The military volvo 303 had that type of 2 link in the rear and it works.
I think they added it because portal axles add a lot of leverage to the leaf spring and they had spring wrap / wheel hop problem even with the low power 6-cyl engine. And they seem to flex ok.

 

Very interested in this - I'm wondering if you could put those links on top of the tube and attach them to an x-member flush with the frame to avoid ground clearance issues....

 

Maybe because running them as the uppers has the housing pulling against them instead of pushing, thus weirdly raising anti-squat since leaves will give a little and let the housing walk under?

I dont even know if that makes sense? :laughing:

 

i dont get it. how does it flex?

 

apparently just fine. with bushings at either end there is a bit of give, but the idea is to cycle the suspension when you are building it and find the arc the axle swings in. you build the link to match that, so it requires a little bit of geometry and measuring, you don't just stick them on there and hope it works like a traction bar. because of where the link is located it actually adds a lot of roll stability where a traction bar adds none really.

i don't think you could get it to work as well above the axle because it puts more of a bending moment on the springs, as well as the fact that i don't really have enough room to do it there. i think you get more of a length change on the top side of the axle as well.

interesting that 303s run a setup like this. so do these dakar trucks front and rear, with leafs, to great success.

 

interesting that 303s run a setup like this. so do these dakar trucks front and rear, with leafs, to great success.

do you know where i could find a high res of that!!!???

 

The two link setup pictured retains articulation only after extensive cycling and measuring to get the perfect length and mounting points that will work in unison with the leaf spring. John at Autofab has perfected them on FS broncos, but every application is different and requires a lot of time and skill to get right. Hope my limited knowledge helped some.

 

So, bolt it up on just the main leaves, cycle it from bumped to aired out, then articulate it side to side while measuring from reference points?

Im guessing it would be easiest to build lower mounts first, then build the uppers later after the cycling/math/eyeballing/measuring party is over?

 

Ugh - too much work.

 

http://www.bmcr.ru/media/kamaz/kamaz_am_260209_dakar574.jpg

i've been studying that picture a lot. i think there is a lot to be learned from these trucks.

 

Have you seen the type, a single over the pumpkin?

I know you don't want to weld to a cast housing but a truss over the pumpkin could be welded too.

A quick search and I found what I am looking to do myself: http://www.jeepaholics.com/tech/bambar/

 

Single bar above diff

I personally wouldn't use any kind of traction device that is rigidly mounted (no shackle or slip joint). An axle attached to a leaf spring DOES NOT move in an arc. Well, I take that back. It may move in an arc if you get the spring shackle length/spring mounting positions just right. Even then I would think the arc would be too large, and the center of the arc would be in such a position that it would be nearly impossible to mount a rigid link that wouldn't constrain the axle from moving in that arc.

I'm sure people have gotten it close, and there's enough give in the joints to make it work, but IMO it'd be much easier/less expensive/less time consuming to just build a ladder type bar with a shackle joint.

 

figured i would update this thread since i got it completed and tested it out a little at KOH chasing for 4450. i was very impressed with how everything worked out, even though on paper it doesn't look ideal.

articulating

doesn't seem to limit my flex anymore than the springs themselves. i've noticed a lot less roll steer, no more wheel hop, no more axle wrap. i can really plant the power down without worrying about whoops or rocks. an interesting benefit is that my rear detroit is much smoother now and i do not experience the "locker lane change" people always complain about. everything i used came off the shelves at PolyPerformance. they got what i need.

 

X2

I debated between a single ladder bar/shackle set up and the torque bars for a while. Decided on the torque bars and I am happy I did. I chose them because they won't let the axle walk like a center mounted ladder bar.

 

how did you decide on the length?

they look much longer than your leaf springs

 

Still seems to me like it would induce crazy binding, but if it works for you then it works.

How did your grease zerks survive for more than 2 seconds of trail use?

 

It won't bind because the leaves will flex. Just like they would if they were wrapping under hard acceleration. the bar just controls that wrap and keeps it to bare minimum.

 

I took the leaf length, divided it by the number of leaf packs, multipled the anti squat number into the diagnal degree and ended up just copying my friends store bought traction bars.

 

yea the zerk didn't last long, i'll just get some of those blank plugs which won't break off.

as far as length it was highly scientific. i bought poly p lower control arm brackets, found the best spot they worked on the frame and that was that. depending on where you put the tabs on the axle will control how the axle pivots around the torque arm, and how your pinion angle will change.

if i was running crazy amounts of flex there would probably be a limit to how much these would allow but i'm not and i never will be on this truck.

 

Any reason why you went below the frame and below the axle?

My neighbor wants me to build him some and I want to go over the axle and inside the frame. He tells me that won't work, but I don't see why it wouldn't.

