Extending a Jeep frame. How?

Hello all,
Im a newcomer to this group and I need advise on the feasibility lengthening the chassis of a 95 Jeep Wrangler (YJ). Ill need to cut and
lengthen the frame 10 right in front of the real spring hanger. Its a box frame 4mm thick. The problem is that I have no idea whats the proper way of doing this design wise. The way I see it with my limited experience is just to make a straight cut, add the 10 extension from a donor frame, re-weld the whole thing and weld some support plates vertically over the welds.
Will this hold? I hear that you shouldnt make vertical cuts and welds in car frames, yet I see this all the time on race cars. Also the service manual of the Jeep says that I shouldnt weld near the corners of the frame box. The jeep is usually heavily loaded and driven on very harsh terrain in the Sahara for long periods of time, so I need this to be bullet proof. Any advice, pointers to web pages or books would be appreciated.
I have an oxyacetylene setup, a 140 Amp Arc welder with a plasma cutter on the way. Im a welding newbie but practicing hard to be able to tackle such a project. Is this something that I can do when I practice enough or should I leave it to a pro?
Thanks. A.B.
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Trying to make a YJ Scrambler? Sounds like an interesting project. Are you looking to swap the body or just extend the tub?
Jim
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Jim Meyer wrote:

What I'm thinking is getting close to the wheelbase of the Scrambler but with very little overhang. The body will remain as short as it is, just wheelwell relocation to accommodate the new tires location. Part of the wheelwell will actually extend behind the body. The new empty frame space behind the body will accommodate a frame mounted structure a la tire carrier style that will hold 2 spare tires, 2 jerry cans, 4 sand mats, hi lift, shovel a small propane tank and a small CO2 tank. Sounds nuts ? :)
The reason for this is: 1) A lifted YJ fully loaded of expedition gear and supplies handles very badly on the road as well as off-road and the extra wheelbase will provide some extra needed stability. 2) Mounting all this extra weight on a regular tire carrier would be asking too much from it no matter how it will be built. 3)I don't like roof racks. Having the weight so high produces an uncomfortable amount of weight shift crossing dunes not to mention the center of gravity that will go through the roof.
A.B.
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    Greetings and Salutations....
On Wed, 08 Dec 2004 18:13:14 +0200, "A.B."

    I have not done this myself, but, from what I have seen, and my general experience with joining materials...I would NOT just do a vertical cut, if I could avoid it. A scarf joint of 45 degrees or so would probably be better for distributing the forces.

    It may or may not hold. It depends on the quality of the weld (not to be TOO much of a smartass *smile*). I suspect that the really good reason the manual says don't weld near corners of the frame box is because those are stress points, and, screwing up the heat-treat of the frame there is NOT a good thing.

    Hum...I don't know that *I* would be comfortable welding up such a project, mainly because hiking through the sand and sun for long periods of time because a frame weld has broken is NOT way up on my list of "fun things". How do YOU feel about it?     My other question is this: Do you want to have a hobby of BUILDING a sandcrawler? Or do you want to go blasting across the sands? If the former...then in a year or so, after you have almost practiced enough, you probably could build it. If the latter...then bite the bullet and pay a pro to do it.     Regards     Dave Mundt
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Dave Mundt wrote:

My feelings exactly :)

It's sort of a crawler but not quiet. I drive with caution and enjoy the scenery but crossing dunes is another matter and we do a lot of that. I'll always have to speed up considerably and try to go above the top smoothly. The front wheels don't go airborne more than a few inches on purpose but the frame should be able to handle the landings if they do.
A.B.
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Just thinking out loud, I'm not an engineer but have takes a few statics & strengths classes. You might see if you can get a piece of box steel that fits the inside diameter and is longer than the 10" piece you are trying to extend with for added support and then also weld plates on the vertical sides, maybe even C shaped sections. Maybe some slot welds could be useful in this application? My personal opinion for the type of welding needed would be MIG or stick with lots of practice welds on similar metal/thickness to determine proper penetration, etc.
Having just learned to weld in the past 3 months (in a class not geared toward certification), I personally wouldn't put my hands on anything structural yet even though I'm turning out what my instructor calls some mighty fine welds. You need to understand many things when it comes to structural welding. I've seen more than one metal sculpture with welds that have failed due to poor welding or what the instructor calls "gluing".
-Tom

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I agree I would not make a straight cut. I would cut a tongue in one side and a groove in the other. This will increase your surface area and not give you a straight up and down joint to stress. The tongue will be pushing down on the bottom of the groove or pushing up on the top. After you have that finished and ground smooth I would box the frame around that joint with C-Channel. Not that expensive and worth the piece of mind in my opinion.

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TT wrote:

How would you fix the internal box in place? rose butt welds? Also I don't think I can find the correct size, is it a problem if I bend a sheet into a C section and box it and use that as the internal box?
I thought spot welding can only be done on thin sheet metal!

I understand the importance of the subject but read very little about it. Any idea where can I find more about it? Books, web sites?
A.B.
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in

Plug welds. Weld the edge of a hole to the inside metal.
Rosebud (looking) welds -I guess- is what you meant.

It does seem like a pretty ambitious first project. ;)
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SLOT welds, not spot welds. Slot welds are where you drill a hole or slot in the material and weld in the hole or slot.
So you would drill a hole (or slot) in the frame so you can see the internal box section where it extends past and then weld around the perimeter of the hole in the frame thereby welding the frame & box section together.
-Tom

&
that
to
useful
metal/thickness
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Due to ill health I haven't been able to do much work around the place for a fair while - my mig welder and auto helmet have been sitting in the shed unused for the past two years or so.
I now need to knock up some frames, and am wondering if my helmet will be still OK - I am not sure how these work, but assume there is an internel battery that gets charged by light - but being in the dark shed I presume it will have gone flat.
So that I dont get a nasty eye dose the first time I try it, is there a way of making sure it will darken safely?
Cheers
David
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Go outside and look off to the side of the sun (or bright light) with the helmet on.
Now wave your hand in front of the helmet.
If it works it should flash between dark & light.
If you wave your hand fast enough it should stay dark all the time.
-Tom

a
unused
still
that
gone
way of

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Leave your hood (helmet) in the sun for A few hours to charge the battery and than use a "scratch" (a spark lighter) in front of the lens while you have the hood on. If it is ok it will darken when the scratch is lit.
Good Luck! H.R. "There is A fine line between "hobby" and "mental illness". Dave Berry
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David
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Thanks everybody for your input. I appreciate it.
As advised by most, I will probably do the frame extension in a few month after doing a few projects first. I will go ahead with the rebuild of the Jeep right away though. I did suspension work before and it turned out good if I may so myself.
Thanks again.
A.B. ShortWheelbase.com
TT wrote:

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Have a look around this site http://www.pirate4x4.com/forum/ there is lots of information and examples of extended frames. One word of caution is that if you just start asking questions they will call you a "newbie" and tell you to search. Lots of good information, lots of bad attitudes.

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