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post #1 of (permalink) Old 11-05-2002, 09:02 AM
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Boxed frame vs AFW for \'74, strength differences?

I am redoing a '74 CJ-5. Planning on keeping the stock (but improved, CTM, etc) axles, and going the 5.0/NP435/D300 route. I wheel in AZ, but not crazy rockcrawling stuff.

My question is how much difference is their in strenght between my frame boxed out properly and an AFW with the nice mandrel bend tubing. My frame has all of the regular cracks expected in this model, but is an AZ frame and has NO rust.

I would love to go with the AFW, but $$$$$ [img]images/graemlins/shocked.gif[/img]!
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post #2 of (permalink) Old 11-05-2002, 09:48 AM
 
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Re: Boxed frame vs AFW for \'74, strength differences?

I decided to box my 81 because of the $$$$ plus I decided to make it a low budget project.You can read about it here
My home page

My feelings are that the boxed frame would be stronger because you end up with the 3/16" thickness all the way through where with the bent ones the metal gets streched and is made thinner. But I'm not a engineer so I may be wrong and I'm sure I'll get set sraight if I am [img]images/graemlins/wink.gif[/img]

I came across this and found it interesting and it made sense to me.Would some of you guys that are more knowledgeable take a look and let us know what your thoughts are?
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post #3 of (permalink) Old 11-05-2002, 11:21 AM
 
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Re: Boxed frame vs AFW for \'74, strength differences?

I am in the process of boxing in my 85 CJ7 frame. I choose to order the frame plates from M.O.R.E. both front and rear. I am very impressed with the fit and size. 3/16 inch steel, with all the holes matching up perfectly. I have some pictures I can post, if anyone is interested let me know. Here's the MORE url.
http://www.mountainoffroad.com
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post #4 of (permalink) Old 11-05-2002, 11:37 AM
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Re: Boxed frame vs AFW for \'74, strength differences?

Looks to me like that Matkins page was written by one of the Klinton Spinmiesters.

The AFW frame rails are not as tall or as wide in the center as the OEM. I AM an engineer and I just swapped my OEM for an AFW and I cut up the old OEM and can see the cross section. I've got no doubt that the AFW is stronger than the OEM. Taller and wider aren't stronger if the metal is thinner and the OEM is light gauge and real light on the inside.

From what I've heard about Matkins, mostly on this board, I wouldn't touch one. You can read about my experience with AFW, there was a problem with the trucking company that delivered it. First it was lost and when it became found, it was damaged. AFW built me a second frame in a week and gave me free paint because they felt responsible for the delivery problems.

As far as the original question, yes you could build a stronger frame than the AFW. I would not suggest starting with the OEM frame, just reuse the body and shock mounts etc. On the downside, most non-structural engineers have a tendency to overbuild. Welding a bunch of pieces together isn't good for strength either (Matkins or homebuilt), certain areas need to be gusseted.
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post #5 of (permalink) Old 11-05-2002, 04:08 PM
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Re: Boxed frame vs AFW for \'74, strength differences?

My original CJ-7 frame was two pieces of "C" channel welded together to create a "boxed" frame from the factory...but the "C" channels are .090" and .060" thick. The AFW frame I got is one piece of 3/16" or .1875" tube (per rail) and has to be much stronger. Their welds are first rate and everything fit on mine.
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post #6 of (permalink) Old 11-05-2002, 10:15 PM
 
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Re: Boxed frame vs AFW for \'74, strength differences?

My only problem with boxing the old frame, is metal fatigue already exists on the old frame which is why it is cracking in the first place...So you are welding new steel to already fatigued steel,it may crack at the old steel side of the weld...or may not.
Having pondered this on many occasions I would go for the AFW frame painted on the inside with Hammerite paint after degreasing it.
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post #7 of (permalink) Old 11-06-2002, 07:35 AM
 
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Re: Boxed frame vs AFW for \'74, strength differences?

I was wondering if that wasn't just a bunch of mumbo jumbo on the watkins site. I guess it would probally be a good strong frame if things lined up. I take that as a miss type then Taz you mean you "wouldn't touch one" correct?

So then are you saying the way I'm boxing and reinforcing my stock frame that it won't be a strong frame? (compaired to stock)
Why would overbuilding be a bad thing?
Why should I listen to you with only 3 stars anyway? [img]images/graemlins/grin.gif[/img]
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post #8 of (permalink) Old 11-06-2002, 09:59 AM
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Re: Boxed frame vs AFW for \'74, strength differences?

</font><blockquote><font class="small">In reply to:</font><hr />
I take that as a miss type then Taz you mean you "wouldn't touch one" correct?

[/ QUOTE ]What are you talking about? That's what it says, well since I fixed it anyway. Thanks for catching that, I wouldn't want that to go down in the annals of history wrong. Besides, CUT ME A BREAK, I just turned 55 today.

I'm not sure what you are doing exactly, but I suspect you are doing some good. Hot rodders boxed frames for years and it was a good thing, of course a new frame is better but they weren't available at the time.

As to the overbuilding, the frame gets to be a lot heavier weight wise than it needs to be and it gets too rigid, not allowing any frame flex. To demonstrate the latter, while I was working at the GM Leeds Plant, a body shop foreman's new car came through on the line. He had it pulled into a repair hole and they double welded it, putting a weld between each existing spot weld. His Monte Carlo rode worse than the typical Jeep. Because he bought it through the Class A employee plan, he had to keep it 6 months. The day the 6 months was up, that car was gone.

If you've got the time, the patience and the means, go for it. What could you loose? For strength, the pieces you box it in with are best if they are a continuous piece from end to end but putting in a few plates, even only an inch wide, at various places would improve the stock frame. Naturally, using a continuous section from end to end means cutting all the cross members loose and having to square the frame when you weld them back in, probably something you don't want to do.

One word of caution, don't make long continuous welds, you'll warp the frame. If you have a way to clamp the frame down, that is good, but it will still be warped if you weld wrong. I'd stitch weld the whole thing and then go back and weld a little here and then a little over there, a little on the top and a little on the bottom.
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