# Re: RSG material?

```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

```