the rails with no room to go up.. Fun project can't wait to get back on the road though.

Ghost said:
I actually learned why longer link are better at Tellico this year. I was climbing a rock and the front looked like it was being pushed under the jeep and the front was rising just not the axle.
Click to expand...
 
It doesn't have to be complicated, or difficult to build, to be effective. It just needs to be strong. The arm angles are more important than the length, so let the length be whatever it works out to as you decide the best (easiest) place for the mounts. There are 3 links out there that work well with arms in the 20" range on up. The amount of axle seperation at the frame isn't very important, just make it so the geometry comes out good. A basic goal could be to make the upper arm as close to level as possible and the lowers with the least amount of angle and yet have good ground clearance on the mounts.

As one more example of length, the front arms on my XJ buggy 3 link are about 25" on the lowers and 22" on the upper......and it's been climbing pretty much everything.
 
Goatman said:
It doesn't have to be complicated, or difficult to build, to be effective. It just needs to be strong. The arm angles are more important than the length, so let the length be whatever it works out to as you decide the best (easiest) place for the mounts. There are 3 links out there that work well with arms in the 20" range on up. The amount of axle seperation at the frame isn't very important, just make it so the geometry comes out good. A basic goal could be to make the upper arm as close to level as possible and the lowers with the least amount of angle and yet have good ground clearance on the mounts.

As one more example of length, the front arms on my XJ buggy 3 link are about 25" on the lowers and 22" on the upper......and it's been climbing pretty much everything.
Click to expand...
So if my upper were a lot shorter then my lower but were close to level then that would be good? I know where I want to put my lower mounts and have an idea where I want my upper but am unsure of all this fancy program stuff and if what I want is going to work or if it is the right way.
 
mock it up & run it thru a full cycle (full bump-droop) & you will see why a lot shorter upper link in no good,The pinion & caster are crazy. I made the mistake myself so TAKE YOUR TIME & DO YOUR homework:rtm:. Use the 3 link calc above to run numbers & Again take your time & do it right the first time cause you will be sorry if you don't:nono:. I'm no expert on 3 links but have learned a ton just doing research & asking more questions than I should of.


Ghost said:
So if my upper were a lot shorter then my lower but were close to level then that would be good? I know where I want to put my lower mounts and have an idea where I want my upper but am unsure of all this fancy program stuff and if what I want is going to work or if it is the right way.
Click to expand...
 
Not too much shorter on the upper, or you risk excessive castor change. If the upper is level, you can handle it being a little shorter, since the arc of movement will be minimized by it being level. You could make the upper in the best place for you, then make the lowers accordingly. The only negative with too much difference in length between the uppers and lowers is excessive pinion angle change, which can bind the u-joint at the pinion.
 
hellbilly04 said:
mock it up & run it thru a full cycle (full bump-droop) & you will see why a lot shorter upper link in no good,The pinion & caster are crazy. I made the mistake myself so TAKE YOUR TIME & DO YOUR homework:rtm:. Use the 3 link calc above to run numbers & Again take your time & do it right the first time cause you will be sorry if you don't:nono:. I'm no expert on 3 links but have learned a ton just doing research & asking more questions than I should of.
Click to expand...
Thank you sir. THat is why I'm in here and asking questions and looking for other peoples hard work. I think I may have a slight advantage over some since I have the tcase a lot further back with the 203/205 behind the aw-4. Then again it may end up like the seat and be a curse. I am also considering redoing the passanger side UCA mount to better fit thte 3 link. If it were moved more toward the passanger side does it cause more problems? And how does the panhard bar work into this style suspension? Does it matter its length? Also the CG link in the text is dead. Anyone got any info on that?
 
The positioning of the upper link isn't that crucial. Usually it ends up being pretty far to one side or another due to packaging reasons.

The panhard is what establishes the roll center. Typically you want it as long and flat as possible, but at the same time it needs to be approximately parallel and equal length to the drag link in your steering. The higher you can get the panhard mounts, the more resistant to roll the chassis will be; however there's a point at which it gets too high and can give you some strange reactions to sidehilling etc (you won't have as good an idea when you're approaching the flopover point). Basically it's gonna just be an experiment to find what works best on your rig, however with all the crap you'll have to fit it around in the front of an XJ I'd be surprised if you can get it high enough to be a problem. Goatman's rear panhard on his XJ buggy is probably one of the tallest I've seen and it works well for what he does.
 
Here are my numbers, What do you think? Concerned about the negative roll center number :huh:. Any idea how to get that lower or what else I could change? I don't any room on the drivers side for the upper link so it has to go on pass side.
hellbilly86
 
Here are my numbers, What do you think? Concerned about the negative roll center number :huh:. Any idea how to get that lower or what else I could change? I don't any room on the drivers side for the upper link so it has to go on pass side.

31_LinkV1.0b.jpg
 
I would definitely recommend more vertical separation on both ends. Moreso on the axle side. This will bring the x instant center back to positive, but this isn't a huge deal either way.

See where that gets you, but 28% AS will give you kind of squishy response under braking (large amount of brake dive). Raising the upper mount on the axle side should make this a little stronger.

A few guys on here run the link on the passenger side, it's not a big deal.
 
Looks like I might need to cut the floor & move the UCA up to get more separation cause I don't want to move the LCA mounts any lower, their already about 3 inches below the frame rail.

You say "brake drive" what is brake drive?

In the vehicle spec cell "sprung Mass CG 'Z', Kinda lost as where to get that measurment?

Sorry for all the questions but I want to do this right the first time around & do really appreciate your help!
Billy

vetteboy said:
I would definitely recommend more vertical separation on both ends. Moreso on the axle side. This will bring the x instant center back to positive, but this isn't a huge deal either way.

See where that gets you, but 28% AS will give you kind of squishy response under braking (large amount of brake dive). Raising the upper mount on the axle side should make this a little stronger.

A few guys on here run the link on the passenger side, it's not a big deal.
Click to expand...
 
hellbilly04 said:
Looks like I might need to cut the floor & move the UCA up to get more separation cause I don't want to move the LCA mounts any lower, their already about 3 inches below the frame rail.

You say "brake drive" what is brake drive?

In the vehicle spec cell "sprung Mass CG 'Z', Kinda lost as where to get that measurment?

Sorry for all the questions but I want to do this right the first time around & do really appreciate your help!
Billy
Click to expand...

I would at least try to increase it on the axle side, then...that should still help with the numbers a little bit. That will also help with keeping the joints from wearing as quickly (more separation = less force experienced in the link).

Brake dive is what happens when you jam on the brakes and the vehicle weight transfers to the front. The amount that this weight transfer compresses the springs is partially described by the AS% number - the higher this number is, the more resistant to brake dive the vehicle will be. SOME brake dive is a good thing, which is why a lot of people will shoot for the 50-70% range for that value. There's no "optimum" number here.

That's your center of gravity. There's a few different procedures you can do to obtain a real measurement, but a good approximation to start with is somewhere between the camshaft height and the top bellhousing bolt height. (this is height from the ground).
 
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