post #1 of Old 06-16-2014, 06:00 PM Thread Starter
BLACKzj52
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1996 ZJ 
 
Join Date: Mar 2007
Location: ohio
Posts: 5,678
ZJ unibody welding question

Hey guys, its been a few months since I last posted.

Anyways, I have a few particular questions regarding welding to the ZJ unibody. I searched but did not really find anything that pertained to my particular situation.


Long story short, a couple years ago I had a friend of a forum member make a long arm crossmember for me because I was short on money at the time. As time went on I began to dislike this crossmember more and more and received the clayton xmember as a Christmas gift.

So now that it has warmed up I have gotten to work on cutting off the old crossmember and the clayton unibody stiffeners (because the clayton xmembe does not share the same dimensions as my previous one).


When cutting off all the old metal and grinding down the welds, I gouged the unibody frame rails a few times with my grinder and sawzall and am left with some areas that need repaired.


I'll post a few pics for visuals

old xmember and unibody stiffeners



Cut off and smoothed down




Test fitting the Clayton crossmember




Gouge where I cut off the old crossmember








Gouges in the unibody rail

^the big hole on the right side of the picture is my main concern




Now my questions:

1. Should I weld the gouges where the crossmember butts up against??

2. How should I go about repairing the other gouges in the unibody rails? Should I just weld them shut and them grind them down? Some of these holes are where the new stiffeners will be welded on if that makes a difference.

3. With having stiffeners previously welded on and welding on a new set, am I severely compromising the strength of the unibody (since the unibody was galvanized and heat treated/annealed from the factory)? Or am I over thinking this?

4. The ZJ unibody is 16ga where it a single layer correct?? And ~1/8" where two layers are sandwiched together (like where the crossmember mounts)?



I appreciate any input that could be provided. I just want to make sure I am doing everything correctly to the best of my abilities.



PS, here is my ZJ




- John - 23 and learning <-- ORIGINAL
- 1996 Black ZJ Limited: 5.9 swap, LA's, axles, absolutely built to hell
- 1998 Platinum 5.9 Limited: DD with some lighter modifications
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post #2 of Old 06-17-2014, 08:07 AM
el_magico
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1995 XJ Cherokee 
 
Join Date: Jul 2007
Location: Denver, CO
Posts: 92
See my responses to your questions below in red.

Quote:
Originally Posted by BLACKzj52 View Post
Hey guys, its been a few months since I last posted.

Anyways, I have a few particular questions regarding welding to the ZJ unibody. I searched but did not really find anything that pertained to my particular situation.


Long story short, a couple years ago I had a friend of a forum member make a long arm crossmember for me because I was short on money at the time. As time went on I began to dislike this crossmember more and more and received the clayton xmember as a Christmas gift.

So now that it has warmed up I have gotten to work on cutting off the old crossmember and the clayton unibody stiffeners (because the clayton xmembe does not share the same dimensions as my previous one).


When cutting off all the old metal and grinding down the welds, I gouged the unibody frame rails a few times with my grinder and sawzall and am left with some areas that need repaired.


I'll post a few pics for visuals

old xmember and unibody stiffeners



Cut off and smoothed down




Test fitting the Clayton crossmember




Gouge where I cut off the old crossmember








Gouges in the unibody rail

^the big hole on the right side of the picture is my main concern




Now my questions:

1. Should I weld the gouges where the crossmember butts up against??
Yes, you should weld the frame rails where you broke through while grinding. However, you will really need to think this through and possibly practice on some scraps. The material is so thin that as soon as you try to weld it, you may make it worse and you will have a bigger hole to fill. Adversely, if your weld is not hot enough, there will not be adequate fusion and welding will have no benefit. If you have an option to TIG the repairs you may have a better result.

2. How should I go about repairing the other gouges in the unibody rails? Should I just weld them shut and them grind them down? Some of these holes are where the new stiffeners will be welded on if that makes a difference.You are going to have to repair the damage done with the grinder, no doubt. First fix all the gouges the best you can. Since it looks like that new cross member bolts flat on the bottom, I would get some additional sheet metal and reinforce the rail. (I have attached a photo of what I mean. I would make the reinforcement parts "U" shaped to get both sides of the rail.) Drill some holes in the new plate so you can weld those areas to the frame rails. Then place a few short stitch welds along the edges and corners.

