Round Steel Tube for Frame/Tongue?

[okedoketear]

Ok, I want to build a new frame for a trailer. I am thinking of using ROUND structural steel tube. Does anyone know the vertical/horizontal strength of ROUND steel tube? I know a lot of people use square or rectangular tube but I think the ROUND tube fits into my design better. Also, if I bent the tube does anyone know how much that would affect the strength properties?
Does anyone have any thoughts or specs? Thanks!

[jay]

i think round would be more difficult to fit, but would look really nice, complimenting the shape of the cabin (assuming traditional tear). bending might require serious proprietary equipment.

my opinion; worth what you paid

[angib]

Round tube is about 60% as strong as square tube of the same overall size and wall thickness. The round tube is about 80% of the weight of the square tube.

Looking at it the other way, a 2-1/2"diam x 1/8" round tube is about as strong as a 2" x 2" x 1/8" square tube and weighs about the same.

If you bend the tube using proper equipment (ie, no wrinkling or kinking of the tube), then strength will be pretty much unaffected.

Of course all the joints will be lots of work - unless you have access to a pipe profiling machine. You would probably need to join the round tubes to a short piece of square/rectangular tube in order to bolt a coupler to it - I don't like the idea of welding a coupler onto round tube as the access for welding (and hence the weld quality) will be very poor.

Andrew