Thanks Jim, I guess that is one of the advantages to a parallel construction.
Would a complementary weld on the bottom cancel out the upward distortion? My thinking is that if the weld on top pulls the ends in that direction, a weld with the same settings on the bottom would tend to pull the ends in the other direction.
Jon
Maybe, but that's above my pay grade. Could you add feet at the ends?
I don't trust my amateur welds in tension like that unless I test them. When I made scaffolding I applied 1000 Lbs vertically and 500 diagonally to the frames, after grinding the welds smooth so cracks would show up better.
jsw
Aye, I can indeed add feet. How much do you think (ballpark) the ends might pitch up, maybe a 1/4" or so?
Jon
Lots of "real" fabricators have been using that method for decades. It DOES work. Don't even need to actually lay a bead. Just heat the back-side (and sides on a square tube) to a bright cherry red with a big hot torch, then quench it quickly. Heat again to almost a dull cherry and let cool slowly to anneal if it is not mild steel.
If you are making two of these you could clamp them back to back with a shim in the middle to straighten them. I've done that with 3" channel iron salvaged from overloaded pallet racks. If 2-1/2" tube is too stiff for your C-clamps, maybe you could chain the ends together and jack the middle apart. Be careful, it's a crude crossbow.
jsw
Ah, indeed I am, thanks Jim.
Jon
Cool, thanks Clare. I don't have anything bigger than a MAPP torch, but I will consider a big weld on the bottom.
Jon
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