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Traction Bar Length?

13K views 45 replies 15 participants last post by  JHill 
#1 ·
for those that have built your own what was your overall length? Is longer better . FWIW, these are not going to be daily driven, Sled pulls only.
I have 2 -8' pieces of 1-3/4" DOM tubing.
 
#3 ·
7' 1" seems to be the # in the search forum for CC SB trucks , mine is a long bed.

Charles, are you saying thats a good thing or bad? binding is usally not a good thing, or do you mean it as locking it in to a fixed position?
 
#7 ·
Mine are 85"(7'1") for my CC LB and work great. If I preload them towards the front(shorten them) as tight as I can with my hands only, they ride normal. If I unload them or preload them towards the rear(lengthen them) any amount the ride is somewhat stiffer than stock. Not jaw rattling but it is firmer.
 
#9 ·
Well, if you have a rear leafpack that is damn near flat, then yes, as it will pattern the arc of the link for the most part. I thought most superduty rear springs had some decent arc to them, course I might have been looking at my 6" springpack one to many times, lol.

If you ran a horizontal link to my springpack it would arc straight up for all intents and purposes (although actually toward the front of the truck slightly) while my springpack would arc the axle rearward and up quite a bit as it compressed because of the angle of the forward half of the spring pack between perch and hangar.

In my case and many others, a horizontal link would travel in a path opposite that of the springpack causing the springpack to have to wrap in the same direction the drive torque would normally wrap it in order to cycle on compression.

In your case it sounds like your leafpack is nearly horizontal itself. If that's the case then what I said was wrong.

Sorry. I must have been looking at to many lifted trucks.
 
#10 ·
ended up @ 88" not counting the eyes on both ends, looks to be just about center of the rear doors. will see, might get them them on tommorrow still need to fab the mounting brackets.
 
#11 ·
So whats your guys consensus on mounting 2 bars, one at the bottom and on on top of the axle and joining them at the frame mount ? As compared to just a single bar
 
#14 ·
:whs:


Remember the axle actually moves front-back when it travels, so if it's fixed at one point ont eh frame and 2 points ont he axle it will NOT move. You can make the front of your bar mount at a shackle, I hear that works, but I'd just simplify thigns and mount it at one point on the axle and one on the frame and be done with it.
 
#12 ·
If you do that the only axle articulation would be in the joints used or in deflection of the link itself.

With heims and a link that did not deflect much the rear axle wouldn't be capable of any articulation.
 
#13 ·
Dieselboy, if you mean 4-link it, yes that will work, but you'll have to weld on large drop brackets to mount the front eyes of the bars to. If you're thinking of making the front of the bars meet at a single point, you will not have suspension travel, it won't work because the bars won't allow the axle to move.

Dave
 
#15 ·
With two points at the axle and one at the frame you have simply made a radius arm. It will still cycle (as long as the arc doesn't conflict with the leafspring arc enough for binding to stop the travel). But it will not articulate. You would basically have a "swing arm" rear suspension. With no ability to compress one side without the other, like when turning onto a road that is sloped away or toward you, or driving over a ditch or similar where the suspension has to articulate. I would expect that if you used Heims it would just lift a tire in the rear in these situations.

In other words, for dedicated sled pulling, no problem. It would do it's job and actually make the truck more of a stable platform. But for driving around everyday where you're turning a lot, without a spool in the rear you would probably get a lot of tire spin and such because of the near complete lack of downforce on the inside tire each time.

Imagine if a four wheeler with a swingarm rear had an open or LSD. It would get stuck on a banana peel.

And a shackle won't effect what I'm talking about. In order for one side to compress while the other remained stationary the axletube would have to twist, or the link would have to bend, joint compress, something. Otherwise it would just lift the opposite tire off the ground before it would let the suspension compress on one side.

This is why radius arm trucks usually have large poly joints that can "soak" up a good bit of movement and allow suspension travel to still happen.

If you want to run a radius arm design (two points at axle, one at frame) then you might consider just using one instead of two. Put on of them near the center of the axletube near the housing and you can control the wrap without affecting the articulation, although you would still need to match up the radius arm arc path to that of your existing leafsprings otherwise they would each travel in different paths and it would initially twist the springpacks and then just bind at a point based on the load applied. Obviously the heavier the farther it will push into the bind, and still "travel" some.

Good Luck.

Two cents.
 
