Need Advice on Roll Cage Project

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I need advice from the experts here.I'm currently building a 'racecar' and will be buying, bending, notching and tacking a rollcage built from 1.5" x .120" DOM (mild steel) tubing.  I would like to tack it in place as I'm building it, but do not have the equipment or expertise to completely weld it up.Would a Harbor Freight 90 amp MIG gasless flux corded welder work to make the tack welds?  I'm open to suggestions here!Would an experienced welder be able to complete the 360* welds on the tubing with my tacks in place?  I'd like to have it TIG welded, but would be okay with having it MIG welded.  Any suggestions to keep me from getting raked over the coals would be greatly appreciated.Pics, info and documentation on the car can be seen here:http://www.brooksbabies.com/porsche/Thanks in advance!Chris
Reply:If you have someone TIG weld it for you, they are going to have a fit if you tack it with flux core.  Also, if you plan on having it TIG welded, you need to clean an prep the tube on the inside also before tacking it together.  If you have it Mig welded, tacking it with flux core will be fine - just make sure you chip all the slag off.
Reply:Cool, thanks for the reply.
Reply:What material will you be using?What kind of racing will you be doing?For starters here are the tubing sizes from the N.H.R.A. rulebook..One more thing..If your using chromoly tubing it must be welded with a TIG..Mild steel can be Tigged or Migged.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterOne more thing..If your using chromoly tubing it must be welded with a TIG.....zap!
Reply:Originally Posted by worldsgreatestwelderNow that I would question. Might be in the rule book but with the recent failures  facing the NHRA, I would think that "rule" might be in question.Jimmy
Reply:Zap: I'm building a car to compete in NASA's 944-Spec class.  CCR's can be found here:http://www.nasaproracing.com/rules/ccr.pdfMaterial is 1.5" x .120" DOM mild-steel tubing (required material and size per the above rules).  Chromoly is pretty much out of the question now, due to cost and the fact that it should be TIG welded (not trying to argue here)...by tacking using an affordable 'hobby' welder, it'll have to be flux core, which adds to the cost of a pro welding it all up for me.Based on the suggestions above, it looks like I will be tacking the material with a flux core MIG (gasless) and will have it professionally MIG welded.  MANY of the cages I've seen in person have been MIG'd and from what I hear about accidents and roll-overs, it is plenty safe.  Thanks again for all the advice!  :cheers:
Reply:I would call whoever is going to weld it before hand and ask them.  Not just for tacking, but whether they'll weld it to begin with.  The shop I worked at, I refused to "finish" other people's work because all of the excess work that it involved.  Poor fitup, no cleaning/tube prep, etc etc.  More trouble than it was worth.
Reply:Originally Posted by TSORIf you have someone TIG weld it for you, they are going to have a fit if you tack it with flux core.  Also, if you plan on having it TIG welded, you need to clean an prep the tube on the inside also before tacking it together.  If you have it Mig welded, tacking it with flux core will be fine - just make sure you chip all the slag off.
Reply:Originally Posted by genikzZap: I'm building a car to compete in NASA's 944-Spec class.  CCR's can be found here:http://www.nasaproracing.com/rules/ccr.pdfMaterial is 1.5" x .120" DOM mild-steel tubing (required material and size per the above rules).  Chromoly is pretty much out of the question now, due to cost and the fact that it should be TIG welded (not trying to argue here)...by tacking using an affordable 'hobby' welder, it'll have to be flux core, which adds to the cost of a pro welding it all up for me.Based on the suggestions above, it looks like I will be tacking the material with a flux core MIG (gasless) and will have it professionally MIG welded.  MANY of the cages I've seen in person have been MIG'd and from what I hear about accidents and roll-overs, it is plenty safe.  Thanks again for all the advice!  :cheers:
Reply:Are you going to be able to get the 944 under 2000 lbs?  On page 44 of the rules you posted state the roll cage must be 1.75" diameter for cars of 2000-3500 lbs if DOM is used.   1.5" tubing is only for cars under 2000 lbs.  I'm pretty sure the 944 will still be over 2000 lbs, even in race trim.Sorry, I just notice the roll bar specs on page 62 contradict the specs on page 44.  That says 1.5" x .120 DOM tubing can be used on cars less than 3000 lbs.  I'd double check which page has the correct specs before I built the cage.PatrickLincoln 175HD
Reply:I was looking over your bright red painted Home Depot "tow hooks" in Installment 9, Mud, Sweat and Tears:  http://www.brooksbabies.com/porsche/inst9.htmMay I suggest, while you have your welder fired up, that you weld those eye bolt rings solid.  One good yank will open what you have now.
Reply:There is another problem you *should* run into as you tack your cage together.  A well-designed cage has most of the bracing meet at common joints called nodes.  When multiple tubes come together in a node you usually end up with joints that are covered with other tubes and therefore need to be welded before the covering tube makes it impossible.Perosonally, even if i was MIG welding a cage I would not want any nasty fluxcore tacks to deal with.  But then again I wouldn't be taking on a project started by someone else, anyway.
Reply:Okay, you guys make some good points.  Thank you for pointing that out.I don't have to tack the cage in place.  I can build it using temporary means of holding the tubing in place.  Do you guys think that would make it easier trying to find a pro to take the job of welding up my work?  This way I get the joints cleaned and prepped just before I take it to them.As far as 'kit' cages for the Porsche 924/944, they are all pretty frightening.  Most bolt to the the sheet metal floor pan, and all of them do not fit very well.
Reply:Oh yeah, I'm 100% sure of the tubing size, material and thickness.  I've confirmed this a NASA tech inspector.Good call on the tow hooks.  I may even try welding that myself one day