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post #1 of (permalink) Old 02-12-2004, 02:50 PM Thread Starter
 
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frame stretch advice wanted

O.K., first off I know I should have run this by you folks before I started.....but the fact is I didn't, so I'm doing it now.

I'm stretching my '76 CJ-7 frame and body 17''. I cut the frame in front of the forward rear spring hanger. I had my local metal supplier form some 12g into C-channels, 33'' long, they will be inserted 8'' inside the frame, and plug welded through holes in the original frame. Then (2) 17'' channels, (1) 12g and (1) 3/16'', will be fitted over the top and plug welded to the inserts and butt welded to the cut frame, as well as welded to each other.

So, my questions at this point are.....
1) Does anyone see any glaring mistakes in the overall plan? (Besides all the overlap surfaces, which I don't see a way to avoid. Weld-thru primer will be used.)

2) (This is my main concern at this point) How much plug welding do you feel is needed to adequately secure the inserts to the original frame?

I was thinking about (4 or 5) 3/4'' holes in each side face,(approx.4 1/2'' x 8'' surface) and (4) 1/2'' holes in each top and bottom.(approx.2 1/2'' x 8'' surface) I am not sure if that would be enough. Obviously I want to get enough holes drilled through the frame before the inserts are in. I don't have any bits bigger than 1/2'' so I will be getting a uni-bit or something for this job, and want to make sure what I get is big enough.

Thanks for making it to the end of this post. If anything is unclear, pipe up and I will try to explain things better.
I welcome all comments, criticisms and questions.

Below are links to a couple write-ups that have inspired me.
Rick Neil's looong cj
Rock taxi
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post #2 of (permalink) Old 02-12-2004, 04:56 PM
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Re: frame stretch advice wanted

I would think JB Weld or Superglue would hold just fine. I've seen the videos of Superglue supporting a man's weight with his hard hat......

Actually, I am just bumping you back to the top, since this is something that has crossed my mind several times.
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post #3 of (permalink) Old 02-12-2004, 06:21 PM
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Re: frame stretch advice wanted

I've been thinking of doing this exact same thing (when I get my new axles). If you wait a year I'll tell you how it went. And if you wait another I'll tell you if it held up.

Actually I was thinking of making the break/extension in the frame right where the frame currently ends. My thinking is that there will be less leverage on the splice the further it is from the center of the vehicle. But I'm a dumbass and you shouldn't listen to a thing I say.
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post #4 of (permalink) Old 02-12-2004, 06:56 PM
 
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Re: frame stretch advice wanted

Meh.. 4 link, it.. then you can put the links/ 1/4 elip. part on the good frame and build some tube stuff for the rear.

Easy stretch without sacrificing strength.
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post #5 of (permalink) Old 02-12-2004, 07:29 PM
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Re: frame stretch advice wanted

Your saying 4 link w/ coil springs? Thought about that too, but I'm not sure on my ability to fab a 4 link. I don't know about (or have looked into) the geometry.

Javajeeper, how far along are you?
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post #6 of (permalink) Old 02-12-2004, 08:05 PM
 
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Re: frame stretch advice wanted

If you can do a frame stretch.. im sure you can do 4 link.. geomerty is just a matter of getting pencil, paper and ruler out..

I've even seens osme people do without.. although their anit-squat and torque steer are noticible.
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post #7 of (permalink) Old 02-12-2004, 08:46 PM Thread Starter
 
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Re: frame stretch advice wanted

</font><blockquote><font class="small">In reply to:</font><hr />
Javajeeper, how far along are you?

[/ QUOTE ]
Past the point of no return [img]images/graemlins/ooo.gif[/img]
The frame is stripped and cut in half. The above mentioned pieces of steel are sitting next to it. A little more prep inside the frame... bore some holes for plug welds... and I'm ready to measure, fit, measure, tack, etc. I just picked up a cheap holesaw set at a pawn shop for 2 bucks...so I'll try that out and see how it works.

I'm really just planning a sua spring lift. This thing's going to be a DD/moderate trail rig, so I'm trying to KISS and still have a rig that works for what I need.
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post #8 of (permalink) Old 02-12-2004, 09:40 PM
 
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Re: frame stretch advice wanted

This is what I do,,,,,,,Draw out the frame rails and crossmembers on the floor of your shop before you start welding. Make sure the drawing is exactly what your going to do and it is exactly "square",,,,the front and rear axles need to track correctly. Line up the frame over the drawing and plum line down to it. I also run a string line along the bottom each frame rail from the front to the back as a reference point and measure from this line to different points vertically before I cut the frame and then match these points then welding the extension (but you have cut it already, so find another jeep like yours to get the measurements from).

Hope this helps
[img]images/graemlins/beach.gif[/img]

Another way, is to use two frames, cut one at the rear spring hanger and use the front half of that frame. Cut the other at the forward most, skidplate/Tcase mount hole and use the rear half of that frame. Sleeve the two halfs together with a 2' long rec tubing inside each half. You need to "squeeze" the width of rear frame half alittle to line-up with the front(I used a "come-a-long"). It looks like it came from the factory that way [img]images/graemlins/grin.gif[/img] .
The rear frame section was from a head-on wrecked jeep,,,,,,so it was free.
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post #9 of (permalink) Old 02-13-2004, 01:18 AM Thread Starter
 
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Re: frame stretch advice wanted

Hey thanks PYRO. That's [img]images/graemlins/goodpost.gif[/img] ... very helpful.
I took loads of measurements before cutting, and also have the FSM with the frame alignment specs, it outlines the plumb-bobbing technique.(not exactly like your method, but I think I'll combine the two.) I feel pretty good about the alignment.

As far as the sleeve goes....not so confident. Could I get your advice on how much of that surface area you think should be welded?
Thanks again.
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post #10 of (permalink) Old 02-13-2004, 02:32 AM
 
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Re: frame stretch advice wanted

I wouldn't plug weld it at all. You'll be putting all the stress on the plug welds instead of spreading the stress load over a larger area. I'd use a 33" long or longer length of 1.5" x 3" rec tubing with at least 3/16 wall inserted into each side rail for the main lengthening pieces. The more tube you can insert into the frame, the more the stress load is spread out and the stronger it will be. You'll need to blow out the "captured nuts" on the inside on the rail that the stock skid bolts too, you can weld in another nut into the insert at the correct location before you install it into the rail. Where you already cut the frame will limit the amount you'll be able to insert in the rear section because of frame rail bending up over the axle. You want the rec tubing insert to be a very tight fit into the frame rail,,,,,If it is a bit loose, weld a few bead lines down it's length and grind to fit. I like to make them so tight, they need to be driven together with a sledge. Weld the joint of the rec tube and the frame rail. After the inserts are welded front and back, grind these welds back and overlay channel on the insert to match the original frame, welding all seams. Then overlap the inside(the side facing the Tcase) and top with 3/16" flat bar stock, 2" wide for the top and 4" wide on the inside. This bar stock extends a few inchs past the rec tubethat is inside the frame rails and weld at all seams. Whe sandwiched layers with alternating weld points will add to spreading the stress load over a larger area. I know this sound like alot of steel But it is needed in this area of the frame, even the original frames are prone to cracking in this area. Then it's done, it's very strong and clean looking.
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