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I say if you take a piece of 1 1/2 x.120 tubing and slide it inside of a piece of 1 3/4 x .120 tubing you will have a piece that is stronger (against bending) than a piece of 1 3/4 x .250 tubing.

What do you think??
 

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paulevans76 said:
why would it be?

IM with him.......I think if you could bond it together the entire length you imight have a comparo.......IM also a cheap bastard and my last 4 link I did I used 1" inside of 1.25" inside of 1.5" all .120 wall and it performed flawlessly.....:D
 

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Nope. The 2" 0.250 is stronger.

I don't have the engineering to back up why, but I know on the bender here, with the hydro setup on it, I can bend 2" 0.250 DOM to about 25 or 30 degrees before the bypass opens up and the bender stalls out.

I can bend 2" 0.120 DOM slid overtop of 1.75" 0.120 DOM, (same OD, same material and treatment, only slightly different ID and a tiny air gap in the middle) to 90 degrees, and only a little past 90 because we only have a 90-degree 2" die.

The way the bender is laid out, assuming one shot bending to 90 degrees, it takes progressively more and more pressure (got a gauge on it, but I haven't paid attention to it while bending the specific materials in this question, more used it to compare 4130 to 1026 recently) to bend farther and farther.
 

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No..
They should be the same strength.


they are both essentially 1 3/4 .250 wall.
 

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Jason M said:
No..
They should be the same strength.


they are both essentially 1 3/4 .250 wall.
Nope.
The 0.250 is stronger since it is one homogeneous cross section. The tube over a tube is two smaller cross sections separated by a small (.0025") gap.
 

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i jsut experienced this today in a bender. i tried to bend .250wall 1.75'' DOM 1026 in a bender and stalled the ram, it how ever, does sleeved .120/.120 tubes of similar diameter without a prob???

i had to heat the .250wall up with the torch and bend it amnually.what a SOB it was and the bend was only 24*........
 

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GOAT1 said:
The solid (.250) wall tubing will be stronger. There is tranverse shear stress in the wall when in bending, the two tubes will slide across each other while the solid wall will resist the tranverse shear. Think of bending a book vs bending a solid block of wood.
My non-engineer ass agrees with this high tech explanation :D

The same principle applies with leaf springs, which you may be more familiar with. Given the same overall cross section, a spring with more but thinner leaves will have a lower spring rate and be able to flex further without bending than one with fewer but thicker leaves. This is because the leaves are able to slide against each other, relieving the above explained sheer stress.
 

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GOAT1 said:
The solid (.250) wall tubing will be stronger. There is tranverse shear stress in the wall when in bending, the two tubes will slide across each other while the solid wall will resist the tranverse shear. Think of bending a book vs bending a solid block of wood.
I agree.

In a pure tensile or compressive load, there would be virtually no difference in strenght, but for bending the slip "plane" at the interface eliminates the ability to develop transverse shear stresses.
 

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Sorry to hijack this one but:

What would be sronger:

2" DOM .250 wall (round obviously) or 2"x2"box tubing .250 wall (square)
 

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Nordic1 said:
Sorry to hijack this one but:

What would be sronger:

2" DOM .250 wall (round obviously) or 2"x2"box tubing .250 wall (square)
The square tubing has a larger moment of inertia (more of the material is further from the neutral axis(center)) so it will be stiffer, and stronger if they were made of the same material. DOM ends up being stronger because the yield and tensile limits are higher for DOM than what structural steel is.
 

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