crossmember reinforcement/more clearance mod

[Kejtar]

OK, I know (or rather I was told) that some have modified their stock crosmember to have more clearance and they also strengthened it... any pics? instructions? I have two slightly bent ones to experiment with ... and I can always go to a pick a part to get one :D

Thanks
Kejtar

[BrettM]

seems to me it would be just as easy or easier to just make a whole new one. that's what I plan to do soon.

[2xtreme]

It was my impression (not my experience yet) that if you run a piece of flat bar (you pick the thickness) strait across from the two rails then you get a flat cross member (flush with the frame rails) and the transfer case will not be dropped from stock, you just need to drill a couple of mounting holes and transfer case mounting holes.

I think when I do it, I would make it wide enought to provide more skid protection also.

Sorry I can not be more helpfull.
Michael

[RCP Phx]

Flat stock isnt strong enough!
http://filebox.vt.edu/users/arebrahi/Jeep%20pictures/RCP%20Phxs%20pics/bybkbrPfhs9WbOXzdKdu+uKF-oMr-qbw0180.jpg

[Cresso]

Any proof that flat stock isn't strong enough?

[RCP Phx]

Probably nothing that would satify you.But I have been fabbing custom parts for over 30 years and I can tell you that I can bend 1/2"x4" flat at that width with no tools.With that size your also talking about a 20lb crossmember.

[XJZ]

Flat stock will bow (but maybe with all that flex you won't need a tranny bushing :) ).

I don't think you can get the x-member perfectly flush because the t-case will hit the tunnel, there's just not enough room up there. Plus you'll have to address a higher rear driveline angle (of course the front angle would be less). Depending on how high you have to jack the t-case to get the member flush, could also have an effect on the fan blade/radiator relationship.

But there's always a way if you really want to do it. Depends on how much time and energy you want to put into it.

Goatman has a modified crossmember that sits more flush than stock, without dealing with all the other issues of a totally flush x-member. You might want to check his site.

[RCP Phx]

1"x4" is the perfect stuff,gives you 1" more clearance!

[Cresso]

I don't doubt that a flat crossmember will flex. How bout any flat stock crossmember failures?

Also, does anyone know how much weight the crossmember does support when sitting still (obviously, the weight it must be capable of supporting is much greater when going over bumps or dips)? I would've estimated somewhere around 100lbs or so....I know I can support it by myself, but I sure wouldn't want to lift it from the garage floor.

[RCP Phx]

Ok,now land a 4000lb jeep on it!You also just changed the nature of the loading on the frame rails.Instead of a vertical loading it now becomes a horizontal loading pulling on the frame rails!Plus your driveshaft is gonna luv you,LOL!

[XJZ]

Originally posted by RCP Phx
Ok,now land a 4000lb jeep on it!


Exactly....what do you do when your XJ is highcentered on the x-member? Your t-case will be coming up through the floor. :eek:

[Cresso]

Good idea, but it didn't answer either of my questions. =)

[Kejtar]

wait.... Goatman has a website? Got a link? IT was his crossmember that I was told about...

Kejtar

[forgiven]

I started with a piece of 1/2x6 bar stock flexes under the weight of the Jeep, I tried it. Then I reinforced the back edge with 2x2 angle iron. No mo flexo. After all that work I still had to use a 1" spacer between the cross member and the "frame" to make room for the t-case. I believe I gained about 1.5" of clearance and I'm sure this crossmember will not bend. I then fabbed skids that attach to the and rear of the CM.

[HossHoffer]

Hey RCP PHX, What kind of mounts did you use and where did they go. I'm going to fab one like your picture but just wanted to know if you used the OEM type tranny mounts.

[RCP Phx]

Originally posted by forgiven
I started with a piece of 1/2x6 bar stock flexes under the weight of the Jeep, I tried it. Then I reinforced the back edge with 2x2 angle iron. No mo flexo. After all that work I still had to use a 1" spacer between the cross member and the "frame" to make room for the t-case. I believe I gained about 1.5" of clearance and I'm sure this crossmember will not bend. I then fabbed skids that attach to the and rear of the CM.

"Holy smokes Batman",now were talking about a 40lb crossmember!

Yeah mine uses the stock mounts,I just added a littlte drop because of my lift height!

