ZJ buildup/ 4-link/ unibody tech

[Elliott]

First of all let me preface this by saying I am not by profession an engineer, fabricator, welder, or mechanic. I am a full time bio-chem student. All information presented in the successive posts are simply my advice with minimal theoretical proof of proposed concepts. Take the following with a grain of salt. Please critique as you may, advice is always appreciated.

I have been wheeling my daily driven ZJ for a few years now and it has more than served me well at Uwharrie, Tellico, DPG, etc. In the next couple of weeks I will be doing quite a bit of work that will be documented here and at www.mallcrawlin.com, both being great sites for technical information. This build will come in a few different stages and hopefully be done by the beginning of January.

1.) Clayton MFG longarm kit
2.) DOM 8pt interior cage
3.) Currie anti-rock/ KORE beadlock rings

Here is the rig as it sits now. 98 ZJ/ 8.8/ HP30/ 4.56's/ spool/ 35" BFG M/T's /5.5" JKS lift/ custom rear bumper/ Carolina poop shop front bumper / along with other things.

Onto the buildup....

 

[Elliott]

1.) Clayton longarm kit

Anyone who wheels ZJ's has heard the name Clayton Offroad before. They make, in my opinion, the best longarm kit that available. However I think I will be modifying it a bit to tailor to future needs of the vehicle and for bling factor.

All ZJ's/XJ's/WJ's/KJ's are unibody, meaning the frame and body are in itself one piece. It is a cheaper way of mass producing vehicles which is all Daimler Chrysler cares about. Trying to design suspension around this can be very tricky but thanks the the popularity of the 4x4 sport almost every approach has been conceived and executed. Manipulating the unibody is inevitable when building one of the afformentioned rigs into a capable crawler. For all information on welding related to the unibody, please take a moment to read the Unibody Welding Bible. Thanks to a good friend of mine Kris Fraser for the comprehensive research on unibody strengths and how to modify them.


Option A: Sleeve the frame rail with chopped 4x4 3/16". Plug weld throughout. This is pretty easy to do with the correct tools. This is pictured below. Graphically shown: Green area being the ZJ frame and the orange part being new sleeve.

Option B: Weld a smaller size SUBFRAME onto bottom of existing unibody. This is what the Clayton kit uses. Links are not as easily mountable to this type of setup and you lose approx 1" of clearance at the frame. Also a pic is shown below.

 

[Elliott]

The plate on the ends are used for the analasys. The force to the frame rail is applied to the 2" portion sticking off the right side. The frame rail is anchored and the opposing end from where the force is applied. The force is 1000LB. This is the deformed DIY Sleeve (option 1).

And here is the subframe (option 2).

If you look at the numbers to the right of the framerails you can see that the subframe actually moves less. This was surprising to me. These aren't exactly the same forces applied while wheeling but it gives you an idea of its strength. Tests on torsional rigidity would need to be run to get a more comprehensive analysis of its true strength. (Thanks to Kris for crunching the numbers on software I can't afford. )

I know this is probably boring for 99% of the readers on here but this kind of stuff really fascinates me and I'm sure someone will have a good appreciation for it. I will update this thread tomorrow as more work is getting done.

T-minus 38 days before I want to be done with all of this. Enjoy.

-Elliott

 

[Falko]

If you look at the numbers to the right of the framerails you can see that the subframe actually moves less. This was surprising to me.

Increasing the moment of inertia (moving metal farther away from the neutral axis of the beam) will inrease resistance to bending forces.

 

[shawn]

Increasing the moment of inertia (moving metal farther away from the neutral axis of the beam) will inrease resistance to bending forces.

Exactly. See ppl try to build shit out of 3/8" PL all the time, when some 11ga with a nice, tall section would be stronger, lighter, and cheaper.

 

[Elliott]

Increasing the moment of inertia (moving metal farther away from the neutral axis of the beam) will inrease resistance to bending forces.

I knew I should have stayed awake in physics last semester. That actually does make alot of sense if analyzed theoretically, I need to stop assuming! Thanks for the input.

 

[benXJ]

very interesting...i will def. check for updates...i still like the sleeving idea. will that (sleeving) help more with torsional rigidity? i need to do something to my frame if I keep wheeling.

 

[UnCDuDe2004]

Man Elliot, hope you have some real good friends helping with this.....

