Re: Rotary Spark Gap

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mark Broker by way of Terry Fritz <twftesla-at-qwest-dot-net>" <broker-at-uwplatt.edu>

CJ,

>Some people have tungsten electrodes but I will have to defer to them on
>how to do that.  The electrodes get really hot so you almost have to have
>some type of metal holder to dissipate the heat.

I drilled a hole down the middle of a 3/8" brass bolt and used a setscrew
through the head of the bolt to hold the tungsten in place.  Works very
well, and I've seen quite a few others using this setup, too.  For The Geek 
Group's big RSG, I designed a turned "bolt" to accommodate some really nice
bulletted tungsten carbite electrodes donated by Marc Metlica (the TC are
really short - the size of a 9mm slug (only it's really 8mm in diameter).  
The electrodes will be press fit into a smaller hole (not very adjustable.....)

>> 4) How do you cut the tungsten electrode smooth and even. 
>
>By a nice brand new file.  File a notch in them and snap the tungsten
>apart.  Then file them flat or round or how you wish.  Tungsten files well
>but it wears the file quickly and it is slow going but can be done
>reasonably easily.


Or use a grinder with a sharp-cornered wheel.  Lacking that, a Dremel will
also work with one of those cutting discs.  Score a corner, and snap the
tungsten (it's quite brittle).  Use the grinder or dremel to grind a flat
edge or 
hemispherical end (DON'T hold the tungsten in one spot on a grinding wheel,
or you will have a nice groove in it!  :-)  Chuck up the tungsten in a
drill press set to high speed, and use some decent 320grit sand papaer 
wetted with WD-40 (or other lightweight oil) to get a mirror-finish.

Mark Broker
G-5 Geek # 10