3. With having stiffeners previously welded on and welding on a new set, am I severely compromising the strength of the unibody (since the unibody was galvanized and heat treated/annealed from the factory)? Or am I over thinking this? The body of the vehicle was not galvanized. As for heat treating, it may have passed through a furnace while on the line, however it is likely that it had not. The welding that was done for the first set of arms and now the new set will definitely affect the areas and make them more susceptible to cracking later.

4. The ZJ unibody is 16ga where it a single layer correct?? And ~1/8" where two layers are sandwiched together (like where the crossmember mounts)?It might be a good idea to take a pair of calipers and double check the material thickness.



I appreciate any input that could be provided. I just want to make sure I am doing everything correctly to the best of my abilities.



PS, here is my ZJ

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1995 XJ Sport 4.0L (Nothing special to list yet)
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post #3 of Old 06-18-2014, 01:52 PM
kippo
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1998 XJ Cherokee 
 
Join Date: Mar 2014
Location: athens
Posts: 146
Thats all you can do is weld up the cuts. It is thin and you will blow through if you dont have your welder set right. If you can grab some scrap the same thickness practice welding some cuts up on it.
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post #4 of Old 07-09-2014, 08:36 PM Thread Starter
BLACKzj52
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1996 ZJ 
 
Join Date: Mar 2007
Location: ohio
Posts: 5,678
Apparently my reply never posted....


Thank you guys for the input.

I have since welded the gouges up. Turned out to be a pain, had to fish some 1/8" scraps into the frame rails where the gouges were and welded those to the existing metal. As I was doing this, I began to wonder if I had been too aggressive with the flap wheel on my grinder and removed some material from the rails themselves when grinding down the old welds. So I have come up with the idea of plating the single thickness area of the rails (between where the crossmember mounts and the rear LA brackets) with some more 16ga (just to go with the same thickness) and then weld the clayton unibody stiffeners on. AFTER welding the stiffeners on, I want to plate the rails from the A pillar support to the rear brackets with some 1/8" steel to stiffen the unibody up further and prevent future unibody failure/distortion from a very flexible suspension. The only thing I have to work out is where to make all the welds overlap because I will be hitting the inside of the plates and sheet metal with weld through primer to prevent corrosion. With welding the 16ga on I am thinking that I will just turn up the heat slightly on my welder and just weld directly to the "outer" piece penetrating both layers. Then with the 1/8" do some rosette and plug welds followed by some stitching.

Anyways, just throwing my ideas out there to see what you guys think. Ideas? Suggestions?


Oh also, I havent welded on the clayton crossmember on yet. I've done SO much practice welding for it but just am being overly paranoid I guess. I know I can do it.. I just cant decide which voltage setting to use on my welder (3 or 4)..

Maybe you guys can steer me straight?


So here are some welds with my Hobart Handler 210 set on a 4 (out of 7) with some different wire speeds.. Dont mind the blobbed up welds, when I began the welds I didn't hit the 16ga sheet in some spots so later on I went back and zapped it.. Made the welds look horrible but oh well.




close up of some of the good welds



And the edge joint. Blew threw in one spot so I had to fill it back in. On 4, it seems to undercut the 1/4" a little bit since its on the edge.




Welder set at 3
*Note* with my welder set at a 3, I have SO much more control and feel very comfortable with laying an awesome bead with this particular metal thickness/joint set up.








^^ I will definitely use the 3 setting when welding on the edges of the crossmember. Way more control, less undercut, better looking weld, etc.



And the joint setup (16ga sheet on top of 2x4x1/4" rectangular tubing with beveled edges which make for an interesting twist and is the reason for all the spatter





oh and heres from the top of the 16ga..


The welds on the top and right are with the 4 setting while on the left and bottom I used the 3.



So any input on which setting to use based off the pics?? I found two separate threads where people used their Millermatic 210 (very similar as my Hobart) set to a 3...

Again, sorry for the book.

- John - 23 and learning <-- ORIGINAL
- 1996 Black ZJ Limited: 5.9 swap, LA's, axles, absolutely built to hell
- 1998 Platinum 5.9 Limited: DD with some lighter modifications
My Build Thead
Facebook
Senior at The Ohio State University
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post #5 of Old 07-10-2014, 07:21 PM
thantos858
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1974 CJ5 
 
Join Date: Jan 2005
Location: Santa Maria
Posts: 1,636
Best way to tell on your current welds is to cut them in half and look. I have seen pretty welds with very little penetration into the surrounding metals.
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