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Q. I noticed you've had a lot of response to the problem of warping a '48 Chevy hood (in the January '10 issue) and whether or not to remove the flange when welding hood sides together. I had a similar experience with my '32 Pontiac hood, and I wanted to share my solution.
This was a two-piece hood that has been welded down the center to eliminate the center hin
My hood was the four-piece style, with a piano hinge down the center. I decided to close the hood side doors and make the top a one-piece unit from the two original sections. After removing the piano hinge, I had a 1/2-inch gap and 1/2-inch flanges, so I used 1/2-inch-square tube and MIG-welded it in with short welds, using wet towels on the hood to keep the heat down. My hood had some nice deep body lines about 2 inches from the hinge line, so I figured it wouldn't warp beyond that.
At the back of the hood the lines disappeared, and I ended up with a 4-inch diameter oilcan in that area. Not being a heat expert, I came up with a solution I think most hot rodders would like: I put in rows of louvers! I figured the stretching of the metal would pull the oilcan out, and it worked like a charm.
The hood is now very rigid, and keeping the flange plus the 1/2-inch tube makes it quite strong. Plus, you get some cooling effect, and the added cool factor of having louvers!
A. I must say, that is a novel solution to an age-old problem, and it came out great! For the record, I don't generally recommend welding any thicker material to sheetmetal panels (with the possible exception of welding reinforcements on the panel edges) since the thicker section will prevent you from stretching out the weld shrinkage with a hammer and dolly. Obviously, your creative solution of using louvers to pull the metal worked great in this situation, but adding louvers will not be an option for every oilcan situation.
Q. What are your thoughts on oxy/acetylene brazing for fabricating operations-chopping tops, frenching headlights, shaving, and pretty much every other aspect of sheetmetal work? I have a lot of experience in brazing from years of building fairly intricate radio-controlled race cars.
Via the Internet
A. Brazing has been around for a very long time, and it has some characteristics that make it well suited for a number of applications. Brazing is a relatively easy process to learn, and the equipment required for brazing is less costly than for any type of electric welding. When brazing, it is easy to build up a lot of material, as is sometimes needed for creating fillets or filling low spots. Brass won't rust, so it's a good material to use on parts that will be chrome plated. While brass isn't quite as strong as steel, if you build up some thickness of the material, the brazed joint can be as strong, or stronger, than the base metal. Also, brass can be used to fill gaps, which is much more difficult to do when welding with steel filler rod.
If you've been in this hobby for some time, you have probably seen a lot of photos in old magazines that show custom cars and trucks being built with the bodywork being brazed, since that was a common way of working back in the day.
Unfortunately, there is one characteristic that limits the usefulness of brass for autobody work, such as chopping the top on a truck or shaving the hood; neither paint nor plastic filler stick very well to brass, so I really don't recommend it for work of this nature. Now that I understand the limitations of brazing on bodywork, if a car or truck comes into my shop with an area that has been brazed, I cut it out and replace it with new metal!
Bronze filler rod is increasingly being used with MIG and TIG welding. Bronze is an alloy of copper and tin, while brass is an alloy of copper and zinc. Paint and plastic body filler stick pretty well to bronze, so many OEM manufacturers are using bronze-welded joints on certain body panels, and it's becoming more accepted in the collision-repair trade, as well.