beefing XJ unibody?

[XJHOX]

After reading this topic on P4x4 I have a few ?s. Is there any advantage to sleeving the unibody on the outside of the (frame?) as appossed to putting in a un cut piece of box in from the interior side? I know we have done that in alot of unibody race cars and it seems to work well when its all tied together. It would be more work in the long run but I think it might be a better platform when you have it all tied together with a interneal cage. Any thoughts from the guys that have done this? Thanks Jason

[Beezil]

"sleeving" is the way I've done it. Of course, you'd need a pretty damn big pressbrake to make your "hat-sections" though....

[RCP Phx]

I dont understand the question?????You can "box" the Uni-body on the outside,but you cant really "sleeve" it on the inside!

[XJHOX]

OK maybe I can try and clear up my ? I see people using what I would call a c channel on the outside of the unibody. Now is what we have done in a few cars is to cut along the inside (interior) top of the unibody and put in a piece of box tube in what would be the frame rail and then weld it up. When you tie it together side to side and w/ a cage its really stiff. I'm just wondering if anyone has done and if it would be any stronger.

[Beezil]

yeah, call it a "U" a "C" a hat section, sleeve whatever....i got you drift, and the answer is yes, it is a great way to reinforce the unibody.....

the question is, how would you make your channel?

making a hat section long enough to cap the framerail requires a lot of tonnage....consult a pressbrake tonnage chart to help you calculate the tonnage required to brake your channels depending on desitred length.....

I've seen one method, where a guy machined one wall off of a rectangular tube for his channels! talk about the long way around the horn, but if you don't have a big pressbrake, you gotta do something!

btw, I just broke some channels tonight, measured 3"x3.5"x3"x24"x.188 HRPO

required 80 tons with a 1" v and a 1/32" radius top.......

[KarmirXJ]

Ignorant Question:anon:

whats a pressbrake

[Beezil]

http://www.usedmachinerysales.com/picture/b0795.jpg

something like this.

[Ghost]

Damn, that would hurt your hand if you weren't careful!

[AZ Jeff]

Beexil's pic of a pressbrake does not do it justice, in that you cannot see how it actually operates in detail. Suffice to say that the area with the yellow/black diagonal stripes is where the flat sheet of metal goes through.

There is hardened steel die just below the striped area (it's the black thing running across the width of the opening.) Below the gap under the die I just mentioned is another mating piece. Once the steel sheet is placed between these two dies, the upper piece is then moved down to capture the sheet between the dies, and in doing so, forcing the steel to conform to the shape of the two die sections. I makes short work of bending any steel sheet, and is scarey to think about what it would do to someone's hands, arms, etc.

[Beezil]

hydraulics are pretty tame, try a mechanical full-revolution!

[roXJeepr]

XJHOX...I see what you're saying but I don't know if it would be any stronger that "capping" the unibody frame or not. But the way you are saying, would'nt it be easier to cut the bottom of the unibody frame out and slip the box up into it than down from above? I know it would be taking metal and structure away, but as long as you're welding it all up anyway, I don't see where it would be any worse than dropping it in from above.

[XJHOX]

Never thought about cutting from the underside. In my street/strip car we did it from the top so we could tie the seats into the cage and what ends up being a nice sub frame. The only weak area is the tranny tunnel. But we weld in plates into that section for more support. I have never done it in a XJ thats why I'm asking ?s now. I put a 4 point rollbar/cage just to try out my new tubing bender and I'm not pleased at all with the outcome. In the cars we have done you can pull the jackstands out from opposite sides and the car will not flex at all. Thats what I want to end up w/ in the XJ, plus I figure it should add some life to the jeep also.

[Safari Ary]

I've been considering doing something like this myself. Wrapping the outside of the frame rail in steel that is. What always stops me is how do I prep the "frame" so that I get a good solid structural bond and I don't have to worry about the frame rusting out from behind the strengthening members. I live and wheel on the east coast predominantly and we deal with a lot of mud/water and a lot of road salt in the winter, so rust is my key concern. Any ideas how to prevent it from being a problem with a project like this?? Thanks

Ary

[Beezil]

I think cutting ANYTHING is totally unecessary...."capping" your framerail with a "U" channel with something like .188 CRS will add CONSIDERABLE strength.....

