Wednesday, August 17, 2011

Ball gap for the Dirod electrostatic generator

I finally have the ball gap to show off. It's not finished—the capacitors (Leyden jars in the old days) are rather crummy and will probably have to be redone but I managed to get some action shots anyway.

Construction is simple, just follow the instructions at the end of the manual. I had to guess at the tubing lengths but this seems about right. The most time-consuming part was cutting the bases off the dummy doorknobs. Sadly, my camera was occupied with time-lapse experiments and I didn't get any pictures of the process. It took a couple of hours, a moto-tool with an emery wheel, face mask and goggles. The trick is to cut the metal in narrow strips, working them down until they're small enough that they can be broken off with pliers. I slowly worked my way around until the knob came loose.

After grinding down the stumps of metal stick out of the knobs I glued them to pipe caps with metal-filled epoxy. They don't look as snazzy as I'd hoped but they do work.

With the capacitors I get a very loud snap with a .75" gap. It's the middle of summer right now; next winter will be the real test.


  1. Looks even better now, how did you go with the winter spark gap test? How long a spark did you get?

  2. I've never gotten around to it. I don't think my "capacitors" are up to snuff. I need to make some better ones.


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