welding chassis on a jig

[eddie m]

in the matter of welding a tube chassis together, some chassis builders tell me to fit and tack all the tubes, then go around and partly weld all the joints that are at the top of the joint, then release the chassis off the jig, flip it over 90 degrees on its side, weld the joints, flip again, weld and so on,
others tell me to weld the tubes as much as possible while on the jig as the chassis is being assembled , ie, fit a tube and weld, fit the next tube, weld it in, untill the chassis is finished, then release it from the jig, and flip it around to weld any joints that were hard to get at.
the second way makes more sense to me, and should keep the chassis more true, but what are you all guys thoughts on this subject.
I plan on bulding a full tube chassis latter this year, and I want to do it right.
all the welding on this is tig , the tubing is moly.
thanx
ed

[broland]

I can't help you on a full tube chassis, but I'm doing a back half job to my car and also adding a cage and I was told, even with everything tacked, do not move the car or even take it off of the jack stands, because everything was levelled up, until everything is completely welded. So with htis thinking, I would think that the best thing to do is try and weld everything up as much as you can. If you'd like to be sure, I can give you the name of a guy whom I deal with at S&W Racecars, that can give you or get you the answer?
Just let me know if your interested.
Bruce

[cope]

I agree; the only way I would flip the chassis is if the jig rotated also.

[morpheus]

I have no problem doing it the way you describe here:

"some chassis builders tell me to fit and tack all the tubes, then go around and partly weld all the joints that are at the top of the joint, then release the chassis off the jig, flip it over 90 degrees on its side, weld the joints, flip again, weld and so on, "

a friend of mine did that and it worked out great for him, it's mild steel but it worked out fine for him.



- jack

[Mike Sherman]

You need to weld it enough in the jig to keep it from moving or breaking when you take it out. The entire thing should be assembled and tacked before taking it out of the fixture (if possible), welding in different locations is important to keep things from pulling too much. Stay with the first advice you were given. Keep in mind it is possible to do most things more than one way. It is just sometimes one way is more efficient than others.

[Guest]

I like to weld that type of stuff in the jig as much as possible. We work to the thousandth of an inch and do have straightening to do afterward...if you're working to, say 1/8" of and inch, the warpage you get will probably be in tolerance. We also notice that in welding circumferential welds, that by going in the same direction around the tube, it will twist the tube in the direction of travel. So we weld like you would tighten the lug nuts on a wheel. I speaking now of tube thicknesses of .035" diameters of 2" and up. Bottom line is that if you tack it real good, like Mike says, weld it where you can then take it out of the jig, you will do just fine.