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chassis welding question

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janjon:
Hello Roo and everyone:
 I have seen pictures on build threads that suggest that maybe some folks don't fully weld every chassis joint in place and on the jig.
I am in the learning process of TIG welding, I have been welding up angled and notched joints, but "cheating" by repositioning the weldment to the easiest orientation to avoid awkward out of position welding. At least to this point. Obviously I would like to (and eventually will) become proficient to the extent I can weld anything, anywhere. Ha.
 My question is, would it work to tack everything really well, weld the accessible joints as fully as possible, avoid overhead welding and joint sections that would be really awkward to get at, and remove the structure from the jig and position it to make any uncompleted welds as easy as possible to complete? I would think in that case one would want to pay attention to symmetry of progress, maybe working side to side, and one end to the other, for example, to avoid distorting the structure overall.
 Or would you say don't even attempt a chassis build till you're fully competent to weld it fully on the jig?

dreracecar:
Tack on jig fixture--- weld off, get some books on welding airplane frame stuctures to learn about welding sequence.

rooman:
Bruce is correct. It is virtually impossible to get to all the junctions while the car is on the jig, let along do a quality job of welding them. As noted welding sequence is important and the aircraft guys (old school tube frame stuff) have it sussed out.  Don Long told me that when he started out he welded one entire side of a car and then realized that the chassis had a big bow in it due to the concentrated heat input.

Roo

janjon:
Thanks for the input!

wideopen231:
I am in process of finish welding my car. I try to only go 1/4 to 1/2 way around  joint then move to next area.I think 1/4 maybe better but when a weld is going great and its so pretty its hard to stop.   I also alternate front to rear.   When a joint is finished I hit it with spray primer to help avoid missing any.   I have been told  1 amp per thousandths of material and  told er80s is tronger weld then the 70 I tacked with.Hoping mixing the two will not cause issue.    Maybe Roo can give advice here. I also try to get chassis upto 60 degrees for little while before welding on it.   Not sure how important but have heard few comments on that also and figure it can not hurt..

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