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Homebrew 3 link - Project Forman

Old 12-26-2017, 10:19 PM
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Default Homebrew 3 link - Project Forman

This thread is kind of an offshoot from my build thread on JF, but I thought I'd share it here. A month ago or so, with a small excess of cash, and a large excess of time I decided to embark on building a 3 link for the DD. Initially I clocked the T-case, and build a flat bottom crossmember out of some 2" x 4" x .250 wall tube. This netted me a completely flat bottom. Unfortunately I don't have a whole lot of fab pics from the crossmember. In addition to the crossmember wrapping up around the side of the uniobody, Five grade 8, 1/2" bolts tie each side on. I cut away the unibody frame and welded nuts inside to mount the crossmember.



The lowest thing on the jeep is now the exhaust, which I intend to take to a local shop to have them bend up a pipe that sits a little bit higher.



Starting on the 3 link meant making the one piece crossmember into a three piece, and making a small skid for the exposed crossmember bolts.




Two 5/8 bolts hold each side of the crossmember together, and 5 1/2" bolts mount it to the frame. I tacked up lower control arm mounts in what seemed to be the best position I could get on the crossmember. and measured for the lowers.




After measuring for lower control arms and plotting it out in the 3 link calculator I figured out where I wanted the upper control arm mount and tacked it in place.



The next step was deciding on a lower control arm length. This decides where the tire will sit in the wheel well. While centering it seems like the obvious solution I wanted to extend the wheel base a little, and improve approach angle which mean moving it forward. With a length decided I tacked the lowers together.



The arms are 2" x 2" x .250 wall. This proved to be much cheaper than DOM when sourced locally and despite being less resilient to torsional load should be ~30% stronger when it comes to bending.

After a quick test fit I was happy with where the axle was, but realized the upper control arm mount wasn't going to work. Being tucked so close to the floor pan there was nearly zero up travel. A quick rework of the design and a run through on the calculator, and I was moving again. Dropping it an inch and a quarter gave me the up travel I needed and have minimal impact on handling effects.



The axle side of the upper link keeps the stock configuration of an axle mounted joint and the "fork" on the control arm. Not satisfied with just welding the 0.120 wall DOM to the fork, I welded a piece of 0.250 wall tube to act as a sleeve, and give a place to rosette weld to.



The mount on the axle side is a machined Currie johnny joint with 1/2" bolt, welded into a beefed up mounting tower from Cheap Jeep Offroad.



With the upper link measured for and tacked up I could run it through full articulation.








This is where it sits at the time of this posting. I plan on having everything burned in and painted by the end of the week. Later to come will be rotating the inner C's to improve caster angle, belly skids, and rock rails. Below is the BoM so far.

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Old 01-14-2018, 07:41 PM
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Default quick update

I got everything burnt in, and fitted up




I tested the waters slowly around the neighborhood, but before long she was up to 60 on a dirt road.




Handling characteristics are as good, if not better than before, and there's zero bump steer or wobble. There's a slight tendency to dip more on the driver side under heavy braking, but not enough to bother me. I haven't had a swaybar in since I did the WJ swap, but I think it's finally time to fab up a bracket for one as the jeep tips quite a bit more when turning.

I got the arms painted and reinstalled last weekend, and have been working on the unibody stiffeners today




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Old 01-19-2018, 06:09 PM
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Great work!
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Old 01-19-2018, 08:05 PM
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Awesome! Thanks a bunch for sharing.
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Old 01-21-2018, 09:35 PM
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You are killing me. It's work like this that makes me cut my jeep up. I'm trying to keep it out of the garage and on the trails. Keep telling myself the short arms are fine, the short arms are fine.

Excellent work. Shown only the final product, I would assume it was supplied by a major vendor.
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Old 02-14-2018, 09:36 PM
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I recently tackled a tranny skid plate. The plate is made of 3/16" steel and the supports are 1" x 1" x 1/8"





Next to come is a transfer case skid plate. This will be a separate piece as the cross member is becoming a bit unwieldy. Still lots to take care of before Easter Jeep Safari!
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