Boulder Bars

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Colorado Special Boulder Bars

Tools Used

Just about everything imaginable!
Welder, 1/2" chuck drill, 1/2" x 16" drill bit, drill press, air wrench and sockets, jack, jack stands, grinder, die-grinder and cut-off wheels plus prolly a whole bunch more!

Fabrication

The concept is fairly simple. A flat steel plate with two standoffs supporting the boulder bars and attached to the frame with 4 1/2" grade 8 bolts. The steel plate and vehicle frame would have to be drilled and the steel would have to welded. The body would need two notches where the support members attached the bars to the plate.

Installation

After a few false starts, we finally got a real clue for what we were doing. The original plan was to use 1/4" steel plate and tube to build the bars and grade 8 bolts and washers to attach the finished bars to the frame. We followed this plan with only minor changes when we encountered problems. We achieved the best results by building the bars in modules, not moving to the next step until the first was completely worked out.

As a first step, we took a sheet of 2"x4"x 1/4" plate and notched it front and rear where the body mounts attach to the frame. Then the plate was attached to the frame using clamps and the location of mounting holes marked with a permanent marking pen. We needed to take care in marking the holes because brake and gas lines run down the inside of the frame. Once the mount holes were marked, the plate was removed and drilled on the drill press, 3/4" up from the bottom and centered on the mark. Re-attaching the mounting plate to the frame, the pre-drilled holes were used as a guild to drill the frame. The long bit (16") was used at this point to make it easy to get all the way through without hitting the body with the drill.

Next came attachment of the standoffs, fabricated from 2"x4" 1/4" steel tube. These were cut to about 6" length (just enough to clear the body and put the boulder bars in final position) and were welded to the frame plate about 1/4" up from the bottom. With those in place, the seam on the rocker panel needed to be trimmed, so they were again placed into position of the frame, and the edges marked with a magic marker. Just a few short minutes with the die grinder and the cut-off wheel and the rocker panel was notched and ready. After a final check for fit, the main boulder bars were welded on to the growing assembly. To add a to the looks, Corbin and I both elected to have tapered ends on both ends of the bars, while Keith and Jeff just wanted tapers on the front with flat backs.

After final shaping, welding, grinding, cleaning, primer and paint we were ready to attach. At this point we found that the holes in the frame weren't always straight, but were close enough that with some patience you could get each bolt fairly flush. We also found that a backing plate was necessary to keep them from pulling through or crushing the frame. We used fender washers as backers to provide more area for the bolts to pull against. We also had to deal with the brake and gas lines. Corbin fabricated some standoffs that attached to the bolts, while I opted for zip-ties to just move the lower lines up and away from the nuts. On the passenger side, we had broken the factory line mounts (they are only plastic) so I created my own mount by attaching a zip-tie to the rubber on the muffler mount. Seems to work just fine.

Full assembly took 3-4 people working 6 or more hours a day right around 5 days to complete 4 sets of bars. Actually, it didn't take that long, we just took a lot of wrong trails, and once we had a good concept, assembly went fairly quickly. Building more sets, we could probably complete a single vehicle in under 4 hours with 3 people. We also found a design flaw. The body mounts compress when going over bumps, and let the rocker panels compress onto the support bars. This results in a loud "thunk" and a strange bottoming out feeling. Thankfully after a few good bounces at Moab, the cutouts conformed enough that the body no longer contacts the boulder bars. Corbin and I were the only ones to have this problem, and mine disappeared after about an hour on the first trail.

A picture of the final assembly can be found here.

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