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Discussion Starter · #1 ·
Here is the dilemma I am facing!
I’m putting a 6-point cage in my buddy’s yj. I have a mig, knotcher, jd model 3 blah, blah, blah…… This is by far not my first cage either. It is my first cage where I have the option of using 2” tube. (Santa Wife Gave Me A Early Gift..2” die)

Option 1. Build the cage out of all 1.5 tube .120 wall…… Blah, Blah, Blah….

Option 2. Build the cage using 2” tube for the main front window hoop, center over the head hoop and the two bars running back and down to the back of the jeep from the center hoop. Run all the rest of the spreads and stuff in 1.5” tube…

Option 3. Build the cage all from 2” stuff….

How much stronger is 2” by .120 wall tube over 1.5” by .120 wall… are we talking 25%? Is the extra strength worth the extra weight? Due to the larger Dia. You can thin the wall and still maintain strength… Would 2” by .095 wall be as strong as 1.5” by .120 wall……

We keep throwing this back and forth….. Use just 1.5by .120 and save weight vs 2” by .120 wall…..

I hope ya-all see what I’m getting at here… This is a yj with 31” G/Y MTR’s, 2.5 Robi Express lift and a 4-banger engine with a Locked rear… A mild to hard trail rig.. Not a Big boy rock buggy … Also what is the weight of this rig…. 2900 Lb??????

Would 2” by .095 be adequate?

I know 1.5” by .120 will be more then sufficient…


What is your thoughts….. beside go to JU............
:flipoff2: ...:flipoff2:
 

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That really Helps........... Thanks....
Guess you dont have a 1-3/4" die...



Dallas at Stinkyfab built this cage for me and the main hoop is 1-3/4". I dont think 2" tube will fit down the side between the dash and door.

MP
 

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MattPascoe said:
I dont think 2" tube will fit down the side between the dash and door.
Not with half-hard-doors it won't... Well you might be able to slam the doors in on it, but on the last 4 YJ's I've put cages in, 1.75 is max you can get in between the half-door and the dash.

I also would not make any main member out of 1.5" tube. It's great for supplimental support/gusseting, but for the main pieces, it just ain't enough. 1.75 is 90% of what I bend.
 

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Discussion Starter · #7 · (Edited)
Well I see what your saying about 1.75" tube, but I don't have that die.........:rolleyes:

Does this look correct for figuring electric weld seam mild steel tube?

Collapsing Pressure Of cylinders and tube subjected to external pressures. The follow formula may be used for finding the collapsing pressure of lap-welded bessemer steel tubes.

In which P = collapsing in pounds per square inch; D= outside diameter of tube or cylinder in inches ; t= thickness of wall in inches.


t= .120
D= 2.00
this would work out as 3814.2 Lb per Sq. Inch?

t=.120
D= 1.50
this would work out as 5547.6 Lb per Sq. Inch?
 

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Potts,

Use your same collapsing pressure on .095 wall 2" tube... you'll find that you don't want to use thin wall tube on stuff that hits rocks :)

Of course, this is collapsing pressure, what you're more interested in is what it'll take to dent the tube. A dented tube will buckle, and thicker wall, smaller diameter tube will not dent as easily, so it won't buckle as easily.

check out www.baertrax.com

owner is my buddy russ. He's got a 4 popper TJ with 36's on it that's got a decently slick cage, all made from 1.5 x .120 wall. mulitple rollover tested on granite and holds up fine.

My cage for my new jeep is being made all from 1.5, 1.25, and 1" tube. (of course, the high impact areas like belly pan and rocker panels are 3/16" wall)

You can do the simple math to figure the relative cross sectional area of the tube between 2" x .120 and 1.5" x .120 the ratio of these two areas will be you ratio of strength in tension and pure compression.

The real discrimator between 1.5" tube and 2" tube is going to be the bending strenth, IE, when the rig rolls, and you hit the center of the spreader on a rock as it goes over, ASSUMING it doesn't dent / buckle the tube, you'll be loading the spreader in "bending." In this case, 2" tube will be considerably stronger than 1.5." I don't remember the equation for bending on a round, hollow tube, but if I remember right it is related to the square of the radius so you'd be comparing .5625 (.75^2) to 1 (1^2). I'll look up the equation in one of my statics books tonight if you'd like.

All in all though, I would say go with the 1.5" tube and it should be fine.

Mike
 

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Pottsy,

Since you are relatively close by, stop on up with whatever you need bent or notched (within reason of course). We'll hook you up. We have 3/4, 1, 1-1/4, 1-1/2, and 1-3/4 dies. It'll do 1-3/4 solid, so capacity isn't an issue.

Always willing to help out a local wheeler.

Matt
 

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big97redtj said:
Pottsy,

Since you are relatively close by, stop on up with whatever you need bent or notched (within reason of course). We'll hook you up. We have 3/4, 1, 1-1/4, 1-1/2, and 1-3/4 dies. It'll do 1-3/4 solid, so capacity isn't an issue.

Always willing to help out a local wheeler.

Matt
If Pottsy doesn't have the right tool for the job, then he'll just fab the tool up himself! He's good like that! :smokin: Wonder if he could fab up a die?? :rasta:

I definetly want to drop by your shop when I move back in the area, you guys hiring? :flipoff2:
 

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If you want to give yourself a headache, here's the physics behind the beam strength of 1.5" tube vs. 2" tube.

FYI, finding the moment of inertia of a tube simply involves finding the moment of inertia of the tube if it were solid, then subtracting the moment of inertia of the hollowed out inside portion of the tube.

All of this info is pretty clearly represented, and is accurate to the best of my memory (been a while since I was a sophomore ME student:flipoff2: )
 

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If I recall my old classes, the strength of a tube goes up in proportion to the "radius squared" (all other things being equal). So you do gain a lot of strenth going to a large tubing. The question is "is it needed"?
 

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foley said:
Potts,

, but if I remember right it is related to the square of the radius so you'd be comparing .5625 (.75^2) to 1 (1^2). Mike
I was wrong, it's related to the 4th power of the radius, so you'd be comparing (.75^4) to (1^4) or .3164 to 1
 
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