2 link front end?

Hey folks. My current curiosity is the front suspension.

I understand the 3-4 etc. link setup but I am curious about a "2 link". I did a search on this subject but didn't really find anything in regards to what I am pondering.

Assume I were to convert to a long arm front end. (don't worry about the benefits/negatives of this alone for now).

I have seen in several long arm setups to run a triangulated arm off the driverside arm to the top of the pumpkin to stop axle wrap. But the panhard (err.. is that the right name.. I am having a brain fart) arm is still retained to keep the axle centered under the rig.

I think we generally know the negatives of a panhard arm.

Why can't we now go to the passenger side control arm and run a triangulated arm to the axle thereby eliminating the need for the panhard arm. For that matter why not run a second one from the driver side control arm as well. It seems that this would effectively emulate a 3/4 link with out actually having to run 3-4 individual arms. As well all of the angles would be based on the original arms, but they would also stay perfectly aligned through out articulation, would they not?

Naturally the primary control arms will have to be pretty substantial material and have pretty substantial bushings on them.. But I fail to see why this wouldn't be a very good setup.

Perhaps is there a problem in independent wheel articulartion?

Thanks,
Morgan

sweetjeep said:

I have seen in several long arm setups to run a triangulated arm off the driverside arm to the top of the pumpkin to stop axle wrap. But the panhard (err.. is that the right name.. I am having a brain fart) arm is still retained to keep the axle centered under the rig.

I think we generally know the negatives of a panhard arm.

Why can't we now go to the passenger side control arm and run a triangulated arm to the axle thereby eliminating the need for the panhard arm. For that matter why not run a second one from the driver side control arm as well. It seems that this would effectively emulate a 3/4 link with out actually having to run 3-4 individual arms. As well all of the angles would be based on the original arms, but they would also stay perfectly aligned through out articulation, would they not?

Perhaps is there a problem in independent wheel articulartion?

Thanks,
Morgan

Click to expand...

What you have described is a typical long arm/radius arm design. A few use only one upper arm running to one of the lower control arms, but most have an upper arm on both sides. You still need the panhard bar (track bar) to locate the axle side to side since you get no triangulation out of only two arms attached to the frame. The only way to eliminate the track bar is to have a triangulated 3 link (an upper V arm) or a traingulated four link, which is basically the same thing just with both upper arms attaching to the axle.

sweetjeep said:

I think we generally know the negatives of a panhard arm.

Click to expand...

No, I don't think we do.......what are they?

I don't see negatives of a panhard bar.........the track bar is your friend.

One of the obsticals to a triagulated 3 or 4 link front (removing track bar) is that there simply isn't that much room. The lower links aren't a problem, but if you build a gusset on top of the axle and try to center a " V " style arm with the axle and framrails, you run into all sorts of stuff getting in the way, one way I have seen it done however is to use a " U " shape to get around the oil pan and such, crawl underneath your rig and take a look, there is nothing wrong with the idea, but you need to work it all out.

On another note... Not having a track bar can give you some pretty good problems with bump steer on the street if you don't design the steering set up right. Think of it this way..... The track bar and draglink move together in a very similar arch, when you hit a bump. the suspension compresses which flattens out the line of the drag link which pushes on the steering knuckle effectively turning the wheels slightly.... now when properly set up, a lifted rig with the track bar positioned correctly will counteract that because when you hit that bump, the arch of the draglink and the arch of the track bar follow each other, so when you hit that bump, both bars flatten out in their arch, the axle shifts slightly to the side as the draglink is pushing on the steering knuckle, effectively canceling out the unwanted steering input. All that happens is the axle shifts slightly to the side, but the wheels remain on a straight track.

So if you swich to a Traingulated link setup, the axle is pretty much Always centered, when you hit a bump, the arch of the draglink has nothing to counteract the steering input its going to imply on the steering knuckle and you end up with some pretty good bumpsteer. By setting your rig up with the draglink as close to flat as possible when it is standing on level ground (like driving around town) you will minimize the effects of bumpsteer.

HTH

Josh

Is this the 2-link you are talking about?



This is found on Willys with Toyota axles often called Slinky; http://www.sierrarockcrawlers.com/slinky/slinky1.shtml

Goatman said:

I don't see negatives of a panhard bar.........the track bar is your friend.

Click to expand...

Track bars are minions of the devil.

-Jon

Yes Brett, I believe that is what he is talking about. Richard and jbrobeck missed the concept totally. I think it will work ok, but space is probably an issue and I don't think one could run the triangulation between the control arm and the axle housing on BOTH sides. As the triangulated side droops, it cannot shift side to side, so the OTHER side of the axle must swing side to side as it moves up and down. Sonny Honneger's old rock spyder flatfender used that style setup back when it was the rage in the magazines. Jeff

the thing I don't like there is (i'm pretty sure) the roll center is way off to the side, that could create some problems on side-hills, and more so one way than the other...

That is a one hell of a fugly welding job

BrettM said:

Is this the 2-link you are talking about?

This is found on Willys with Toyota axles often called Slinky; http://www.sierrarockcrawlers.com/slinky/slinky1.shtml

Click to expand...

Glad to see my twisted thoughts weren't entirely for naught!

Richard: I am not sure you followed my thoughts. But the picture that's been posted is exactly what I was thinking. Only, perhaps not on such a grand scale. And (in my head) the left side wouldn't be a double bar, it would be a single with a rod extending to the top of the diff housing.

In a sense mirror the picture's right side (to fit under the XJ, IF it's possible) and add a bar to prevent axle wrap.

