I guess you could call this a Junkyard Tig Welder. The idea is you can mount a regular Ford 130 amp 3G style alternator on to your air compressor (or similar motor) so that you can use the belt drive off of the compressor to turn the alternator. Using a battery jumpstart box to give the field its current, then regulate the current through a headlight dimmer switch. Then hook your Tig torch up to the case of the alternator and run the ground clamp to the output stud.
Basically the motor from the compressor will be able to spin the alternator fast enough (approximately 6000-7000 RPM's) to generate the necessary power. You will probably have to put a v-style pulley on the alternator for sufficient tension. The green wire on the alternator is connected to the case as is the torch and the negative side of the jumpstart box. The blue wire is the field current, which runs to the dimmer switch so that the current from the jumper box can be varied to the desired output for the alternator, and then it goes to the positive side of the jumpstart box. Then the grounding clamp is connected off of the positive stud on the alternator.
Fortunately alternators are rated for 100% duty cycle so once you get it started (you have to scratch start it) it can keep going. At the full 130 amps you limited to about 3/16 maybe 1/4 inch metal. If you really want to get fancy you can run a wire from the negative side of the jumper box to a micro switch on the handle of the torch and tie it to a relay between the dimmer switch and the battery so that you can stop the arc and continue to hold the torch in place to cool the weld with the shielding gas. Other than that the only other things you would need would be an accessory kit for tig welding and a gas bottle with argon.
I know there are allot of people who like to, or would like to do their own fabrication and the price of a good Tig Welder can run from about 2000 to 5000 dollars which makes it just a little pricey. So, if there was a way to get those results for about 300 dollars I thought I should pass it on. I cannot take credit for this idea but, there a number of people where I got it that said it works great but as with any kind of welding it takes a few times to get the touch. I am currently in the process of collecting all the material to put it personally to the test and hopefully can have some decent results. I am also including some pictures and a simplified diagram.
Tech article by Richard Burris (ricks77eb)