When you are looking for strength, do not choose aluminum. Particularly not aluminum extrusions. I hope you don't love your camera.
Had a satellite dish made entirely of aluminum once upon a time. It kept cracking the trunnions that supported a 20' dish. Manufacturer tried several ways to repair it, different alloys and such, but what worked was to replace the aluminum trunnions with steel trunnions. The steel was more than twice as strong as the strongest of the various aluminum alloys they'd tried. The 10-ton jackscrew that raised and lowered the antenna put the trunnions in tension to raise the antenna, and compression to lower it, and the aluminum was simply not strong enough.
Why was this important to me? I used to have a photo of myself on the base of the antenna, with the antenna up over my head. That photo was taken about 2 minutes before the cracks were discovered for the first time. The antenna itself weighed several tons, and the hardhat I was wearing wouldn't have helped much at all if the thing fell on me. Before I was up there, several of my people were up there, too. Could have killed any of us. You're mounting this thing over your head. It doesn't weigh tons, but it could still give you a pretty good whack on the head. You don't seem to wear a hardhat in your shop. You might want to get one. Or make the thing of steel, and it will be that much stronger. Go ahead and put the springs on it, too. And friction locks for the joints. And forget might, get a hardhat anyway! Paranoia pays!
Bill
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