build diary

November 7, 2004: I've done it!
I started by remaking the tool once again with a larger wheel, as I'd seen a bit of distortion at the end of one of my failed bends that was due to the small radius of the wheel and to some overly-chamfered edges. A 2 1/8" hole saw and a piece of 1/2" aluminum plate and I had my new wheel. I was smarter about the order in which I measured, drilled and welded on this one so it ended up with tighter tolerances than before. It was so tight, in fact, that in one of my bends it started to tear up the metal. Some good oil solved that problem on the next bend. But the real secret was in the aluminum channel.

On a trip to Home Depot yesterday, I decided to look at what they might have to offer. I was looking for some 5/8" channel with thicker walls, as it appears that Ron Champion used 5/8" from a badly-labeled diagram. I didn't find that but I did notice that the 1/2" channel appeared to be softer. It was a slightly lighter colour than the one I'd been using and seemed to have a more satin finish. It was also about $3 cheaper for an 8' length, so I bought some home. I annealed it with the propane torch (the temperature of this is just about perfect - burn off a Sharpie line and you've got it) and it bent beautifully. So that was the problem all along. Whatever kind of alloy I was getting from the local fabrication shop was less excited about bending than the cheap stuff sold in every hardware store. The display was labelled "SteelWorks" and it's carried by Lowes, Home Depot and Tru-Valu. So, the tricks to a perfect bend are the correct aluminum, annealing, no slop in the form and some lubrication. I don't think many of the other things I tried matter. Now I just have to bend the bottom form but that will be easy enough to do by hand. I have the piece of plywood that I cut out of the bottom to use for shaping and some test bends indicate that this is pretty easy. Then it's just a matter of mounting it to the car and I already have ideas there.

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