OK, so I took my car to a friends house to weld in my roll bar. Hes welded on race cars before, but mainly bar-to-bar type welding, never thick to thin metals. He got to welding the floor plates to the floorpan and after about two inches or so we noticed a hole. He was able to fill it, but between both plates, he had about 6 holes! Again, he was able to fill them in, but as far as structural integrity goes, should that affect the bar or floorpan? He said he doubt it would, but I was just wanting an outside opinion.

Also, is there a way to avoid blowing holes through the floorpan other than turning the heat down on the welder? We tried that but we couldnt get a good bead going all the way around. Im thinkin the hardest part is done, the plates for the rear strut bars sit right over the rear frame rails so even if it blows through it there, I doubt it would blow through the frame.

But all in all, the welds look pretty good. I was just wondering if I need to reinforce around where there were holes, either for NHRA rules or my own safety. Ill try and get some pics up tonight if that will help. The biggest hole I couldnt even stick my pinky finger through. Thanx guys!

 

if you're burning holes you've got too much heat. It's not neccessarily the heat range of the welder, but time spent in an area also. That's why when welding in panels(for body repair and such) they spot weld only. You spot a little here, then over here, then over here, etc. By continously moving around you keep from getting the metal in that area too hot. You just have to keep spotting until it all welded.
- As long as the burn through holes are welded shut, you're fine. A good weld is stronger than the factory tin anyway.
- the "frame" in our cars is the same sheet-metal that the floor is(unibody). The rear "frame rails" are no thicker than the floor. The strength is in the bends.

 

you can lay a plate of copper or aluminum underneath the sheet metal you're welding. They won't weld to the metal, but will act like a heatsink, and will back it up, so you don't blow the metal away. Copper will pull the heat away fastest.
Also, there's a heat blocking foam from eastwood I think, that might be worthwhile looking at.

 

I thought the rear frame rails were made like the front frame rails? Meaning like where you would normaly jack up on the car to take off a front wheel, I thought it was thicker metal? I dont see why they would make the rear section of a car, expecially a part that the bumper bolts onto, soley out of sheet metal. Im not sayin Im right, Ive just always thought different I guess.

 

The whole car is the "frame" All stamped sheet metal spot welded and glued together. The K-member up front under the engine is a thicker metal but the "frame rails" are still all just stamped sheet metal.

 

ok, I always thought a unibody was basically the front and rear of a full-frame'd car with the middle cut out and the frame itself just molded into the car. But either way, would it pass tech with those holes, being filled in that is? I can get some pics sometime if it would help, but the rest of the welds along the plates were pretty damn good. Just didnt know how picky tech was about it.

One more thing, about how much does it cost to get the roll bar certified? Just so I dont have to always peel up my carpet to show the welds and plates. I dont even know anyone around here that certifies them.

 

Does it even need to be certified? If not, don't worry about it. As long as the welds don't look like they're big piles of bird crap, you should be fine at tech.

 

^^^ he's right on that one. Unless you're running really fast in a very specific class(NHRA or IHRA) they don't check certifications, just that it is there.

 

You need to feed the wire into the thicker plate more, that way you can get a good hot bead without burning holes in the thinner stuff. My brother did that when he put his roll bar in, he’s like “if a monkey like you can weld I don’t see why I can’t get this done….” A few hours later he’s called me up to see if I could come over and fix all the holes and finish welding it.

 

I still havent had a chance to go back over there and finish the rest up with him yet. But he thinks he can weld the other 2 plates in no prob. Hopefully...