Unibody Welding

[cardot33]

I'm borrowing a matco mig welder from a buddy of mine. the wire speed was set VERY low, but I know I was putting too much heat onto it. I think it was put at a little over 5 out of 10. I should've taken more time to do it, but my dad needed my help to bale straw so I was in a bit of a hurry. funny how you mentioned that bmw, we were just talking about body welding at work today.

[Daguse5853Z]

Do you guys prep the metal before you weld it? I always take a grinder or stiff wire wheel to what I'm going to weld. The barer the metal the easier it is to weld.

[cardot33]

yea, prepping the metal is a must, I used a wire wheel on a grinder.
my alignment is still the same as before btw.

[Alxsmt]

not sure if your worried about this but dont crash. spot welds are where they are to absorb the impact. also on the other sides of your welds (inside the car) will rust if ya dont treat it, may not be a consern but just a heads up if you didnt think about it

[neo71665]

not sure if your worried about this but dont crash.t

Pretty sure thats everybody's mindset

[danbettis]

The best thing to is add more spot welds, lots of spot welds. That is what alot of people are doing club racing wise. A good body shop has what is needed. In the end, the car come out stiffer and lighter. Not to mention you do not risk weakening the structure with all the heat bead welding.

[cardot33]

The best thing to is add more spot welds, lots of spot welds. That is what alot of people are doing club racing wise. A good body shop has what is needed. In the end, the car come out stiffer and lighter. Not to mention you do not risk weakening the structure with all the heat bead welding.

yea I've found spot welding is just all around a smarter way to go about it. I originally thought if I just had a lot of spot welds it wouldn't hold much, like tacking two pieces of metal before welding them. after welding on my car and welding my sister's trampoline I realized. it's actually strong because of all the reinforced spots spread throughout the chassis. I'm tempted to take a second try at this and just cover it back up again once I get my spot welds done. very tempted.

as for the foam, where do you get it? I would guess that expanding foam Great Stuff, but that seems like it would be pretty flamable to me.

[woody90gtz]

Do NOT use "great stuff" foam. It an open-cell foam that absorbs moisture out of the air and will rust your car from the inside out. I heard a horror story from a guy on NastyZ28 who used it a few years ago to quiet some rattles.

Structural foam is a 2-part catalyzed closed cell foam that is waterproof, and probably a few hundred times stronger than "great stuff." I have had issues trying to find where to buy it as a DIY kit.

[cardot33]

so how do we get this high density foam? if I have to buy a lot more than I'll use on one car I can always make my money back doing other cars. so how about buying it commercially?

[danbettis]

What about paint and body supply shops?

[cardot33]

anybody i know around here doesn't know what I'm talking about. at least none that I know of. I'll keep looking around.

[danbettis]

A friend is teling me the cars with structual foam in them are usally precast. There are a few that are injected. More imporantly he says you have to get the metal extreamly clean or its a waste. The bond it makes with the metal is where it gets is strength and keeps it fomr making noise it self. Even the precast blocks are glued in. Also there is a big differance between structural and the acoustical foams. Mainly thier expansion rates. The acoustical expands alot more and can break welds and rip sheet metal, but is not very strong compared to the structural stuff which will expand much less.

Dow BETAFOAM and 1908 Fusor Terocore Structural Foam are what OEMs are using and suggest in repairs.

[jman093]

You can try buying it off of here. This is the exact stuff Sport Compact Car magazine once used on a 300ZX.

http://www.grainger.com/Grainger/HANDIFOAM-Foam-Kit-4KK28?Pid=search

[danbettis]

The does not look to be structual, looks like more of a sealant.

[jman093]

It's 1.75 lb/cu. ft polyurethane STRUCTURAL foam.

Here's SCC using it since you won't believe me:

http://www.modified.com/projectcars/0006scc_project_nissan_300zx_part_5/index.html