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Old September 28th, 2006, 03:07 PM   #1
dngrous_Jeep
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Default Frame repairs?

Okay, since feedback on parting out this Jeep has been rather weak, I'm thinking I might rather build it as a trail rig, as originally planned. Here's a couple pics of what changed my mind to parting it out, but what will be involved in properly repairing this frame? I've crawled all over underneath, and these are the only two pad sections of frame. Can a new section of steel be welded in without removing the body? I know the leafs will need to be dropped, and the old frame/bumper will be removed. I'm planning on going to 2x3x3/16" steel, and cutting the old frame at the top of arch above the axle. It will have "splints" welded in on the sides, so to speak. Meaning, I'm not going to just butt weld the new steel to the old frame, it'll be reinforced.
Thoughts?

(and if you just say it's not worth it, scrap the Jeep for steel, keep your thoughts to yourself. I've heard all that before, although it was from a guy with a Vette in his driveway)




Oh, and the body will be replaced eventually. I just don't have the $1800 to replace it all right now.
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Old September 28th, 2006, 03:26 PM   #2
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IMO, you aren't going to repair that with the tub on.

If you sectioned the frame through that rust, there most likely isn't enough to weld securely to.

As posted in the other thread, first you have to figure out just how much rust your REALLY have. THat means cleaning the frame down to good metal and getting our your hamme rand chisel to find the soft spots.

If, and this is a big if.... IF is all 100% forward of that point, myself, I'd cut off the frame at that point, and refab a new rear frame section of 2x4x0.120 or 0.188 wall tube. Then weld fishmouthed scab plates over the seam.


But my gut feeling is that rot goes worse than it looks on the surface. And that possibly the top and very likely the bottom sides of the rail are also suffering internal rot.

I recently DROVE home a toyota that looked better than that frame, and it broke in half literally across the jackstands when I lifted it.

Also had an 81 CJ-5 with similar rot, same thing, I was standing in it, and the frame snapped in half, and it didn't have any perforations like those.

My current Toyota, I had minor rot in that area on the inner rails, about a 6-8" x 1/2" rusted/cracked area. To repair, I took it all down to bare steel, welded 1/8" plate covering the area 2 feet in each direction. all seams are at angles, and I also strapped the bottom of the rail with 1/8 flat stock, which is then seam welded to the plating.

Its held up well so far.
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Old September 28th, 2006, 03:34 PM   #3
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Quote:
Originally Posted by Haggar
If, and this is a big if.... IF is all 100% forward of that point, myself, I'd cut off the frame at that point, and refab a new rear frame section of 2x4x0.120 or 0.188 wall tube. Then weld fishmouthed scab plates over the seam.
#1. Why such thin metal? I prefer to weld heavier stuff.

#2. Not sure what you mean by "fishmouthed scab plates"?? Sounds like a Scandinavian delicacy... I was fully intent on welding plates over the seam, making the frame thicker at that point.

#3. If all else fails, what should I expect to spend on enough steel to build a new frame, if I kept it simple? As much straight lines as possible, 2x4 construction, risers built to adapt to the body? I've had some experience in fabricating things, although I never paid for the steel, so I have no idea what to expect it to cost.

#4. I was intending to build the rear section of the frame in a jig, and then weld it on as a subassembly, to keep everything square, and prevent twisting. Gussests are my friend. I'd be using a 4x4 piece of 1/4" thick box tubing as my rear bumper, and also an integrated trailer hitch. (I already have the steel for the hitch, I used to work at a place building hitch assemblies)

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Old September 28th, 2006, 03:38 PM   #4
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You should be able to get a frame cheaper than what the steel would cost you to repair it.

Have you checked the "good" sections with a screwdriver, like Jesus mentioned in the other thread? I have had plenty of Jeeps, and I know what a bad frame looks like, and what it takes to repair them. I had a Scrambler that I got from Craig that had rear rails that were better than those, and thought about back halving it because it was a Scrambler with a decent tub (Just the floors were bad) I decided it would be both cheaper and easier to buy a premade frame.
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Old September 28th, 2006, 03:43 PM   #5
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You should be able to get a frame cheaper than what the steel would cost you to repair it.

