Ive been a pro welder for 2 years, maybe i can help a bit.. Sorry if i spell stuff wrong, my english is a bit sucky..
Now, i dont know anything about american voltages or amp standards, but I tried welding with an extension chord here in europe once, and it worked flawless.. If you have a good cable, it should be no problem. If you use a cable reel, ALWAYS unreel the whole thing or you will frie your cable.
I dont know how amateur welder you are, but did you setup your welding machine properly?? Seems you're using a mig/mag welder? The ones i uses for work had power settings and wire output settings... Different thickness of steel needs different settings. Thicker steel needs more power (deeper penetration), but more power needs moor wire.. Less wire gets better penetration but bad looking results and makes it harder to weld. Too much, and you'le notice :D . Always practice on 2 pieces of scrap metal of same thickness as what your working on before you go welding your real stuff.
If you weld pieces of different thickness it can be a bitch. Thicker metal absorbs more heat before melting. Pre-heating can help. Also depending on what and how youre welding, you may also wanna grind thick metal pieces to form 'a V or Y shaped welding area' before you start welding. That way you get better penetration too. If your welding machine isn't capable of doing the weld in 1 run, you could do multiple layered welds in "the V " But you wont get a good looking result. Again: always practice before welding your real stuff!!!
As said, windy conditions can totally mess up your weld becouse of the shielding gas being blown away. More shielding gas can help, but be aware, too much gas WILL suck oxygen into your weld by whirling. Just blocking the wind might be a better option. Also old paint can make it much harder to weld, removing it before welding will help a lot.
Good luck on your build!
Last edited by knakker123; 02-19-2012 at 10:59 AM..