Success with the Shields
6/15/01 Success with the Shields!
After a few weeks of research, and practice, I’ve succeeded in creating one exhaust shield!
I decided to order 1100 series aluminum to make these shields. 3003 would have worked fine, but I decided to heed François’ advice since I can’t fault his past experience. 1100 aluminum is basically pure aluminum, and is the most malleable, so I would probably have the best shot at making it with this stuff without stress cracks.
I ordered my 0.032″ aluminum from http://www.mcmaster.com/. They have an unbelievable catalog with all sorts of stuff, and they’re in N.J. so the delivery was quick. I ordered a 24X36 inch piece, enough to do a couple of shields in case I made a mistake, and it cost about $21 bucks with shipping.
After cutting one shield out, I decided to completely finish one shield so I could foresee the problems before I ruined two of them! I filed all the cut edges to remove all the burrs and imperfections because I learned this is where the stress fractures will begin. The tight radii for the spark plugs were very tricky, and I don’t think this would have been possible without annealing the metal in between shaping.
I hammered the aluminum over the plywood bucks I made a few weeks ago, until I felt the aluminum “work harden.” Patience was imperative because if I tried to rush the process, the aluminum would reach it’s stretching limit and crack. After annealing it with a plumbers torch, the metal would get malleable again, and I could hammer and stretch it some more. This shot shows a detail of a finished shield where one layer of aluminum is folded over the inner layer, and insulation is sandwiched in between. The extra “scalloped” radius is to clear the spark plug boots.
Another detail is the outer edge of the shield. After folding over the outer edge to 90 degrees, I carefully scribed an even line to cut off the excess material. This gives a nice even edge all the way around the shield when it’s folded over and hammered down, as you see here.
The next step was to bend the whole shield into a large radius curve. Since my engine and exhaust headers are at François,’ I was able to get just the right curve. The final step will come when I tighten the header bolts, and get the shield lined up before I drill the attaching holes. I’ll do that when I finish the other shield.
My first shield took roughly 4 hours! I’m sure the next one will take less time, but the satisfaction of watching all the steps I took work without problems was great. I have to thank everyone who offered advice and guidance through this process. I left the shop today with such a sense of accomplishment, even François was impressed!
A separate thank you should be sent out to Kent white at http://www.tinmantech.com/ . His advice helped give me a good starting point on how to anneal and form aluminum. His site has a wealth of information on metal forming, and I’m putting my order in for some video tapes to learn more.
Now if anyone feels less adventuresome, but needs new exhaust shields, let me know. You might be able to talk me into making you a set!
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