Re: RSG material?

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

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.....                                                      
>  

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