I used to play with carbon arcs made from dry-cell cores and a "salt water rheostat", direct off wall AC (110v.) Ahh, those lovely 60s "science experiments for kids" books...
...Dad had a motor generator set, which comprised a 1/3HP motor coupled to a car generator (note generator, not alternator), which he built for charging vehicle batteries. Great for powering model trains, great for drawing big arcs from carbon rods out of batteries. It didn't seem to object too much to the output being shorted out. Oh, and none of that silly H&S nonsense, there was no guard over the drive shaft, in fact the drive shaft worked well as a carrying handle.
My father's tool chest was full of ancient torture instruments. I remember when I was small, being so scared of his drill - the one that spit fire out the sides while it ran. It was really sparks from the barely insulated brushed motor.
the one that spit fire out the sides while it ran
I made this in my youth too.
Bringing the carbon electrodes (rods) together shorts out the 120 hot to neutral, very bad.Add the iron, the iron limits the current.The electrodes starting to get red hot due to small resistance of the rod ends, air ionize, the arc starts, you move the rods apart, the arc grows to about 1 inch.I used a hot plate .