RE: Spark gap metals

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Steve Conner" <steve.conner@xxxxxxxxxxx>

> Why are ya'll so concerned about the metal your spark gaps are made of?

Just to be different- mine is made out of brass :-P It's a sort of distant
relative of the Terry Blake propeller gap.

http://www.scopeboy.com/tesla/tcpropeller.html

The electrodes are brass machine screws (the fixed ones M4 metric and the
flying ones M2.5) They work fine but do seem to burn away quickly. It's only
had about 15 minutes of runtime and the screw heads have already lost enough
metal that they don't look quite circular. The whole area around the gap is
covered with a sort of fine white dust which I guess is the vaporised
remains of my electrodes.

I would rather have used tungsten to make it last longer. But I couldn't
think of a way to mount tungsten electrodes safely in a rotor of this
design. If one were to come loose it would fly out like a bullet. I
considered using steel screws with tungsten pieces brazed to the ends but I
couldn't guarantee that they wouldn't get hot enough to un-braze themselves-
in fact I can't even remember if you can braze tungsten.

The bearings are shot in the gap motor anyway- that's what I get for
salvaging a motor from a $20 vacuum cleaner- so it's probably time I built a
new gap or replaced it with IGBTs :-)


The coil that uses this gap runs with a 10kV @ 100mA DC supply and produces
40" arcs.

http://www.scopeboy.com/tesla/fryingtonight2.jpg

Steve Conner