Trick to welding under car?

First things first, clean the $#!t out of your weld area, the better your prep the better your weld. Find a good position where you aren't directly under your weld (as best you can) Keep your beads short, so as to keep your sheet metal from warping.
I'd recommend making a mock setup of your work space & work with scrap metal to get a better grasp on how you want to approach this, finding that comfortable position is 60% of the battle, the other 40% is keeping buckshot out of your sleeve

I had issues with this too, but was eventually able to do it. I think I might have slowed the wire down a tad, or maybe increased the speed a little. Can't remember now, but it did get easier after doing it a couple times and adjusting the machine. I also got the car up as high as possible, but was still on my back. Wear something thick, and you can put starch on the shirt to help the beads roll off your shirt.

I have found that increasing the heat and wire speed helps when welding up. I don't know if it's a gravity thing? But it works for me.

I weld upside down all the time. Be careful with starting too hot as you can still burn through the metal. Find your optimum welder setting as if you were welding in a normal position and start there. I turn the gas pressure up about 5-10 psi to ensure complete coverage of the weld area with gas. Some welding gasses, such as argon, are heavier than air and does not float like helium so that few extra psi helps propel it onto the work piece while upside down. Also, like others have mentioned, comfort, or at least a position where you can keep a steady hand for the length of the weld is key. You may be uncomfortable, but if you can hold the position with a steady hand just long enough to weld your bead (however long or small) your good. CLEAN THE AREA.... THEN.... CLEAN THE AREA. I wipe with acetone or brakekleen to get any oils off the metal if I think some may have smeared on there from cleaning. A wire wheel on a 4 1/2 angle grinder will be your best friend here. All other welding practices stay the same as if you were in a 1G or 2G (read "normal, easy") positions. Hope this helps. Best thing is.... Just do it man. See what happens. That's learning, and by the end of the day, your butterflies will have moved to someone else's stomach!

I turn down the wire speed just a touch.

NMEMJCM said:

I weld upside down all the time.
<snip> CLEAN THE AREA.... THEN.... CLEAN THE AREA. I wipe with acetone or brakekleen...

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NO!! NO!! Danger Will Robinson!! Welding heat will release deadly phosgene gas.
Read the Link, Google , but don't let brake cleaner anywhere near welding.

Hi,
I guess it goes without saying, own an auto-shield.
I always laid a little to the side, with only the appropriate side of the body raised. This gave a little better angle, as well.
Good Luck!

Dharrelson.... I am a licensed and certified TIG and ARC welder. You would think I would know that, and I did not, thank you for the info!!! after talking to a chemist at work, there is almost as much of this poisonous gas in a lit cigarette, so.... don't clean your work area with brakleen or lit cigarette's because they can kill you.

NMEMJCM said:

Dharrelson.... I am a licensed and certified TIG and ARC welder. You would think I would know that, and I did not, thank you for the info!!! after talking to a chemist at work, there is almost as much of this poisonous gas in a lit cigarette, so.... don't clean your work area with brakleen or lit cigarette's because they can kill you.

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Geeze, guess I fell for an urban legend. I didn't notice 'til after I posted that that all of the warnings referred to the same story, so never mind...