I've done it on two rigs so far. my current vehicle does not have FULLlength subframing, but it does in certain sections....

[vintagespeed]

Ok, here's more 'dumb' input. Why not cut off the unibody sections you want to reinforce from a donor XJ at the junkyard? Channel them to fit either inside or outside of your existing 'frame'. This way, all the bends are there already & you can mostly just overlap the sections?

[nosshane]

that sounds like a good idea since it will already have the right bends. 1991 xj shaved dana 70 in rear locked. high pinion dana44 in front. 4.56s interceptor transfer case. 8in rockready heavily modified skyjacker lift. quarter in. angle iron rock guards. homemade roof rack. 36/12.50/16 tsls. 9000lb hydralic winch.

[Big Bear]

If you where going to go to that much trouble to beef up your unibody. Why wouldn't you just get rid of the uunibody and build a whole new frame? You could tie in all of the little extras you want with ease that way. Either way it sounds like alot of work for nothing to me. :passgas:

[Beezil]

the unibody gauge thickness is pretty thin. It is strong because it makes a SECTION. I wouldn't expect you'd gain much additional strength by merely adding another thickness of the same measly material by wrapping it over the same section. This is a situation where material thickness alone adds strength, since you can't gain any from not being able to form new sections.

[Safari Ary]

Originally posted by Ary'01XJ
I've been considering doing something like this myself. Wrapping the outside of the frame rail in steel that is. What always stops me is how do I prep the "frame" so that I get a good solid structural bond and I don't have to worry about the frame rusting out from behind the strengthening members. I live and wheel on the east coast predominantly and we deal with a lot of mud/water and a lot of road salt in the winter, so rust is my key concern. Any ideas how to prevent it from being a problem with a project like this?? Thanks

Ary

Anyone??

[DeadEyeJ]

Ary, I have always pondered the idea of a sacrificial anode on a vehicle. They use them in swamp coolers (out west), steel bridges, and underground steel storage tanks. The basic idea is to connect the structure electrically to the anode. The anode oxidizes easier than steel and thus corrodes first. Any oxidation the steel would have done gets transferred to the anode. So, no rust. Just have to replace the anode when it disentegrates.

This SHOULD work on a vehicle. I have seen it on boat outdrives for years. Anybody seen a setup like this on a car/truck before?

Jared

[KarmirXJ]

Beezil, Ive always been woundering this... instead of sleeving or boxing in the sub frame why cant you just remove it entirely. then you would have the problem of water getting inbetween and rusting. you could have |_| shaped or box just welded, to the floorboard? would this be another smart way of doing it or no?

[Safari Ary]

Originally posted by DeadEyeJ
Ary, I have always pondered the idea of a sacrificial anode on a vehicle. They use them in swamp coolers (out west), steel bridges, and underground steel storage tanks. The basic idea is to connect the structure electrically to the anode. The anode oxidizes easier than steel and thus corrodes first. Any oxidation the steel would have done gets transferred to the anode. So, no rust. Just have to replace the anode when it disentegrates.

This SHOULD work on a vehicle. I have seen it on boat outdrives for years. Anybody seen a setup like this on a car/truck before?

Jared

So essentially running Zincs on an automobile. Interesting idea, never thought about it before....

[Anthropy]

That is all that galvanized steel is - zinc coated.

Tom

note: If welding, torch cutting any kind of zinc coated material, always have plenty of ventilation. The zinc fumes are bad for you.

[Beezil]

Karmir, while the idea would certainly work, I think the process would be ridiculously labor intesive compared to "capping" the frame with a formed hat-section.

I think everyone who considers the mod finally comes to the realization that it "isn't worth it" since for as many times as I've seen the "tubular re-frame" subject come up, no one to my knowledge has actually done it!

[XJHOX]

Ary, I hear you on the rust thing. I was just thinking about having a good layer of line-x or something like that applied when it was all done. I live right on the lake in Erie PA all kinds of lake effect snow, unfortunatly we get the salt w/ it.