Have you checked the "good" sections with a screwdriver, like Jesus mentioned in the other thread? I have had plenty of Jeeps, and I know what a bad frame looks like, and what it takes to repair them. I had a Scrambler that I got from Craig that had rear rails that were better than those, and thought about back halving it because it was a Scrambler with a decent tub (Just the floors were bad) I decided it would be both cheaper and easier to buy a premade frame.
I didn't know steel was THAT expensive... Assuming I can weld in the new frame piece from the top of the wheel arch, I'd only need 64" or so of 2x3 steel, and maybe 60" of 4x4 steel....

I didn't check with a screwdriver, but I was beating the shit out of the frame with a heavy ballpeen hammer, and only surface rust was flaking off, just like anything on an old frame would do.

Other than the $1800 mandrel-bent option from Quadratec, where can I find a pre-fabbed frame? For less than the repair steel would cost, that is.....
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Old September 28th, 2006, 03:57 PM   #6
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Check the classifieds- frames generally go for around $100-$150 for a CJ5
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Old September 28th, 2006, 04:01 PM   #7
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Quote:
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Check the classifieds- frames generally go for around $100-$150 for a CJ5
Truth be told, I'm scared of pulling this body off the frame.... I have a feeling it's held on by rust, rather than bolts. And once I try to pick it up, it'll quite likely fall into two pieces. :tonka:
I'm gonna call the steel supply shop and pick their brains, too...

Steel shop said $67.08 after tax for 12' of 2x3 x 3/16". I figured rather than going with the 4x4 rear bumper, I could avoid the extra charge for cutting a smaller piece. So, that would be enough steel to have the rear bumper be made of 2x3 full-width, and probably all the frame work it needs. (assuming it's good frame in front of the rear axle, which I believe it is)

Last edited by dngrous_Jeep; September 28th, 2006 at 04:10 PM.
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Old September 29th, 2006, 10:31 AM   #8
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Well, the rest of the frame is solid. So, I'm going to work on getting the Jeep running, and then focus on frame and cage work. I've decided to go all-out redneck on it, and build a wooden bodytub, using only the firewall and dash from what it has now. Front fenders will be flat tube-style, stock hood and grille.
Sawzall blades are cheaper than new parts.
I'll post up progress pics, when it starts coming together.
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Old September 29th, 2006, 11:16 AM   #9
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Answers to a few:

Why such thin metal.... how thick do you think your frame is? My toyota frame is 3mm (0.120") on the outside and top/bottom and 2mm (0.080") on the inside boxing.

Most people do everything overkill, which is a waste of weight. Building half the frame stronger than stock just makes a weaker point at the junction to the old frame, and forces that old section to take more of the flex load. I prefer to not have one section of the frame significantly stiffer than others.


Fishmouthing means that any plate you weld to your frame should be shaped like this:

<

or like this:

>

It should not end in a vertical seam like this:

|

That will create a stress point that is more likely to crack. If you look at many factory frames that are not 100% boxed, the area where the boxing ends isn't usually a straight line, its often got a wedge cut out of it, like the mouth of a fish :-)

Also, Welding your frame changes the local crystalline structure and carbon content, which can make is significantly harder and more brittle in that area. More reason to take extra measures to avoid stress cracking.


A scab plate is a plate you weld over another weld. So, say you lop off the back fo the frame and then weld on a new rear section. You should then weld another plate, with the diamond and/or fishmount shape over that weld. That way that plate spreads the load out so its not all on that first weld.


I guess you just have to look at it all and figure whats right for you.

This winter, I'll be building a frame from scratch for my CJ3a, I'll post that as a write up. Early Jeep frames are so easy to fab, its not worth it to plate, box, and strap the old one. But it will be a few months...
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Old September 29th, 2006, 11:57 AM   #10
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You have some very valid points, and thank you for explaining it all so clearly. Hopefully the thinner box steel is cheaper, too.
The scab plate is pretty much what I meant, when I said "splints". I guess different terminology can confuse.
I also knew that welding changes the hardness of the steel.
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Old September 29th, 2006, 12:18 PM   #11
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Yeah, the 0.120 wall should be cheaper. I think a standard replacement frame from someone like matkins is 2 x 4 x 0.120" wall, unless you go for the extreme frames which are 0.188 wall.

Always here to help I need to dig out my old engineering books on all the different properties of steel, one of thes days.. martensitic vs austinic, etc..that was 14 years ago I did my mechanical engineering classes. Wow. I feel old now.
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Old September 29th, 2006, 12:48 PM   #12
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martensitic vs austinic, etc..that was 14 years ago I did my mechanical engineering classes. Wow. I feel old now.
Wow. I feel confused now.
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