Giant erector set filter: I am looking for fittings used to join square tubular steel in various ways without welding, for purposes similar to a large erector set. This is for self-fabrication of a large solar panel mount. The pipes I am using are square in cross section measuring 4 inch x 4 inch or 3.5 inch x 3.5 inch. I'm looking for straight splice joints, T, L, X, and 45 degree angles.
If any mechanical engineers want to take pity on a computer geek attempting to build a huge erector set, please point me in the right direction. First I'll say that I'm not attempting to build anything that will be inhabited by people or animals, individual pieces can be lifted into place by two people, and it won't rise to a great height off the ground, so the risks should be negligible.
I am working with square cross section 4" x 4" (4 mm wall) and 3.5" x 3.5" (3 mm wall) tubular steel in pieces not longer than 3 meters. It generally resembles the products found on the second page of this PDF file
To keep welding to a minimum and because the structure may need to be assembled and disassembled occasionally, I am working with M12 size bolts/washers and drilled holes for attachment of the tubes. The 3.5" tubes fit slide inside the 4" pipes like a sleeve, to create legs that can raise or lower in height by moving the position of the holes and bolts.
I know something like this exists but am not sure where to find it: Imagine I have three 4" square cross section hollow tubes and want to join them in a T shape using only drilled holes in the bolts, and bolts/washers/nuts. I am searching for the prefabricated welded "T" piece (other shapes) to accomplish this sort of thing ( in the same general way as this joint for round pipes
), and hopefully some basic CAD schematics for it...