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Exo Cage using square tubing Q's

B

barillms

NAXJA Forum User
Location
Eastern Ohio baby!
My MJ is going to be gaining much steel this winter, and I cannot or do not have the means to bend round tube in my garage. I'm looking at some of the Exo cage idea's I've see on here, the only difference is I'll be using square.
I actually think I'll be doing an external/internal combo.

1. What type of square tubing should I use? Type of steel? Wall thickness?
2. What size square tubing should I use? Is 2" big enough?
3. How much should I expect to pay for 2" square by the foot?

Just curious, I'm not concerned with looks... I realize round would look more trick and cleaner, but I'm going to make due.

ALSO: I'd like to shorten my MJ longbed's wheelbase a little, and whack off the rear of the frame, shorter bed. Any suggestions? YJ leafs possibly?
Thanks
 
its not a question of looking "trick and clean" its a stress comparison question. circular tubing is stronger in more directions than square tubing.

metal shops in your area do have the means and should bend some steel to what you want for a couple bucks

dont just jump into fabrication with out researching first... it doesnt pay to just go in blind and "make due". im sure it would give you SOME level of protection, but i doubt it would be that much for the work youd be putting into it...
 
Last edited:
I'd not really recommend building a square tube exo...



But, I will stand fully behind the use of ASTM-53 pipe. 1.5" Sch40 works great and can be bent using a sub-$100 bender. Unfortunatly, people might tease you saying that your rig 'needs more spriklers' or is built to 'only handle poop'.




Now, let the flak cannons begin firing!
 
a perfectly safe cage can be built from square tubeing, but it will be heavier and uglier than round tube. a perfectly safe cage can be built from good pipe, but it will be heavier than DOM of equivelent strength.

it's impossible to make recomendations on siz/grade of tubing to use without design being an integral part of the discussion. a cage could be built out of 200' of 1.5" chromoly and a cage of equal strength built out of 100' of 2" schd40 pipe.

as for MJs, I don't think there is any point in doing an inner/exo cage. this is a good thing for XJs because design benefits greatly from an X at the B-pillar which is only possible by going inside. On an MJ you can just put an X right behind the cab and accomplish the same thing.
 
This is why submarines are round. The pressure is distributed on the surface of the round tubing equally, there are no points that the pressure or stress will attack more than others. You can stand on an empty soda can just fine, but once someone just lightly flicks the side, it's done for, and collapses because the pressure is no longer being distributed evenly.
 
begster said:
This is why submarines are round. The pressure is distributed on the surface of the round tubing equally, there are no points that the pressure or stress will attack more than others. You can stand on an empty soda can just fine, but once someone just lightly flicks the side, it's done for, and collapses because the pressure is no longer being distributed evenly.
Click to expand...

Submarines experience hydrostatic pressure, which means that pressure is uniform across all surfaces, regardless of shape.

There's no such argument as "square tube is stronger than round" or vice versa. What are you comparing? 2" OD round to 2" square with the same wall thickness? The square is stronger in that case but is also heavier. How about equivalent weight (a.k.a. equivalent cross-sectional area)? Then round is stronger.

As was just mentioned though, discontinuities and imperfections greatly reduce the effectiveness of the structure. With a square-tube cage you are most likely going to be cutting/mitering/welding at every bend. This gives a lot more possibilities for failure points to occur vs. a smooth bend in tube (with a bending die of the proper radius). With enough triangulation and gusseting you can make it just as safe, but it'll weigh 2x as much as an equivalent bend tube design and look like ass IMO too.
 
Thanks man. I don't care about looks.
I'm using square tubing because I have to.
Some of you guys are nuts about overkill, you go way overboard with this gotta be strong and perfect crap. Build a Jeep and wheel it. If it breaks, fix it.
Submarines!
 
it was an example.
its about stress distribution. why do you think most guys build cages with pipe? because they have it laying around?

whats the point of having an ill-designed cage. the point is to protect you, not have the appearence of protection.

like stated above, youll need a thicker heavier square tube, and more of it to get a decently strong cage.
 
barillms said:
Thanks man. I don't care about looks.
I'm using square tubing because I have to.
Some of you guys are nuts about overkill, you go way overboard with this gotta be strong and perfect crap. Build a Jeep and wheel it. If it breaks, fix it.
Submarines!
Click to expand...