I need to draw this out and post a picture I think..

As to Richard's "what's wrong with the trackbar". I think the most clear example is that as the axle drops it pulls to one side. Which is really all I would like to try and avoid. Plus hopefully fewer parts/pieces/joints/etc.

I am thinking something like Jbrobek is stating. In the end it's a triangulated 4/5 link, but you only have 2 points mounted to the body of the Cherokee.

I haven't yet thought much about the bump steer as I don't fully follow it. Actually, not that I type it out and talk to myself, I can see how the trackbar does indeed cancel bumpsteer, kinda.

So let me ask this addition.

If I recall correctly, the front end is a non-triangulated 4 bar setup right? 2 lower arms, 2 upper arms and a trackbar.

So if we convert to a long arm (just say) and then run the bar from the left arm to the top of the diff, and keep the track bar, do we still need the upper arms?

a trackbar/panhard is the only way to eliminate bumpsteer on a vehicle using a draglink.

if you're worried about the axle behaving non-symetrically with a trackbar, the picture posted above of Slinky will be FAR worse in this regard.

I think this is an entirely impractical suspension design.

sweetjeep said:

As to Richard's "what's wrong with the trackbar". I think the most clear example is that as the axle drops it pulls to one side. Which is really all I would like to try and avoid. Plus hopefully fewer parts/pieces/joints/etc.

Click to expand...

First off, that setup is scary to me. Looks like all kinds of handling problems. I wouldn't want it on anything at highway speeds.

Second, TB are just fine when used correctly.

If you want more even drop out of your front end while on a hoist then go with a Three link, one upper and two lowers with a TB. This give the most amount of free movement other than the triangulated 4 link. A few of us run this and have seen the beneifits while crawling.

hinkley

After discussing this with Goatman I used the 3 link you described below. It DOES allow the front to drop really low (damn springs popped out on Hell's Gate, gone to taller springs!). If it's well made there appears to be no problem with only one upper link. Goat sure wheels the shit out of his with no problems.That's why I used it as a model for mine.

Mark Hinkley said:

First off, that setup is scary to me. Looks like all kinds of handling problems. I wouldn't want it on anything at highway speeds.

Second, TB are just fine when used correctly.

If you want more even drop out of your front end while on a hoist then go with a Three link, one upper and two lowers with a TB. This give the most amount of free movement other than the triangulated 4 link. A few of us run this and have seen the beneifits while crawling.

hinkley

Click to expand...

Cool. So is there is there a particularly most common location for the upper links when in a 3/4 link system?

Danno said:

After discussing this with Goatman I used the 3 link you described below. It DOES allow the front to drop really low (damn springs popped out on Hell's Gate, gone to taller springs!). If it's well made there appears to be no problem with only one upper link. Goat sure wheels the shit out of his with no problems.That's why I used it as a model for mine.

Click to expand...

Yeah, you got me on that one. I missed what you where going for completely.

I'm still a big fan of a track bar.....who cares if the axle moves sideways slightly as it cycles, it affects nothing as long as the steering is set up properly. Plus, it's relatively easy to raise the roll center by raising the track bar mount on the axle, as long as you run hysteer so the drag link is also high. Also, when the steering and track bar are raised, the track bar flattens out, reducing the amount of any sideways movement of the axle. If you look at an axle with a track bar articulating, you'll see that it doesn't move sideways, anyway, it only moves sideways when it cycles straight up and down, and then who cares.

As far as where to put the upper arm in a three link, who knows for sure. I like the passenger side, where mine is, but others put it on the drivers side. The best location really depends on the angle of the arms and the torque loads on the axle, but I don't know how to figure that.

Ack.. I must admit my stupidity.

I was seeking a front end lift for my Cheromanche and in the process went to Rusty's place and among the goodies I saw their long arm setup.

This is EXACTLY what I have been thinking about. Exactly.

Sorry folks.. but if it's any consolation I did learn quite a bit about all this stuff.

sweetjeep said:

Ack.. I must admit my stupidity.

I was seeking a front end lift for my Cheromanche and in the process went to Rusty's place and among the goodies I saw their long arm setup.

This is EXACTLY what I have been thinking about. Exactly.

Sorry folks.. but if it's any consolation I did learn quite a bit about all this stuff.

Click to expand...

Ah ha.......so I didn't miss it!


:laugh: :laugh:




Good discussion, though.

here is Rusty's system:


are you talking about doing this without a trackbar?! you can't do that. It would be like running a triangulated 4 link that only has 2 degrees of triangulation; technically it will resist side movement, but practically it won't at all.

sweetjeep said:

Ack.. I must admit my stupidity.

I was seeking a front end lift for my Cheromanche and in the process went to Rusty's place and among the goodies I saw their long arm setup.

This is EXACTLY what I have been thinking about. Exactly.

Sorry folks.. but if it's any consolation I did learn quite a bit about all this stuff.

Click to expand...

Richard,

I missed it, I thought he said he wanted something for the front end with movement!


hinkley

to add to what Richard has said about trackbars.....the all coil TJs run them in the front and the back. Also the Unimog Mercedes army trucks use them front and back and NASCAR racers also use TBs and you see them do a lot of adjustment on them as the race goes on to improve traction. Not a perfect design but they do work well.

TBs? I assume that is short for track bar. Panhard rod is the term I have always used. TB makes me think traction bar. oh well. Just like a "swaybar" is really an antiroll bar.

does a tj use a triangulated rear and a panhard rod? or is the suspension nearly a mirror of the front?