[XJZ]

Guys:

I was thinking about not only capping the frame rails, but capping the *whole* vehicle. Talking about protection!! What do ya think?

Oh, and I have a 2-door, so that would make it a little easier.

[Ed A. Stevens]

Keep the goal in mind: adding rigidity to the suspension mounts, and the frame that ties the suspension together.

Adding slabs of steel to the unit frame section will help, but a crossbraced full cage is much better at improving torsional rigidity. The question of how to tie the cage to the unitframe section is a good quest (and should be the reason to sleeve, slab, or tube the factory frame section).

Do you need to build a full hat section over the unit frame section to add enough strength? How about the suspension mounts (LCA, UCA, Spring hangers, coil buckets, & shock mounts)?

What if you added a simplified bridge between the front and rear suspension mount assembly sections, in the area of the unitframe, with just enough material to weld a cage to the enhanced frame structure? Maybe incorporate full sections (hat or other: 3x3x0.188) at the mount points?

The anode idea has merit, although good primer and thick paint on clean metal helps considerably to extend the metal's life.

BTW, nice press brake. I worked a mechanical cam actuated Engel Bendall when I was the foreman for a sheetmetal shop. Fingers usually stayed away from the press, but a novice operator would sometimes get his face too close to the steel as it kicked up on either side of the press (mostly scrapes, but it can get ugly with 16-gage and thicker stock).

[BLUTO]

There was a thread on this foruma month or two ago about the same thing (roughly). T & J Fabricators (or Manufacturing?) is building a tubular support that bolts to front LCA and rear spring eye...and follows "frame rail" between the two and gets welded along the way. They charge about $400 :eek: for this piece. There was a write-up about it in a recent Off-Road magazine. Another member fabbed his own version and it looked real nice :thumbup: .
I did a search for it last night, but couldn't find the thread or the pics on it. It was a nice set-up to tie some rockrails into too. Another member installed it on his DD and said it really made his XJ drive much better.
BLUTO :)

[Beezil]

the press brake picture I took from a used machinery place....not mine....

actually, we only have one down-acting.

all of our other brake presses are up-acting...

I can't stand up-acting. I'm glad the fad is over, it seems the market has shifted back to down acting.....

can't wait for fabtech.

[CW]

Originally posted by BLUTO
There was a thread on this foruma month or two ago about the same thing (roughly). T & J Fabricators (or Manufacturing?) is building a tubular support that bolts to front LCA and rear spring eye...and follows "frame rail" between the two and gets welded along the way. They charge about $400 :eek: for this piece. There was a write-up about it in a recent Off-Road magazine. Another member fabbed his own version and it looked real nice :thumbup: .
I did a search for it last night, but couldn't find the thread or the pics on it. It was a nice set-up to tie some rockrails into too. Another member installed it on his DD and said it really made his XJ drive much better.
BLUTO :)

Here is that thread

http://www.naxja.org/forum/showthread.php?s=&threadid=6443&highlight=stiffeners

[JJacobs]

This isn't the one I was looking for...
http://www.vtcar.com/photoimg/building/br2.jpg
but it's a start. The subaru full-rally cars probably have next to no load on the sheetmetal, there's so many tubes.

I'm no eng-uh-neer, but it would seem lots of tube reinforcement would do far more than channeling the rails. Wouldn't stiffening the rails just put extra load in the sheetmetal adjacent to them under flex?

When I cut the full roof off my xj and caged it the structure stiffened, but as I didn't use diagonal bracing on the quickie project it's taken on a noticable twist when viewed from the end. I don't think channels would have helped.

[KarmirXJ]

if you build a cage...... then tie it into the hat section underneath the sub frame would that be much better???

kinda like this.

PICTURE (http://community.webshots.com/s/image7/1/43/1/86514301lNxHTX_ph.jpg)






if this dont work im just gonna carve an XJ out of SOLID BLOCK of STEEL :D

[KarmirXJ]

ok for some reason I cant post my pic on the board, it keeps saying "forbidden" someone help me out on this one.... the pics are in my Sig... lower right hand corner...