[FatXJ]

It's all in the design. A piece of flat stock will bend no matter how thick. Now if you add ribs (perpendicular steel supports) to the face of the stock then the ability of it to flex is eliminated.

Basically make it 2 dimensional and you're all set.

[vintagespeed]

Originally posted by Cresso
Any proof that flat stock isn't strong enough?

Sure, take your ruler that you drawing up that custom suspension with and grab it at the ends. Now flex it in the middle. That's what your crossmember is going to do. :D

[XJZ]

Kejtar....not really a site (sorry)...online photo album. :photo: ..I believe the photos are in there somewhere...

http://fototime.com/ftweb/bin/ft.dll/home?inv=383E99C5633A988

[Bent]

Even us Carpenters know that flat anything is nowhere near as ridgid as that flat anything with at least one "sheer panel". About the only way to reduce flex in a flat pc. of stock would be to "laminate" more than one layer one on top of the other(s). At best, this provides wery limited results until the thickness begins to approach the width. Think of the second or perpendicular surface as kinda like a gusset. The thicker stock at the horiz. surface does resist crushing better than thin does. Hovever it is the vert. areas that helps even the stock sheet metal cross member resist the amount abuse that they do. Think about this, when was the last time anyone has seen a bridge that was only a single horizontal ribbon with no other vertical supports of any kind?

[Cresso]

I don't doubt that a flat crossmember will flex. How bout any flat stock crossmember failures?

(deja vu)


Notice that I've never disagreed with anything said here. What I'm asking for here is more than an educated guess based on what people expect flat stock to do. I'm asking for someone who ran a flat stock crossmember to show us how it failed. Flex does NOT equal failure. flex equals flex. Over a long period of time, flex will fatigue metal until it fails. What period of time is that? What is the mode of failure when it happens to a crossmember like this?

Anyone with answers or am I gonna get more spobi? =)

[RCP Phx]

My 20 old son is just starting to listen now too!Its a wonderful life.These arent guesses but real life design issues!

[vintagespeed]

Unbelievable this guy. No one has any idea because no one would build one like that. Hello? Why dont you whip one up & show us all the pics of how great it works. Talk about vibes.....and I wonder how many dents it's going to put in his hood? Any guesses on the number of rear ujoints he goes through? :D

[2xtreme]

I appologize if my previous post made so much trouble. I applogize, after doing a little looking at the photos I have of other cross members I would have bent each side of the cross member up (making a U channel). I thougth (I have not checked on mine) that the trans mount sits basically flush with the frame rails? Maybe I am wrong. I know that I have seen several pics of them and they are flush with the frame rails, maybe they did more work than what it looks like??

Michael

[Bent]

The failure of the flat stock crossmember would not be itself. The flex that it would allow dependant upon it's thickness. By thickness, I mean within the realm of reasonable definition. In other words, exclude 2" wide by 3" thick. I think you get my point since you are trying to limit hight. "Metal" by by defenition will flex and return to it's original shape within the limits of molecular structure. In this case, the crossmember is not the "weak link". That could be your frame rails over time, transmision or any other component that would rely on what was a ridgid structure. If you are looking ONLY for the failure to occur on the solid flat stock, you may have to replace alot of other things around it many times before that may ever happen. I'm as much for over kill as the next guy. But first I like to find out which way the barrel is pointed. :D

[Kejtar]

cool.... this is what I was looking for:
pic1 (http://www.fototime.com/ftweb/bin/ft.dll/standard?pictid={EA7E67C2-FFF9-11D6-9867-00C0F05AE12E}&exp=f&moddt=37798.1255208333)
pic 2 (http://www.fototime.com/ftweb/bin/ft.dll/standard?pictid={EA7E67C1-FFF9-11D6-9867-00C0F05AE12E}&exp=f&moddt=37752.7822176389) Now I can start planning for my second project :D Maybe I'll have it ready for Moab?


Btw.... flex means extra travel so that your shafts, tcase and ujoints will be working overtime as you're going over bumps and rocks so even if the crossmember survives you're more then likely going to damage something else. Furthermore if you're going to have the middle of the crossmember flexing in and out I can already see it loosening nuts/bolts that support it as well as braking the nutzerts inside...

Kejtar

[RCP Phx]

Now Im confused,thats a stock crossmember????

