Single-Axis East-West Sun Tracking Ground Mount Design

[400bird]

I got a great deal on 4 1/2" galvanized hexagon pipe for mounting.

Wow, that's a unique score! Hexagon pipe sounds expensive, someone must have screwed up an order of you scored it cheap.
What's the wall thickness?

 

[Fearless]

Wow, that's a unique score! Hexagon pipe sounds expensive, someone must have screwed up an order of you scored it cheap.
What's the wall thickness,

12 gauge. They were even the perfect length of 11' 8". Only $30 each.

 

[400bird]

That is a good deal!

 

[Fearless]

Picking up the final piece to the puzzle today or tomorrow, the slew drives.

 

[400bird]

Cool, what did you end up getting for the slew drives?

 

[Dave911]

12 gauge. They were even the perfect length of 11' 8". Only $30 each.

Those sound like good columns to support a porch, if they are used in compression.
But if you put a bending moment on them they will tend to buckle and bend over. Max moment will be just at the column/concrete junction. 12 gauge is very light for such a large section.
If you fill them with concrete that will help prevent buckling. Better yet, get some 5+" square steel tube. My guess would be at least 3/16" wall. Or get some 5+ in Schedule 40 or Schedule 80 pipe. Make sure you put it in concrete and go down 3 1/2 ft or more. Don't overlook scrap steel. I understand that used drill stem pipe is available in large quantities in Texas as scrap. I know its used a lot for fences but they must have larger sizes that are used for deep wells. If you do some calculations on the max force on your panels if you get hit with an 80+ mph wind with your panels up, you will be shocked.