I use a plasma cutter. On the small ones I can cut up about 30 an hour, takes about 1 hour after that to clean up the winding. They average around a pound and a half of copper per unit. If they were properly evacuated you won't get the burnt freon smell. The bigger a/c compressors yield 4 to 7 pounds of copper and don't take that much longer. Unfortunantly a lot of bigger a/c compressors have copper clad aluminum winding in them.