[Cresso]

Whew, this is painful. I'm not disagreeing with anyone. I'm not saying a flat stock crossmember will work. I just want indisputable proof that it WON'T work. I haven't seen that yet. This is sorta like the guys on JU saying a Cherokee will fold in half if you take the doors out. I don't know that taking the doors out won't fold it, but I'd never say taking your doors out WILL fold it unless I've seen it happen. Please, no one take this personally.

[BrettM]

Originally posted by Cresso
Whew, this is painful. I'm not disagreeing with anyone. I'm not saying a flat stock crossmember will work. I just want indisputable proof that it WON'T work. I haven't seen that yet. This is sorta like the guys on JU saying a Cherokee will fold in half if you take the doors out. I don't know that taking the doors out won't fold it, but I'd never say taking your doors out WILL fold it unless I've seen it happen. Please, no one take this personally.

That's like saying "will wood work for making control arms?" then after everyone says "NO!" asking "show me proof?"

No-one has done it because it would be stupid. You won't break the crossmember, but your drivetrain was meant to be held pretty much stationary (maybe a few 1/16ths movement in the motor and tranny mounts). If you start letting stuff flex around you WILL have major problems.

If you want to use flatbar, I would suggest at least an inch thick.

[XJZ]

"This is sorta like the guys on JU saying a Cherokee will fold in half if you take the doors out. I don't know that taking the doors out won't fold it, but I'd never say taking your doors out WILL fold it unless I've seen it happen."


Dude, you are the perfect exemplification of JU. But I like the irony.

[Goatman]

Alright, like Jim said, you won't get a testimony on someone's flat crossmember that failed because it's so obvious that it won't work that no one (at least around here) would build one. The reason you want it as flat as possible is for ground clearance, which also means that it may have to support a major part of the vehicle's weight at some point.......which means it needs to be built with some structure. So, whether you're satisfied with the answer or not......that's the answer. For reference sake, I have bent the sh!t out of a stock crossmember, bent it up in the middle nearly two inches and the t-case was banging on the floor.

BTW, if you only believe what you see, then you can only learn from experience. There isn't enough time in our lives to experience everything, so sometimes we just need to figure things out. :rolleyes:

I see Kejtar posted links to my crossmember. It's very easy to make, and plenty strong enough. It's been on there for three to four years with plenty of hardcore use, and it hasn't bent yet. I don't think the bottom of the trans mount is flush with the bottom of the frame rails, it looks like it's lower by a little bit. You also want a little thickness in the crossmember so the trans mount studs are up inside the crossmember, or they'll get the crap beat out of them.

To make mine, I cut the bottom off of a stock crossmember, just below the seam line, with a cutting torch. Then a piece of flat 1/4" was attached, and you can see how it bends up a little on the ends. I did add some support along the edge on top to increase it's strength, and had to clearance for the front driveline.

Here's a link to pics again, the two of the crossmember are at the bottom: http://fototime.com/inv/DFCDB9A8BDAF591

[JnJ]

First off mine is flat, and the t-case does not hit the tranny tunnel. I started with 1/4"x6" flat stock, during fitting test I bolted that alone up. The weight of the drive train caused it to bow. Now I'm no genius, but even I could figure out this is bad, so I used some angle on the back and front side to make it good and stiff.
If you really want to see a flat stock crossmember fail, I think you'll have to do it yourself, I don't believe the folks here are foolish enough to try it.

[Kejtar]

Originally posted by Cresso
I just want indisputable proof that it WON'T work.

Umm.... ok... lets put it this way: you have been given the "mechanical" reasons why this would be bad. If you want proof then I really do suggest you make one and then report on results after 3 months of use, 6 months of use and a year of use if you make it that far. Be prepared though to suffer the consequences of a domino effect failure of components: from potential pumkpin problems to unjoints, drive shaft, transfer case and tranny/engine (a flexing crossmember will make the engine constantly rotate). Keep in mind that your failure can even include a fan through the radiator if you flex enough!!

Kejtar

[Ted Z]

it may work....but the torque from the drivetrain and the extra weight of the drivetrain pushing down on it when ya hit a speed bump or pothole even, will make it useless very quickly. And the concensus of the group is standard fab "rules" you basically don't use flat for anything but mounting plates and gussets... same reason bridges are not just a flat piece of concrete or metal. in designing anything you must design with a "safety" factor in mind, keeping the item being designed 2-3 times stronger than it needs to be.