Brad

 

[spykosshow]

You done yet?

 

[Elliott]

After 2 days of grinding, welding, wrenching, pounding, jacking, cleaning, breathing in 10 pounds of paint and metal particles it is finally done. Well I guess its 95% done. I had to hack the exhaust up to have clearance for the rear uppers. I wil be replacing the Flowmaster 40 with a smaller Magnaflow unit. Also I had to chop off the sliders mount on the rear. These being welded all the way onto the unibody made this a pain in the ass to say the least. I'll attach those again at some point.

All I can say is wow. It rides better than it did when stock. I took a buttload of pics during the install and we flexed it out on the forklift. I am going to post the pics later tonight as the cord to my digi cam is in Chapel Hill.

Also.. big thanks to Richard (sharksanddanger), Brad (UncDude2004), Zach (muddin150), and Dave (BigDaveZJ), without whom I would still be taking off the first bolt. Thanks guys!

 

[braxton357]

Exactly. See ppl try to build shit out of 3/8" PL all the time, when some 11ga with a nice, tall section would be stronger, lighter, and cheaper.

Very true. On the other end though, you also lose ground clearance and something hitting .120 wall will do a lot more damage than hitting .375. Things to think about.


Either way, that heep has come a long way and will be pretty rocking by next year. Why didn't you just go ahead and build your own radius arms rather than buying?

 

[Elliott]

Either way, that heep has come a long way and will be pretty rocking by next year. Why didn't you just go ahead and build your own radius arms rather than buying?

Yeah its a little different. Still a turd though. I was going to buy the complicated parts of this kit and build the rest, but Clayton remembered me from Grand Slam East and gave me an offer I could refuse. One day I'm sure I will build a kit completely from scratch, I just don't have the time to do that now, being a full time student.

 

[Elliott]

Well we got started on this on friday at around 5:00 pm. I had class earlier that day and Richard was shopping for a SuperDuty.... lucky bastid. Anyway here is the kit in its entirety. Clayton's 4 link hard arms.

Getting everything off the ground to work on.

Grinding the mass amount of undercoating off of the unibody framerails is a real beeyatch. They pack that on thick at the factory.

Had to cut the rear mounts of the sliders off, this took more time than anything else. Definatley should have bolted these on 3 years ago but hey they're off now.

Got the tranny crossmember, front LCA brackets and subframe welded on. The subframe is stitch welded as-per the directions. So I guess it will be fine

 

[Elliott]

After that was done we moved onto the rear. The rear was much more work. No matter how flush you plasma the mounts off there is still going to be ALOT of grinding. The rear trackbar, and upper control arm mounts have to be chopped off to make room for the new truss.

After setting the lowers at 32.5" I adjusted the uppers in correspondence to the pinion angle at 11*. Now time for the new truss. Richard's welds are QUITE nice.

 

[Elliott]

Heres how she came out...

The only 2 incidents we ran into was the rear mount on the sliders interfering with the control arm mounts. Grinding those off took forever. Also while grinding down the trackbar mount that was plasma'd off, I knicked the stainless brake line so I had to get a new piece, bend it, flare it, install it, and bleed the brakes. Annoying but not a big deal.

Overall I am very pleased with the kit. Now with some longer shocks I will be riding nicely on the trail.

 

[Elliott]

My favorite pic.

 

[CJ2YJ2TJ]

purely badass. thanks for sharing the pics and info

 

[GMAC]

i like it. it looks very nice just hangin out on the floor alone. looks like flexes pretty good

 

[Hammerite_05]

looks good man!

 

[sharksanddanger]

get those shocks and lets get out and wheel that thing..

 

[jeepbme]

Might have trouble gettin an Inspection Sticker on there with that exhaust

 

[Wolfpack OffRoad]

Very nice! Thanks for making the rest of us jealious.

 

[1stgenxxx]

nice ride man....keep the pics comming

 

[Elliott]

Tested out the new suspension today on a little shakedown run to Uwharrie. Everything worked flawlessly, with the extended wheelbase I have a good amount of trimming left to do, especially in the rear. But it worked great, I am very happy with how it worked, I just need to fine tune a couple things.

 

[Joel]

The ZJ really looked good today Elliott. I like what you have done with it.

Got a link to the rest of the pics you took today?