Info that I have come across,
source: http://www.offroadfabnet.com/forums/showthread.php?t=5499&highlight=square+round
A round tube will be structuraly the same around the entire circumfrence. So if you hit a round tube at any point it's going to be the same (relitively) strength the whole way around. With square tube you basicly have 4 really strong points that lose some of their strength as you work twords the center of the tube. So in the eventuallity (or probability) of a roll over if Murphy (Law) is anywhere nearby the contact is going to take place at the weakest point in your design or material.
One of the reasons why people don't build chassis with square tube is the strength to weight ratio compared to round tube. A 1.75" round tube is going to be significantly lighter and stronger then a 1.75" square tube. The 1.75" round will almost slide into a 1.75" square. The corners add a lot of weight and little for strength.
The other issue I foresee is bending the square tubing. Even a good quality draw style bender is going to have some warpage or collapsing at the inside of the bend point. This then makes your bend the weakest point of the cage and prone to collapse. And if your cutting and welding to make bends your weld or the material around your weld will then become the weak point. And for the record I am not picking on your welds at all. For all I know your the best welder in the world it's just at that point the metal around your weld becomes the issue!
One last question/comment... Do they even make DOM square tubing? All the square tubing I've used or seen has been a CREW/HREW style tubing... Big ugly welds down the inside of the tube. Not exactly ideal for a cage expecially on a heavy rig like an International!
With that being said I have seen entire buggies made out of square tubing... But at the same time I've seen buggies made out of SCH40, SCH80, and others out of HREW. At that point it's not a matter of when the cage fails but how bad it will be when it does!
Paul G.
Alot of that doesnt make sense to me, in the real world. How is it I can smack a piece of round tube on something, and bend or dent it, whereas same thickness sq tube, will just bounce off and hurt my hand?
Ive also read sq is stronger than round, more surface area to spread the load on.
