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Fwd: Rotary Gaps (bunched and unequal spacings)

In a message dated 97-01-02 05:39:48 EST, you write:

All, 

 >  Here's a quick overview of some rotary work I did a few of years
 > ago including bunched and unequal gap spacings:  
 > 
 > 1)  Synchronous gap:  Used 8 spinning electrodes, 2 fixed electrodes. 
 > The 8 spinning electodes were bunched into two clusters.  Because these    
   >clusters centered closely around the peak of the AC sine-wave, EVERY GAP  
  PRESENTATION
 > ACTUALLY FIRED  (this was verified by o-scope).   The net result of this
 > design was that the TC output and behavior was identical to a traditional
 > synchronous gap which had perhaps 10 or 12 EQUALLY SPACED electrodes (no
 > clustering), since in this case firing would not occur on every gap
 > presentation since voltage would be too low at some presentations (the ones
 > that occur at a low point on the AC sine wave).  Only advantage I see in 
the
 > clustered design is that fewer electrodes are needed, less drilling, etc.
 >  Disadvantage is you need a greater range of phase adjustment on the rotary
 > for initial phasing adjustment.
 
 > 2)  Synchronous gap:  Same as above, but the spacing of electrodes within
 > each cluster was varied such that electrodes near the center of the 
clusters
 > were spaced closely whereas electrodes farther from the cluster center were
 > spaced farther apart.  The plan here was to give the capacitor more time to
 > charge when AC voltage was at low points on the sine-wave, but less time to
 > charge when AC voltage was at a high point (peak) of AC cycle.  The result
 > was that the capacitor WOULD NOT have time to charge fully at the AC cycle
 > peak, but would charge fully at lower points along the AC sine wave.
 >       The overall result of this design, was that each of the 8 firings of
 > the rotary occured at the same voltage level.  In this sense, the system 
was
 > like a DC powered system, but without the complexity of a DC power supply.
 >  (an o-scope was used to verify that all the gaps fired at the same voltage
 > level--they either all fired, or none fired.  In a normal rotary, more
 > presentations fire as the input voltage is increased--at least if you're
 > using external series gaps).  Of course this technique (firing at same
 > voltage level) limits the available power of the system since the peak 
energy
 > is never utilized, but this is easily compensated for by using a main
 > transformer of a proportionately higher voltage capability.
 >       This technique may be very useful for precisely controlling dwell and
 > quenching.

 > 3)  Non-synchronous gap:  Used 8 spinning electrodes, 4 fixed electrodes,
 > 2500 RPM, about 650 BPS.  Of the 8 spinning electrodes, 6 were spaced
 > equally, but 2 were not--they had a greater spacing from the previous
 > electrodes.  The gap was symetrical however.  This arrangement seemed to 
give
 > a longer spark as compared with a rotary with equal spacing between all 8
 > electrodes.  The occasional greater spacing may have allowed the capacitor 
to
 > charge, at that point, to a higher voltage thereby giving out a tremendous
 > spark burst.  I suspect this is what was happening, because the sparks were
 > not consistantly long, but instead, a long spark was thrown out every few
 > seconds--corresponding perhaps to the coincidence of the wide electrode
 > spacing and the peak of the AC cycle.  The thing I liked about the system,
 > was that the occasional long sparks, when they occured, were 
psychologically
 > surprising to one's mind, making the display more exciting, at least to me.
  
 > John Freau