[TLange]

I don't have a digital camera or a photo to show you how I did mine. I'll try to explain it the best that I can.

I used 1x2 retanguar tubing, 1/8" wall. I welded two pieces side by side and flat. This gave a cross member that is 4" wide, 1" tall and goes from uni-frame rail to uni-frame rail. I then took two 6" long pieces and welded those to the ends of the cross member in such a way that it kind of looks like a TC lowering kit. These two short peices are cut at 45 degrees on the ends so the bolts that go into the uni-frame sit inside the tube, not exposing them to rocks. The ends of the cross member are cut 45 degree as well just to make it better and maybe help keep the corners from snagging on stuff. The tranny mount sits right on top of the crossmember. I have 1" holes cut through the bottom wall of the CM and 3/8" hole drilled through the top for the tranny mount, again, protecting the bolt heads from rocks. I also have the Mopar TC skid mounted to it.

The stock CM hangs down around 3" and the the tranny mount sits 1/4" below the uni-frame. My CM hangs down 2" and the tranny mount sit 1" below the uniframe. It gave me an extra inch of clearance and at the same time a 3/4" TC drop relieving driveline angles slightly.

Why did I use two 1x2 pieces instead of a single 1x4 piece? Two 1x2 pieces welded side by side is much stronger then a single 1x4 piece. You've got four vertical walls instead of two.

I've hit it hard several times and high centered on it a few with no damage. It's been on my Jeep for about 3 years.

[4ward]

Here's a few shots of mine.

Here you can see the initial construction:
http://www.montypics.com/pic.php?url=/OneTonXJ/2003-07-18/1058550408_crosmem1.jpg

A little farther along:
http://www.montypics.com/pic.php?url=/OneTonXJ/2003-07-18/1058550458_crosmem4.jpg

Finished (sort of):
http://www.montypics.com/pic.php?url=/OneTonXJ/2003-07-18/1058550486_crosmem8.jpg

As you can see, the driveshaft cutout was on the wrong side of the crossmember. I cut the other side out and welded that chunk into the incorrect hole. All I can say is this was one of those 2 am been drinkin and workin' on the jeep projects.

I ran straight across the frame rails, didn't allow for the 3/16" +- drop that the stock one allows for. It's nothing that can't be overcome with a shim :) One of these days, I'll actually make up a batch and sell them.

Sean

[Kejtar]

I like it!!!!!

[vintagespeed]

LOL, just flip the picture horizontally and it'll be great for your advertisements. Looks pretty good beef wise.

[Rev Den]

Originally posted by Cresso
indisputable proof that it WON'T work.

OK....I have been holding off on posting on this, due to pride....but here it goes.

My buddy and I replaced the stock crossmember on his CJ-7 with a flat piece of 1/2" diamond plate. 2 weeks later we replaced it after getting cracks at every bolt hole, except the 2 bolts that broke off. Chalk this up to ignorance, and youth.

If the folkes on THIS board say it won't work, trust them. Chances are SOMEONE has tried it.

KnuckleDome (Name changed to protect the stupid)

[RNMedic]

okay Sean I am gonna add that to my wish list. My I need to learn how to weld.!!!!!

[Ron S]

1/2"x 13" x member with rubber tranny mount and a notch for t-case clearance (replaced with 1/8" thick plate). counter-sunk mounting bolts for the t-case and to mount to the frame rails. had this set-up for over a year now and works very well for me.
chill,
RonS

[vintagespeed]

LOL, chilled. Let's see some flex pics.

[Willis]

OneTon, how thick is the material you used on that x-member? Looks pretty thick (5/16, 3/8?). If so, seems like overkill. If making one similar to yours (boxed), I'd think 3/16 would be thick enough, wouldn't it? Also, how wide (front to rear) is it?

Thanks,
Steve

[4ward]

I go overkill, but not that far. Top is 1/4", bottom is 3/16", and the sides and ends are 1/8". It's still probably a little too much, but I haven't been able to bend it, and my lower control arms are mounted to it.

The production ones will be 3/16" top and everything else 1/8". I'm gonna be putting 2 on test vehicles to see if they can take it.

[Goatman]

That crossmember can take quite a beating. That's one place I wouldn't worry about a little overkill.