build diary

October 31, 2004:
From the front.
I'm fairly happy with the appearance of the windshield although I'm hoping the final result will be a little more transparent.
entry 661

November 1, 2004:
The windshield glass is cut!
I'm impressed. The glass shop (The Glass Brokerage in Grand Junction) quoted about $36 to cut the screen and said it would be done "maybe today, might be tomorrow". Three hours later they called up and told me it was done - and the final price was only $31. Now that's a company I like to work with!

I've put up a diagram of how I arrived at the shape for my windshield. One thing to note is that the CMC scuttle was close but not quite symmetrical. I'd recommend careful shaping! Tomorrow I'll build a tool to bend the aluminum extrusion as suggested in the Locost book - one of my rare uses of the tome - and see how that works out.
entry 662

Some details on the shape of the windshield.
I put a nail into each of the three locations marked by a circle and then put a piece of welding rod between them - over the middle one and under the two on the sides. This gave a nice constant curve.
entry 663
A view of the welding rod being used to shape the top of the windscreen.
entry 664
The glass for the windshield is cut!
entry 665

November 2, 2004:
I fabricated a tool for bending up the aluminum channel as seen in the Champion book.
The problem is that the channel buckles every time I try to bend it. I'm using 1/16" wall aluminum - thicker might prevent it from kinking, but it would also make this quite difficult to actually bend. Hmm. I might take it to the professionals.
entry 666

Hmm, the aluminum channel doesn't seem too happy about bending into shape.
Every time I try, it buckles.
entry 667

November 3, 2004:
Upon a suggestion from the Locost mailing list, I tried annealing the channel before bending it.
This is accomplished with a propane torch. It certainly made the channel easier to bend but it didn't prevent it from kinking on me. Tomorrow I'll wander down to my local fabrication shop to see what they think about it.
entry 668

Annealing the aluminum to make it more pliable.
entry 669
Nope, the annealed channel didn't work either.
Easier to bend and with less dramatic kinks, but still not good.
entry 670

November 4, 2004:
Well, I've been innundated with helpful suggestions about the windshield!
Thank you everyone. There's a lot of information and a lot of interest in how to accomplish this. After talking to my local fabrication shop, I'll try annealing the aluminum several times before attempting to bend it and letting it air cool. I'll put a 1/16" shim in between the plywood and the channel to take up a little bit of slop that's letting it kink inwards. Once I've tried the bend and if it kinks again, I have been given a set of instructions on the best way to "tuck" the channel back flat again. Right now the channel is cooling down from the initial annealing attempt...
entry 671

November 5, 2004:
Closer.
I've made a number of improvements to the various tools involved. Lots of annealing with a propane torch (and a certain amount of melted aluminum due to an acetylene torch) was the start. I also tighened up the tolerances on my bending tool which seemed to help a little and added a clamp to hold things in place - but what helped most of all was putting a metal shim on the side of the form. See, my channel was 1/2" x 1/2" x 1/16" wall. If you do the math that means there should have been a 3/8" gap - like my form - but it was actually more along the lines of 1/16" greater. This gave the aluminum the opportunity to squish inwards. Removing this option seemed to make a big difference. It's still not perfect but it may be enough to accept for the time being. One tip from a successful builder was that his channel was 5/8" x 5/8" x 1/8". Perhaps the thicker wall is less prone to buckling. I might give that a try as well if I can find it at a hardware store this weekend.
entry 672

My original bending tool.
The tolerances are a little high. Could this be the problem?
entry 673
The New!
Improved! bending tool. Tighter tolerances. Is it good enough?
entry 674
Aha!
A clamp added to the form kept the channel in place and a metal shim ensured there was no play. It's a very good bend but not perfect.
entry 675
There's still a little crimping in the channel after being bent.
entry 676
The next challenge - how to bend this?
entry 677

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.
entry 678

Yet another version of the bending tool, this time using a larger wheel.
Nice tight clearances and a decent bend - but I should have used some lubrication to prevent scarring like this.
entry 679
Success! A perfect bend.
entry 680

November 9, 2004:
The bottom bend was done by hand on the piece of plywood that had been cut from the bottom.
The shape was then tweaked slightly against the main template. A simple and quick job.
entry 681
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