After becoming reasonably good at welding, I discovered that I really needed higher amperage than the Lincoln 175 was giving me. Particularly for welding aluminum. I sold the Lincoln and bought a used Thermal Arc welder. Unfortunately it did not come with an Amptrol. So, rather than spending $150-250 to buy one, I spent 3-4 days making one.
|Ideally, I would have used gears to turn the potentiometer, but that would have meant spending money..
Also, I was too lazy to draw up a picture, so I made a couple mockups of the pulley arrangement first..
|Since I didn't have a working lathe at the time, I made the pulleys on the RF40. Although getting everything lined up properly was a pain, actually making the pulleys was pretty straightforward.|
|Here's the turning tool that I ground out of high speed steel for cutting the groove in the pulley.|
|I made most of the pieces out of scrap metal I had laying around. The U bracket is a piece of square tubing with one face milled off.|
|The piston is a piece of 1/2" drill stock with slots milled in either end.|
|I used a piece of 2" square aluminum tubing cut in half for the side plates.|
|I originally tried using steel picture-hanging wire to go between the pulleys but it proved too stiff.|
|Ultimately I used nylon picture-hanging wire, although eventually I got some very fine throttle cable wire which worked very nicely.||This block is for the spring tensioning.|
|The axle to hold the pedal-plate was hard to make because I used M6 screws in 3/8" stock which was hard to center on the mill.|
|All assembled.||It we even works so far!|
|I used a DB9 printer cable with one end chopped off for the signal wires. Here I'm soldering the leads to the pot.||I made a cable clamp from a piece of shim stock folded over so there were no sharp edges.|
|Ready to weld!|
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