I somewhat agree with you. Most of us want a cage to protect our sheet metal in a flop or the typical roll. When it comes to protecting the occupants, sheet metal by itself does a very good job of that, and any additional cage material will be fine in all but the highest speed rollovers or an atypical multi endo type roll down a long hill.

I wouldn't want square tube because of looks, added weight that is mostly above COG. And it's a lot more work to make the notched bends and the welding come out good.

But hey, prove everyone wrong and make a good one!!
 
if you haven't bought it yet, why must you use it, as opposed to something else? you could buy around tube bending machine with a hand pump hydraulic and save some money on materials.
 
jeppo said:
if you haven't bought it yet, why must you use it, as opposed to something else? you could buy around tube bending machine with a hand pump hydraulic and save some money on materials.
Click to expand...

wondering the same thing as well.
 
How much are these manual benders? And what are their capabilities?
Bend 90s? I'm just trying to figure what would be easiest for me at my house with the tools I have. If I can notch a piece of square, bend it... weld the notch shut this seems way easier. I have an MJ and this exo cage I'm planning to do isn't going to be very complicated. It'll be functional.
I have no front fenders or anything, no roof, no doors. I need some support.

As far as getting hung up on things, I don't care. I'll rip the bark right off the trees. We don't have huge boulders in Ohio. Anyway, I'll put KY Jelly on my cage before I go out so I can slip and slide my way throught the tight stuff.

It seems like being new to bending round tube, you would have alot of wasted material when you mess up the angles.
 
barillms said:
How much are these manual benders? And what are their capabilities?
Bend 90s? I'm just trying to figure what would be easiest for me at my house with the tools I have. If I can notch a piece of square, bend it... weld the notch shut this seems way easier. I have an MJ and this exo cage I'm planning to do isn't going to be very complicated. It'll be functional.
I have no front fenders or anything, no roof, no doors. I need some support.

As far as getting hung up on things, I don't care. I'll rip the bark right off the trees. We don't have huge boulders in Ohio. Anyway, I'll put KY Jelly on my cage before I go out so I can slip and slide my way throught the tight stuff.

It seems like being new to bending round tube, you would have alot of wasted material when you mess up the angles.
Click to expand...


ok just my $0.02 imho if you have no roof, doors, fenders ect on you mj the cage become super important due to loosing allot of the structure in your rig. if the cage is not built correctly you going to end up with a taco rig. and if its not built to withstand the forces exerted on the cage in a roll whether its to the side or an endo your going to end up hurt or kill due to the cage collapsing or folding so you contact immovable objects.

as for the square or round tube debate imho round is allot better for a material selection. it is stronger giver the same size and wall thickness especially when square is bent.
 
barillms said:
It seems like being new to bending round tube, you would have alot of wasted material when you mess up the angles.
Click to expand...

Just don't bend it too far...? Layout for single-plane shapes (hoops, door bars, etc) is easy even if you've never done it before.

As for capabilities of a manual bender - exactly the same as any other bender. You just have to work harder at pulling the handle.

falcon1235 said:
as for the square or round tube debate imho round is allot better for a material selection. it is stronger giver the same size and wall thickness especially when square is bent.
Click to expand...

But...it isn't stronger given the same size and wall thickness.
 
85cherokeechief said:
Given the exact same material, square tubing is stronger than round tubing in bending. Round tubing is only stronger in torsion, which should not be experienced in a roll cage.
Click to expand...


He hasnt been talking "bending", I think he is talking cut/weld...
 
Ludakris said:
He hasnt been talking "bending", I think he is talking cut/weld...
Click to expand...

Wrong bending. 85cherokeechief (and myself) are referring to bending stress as a result of loading on the cage members. And also buckling (same rules apply).

By 'stronger', what is meant is that for a given loading, the maximum stress in a piece of square tube will be less than that in a piece of round tube of the same outer size and wall thickness. This gives a larger factor of safety for that loading in considering the yield and ultimate strength of the tube.

Any discontinuity will lower this factor of safety, like a sharp bend, a weld, a cut, or dent. Thus negating any strength benefits from the square tube.
 
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