Got a newb question. I am building my first rod/car. It is not going to be road legal and is really just a race car to get some cheap fun from. I'm remaking a trans tunnel to fit a larger Rover v8, and the plan is to seam seal, paint and underseal what is pictured, leaving it frequently tacked every inch as shown. I remember reading somewhere that fully welding sheet metal ( I used 20gau) in areas such as this isn't totally nessesary, since it doesn't always make it stronger and can easily cause warping. Is it ok to go ahead and weld it no further? The car is seperate chassis by the way.
Since it has limited structural loads, I would think your plan of attachment and sealing is adequate. Ray
If you're good with a TIG, then go ahead and weld the seam. Of course, if you were able to do that you probably wouldn't have asked in the first place... If you're like me and lack those skills, 20ga is hard going with a MIG and you'll never get a good continuous weld anyway. What you're doing is more than adequate if less than aesthetically perfect. It's what I've done. Was reading yesterday about a Terocore structural-foam strip OEs can put between overlapping panels and spot-weld thru, to provide continuous bonding over the rest of the seam, seems like it'd be an excellent thing to use in floorpan, etc. replacements if you could MIG plug/tack-weld thru it.
I would skip weld it at the very least say 1" welds. I don't know how rigid your frame is but when it flexes those tacks will pop loose.
Fit it so it would seal well (especially hot air from the motor), add some sort of thin weather stripping and screw it down. You never know when you have to get to that side of the tranny, etc. Gary
If you run just a half inch bead spaced out 1-1/2" you wouldn't have to worry about the tacks popping loose or creating too much heat. I wouldn't think it necessary to completely weld it up as long as you seal it. IMO: One of the biggest keys to welding sheet metal is patience. It takes a lot less time for you to wait on the metal to cool the first time than it does to warp it and have to remake it all over again. Good luck!
Do it to as much as you want. On my old Austin Healey 100-6 you could remove the enire bell housing / tranny cover in one long piece. It just screwed to the floor pans and the inside of the firewall. Or you could weld the whole thing up solid and perhaps leave some removable covers here and there to get at the linkage, senders, etc. if they couldn't be worked or adjusted easily from below. Gary
Good job so far. At this point seems like you are 1/3 there, as far as tack welding the seam. I'd finish tack welding it entirely, and if you are skilled enough do some 1" beads. Check with a light bulb underneath in the dark to see if there are any pinholes that need tack welding closed. Then grind the welds smooth as you want. Take your time and reap the rewards.
nice work. I think he meant are you sure you don't want to make some of the cover removable? I like having access to the top sides of parts for service(esp on a race car). if you can get to everything from the underside of the car, & don't mind working on it that way, then weld & seam seal it up. if you want to be able to remove the cover, then use some type of weatherstrip or silicone to seal the seams.... the drop light under the car in a dark shop works real well to see where you have missed. I have seen floors crack right next to the welds when the chassis twisted alot.....
As long as every joint has good overlap then spot welding will work fine. On butt joints I don't know if the seam sealer will last long term.
screws and good quality sealer foam or tube type should do for the long term. did a search on the Henkel product Terocore Structural Foam Strips and only found it on big commercial sites.
Look at the way the factories build new cars. A spot weld every 2 or 3 inches is plenty strong. When arc or mig welding I like to make the tacks at least 1/2" long to be sure they penetrate. Then grind off any big gobs and seal the seam with butyl rubber calking. Do not grind the weld too far or you will weaken it just smooth it off.
As stated above by a couple of people, I wouldnt leave it as just tacks. I would make the welds about half-an-inch to 1-inch in length with about a 1 inch gap in between, then seam seal.
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