By: John Nutter - 8/1/2002
Getting Axle Wrap and Wheel Hop Under Control
After years of patching and repairing my old ladder bar it was finally time to build a new one. There were a few shortcomings to the original design that I wanted to improve upon. I also wanted to write an article specifically about building a ladder bar because I had been asked so many questions on this subject over the years.
|The new ladder bar compared to the old bar.|
|The new bar installed in the Jeep.|
|Testing the new bar at the Badlands OHV Park in Attica Indianna.|
I'll make a quick mention of where this ladder bar is used and what it's used for in case anyone hasn't been following along. I installed the old ladder bar years ago when I first went spring over in my CJ7. It's used on the rear axle, and it's sole purpose was to eliminate axle wrap and control the pinion angle without binding the suspension. The threads at the leading end of the bar allowed it to twist, which prevented binding as the axle articulated. The shackle at the leading end allowed the bar to effectively change length to prevent bind as the suspension cycled up and down. The bar controlled wrap very well and still allowed the suspension to flex as if it weren't there, but I gave absolutely no thought to anything beyond that.
One of the down falls of the old bar was that the geometry was never quite right, especially not after the drive train was raised and moved forwards. I believe that it had too much anti-squat to start with and relocating the drive train didn't help. This was not a big problem, but it did lead to some annoying bouncing when the rear shocks went bad. The old bar had done it's intended job very well, holding the pinion angle steady and absorbing the energy from bounces and other impacts. I had never broke a single part from axle wrap or wheel hop while using this bar, so I considered the bouncing to be nothing more than a nuisance. It was still a nuisance that I wanted to eliminate.
Aside from the geometry, there were some other changes I had been thinking about. These were mostly things that had been incorporated into the bars I'd helped friends build in the mean time. I wanted to build a new bar out of heavy wall tubing, and I wanted it to use standard polyurethane bushings of some sort. Upgrading the threaded part from the 7/8" Wagoneer tie rod parts to 1" F150 tie rod parts would help with the strength. I also wanted to make the bar longer, in part to reduce the stress on the leading end and in part to reduce anti-squat. I also wanted to make a stronger cross member for the shackle end of the bar and I wanted to place the shackle in tension. My old design had the shackle under compression during acceleration which I always felt had the risk of inverting the shackle.
The first step in building the new bar was to gather the materials. My previous bar had been built from 100% recycled materials - whatever was laying on the floor of my shop. The new bar would be made from 1.5" x .25" walled DOM tubing. The bushings were standard polyurethane CJ rear shackle bushings. These bushings have a 1" OD and a 1/2" id and are about 3" wide overall. 1/4" x 3" mild steel was purchased for the mount on the axle end and the mounting tabs for the cross member. The shackles from the old bar were re-used.
The next step was to give some thought to the design. My thought was to make the bar longer. Some of the bars I'd help build after my original bar had been longer and had no bouncing, so it seemed like a reasonable thing to try. I also wanted to be sure to put the shackle under tension and I needed to fit the cross member as high as possible while still staying below the exhaust pipe.
When the actual building began I started with the mount for the axle end of the bar. I tried to make the bushings as far apart as possible without hanging the lower bushing below the axle tube and without risk of hitting the upper end of the mount on the floor at full compression. I made some templates for the main mount pieces out of cardboard and did some measuring. Everything seemed OK, so I cut the actual mount from the .25" thick mild steel and tack welded the main parts of the mount in place. More bracing would be added after the bar was finalized.
|Removing the old ladder bar mounts.||There is no need to make the bar hang below the axle tube.||Cutting out the new mounts. A card board template was made first.|
|Attaching the new mounts to the axle.||The mount on the axle after the bracing was added.|
The cross member at the forward end of the bar was one of the simplest parts to make. 2 side plates made from the .25" mild steel were clamped to the frame rails, then the length of the bar for the cross member was measured and cut. Angles were cut on the ends of the bar because the frame is angled inwards at this point. Once all the metal cutting was done the bar was tack welded to the side plates while they were still clamped to the frame. This ensured that the cross member would fit well. Bolt holes were drilled through the side plates and frame and the cross member was bolted in place. The final piece of the cross member was a 2.5" long piece of the 1.5" x .25" DOM tubing. This would be the sleeve for the lower shackle bushing. This tubing was welded to the cross member directly in front of the ladder bar mounts on the rear axle.
|The new cross member compared to the old.|
The bar itself came next. Three sleeves of the DOM tubing, each 2.5" long, were cut for the bushings on the bar. The rear bushing and sleeve assemblies were bolted in place on the axle mount. At the front, the bushings for the sleeve that was welded to the cross member were installed, then the shackles, sleeve and bushing for the forward end of the ladder bar were bolted in place. The weight of the Jeep was set on the rear axle at this point, so the bar would fit properly at static ride height. The first part of the bar to go together was the threaded parts of the F150 tie rod. The adjusting sleeve from the F150 was cut in half, fish mouthed and tacked to the bushing and sleeve assembly at the top of the shackle. The length of the main part of the upper bar was measured next and the bar was fabricated and tack welded in place. The lower bar was next. The forward end of the lower bar required a long sloping cut to mate it to the upper bar. Once the slope was cut and ground to fit the lower bar was tacked into place while everything was still on the vehicle. The vertical bars between the upper and lower were tacked in place next. Building the bar in this order and tack welding it together while it is in the vehicle and the vehicle's weight is on the axle ensures that the bar will fit properly.
|The threaded part for the leading end of the bar. This allows the bar to twist when the axle articulates.||Test fitting the mounts and the upper part of the bar.||The forward end of the upper bar.|
|The F150 tie rod stub was welded to the upper bar.||The completed upper bar.||The lower part of the ladder bar ready to be tack welded into place.|
Between the time I built the bar and the writing of this article I've had the opportunity to test it at the Badlands OHV Park in Attica Indiana, at the RPM 4x4 event in Wisconsin and on private land. I've been very happy with the new bar. It controls axle wrap without binding the suspension in any way, and the bouncing problem appears to be greatly diminished.