I'm just going to take this a bit off topic for a moment... In bicycles, there are two kinds of frames... round tube frame (including oval tubes) and square tube frame. The round tube frame has been tried and true to BMX and just about every ramp you can throw at it. BMX to bikes, in case you didn't know, is the equivalent of us dropping our road rig on the trail and seeing what it can do. Square tube bikes however, are more akin to racing on a track, very-low air time, and super light weight components. If you use a round tube bike for racing, you pretty much don't lose anything, but if you use a square tube bike on a BMX course, you will invariably break it because a 4 line weld is not nearly as strong as a single circular weld.
Case in point... I have a Redline BMX bike in High School... It has a round tube frame and I am very hard on it on purpose to attempt to break it on the trails. It takes me over a year of hard ground pounding and extreme air on table tops, valleys, and every other natural - or unnatural - trail feature you can imagine to break the main bar-fork weld on this bike. There is no chance any other part broke before or since. The dropouts were 3/8" thick monstrosities, and the tube was nealry 2 inches thick on the main bar.
My friend finds a Hawk for really cheap... like $30.00.... this bike sells off the showroom floor for over $500 at the time, and it is designed for high speed low drag racing. It weighs in at about 5 lbs total weight, is 100% aluminum frame, but is reenforced like a tank with double welds at every point where the manufacturer thinks it could break. This thing is designed to go fast, get a little air, and be as light as possible while doing it. We take it to the same trail where I broke my Redline.... it was only $30.00 remember... and take it off the table top. The bike is so light, my friend gets about 6 feet of air off the first table top... he comes down on the pedals, back tire first, and as he slams the front tire into the dirt to regain traction, he splits the frame from the main bar just as I did after a year of riding the Redline.
Square tube is not meant to handle high amounts of torque or shearing force... it great for direct force like a jack extender like I saw in another post, but breaks under the slightest pressure from anything that we would put it through if it were a driveshaft or roll cage. That's why we use round tube for just about everything on our vehicles. Rectangular tube is another story entirely, and should not be confused with square tube when reading this.
