This might come in handy on your next automotive project. Here is an extensive thread on how to build a TIG welder using scavenged parts. The setup uses a 130 amp alternator connected to an air compressor motor. The negative side of the alternator is attached to the torch and the positive to the ground clamp. The alternator field is supplied by a battery with a headlight dimmer to regulate the input power which in turn regulates the output amperage. People have been using similar setups like this to do track side repairs for many years. The pictures have disappeared from the thread a while ago, but here is a link to a site that stole them wholesale.