Dual triangulate four link

Down&Dirty

Well-Known Member
Joined
Jun 26, 2005
Location
Greenville SC
How much triangulation does it take to rid myself of a trackbar? I am working on getting a 60 in the front of a CJ5 and I can't find anything on how much triangulation it takes to keep the axle centered. This is on a full hydro steering setup so I don't have to worry about any drag link problems. Is this a case of triangulate as much as you can and hope it works? Right now I have the lowers pulled from as far out on the axle as possible to inside the frame rails. The uppers go from the middle of the axle to just inside the frame rails. Short of dropping the lowers down a little, adding a new crossmember and a 2 piece front driveshaft I don't see how to get any more triangulation.
 
A trackbar is the perfect solution to side force/loading, as it is directly opposed to such force. If the triangulation is at a 45 degree angle, 50% of the load on the link translates to front/back force, and 50% remains side loading. What this means is that if you have 1000lbs of force from the side, you are putting about 2000lbs of force into the link and joint. Beyond 45 degrees, it increases exponentially. For example, at 60 degrees, you are looking at about 6.5 times the force, or 6500lbs of force in the link and joint on a 1000lb side load.
 
Do you have a pre planned design, or are you putting it where it fits. I would recommend getting the 4-link calc off pirate and playing with that first.

And pics help.
 
jeepinmatt said:
A trackbar is the perfect solution to side force/loading, as it is directly opposed to such force. If the triangulation is at a 45 degree angle, 50% of the load on the link translates to front/back force, and 50% remains side loading. What this means is that if you have 1000lbs of force from the side, you are putting about 2000lbs of force into the link and joint. Beyond 45 degrees, it increases exponentially. For example, at 60 degrees, you are looking at about 6.5 times the force, or 6500lbs of force in the link and joint on a 1000lb side load.
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So I guess what you are saying is that the 8 or so four links that I have built with no trac bar, most with alot less than 45 deg seperation won't work?
 
Down&Dirty said:
Is this a case of triangulate as much as you can and hope it works? QUOTE]

Thats how I do it. Look around on pirate at other people's four link designs, read their comments, see what works, and what looks like it will work/fit for you.

I've never used a calculator, alot of times what looks good on paper, just won't work in the real world.
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rockmafia said:
So I guess what you are saying is that the 8 or so four links that I have built with no trac bar, most with alot less than 45 deg seperation won't work?
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You need to work on your reading comprehension. He said a track bar works better from an efficiency/strength standpoint. And it does.

It doesn't mean it's the perfect solution in every situation.
 
Every suspension I've had with a track bar sorta sucked as far as strength went. I ripped mounts off, then beefed them up and bent the track bar. I also tend to beat on my stuff a little more than most though. Depending on what your intentions are for the vehicle a track bar system may be fine, they seem to require a little less engineering than double triangulated 4 link. But, if you're really going to be hard on it, I'd rather have the 4 link. My .02 for whatever it's worth.
 
saf-t scissors said:
You need to work on your reading comprehension. He said a track bar works better from an efficiency/strength standpoint. And it does.

It doesn't mean it's the perfect solution in every situation.
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Maybe I should have answered differnently instead of being a smart ass.

I don't like trac bars for larger, offroad only rigs. I've seen alot of broken trac bar stuff. Then again it's like ford vs chevy, everyone has a different opinion.

Main thing is I don't agree with the math. I don't beleive the forces increase that much (in the real world), otherwise my double not so trianglelated four link would have broke by now.
 
As already stated, Im not saying it won't work, Im saying the forces are higher.

As far as breaking trackbars and such, an offroad rig sees totally different forces from a street rig. On a street rig, its pretty much just side force from cornering (handled by the trackbar) and front to back force from accelerating and breaking. You don't have to agree with the math, but it is right. Remember, 6500lbs axially in a 1/4" wall 1.5" OD tube is really not that much, and 1000lbs is obviously much less. The forces and such associated with binding and suspension flex act much differentlyer, and cause havoc on a trackbar, which is why a 4-link is better offroad.
 
I understand. Probably 50% of the time, I have to type 2 replies, the one where I say what I would like to say, and then the one where I say what needs to be said.
 
BIGWOODY said:
Every suspension I've had with a track bar sorta sucked as far as strength went. I ripped mounts off, then beefed them up and bent the track bar.
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Yeah, that's other side of the argument -- the downside to putting all the side load through a panhard bar is that you put all the side load through the panhard bar.

Figure in most cases with a dual-triangulated four link, you're distributing those side loads through all four mounts.

The only other useful advice I have is that I don't think you'll be able to go cheap in a front suspension by using rubber bushings in any of your links. Gotta use mechanical joints at both ends of all of the links to minimize deflection side/side.
 
panhard

It seems to me the 4 bars share the side load better than one panhard bar that takes all the force.
 
1 panhard, 2 triangulated link with twice as much load, it pretty much balances. A trackbar/panhard is more precise simply due to the direction of the forces and slop in the joints.
 
