Re: RSG material?

[FutureT-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

In a message dated 9/15/00 11:21:29 PM Pacific Daylight Time, 
tesla-at-pupman-dot-com writes:

> Original poster: Hollmike-at-aol-dot-com 
>  
>  In a message dated 9/15/2000 8:30:43 PM Mountain Daylight Time, 
>  tesla-at-pupman-dot-com writes:
>  
>  >                                                                       
>  >  I've also seen static gaps used in series with the RSG.. what's the   
>  >  point? ;) Seems like the motion of the flying electrode would quench  
>  >  the gap reasonably quickly. I get the feeling I'm missing a crucial   
>  >  detail here.....         

Mike,

You're correct that the ringdown and quench usually occurs
before the mechanical dwell time becomes a factor.  But these
series rotaries tend to quench faster anyway due to the effect of
the multiple gaps.  Not because of the lack of any stretching
effects or anything to do with the mechanical dwell, but simply 
because multiple gap tend to quench better.... even multiple
static gaps quench better than single gaps, but tend to have 
higher losses.  

John Freau
                                        
>  >  
>  
>  I am not a mathematician(but am gonna try anyway), but the dwell time is 
>  probably much longer than you'd think.   If you take a 1 foot diameter 
>  disk(i.e. the center of the electrodes are 6 inches from the axis of 
>  rotation)  and it is spinning at 60Hz(377 radians per second), the 
electrode,
>  
>  if I did the math correctly, is moving at about 2262 inches per 
>  second(someone should check this for me).  If the electrodes are 1/4 
>  diameter, the time it takes for the moving electrode to pass the 
stationary 
>  electrode is 0.5/2262 or .22 msec.  This is assuming the spark initiates 
at 
>  the moment the leading edge of the moving electrode meets the edge of the 
>  stationary electrode and can conduct until the trailing edge of the 
> electrode 
>  has passed the stationary one(0.5 inches of travel).  Now, assuming your 
> coil 
>  operates at, say 180kHz,  It can oscillate 30 times(about enough to decay 
to 
> 
>  near zero volts) in 0.166667msec.  In other words, the whole decay has 
>  happened before the electrodes can quench the arc.  At higher TC 
frequencies,
>  
>  the situation is even worse.  
>      I imagine that most coilers space the stationary electrodes at a 
>  sufficient distance to alter the 'real' dwell time to allow quenching of 
the 
> 
>  arc, but some use a static gap in conjuction with a rotary to cause much 
of 
>  the voltage drop to occur through the static gaps.  This will not allow 
the 
>  arc in the rotary gaps to 'stretch'  from the inductance as much and helps 
>  shorten the effective dwell time.
>  Hopefully, I did this all right :o)   comments? corrections?
>  Mike
>