rotating static gap

To: tesla-at-pupman-dot-com
Subject: rotating static gap
From: FutureT-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Mon, 25 Oct 1999 18:04:58 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

All,

One of the weaknesses of a static gap is its tendency to heat up
and begin to fire at a lower voltage, thus shortening the TC's output
sparks.  Often this is dealt with by using multiple static gaps, or
powerful air blasts or fans.

An idea that might work well is to use a thick flat rotating metal disc or
rotor with a stationary gap positioned near each side or each edge, 
such that the sparks
will jump from one fixed gap, to the rotating disc, and then from the
rotating disc to the other fixed gap.  The purpose of the rotating disc
would be to draw the heat away from the gap area as the disc turns.
No part of the disc would tend to heat up very much, and if the disc
rotated rather quickly, this might help to cool it from windage also.
The metal disc should be made from a heavy metal
to provide a heat sinking action, and it could even have fins on it for
cooling, but the fins should not be arced to of course.  The middle of
the disc could be made of plastic or phenolic to insulate it from the
motor or gear motor which would provide the motive power.

Another approach would be to use two rotating metal discs, separated
by the proper spacing to behave as a spark gap.  The discs could either
rotate in the same direction or counter-rotate.  

      ascii drawing showing the two rotating discs and two fixed electrodes,
      but they would all be closer together:  

                                            - O O - 

By cooling the gap in this way, it may be possible to use fewer gaps,
for lower losses, without any air blast methods.

In any case this gap although it is rotating, will behave exactly like
a static gap rather than a rotary.  Thus, it can be used in a NST
system for those do not want to bother with a sync rotary.  This
method would probably be of most use at higher powers levels at
which traditional static gaps begin to fail.  This gap is not intended
to be a replacement for a rotary.  It is simply to provide a cooler
running replacement for a static gap.

I realize that most ideas have already been tried by others, so I would
in no way be surprised if this technique has already been tried.  
Nevertheless, some are probably not familiar with it, and may want to
experiment with it.  Let me know if you still have questions about it or
if my description is not clear.  I'd also be interested to hear from anyone
who may have already tried it, or tries it in the future.

Cheers,
John Freau