#16 ·
Charles,
A radius arm like you describe only works with coil springs, not leaf springs.
The leaf springs MUST move front-back to function. I know someone who made short ladder bars with top/bottom mounts on axle and a single mount at frame and he loaded the bed with the bucket of a large Excavator (ie pushed down with the machine) and the truck didn't budge. Having said that, probably good for pulling but it's got to be stressing parts that weren't meant to be stressed like that.

I'd just avoid that set-up altogether. No benefits whatsoever no matter how you look at it...
 
#17 ·
Charles I'm not going to post pics to prove you wrong, some people need to figure some things out for themselves. My bars are two points attached at the axle and intersect to one attaching point at the front.(not on the frame :D) Yes there are heims at the attaching points and it doesn't hang a tire in the air at any time. It has full travel up and down. It took a lot of trial and error to get it right. I've taken a lot of jabs for the "jungle gym" under the truck but it works.
 
#18 ·
I'm going to take a wild guess and say that the locations for the link ends on your buddies truck had more to do with where he could get a welder and a tab than to do with the geometry from where he plotted it all out and struck the arcs for the spring and link...

If you give a damn enough to plot it out (even on paper if you don't like or have any CAD program) and mirror the path of the spring with the link arc it will not bind.

However, nobody does that. They just weld some chit up under the truck and hope for the best.

My F-350 Trail truck has lower links no longer than 3 or 4 feet, but they arc in nearly the same path as the leafspring and they do not effect suspension cycle any discernable amount throughout the full range of motion that it sees.

You can jump up and down on the back and cycle it with sheer bodyweight. If you want to bind a truck suspension with link placement, you can. But you can just as easily not if you place your links with some forethought.
 
#19 ·
i just have one bar mounted underneath the axle and about 6' long. i seem to have great travel, no bindin, and no wheel hop. o and they are at a slightly less angle than the drive shaft.
 
#20 ·
Just build a bar that goes to a shackle, and then use a shanked heim joint on the top for preload...

Now your axle can articulate, flex, but can't rotate.
 
#24 ·
Get a good heim and you wont have to "hear it clink and clank" I have WAY more abuse on my traction bar heim then any of these trucks will ever see, and I have yet to hear it make any noise...

I would blow out a poly bushing, I know this because the shackle is mounted with a poly bushing, and it gets blown out twice a year...

JJ's are good stuff, and I run the 1.25" shank JJ's on all my links.
 
#27 ·
I would also like to see you make a poly bushing that has 360deg of rotation with the axle... :pointlaugh:

What do you need 360deg rotation on an axle for? It is not a hellicoptor blade.
 
#26 ·
Don't worry about it. Drive a truck everyday that actually gets driven everyday with Heims on the suspension and your attitude will change when you start to develop a slight tick because you're loosing your mind a little bit more each time you hear it clunk. And if it's not doing it yet, just give it time. A poly joint will never do the clink, clank, clink, clank, clink, clank horsesh*t.

If you are destroying poly joints blame yourself. Because you were the one that chose their size when you made them, unless you bought them pre-made in which case, you bought them too small.

And show me a heim joint with 360* rotation? Are you referring to rotation about the mounting bolt? If so, poly joint will do the same. Are you referring to rotation perpendicular to the bolt, or what is most commonly labeled "misalignment"? If so, how does the bolt connect the heim if it's rotating 360 degrees and shearing it off? But most importantly, how many street driven superduties have even remotely enough suspension cycle to warrant any of that bs?

It's an F series Ford truck, not a rock buggy.

I think your love affair with trillion dollar heim joints will wane in time. They are the coolest thing since sliced bread until you start getting tired of replacing them. And how much do they cost? How many poly joints would you have to wear out before the cost equalized?
 
#29 ·
I think those don't have enough section and they will deflect under the force from a heavy truck getting traction with a hot diesel engine pushing it. I built a set of similar section once before and had to take them off after having someone else drive the truck so I could see if they were deflecting like I thought they were.

I also modeled them in solidworks and had a buddy transfer it to a simulation program he had and they showed to deflect just as much as I thought I had seen them. It created even more spring energy and powerhop than no bars at all.

They seem to have patterned their design toward matching the driveshaft angle. That doesn't necessarily have anything to do with the suspension movement, that's why the driveshaft has a slip yoke. They also look to be using Heim joints. I've tried to make my point on those. Choose them if you wish, maybe they will work great.

That's all I can see from the pictures. Now take that with a grain of salt, because I'm just a barnyard fabricator. I am definately no expert. They may have good reasons for doing what they're doing and I may just be missing them. But similar links did not work for me once upon a time.
 
#30 ·
Modelded in Solidworks, tested in a simulation program and barnyard fab don't seem to go together all that well. :poke:
 
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