I went to get some 4- and 8-gauge copper wire with which to build the full-scale chest frame. After I measured off enough 4-gauge wire to make two outer frames, I was pretty surprised just how heavy it was. So before I cut the wire off the reel, I decided to have a look around and see if I could either get thin copper tubing (and fittings), or some kind of round plastic stock (and fittings) instead.I stumbled upon a kind of polyethylene drip irrigation tubing that also has most (but not all) of the fittings I’d need to build the frame. It’s much lighter than copper — in fact it’s even lighter than my original aluminum frame. The 1/4″ PE tubing is thin, and usually comes in reels or rolls, and is therefore perpetually curved. But I found these six-inch risers that were very straight and actually have thicker walls than the usual PE tubing that comes on reels. Plus, no one segment in my frame is longer than six inches, so the short riser length didn’t actually introduce any problems. Polyethylene turns out to be a lot easier to work with than any kind of metal—big surprise there! Above you can see my plan for the segments and fittings. (Is there anything Excel can’t do?) There’s no “+” shaped fitting available, so I had to do some hackery (the red points), where I drill the fittings and push 10-gauge wire tight through the holes, as you can see me doing for an elbow fitting in this other picture. Putting the risers onto the fittings seemed hard until I discovered that if you warm up the ends of the PE risers with a blowtorch they slip right on.
Below you can see the partially constructed frame, which I’ll finish tomorrow. It’s very light, and already relatively rigid, before even the addition of the crossmembers. I’m glad I discovered this material – and that I get to forget about my bad metalwork!