minimizing anti-squat with leaf springs and anti-wrap bars...

[Rich]

Part of the reason for the bugy-fication is to help the FJ climb better.. Last year, it was hampered by too much rear weight, but alot of it was too much anti-squat in the suspension, and the resulting hop.

The drastic increase in anti-squat was caused by the installation of a ladder-style anti-wrap bar. It's about 33" long, and the upper bar is nearly flat.

Without getting too deep into the calculations, I don't think I can really get the anti-squat down all that much without separating the upper and lower bars.

Mind you, much of what I'm doing now will help to reduce the axle hop... (center limit strap, shocks vertical with better damping, less weight on the rear axle, some cushion in the driveline)

Here's a few pics from when it was first installed...

The inquiring, engineering goober in me wants to know...

(pre-emptive - a 4-link is not in the timetable right now, so don't even mention it)

 

[drkelly]

I really wish I could weigh in here with some useful information because I am running a shackle flip if you followed the other thread and a traction bar also. I originally had the 5.5" lift block on top of the stock wedge block (pic in other thread) and no traction bar when I first lifted my Bronco. As you can imagine it had horrible axle wrap and would buck when climbing if forward progress stopped. I then did a shackle flip, and also removed the third leaf from the spring pack to soften the ride since I had lost about 200 lbs from the rear of the vehicle by removing the rear seat and tailgate. At this time I also built a traction bar. The vehicles manners were much better. I could sit on an obstacle while climbing and spin the tires with no bucking or hopping. I was very happy with the way it would climb. I really did not know what I was doing though. I just copied the many others I saw on the internet and trail. My main criteria when building it was to get good seperation at the axle end, make it as long as possible, mount the frame end as low as possible without hurting ground clearance, mount it as close to the center of the vehicle as possible, and not have the lower of the two axle mounts too low for dragging against rocks. I could measure mine if anyone wants to know, but it was fairly long. The biggest thing I did not like about the traction bar was that when the side of the axle with the bar attached drooped, and the opposite side stuffed, the front half of the stuffed side leaf spring would really distort and bend up. This had to be limiting flex. I am going to try some 63" chevy's on my truck this go round without a traction bar. I figure I will probably end up with links in another year or two but this will be fun to experiment with.

Here are a few pics of my traction bar:

 

[Yay!Gurrr]

rich, what causes hop? suspension loading/unloading due to torque, traction and suspension design...

First I really don't see anythign majorly wrong with your current bar, it seems long enough and has a good angle.. Honesly i think your problems were purly from the added weight and good traction.

Id, See how things work now and go from there... Possible air up a little (seriously) people always mention what psi (of air pressure) they are running but fail to mention their tire size or what thier rig weighs, that is what give your psi (Pound per square Inch) of tire footprint... Blah blah blah....


Anyway keeping my origianl plan on my heep. Im gonna be trying out an old school trick with a new twist... Get this they are called traction bars (aka slapper bars) will be somthing like in the pic... I want a little axle wrap

edit: i guess its not overly clear in the pic. But basically it will be a 2" box tube that is integrated with the spring plate and sits over the leaf spring, im retaining the stock YJ snubber you see in the pic and will add one on the the tube...

 

[Yay!Gurrr]

also a good thread on pbb. The last post (as of now) pretty much sums it up..

http://www.pirate4x4.com/forum/showthread.php?t=351224

87yj says -

It's been stated before, but seems like everyone keeps forgetting...the routing or angle of the links doesn't matter. It's where the forces are being routed. Wrap starts as a torque around the centerline of the axle. It's reacted (controlled) by the lever arm we attach. However you fab the link, the force path it still centerline of the axle to center of the joint. Route the links however it works best...worry about the lenght of the link, where you put the shakle and angle of it.

For the length. The shorter it is, the more it will try and pickup on the rear of the vehicle as it limits wrap, until you hit verticle (can we say bam bar). If you could put the link behind the axle, it would load (squat) the rear under acceleration. Longer (think of the link going all the way to the front) will make the vehicle less sensitive to acceleration rise in the rear. My thought is that if the link is short, when tires slip and grip it will cause the rear to rise and fall back down. So once hopping starts, the bar will actually help you continue hopping. Putting on shocks that offer more dampening could by a realatively easy way to reduce hop by not letting the rear load and anload as quickly.

My personal though on shakle angle is to set so it never goes forward of 90 degrees - typically that will be at full compression.
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which reminded me that i thought you had an odd shock angle, liminit thier efectivness? (its been a while)

 

[BIGWOODY]

I ran a set up like the one pictured on my scout many moons ago, it worked. The Scout was on tons/39.5s and weighed a freaking ton, but didn't really hop at all.

 

[Rich]

yeah, my old shock setup sucked. sooooft shocks, angled way in. It wasn't helping anything.

As for airing down, I'm gonna have to re-measure it now that the rig weighs alot less.. I think at least one good shakedown run purposely trying some steep hills, acting stupid, will be required to tune this in...

 

[Franklin]

Didnt someone have a chart that showed % loss of dampening for every 5* that the shock was not perfctly vertical?

 

[rockcity]

I don't think the top angle of the bar really matters. You must look at the imiginary line between the CL of the axle and the CJ of the pivot of the bar. However, I think the location matters. Where? don't ask me. I'm still trying to work out my 4 link.

from what I"ve seen, the angle of the shackle should be about 90* to the CL of the axle. don't know how accurate the info is, but thats what I remember seeing on vehicles and on bbs.

Rob

 

[StudNuts]

I just ran a center limit strap. It works pretty darn good. I dont have that much AS to begin with, but when the rear starts to break traction on a grippy surface it wants to pull up, I tossed the limit strap in and that cured it for me.

 

[SSWaters]

I might be showing my age, but, on leaf springs that thing you're talking about "yager" looks like those trac bars that either Rugged Trail or Skyjacker used to make. It was mounted to the top spring plate with a rod that went straight forward into a dropped bushing mount. There also was that Traction Lift they used to make that gave you 2" lift. It was made out of about 3 or 4 leaves about a 18" long with a U bolt and keepers that were about an 1" or 2 off of the springs. When axle wrap wound it up they would go up against the springs and stop it. They quit making the Traction Lift because people were putting them on the front and rear .