 

Look at it like it were a link suspension. With the leafs being the upper link. Seperation is the key. I run blocks to level out my truck, although only an inch and a half, but since the leafs do more work than an upper link not as much seperation is needed. By placing the bars above, the axle can still roll under the springs.

 

How? If you are far enough above or below the axle it seems that it would stop axle wrap. Right? Or what am I missing?

 

Not saying your idea won't work, but it will be a lot less effective than below or in front of the axle. I had the same thoughts as you, but once someone pointed out a diagram like this one, it became a little clearer.

 

OK,

I've had a long day so I really may be making a fool out of myself, but it wouldn't be the first time. :flipoff2:

So one is pull force, and one is pushing force. But how is it not doing the same thing? Sure the pivot point is on top of the axle so the link would see more force, unless it is moved even higher. But other than that, looks like it does the exact same thing to me.

 

Leafspring tech, goody, question time..........

Hmmm, ok, so the SOA setup make the springs as top links, so a SUA would make the springs as bottom links so the rods should actually go on top of the axle, right??

time to pick some brains..........

What i see here is for a rear setup with pretty flat springs, now, what about on a front axle where the shackles are at the rear and the springs are under the axle?? spring arch is more in this configuration. With the same principle the torque rods should run forward to the fixed spring mount, as near as possible?? or some seperation at the chassis end could work better?? All considering this is for a daily driven rig with no crazy flex.

I did search but leafspring tech around here seems long gone and dead.........

Current thought in my books is to go with 1 link top of the axle pretty much in the center....... no seperation at the chassis end.

Flame suit on...............

Grem

 

Current thought in my books is to go with 1 link top of the axle pretty much in the center....... no seperation at the chassis end.
Grem

This sounds like what the early SA Toyota's ran on the front end. The links were more offset than center, but went from top of axle to pivot side of the springs.

 

No idea, but i would think you would not have enough spring wrap with a spring-under front end to even bother with it.

 

i wouldn't bother with a SUA setup, there should be almost no wrap anyway.

i didn't really get any of this either until i started drawing pictures of what the forces involved are doing, and don't forget about equal and opposite reactions. its the same principle as drag bars on old race cars tho. because a leaf spring has some bend to it, you need a way to control said bend which is what creates axle wrap. adding a solid link will create a path for the axle to follow, prevent the axle from rotating or walking, and a pivot point for the leaf to "bend" around. as it "bends" around the pivot it puts force back into the chassis planting the tires like a regular link suspension. the easiest way i can explain it is to think of it as a 4 link suspension with non-fixed length uppers.

if you put the links above the spring, you are just creating a pivot point for the whole axle to swing around. the axle needs to be located between the spring and link to work right. think about it: when was the last time you saw a 4 link with the uppers and lowers both above the axle centerline?

 

think about it: when was the last time you saw a 4 link with the uppers and lowers both above the axle centerline?

On comp buggies? All the time.

Jesse Haines old Single Seater comp buggy:

Torchmate Buggy (although they are now below axle centerline, new rear housing)

There isn't much of a reason it couldn't go on top in my mind, it would act the same if the separation distance was the same?

 

Yes, it is doing the same thing as if it were mounted below the axle. BUT, the main differences are the seperation and clearances. If mounted below the axle, there is the distance from the bottom of the spring to the mounting point BELOW the axle tube (i'm thinking about 8-10", but I dont have a vehicle in front of me to measure).
To get the same amount of leverage by mounting it on top of the axle, I think the mount would have to be at least the 8-10" (equivalent to the other mounting option), if not more to make up for the leverage created by the axle mounted below the spring. To get this distance above the axle, the mount will be pushed up between the frame rails and might hit the body (if it has one)

I would assume the top mounted option would work best for a spring under design for the same reasons.

 

Can someone confirm or deny what im thinking, and make me understand this?

When running a spring-over application on the rear axle, with anti-wrap links on the bottom as shown in this thread, the links will reduce anti-squat

When running a spring-over application on the rear axle, with anti-wrap links on top the links will add anti-squat

Obviously this is a gross generalization that does not take into accout link length vs. spring eye to pin length, degree of seperation and many other factors


The above is how im picturing it in my head. Am i right?

 

No :flipoff2:

If I am thinking of this right, it technically doesn't matter as the AS will be dependent on the link angle. That said, in most applications, the link on top of the axle should be flatter, so if anything, I think you are backwards.

 

Andy has it nailed with a nice sytem. I don't have pics here but search our the UA superduty we did last summer, it has a similar system that takes a load of torque, 42's and 10K# truck very nicely.

If you put the link on top you're putting the leaf spring in compression. It's like pushing on a rope. Leaves like tension.

We sometimes use bushings in both ends to give a little more room for things to move while still preventing wrap, we always use a bushing in one end.