Rear Traction Bar setups

[HOONracing]

Ive been think about a anti axle wrap traction bar for the rear of the race truck. Running 64" leaf under setup with about 18" travel strapped.
I'm thinking about doing a single bar on a shackle where it mounts to the frame.
Is anyone running a traction bar?
What setup, do you like it, pros and cons to this?
Pics please!

[Wrightracing.net]

I have never had to need for traction bars on my leafs. I have been fortunate to have a good combination between quality leaf springs and horsepower. The top range of HP on my Bronco is just under 300hp so I am not twisting the axle.

First thing is why are you considering a traction bar setup. Are your wheels hopping or other symptoms of a twisting axle?

Now that being said I have contemplated the designs. I am not a big fan of the ones like AutoFab do to it hanging down in front and exposed to damage. I have rebuilt a couple setups for fri ends that dropped them on to rocks. It most cases I ended up re doing the links with thicker .250 dom or 4130. In those cases the bars survived hits or at worst bent a little.

The design I like and have only seen a couple times is the over axle bar that tucks up in the suspension. The mount on the axle tubes is on top and go forward to the frame or a crossmember. The length should be a little longer than your front half of the leaf spring. I like it at least as long as the drive shaft to avoid any binding. I also like using delrin bushing for a daily driver over hiem joints.

[VintageIronFab]

Why not forget the 2-link and use what I believe is called a snail wrap-- what I am talking about is a half-leaf that goes from the front of the spring to just past the u-bolt plate. Lots of leaf sprung race trucks use that setup. Best part is there is zero hang down or anymore work than just bolting up the spring pack.

[HOONracing]

My leafs already have a snail wrap. I still think im getting to much axle wrap with those.

Im thinking about something lile this, what do you guys think?

[HOONracing]

[Rmc]

Why not forget the 2-link and use what I believe is called a snail wrap-- what I am talking about is a half-leaf that goes from the front of the spring to just past the u-bolt plate. Lots of leaf sprung race trucks use that setup. Best part is there is zero hang down or anymore work than just bolting up the spring pack.

National calls that military wrapped eyes on their springs. I'm guessing for an old govt contract?

[baja-chris]

Hoon, if that is a shackle that it's attached to so it can swing then I like it. What I don't like about most links is that they fight the leaf. The leaf has curve to it and as it cycles up it flattens out so the length from the front spring eye to the spring plate on the rear end has to grow a bit as the curve of the leaf un-curves. Most link bar setups don't deal with this very well. Using soft bushings like Poly and leafs without a lot of arch minimizes the issue. But the setup you show eliminates the issue. I like it.

[Wrightracing.net]

Like Chris said, I like the shackle setup also.

[HOONracing]

Thanks for the reply guys. I'm going to give it a try with the traction bar being as long or longer then the driveline. Well hopefully this will give the leaf spring a little longer life as we broke one leaf and bent the other side, both main leafs at our last race the Motion Tire 300. I will have it apart so I will cycle the system many times to make sure it is cycling properly.

[BDKW1]

Unless you are going with the floating shackle type set-up, the bar needs to be about as long as the front of the springs. Even with the shackle I wouldn't make it much longer then the springs or it will be fighting them.

[MOSS2]

I disagree that it should be as long as the springs as above. The pinion angle change would be huge over 18 inches with that. The pinion angle of a leaf by itself does not change as if it pivots on the front eye. I think the longer version would have more success with the shackle but it will still not completely match the spring. I would cycle the spring and measure pinion angle through the travel then you can play with different ideas on CAD or paper to try and get as close to the springs natural compression.

[HOONracing]

I disagree that it should be as long as the springs as above. The pinion angle change would be huge over 18 inches with that. The pinion angle of a leaf by itself does not change as if it pivots on the front eye. I think the longer version would have more success with the shackle but it will still not completely match the spring. I would cycle the spring and measure pinion angle through the travel then you can play with different ideas on CAD or paper to try and get as close to the springs natural compression.

I totally agree with you on this. I'm thinking that having it closer to the length of the driveshaft would work the best and use a shackle on the frame side. I know my driveline plunge was less then a 1/2 inch closer to a 1/4 if I remember correctly. The was with 18 inches of travel. Time to tear it down and cycle it to see where I'm at with the pinion angle change.

[Tchajagos]

How much harder would it be to separate the bars, effectively making a 4 like that keeps the pinion angle with the leafs?

[Tchajagos]

By separate I mean split vertically. Having 2 bars on either side vertically. But if the pinion angle change is tiny for your cycle it may not be worth the extra time to design it. Although you would be able to tune it better.

[BDKW1]

I disagree that it should be as long as the springs as above. The pinion angle change would be huge over 18 inches with that. The pinion angle of a leaf by itself does not change as if it
pivots on the front eye. I think the longer version would have more success with the shackle but it will still not completely match the spring. I would cycle the spring and measure pinion angle through the
travel then you can play with different ideas on CAD or paper to try and get as close to the springs natural compression.

Long would be good for pinion angle yes, spring wrap, no. The front pivot point will not be all that much different from the Auto fab style links. Cycle one and see for yourself.

[Rmc]

As the spring flattens and the length changes it should rock the axel but hold it at this fixed location front to back until the spring re-relaxes right? I'm not sure I see a great advantage to the shackle type over standard. I realize the shackle type would move with less restriction. Wouldn't standard traction bars attached to the top side of the axel perform the same way? I'm thinking less bind between the bar and the rotational force applied to the axel/spring. I guess I'm trying to say the top mounted bars would have a lesser bind agianst the springs length change allowing a lesser bound rotation of the axel?

[Rmc]

I'm thinking for a top mounted traction bar set up the pinion angle wouldn't become ideal until into the stroke a ways in comparison to the shackle type where the ideal angle would present at at points in the axels up down motion. The shackle type should work better but just trying to see if I'm understanding the concept correctly.

[MOSS2]

I disagree that it should be as long as the springs as above. The pinion angle change would be huge over 18 inches with that. The pinion angle of a leaf by itself does not change as if it
pivots on the front eye. I think the longer version would have more success with the shackle but it will still not completely match the spring. I would cycle the spring and measure pinion angle through the
travel then you can play with different ideas on CAD or paper to try and get as close to the springs natural compression.

Long would be good for pinion angle yes, spring wrap, no. The front pivot point will not be all that much different from the Auto fab style links. Cycle one and see for yourself.

I think we are talking about different setups. The Photo is a radius arm it does not pivot on the axle end like an Autofab link. The axle stays at the angle that the radius arm changes so there is no spring wrap unless your arm flexes. The problem is getting the pivot point in the right place to come close to the natural spring 'wrap' during compression. Yes if you pivot both ends of a link and shackle one end it will do nothing but make your truck heavier. 3 or 4 link and floating the springs is probably the only way to not have them fight each other. I am disappointed to hear about this problem on the spring under. Everybody said that was supposed to work better for spring wrap and life.

[BDKW1]

This is the set-up I am talking about.

Since the bar is so long it is swinging a large radius. This will be different from the arc the springs move in. The shackle is there to account for the length change due to the 2 diverging arcs. Pinion angle will be fixed by this bar as it has 2 mounting points on the axle. It will bind up the springs to a certain extent as it cycles as it does not swing the same arc as the leafs.

[RyanDS650X]

Autofab 2 link for comparison.