Home Forums Hunting & Shooting Hunter's Campfire Strength of square vs rec tube

I tried to find the answer but it’s all in Engineer speak which I don’t understand. Simply stated, which Is less likely to bend along its length .120 wall 2x2 or .120 wall 1x3 (using the 3” side)

Which will resist twisting the best?

Define 'bend'.

If the 1x3 is carrying the load with the 3" side bearing the stress it will resist better than the 2x2, otherwise the 2x2 wins. Not unlike how an I-beam works

the square tube. By a lot.

The square tube

1X3 will twist like a coil spring but it will carry more downforce with the wide side vertical. What are you building? We used a lot of 2X5 tubing for building round track race car frames, with appropriate cross bracing and roll cages. It's strong, and fairly lightweight.
Jerry

I don’t have tables for tube that small so I compared 4x4x1/4 and 6x2x1/4, which are both double the size you are looking at. The 4x4 is 4 times as stiff in bending as the 6x2 bent the weak way, about the same as the 6x2 bent the strong way. And twice as torsionally stiff.

So the same result hold true for the shapes you are looking at, at roughy the same ratios.

Basically a swing out hitch haul. Didn’t want to overbuild it to the point that it weighs 100lbs but I also don’t want to put something heavy on it and twist it all to hell if I hit a big bump.

Check out the Aluminum hitch hauls at Harbour Freight. It might be less than the cost of materials to build your own.

1X3 will support more than a 2x2 with same thickness and material.

The more research I do, the further down the rabbit hole I go. Here’s what I think I understand... In laymen’s terms, I can treat each tube as a “ I -beam” in that the top and bottom of the tube is treated like the flange on a beam. The wider the flange, the more torsional stability the tube has. The taller the web (side wall of the tube) the stronger the resistance to deflection longitudinally. So the 2x2 better for torsional forces (twisting) and the 1x3 is better for less longitudinal deflection (sag).

Now an engineer will chime in and tell me everything I think I understand...is wrong

Engineers built the "unsinkable" Titanic.
Jerry

Using simple beam theory (stress = My/I), for a given simple bending scenario and same applied loads/boundary conditions, I'm seeing the 1x3 tubing developing about 90% of the stress as the 2x2. So yes the 1x3 is stiffer (in bending) for Hookean materials assuming elastic conditions are maintained.

Amateurs built the arc!

Yeah, but they had a better engineer supervising the construction!
Jerry

I see what you did there...

Agreed

Hands down round tube is stronger.

There is a reason modern high stress crane booms are built with round tubing.

Delete. Unnecessary post.