RE: Thorated vs Pure Tungsten

To Terry (specifically) and All,

Please reconsider your design for a "safety gap."  I worte to you
before, about using either brass or copper sphere electrodes,
for this purpose.  They can either be solid machined pieces, or
hollow-spun units.  The solid pieces are needed where you are
operating at a.c. input levels above about 5 Kva.  The "ball gap"
offers a very well defined E-field stress line model, between the
two electrodes, assuming that they are polished and very smooth
and of a constant radius of curvature.

Why do you persist in trying to use (either thorium or solid
tungsten) for a *safety gap* application?  It makes no sense to

As far as using the solid tungsten rod stock (for the rotary 
electrodes only,) this makes good sense to me.  However, I feel
that for the most accurate "timing" (in a sync. rot. gap 
application,) you can't do better then using the 2% thorium doped
stationary electrodes.

I've had a *lot* of experience, with all this, at power levels now
above 125 Kva a.c. input.  This was with the experiments on 
13M.  There's much more to be written, about rotary gaps at
such high power levels.

Whereas many on the List are using single (or multiple) neon
sign transformers, MOT's, potential transformers, and such,
still the same, when an experimenter uses much more then
2 Kva a.c. input, I beleive what I've written above, holds

The "traditional" ball-type safety gap just can't be beat, for this
application, in my opinion.

Best regards,

Bill Wysock.

> Date:          Tue, 15 Jun 1999 17:53:43 -0600
> To:            tesla-at-pupman-dot-com
> Subject:       RE: Thorated vs Pure Tungsten
> From:          Tesla List <tesla-at-pupman-dot-com>

> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
> 	Today I replaced the 2% thorium electrodes with pure tungsten.  The gaps
> actually fired much sooner with pure tungsten??  However the firing voltage
> was more stable.  
> 	I think the firing voltage depends mostly on the rather sharp edges I left
> on the rods.  I will try to really round them out and see if that helps the
> stability.  In retrospect, the sharp edges only make high field stress
> points.  However, the thorium electrodes do seem to suffer much more from
> ionization caused by the radioactivity and thus like to sporadically fire
> far too early.  I may end up using ball bearing electrodes to get a much
> more stable firing voltage for the safety gaps.  I assume cobalt drill bits
> will cut through ball bearings to mount the shafts that hold them?...
> 	I definitely would stay away from thorium and other radioactive
> electrodes.  Pure tungsten is supposed to wear faster but the worry of
> radioactive dust getting in one's lungs during the difficult cutting and
> grinding of this gnarly material out weighs that.  "Playing" with the pure
> tungsten is far better than worrying about dust particles from the thorium,
> or cesium, or lanthanum...  Some claim good wear from non radioactive
> alloys of tungsten too, but this is getting to be too complex as it is...
> http://www.arcsmith-dot-com/wni/products/tungsten/tungsten.htm
> explains much about these rods...
> I still find myself strangely drawn to the 3/8 inch diameter rods :-))
> Cheers,
> 	Terry
> BTW - If all elsa fails, I still have 100+ Victoreen gaps :-)...
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