Welding Floor Pans

[Tumbleweed]

I know I have read this somewhere but I'm getting ready to mig weld in my floor pans. I am going to butt weld this time as I did not like the look of the overlap in my last restoration. I thought that I had read somewhere that backing up the welded panels with copper or brass is a good heat sink but also gave a smooth welded surface on the oposite side, and the weld would not stick to the brass or copper bar. I have not tried this technique but thought I would ask the question. Anyone tried this? Thanks in advance..George

[rocketeer]

I use copper and aluminum. I took a 3/4" copper pipe about 18" long, flattened 12" of it, and bent the remaining round part upward slightly to act as a handle.

For the majority of my welding I use flat aluminum stock purchased at Lowes as a backer, 2 or 3 inches wide and cut to varying lengths depending on where it needs to fit.

I also use butt-welding clamps:

http://www.northerntool.com/shop/tools/product_200381757_200381757



Larry

[Tumbleweed]

rocketeer, thank you. I'll drop by today and pick up 2 sets from my local NT store. Using aluminum and or copper did you get very smooth weld on the opposite side?

[rocketeer]

Using aluminum and or copper did you get very smooth weld on the opposite side?

No, not perfectly smooth. Backing up the welding is more to keep the weld from blowing through and to help prevent warping. I don't know how experienced you are with MIG so if this is redundant just ignore it. When butt-welding sheetmetal the best way is to stitch it. Apply a stitch every few inches, let it cool then stitch halfway between those stitches, let it cool, then fill in the remaining space, again allowing time to cool. Butt welding sheetmetal it's very easy to overheat the metal and end up with ripples and bulges from warping.

Larry

[Tumbleweed]

Thanks again Larry, the information is great. Always good to get helpfull suggestions. I plan on playing with the MIG again tonight with my new clamps and back up material to see how I do. It has been over 2 years since I last worked on the MIG. I'll run a few practice beads and stitches to see if I can get tuned in again. I did have a problem with welding holes and seams on my wagon project but I did not use a heat sink either. I'll let you know how it turns out.

[Gunslinger]

There is another option to butt welding if you want to consider it.  You can overlay the new pans with a 1/2 inch overlap, clamp your backing material to the back and spot weld the new pan on top of the old one.  I used this method to fix the weld seam on my hood.  You don't need to drill holes in the top sheet as the weld gets plenty hot to burn through to the under sheet, and the backer keeps it from burning through completely.  

The problem you run in to with this light gauge metal is that it warps when you add heat, MIG welding tends to push the heat ball in front of the weld wire, so the longer your runs the more heat you push, consequently it warps.  Thats why the method Larry suggested is critical on a butt weld, weld an inch and move so that it doesn't overheat the seam and warp the metal.  Practice a lot!!!

[Tumbleweed]

I'll probably run a number of spot welds or short stitches. Certainly will practice again on some scrap metal the same guage as I am welding. I tried to do do this last night but we had a mean lightning storm in the Ft Worth area. I figured I better not play with electricity. I got some copper and scrap alum. yesterday from work. We are expecting bad weather again tonight so looks like Saturday before I can let some sparks fly. Now that I know how to post pictures I'll send a few if the welds are good!

I'm going to have my Jeep dipped to remove rust in a few weeks. I found a place in Arlington called Metal Rehab (the GM there has an M38) the cost was reasonable and an alternative to blasting. They will also prime my Jeep for a little extra. I got my pans from Classic Enterprise a few days ago and they look great. They are heavy guage and plenty of material all the way around in case you need to cut more floor out.