Re: Spark Gap Tubes

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

Original poster: "Harold Weiss" <hweiss-at-new.rr-dot-com> 

Hi All,

I've found that the thoriated rods seemed to settle my rotory gap down quite
a bit.  They will help prevent non-firing gap presentations, which in turn
helps prevent over-volting caps and xfmrs.  In a fixed gap they would likely
cause problems with quenching if airflow thru the gap is low or nonexistant.
This downside is still useful in the safety gap, as it can promote it's
firing even if misadjusted a little.

David E Weiss

 > Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com>
 >
 > Radioactive elements are sometimes added to arc welding rods to yield a
 > more stable arc.  But the spark gap in a TC has very different goals.
 > We WANT our gap arcs to extinguish (quench) as soon as possible, so such
 > additives would actually be counterproductive.
 >
 > The tungsten welding rods used in rotary gaps sometimes have thorium and
 > such additives, probably because this is what the builder had available
 > (or he thought it would sound cooler).  As far as I know, no one has
 > ever made a controlled study comparing the use of thoriated rods vs.
 > pure tungsten rods.  It would be cool if someone with an RSG could
 > replace some of the rotating electrodes with pure vs. thoriated
 > electrodes, and with a scope, see if the quenching differs on successive
 > bangs.  My guess is that if there's any difference, the thoriated rods
 > would not quench as well and would have somewhat inferior performance.
 > Thoriated rods may also represent a hazard when cutting them if the dust
 > is inhaled.
 >
 > Gary Lau
 > MA, USA
 >