The plan is to use JJ at all ends of the links. I just picked up the coilovers and the new ram should be on its way tomorrow along with all of my suspension joints. I have enjoyed the discussion on here about the differences, but for me it is a mute point. It will be a dual triangulated 4 link. I watch rigs and have had rigs up until now with a tracbar. I don't like the setup. It is much harder to get the suspension travel that I am looking for with the extra bar there. The trackbar limits how close to the frame I can push the axle and still get a lot of droop out of the system.

I am shooting for 4-6 inches in compression and 10-12 in droop. Or as close to those as my driveshaft will allow. The plan is to build for these numbers and limit the travel until the money fairy drops enough money at my place for new driveshaft parts. The lower links will be 2 inch 3/8ths wall DOM and the uppers will be 1.75 inch .120 wall DOM for now.
 
jeepinmatt said:
1 panhard, 2 triangulated link with twice as much load, it pretty much balances.
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Check your math again, boss. That's one, two, three, FOUR links, hence the name. Considering that none of them are exactly perpendicular to the load, they're all seeing some force, so... 4 links / 2x load == twice as strong.

Well, not really, but for the purposes of discussing hypothetical failure modes of fictitious suspension builds, it'll have to do. I don't disagree with you on the deflection issues or the design efficiency... but a double-triangulated four link definitely wins out on redundancy.
 
Welcome to another internet pissing match...but since Im still up at 2am...

Check your math. The divergent end of the triangle (with 2 points mounted a distance apart) on the axle does not contribute to the side load resistance in any noticeable manner, because it is practically a pivot at the frame end (where the triangle converges). Imagine if you remove the set of links where the triangle converges on the axle, what is to stop the side load? Does that make sense? Some of these things are hard to explain well.

Also, a 4-link doesnt have to be triangulated as such. It could be have triangulated lowers and straight uppers, or vice versa. As such my math still stands.
 
your 3 link was built like that because I couldn't fit a 4th link in there without redoing the exhaust and everything else on the driverside frame rail. I think the front coils are limiting the front travel! I think with the coilovers and turning the top center mount on the axle ,with a jj on both ends of the top link you'll be happy. I never wished it had more flex, the back is a monster and carrying a tire every now and then is not a bad thing. It actually adds a little stability, too much flex will aid in the suspension unloading on side hills. just my opinion I know this jeep inside and out. btw , I'm glad to see tons going under it!!!!
 
I am hoping to balance the flex out a little bit. The coils were definitly the limiting factor in the last setup. I am trying to remove the tracbar so that I can push the front end down a little bit. I also have to redo the exhaust because it finally caved in the rest of the way closing off the passenger side. Now it has blown out the seal going from the manifold. I think that this is going to push the wheelbase out a little bit and I will probably just have to add a rear winch to keep everything from unloading on sidehills. Last trip out I snapped yet another 44 shaft and since I was breaking at least one a trip I got pissed enough to do tons. I was going to go with rocks, but I think that axles, suspension, wheels, and tires would have taken all my money and credit cards.

Force wise in the suspension, at both ends of the triangle the links don't meet. This small amount of seperation prevents the solid body approximation from working and also removes the pivot point. The axle will still pivot around with just 2 of 4 links but this is due to deflection in the JJ. I also want to step away from the 3 link because lately big drops have been where I am having my fun. With the added weight of the 60 and also the potential weight of new tires and wheels I want to make sure I have a little redundancy built in.

It has worked great in the last configuration, being able to follow everyone on tons and coilovers almost anywhere. But it was between fixing this up or a ground up buggy and with school starting jan 10th I figure I better get this finished now. The goal being a much more reliable rig so I am not replacing a part every run. In school that is not an option.
 
jeepinmatt said:
Welcome to another internet pissing match...but since Im still up at 2am...
Check your math. The divergent end of the triangle (with 2 points mounted a distance apart) on the axle does not contribute to the side load resistance in any noticeable manner, because it is practically a pivot at the frame end (where the triangle converges).
Click to expand...

You can't induce fictitious rotating vectors on your imaginary suspension with a hypothetical side load. The converging links might "practically" make a pivot point... except that they don't, because they never actually converge. And what you're looking at in plan doesn't really exist once the axle housing is 20* or 30* off camber to the chassis. Four links, four vectors, four paths to distribute load.
 
This pointless, I don't really care to argue about it, so here's my last word. Just go try having both triangles (upper and lower) converge at the frame end, and take pictures when it rips off or you run off a hill because it can't drive in a straight line.
 
jeepinmatt said:
Also, a 4-link doesnt have to be triangulated as such. It could be have triangulated lowers and straight uppers, or vice versa. As such my math still stands.
Click to expand...
I really don't want to get into the pissing match but, I have to ask. Have you ever built a working 3,4, or 5 link in an offroad vehicle? Math is great and I know it doesn't lie however, pretty much everything I've ever seen built without triangulating both the uppers and lowers or adding a track/panhard bar, will flex steer like a mofo.
 
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