Re: Primary Coil strike rings

The purpose of the strike ring is to divert the spark from the 
primary inductor and send the energy to ground.  The reason that a strike
rail is put in place is that the capacitors and transformers that make up 
the primary can't handle the electrical stress placed upon them by a direct
hit from the secondary. This makes sense from a practical point of view too.
If a tesla coil is putting out multi kilovolt sparks at high frequency, 
the sparks will easily (or eventually) puncture the dielectric of your fine 
$200 Condenser Products capacitor.  

The "technical information" that I relied on were descriptions of how to do it
combined with the ol' calibrated eye.  The one important thing to remember
is that the "loop" should not be closed electrically.  In other words,
you want the topological equivalent of a C, whose ends overlap but don't touch,
rather than an O which is an electrically closed loop.  The O will drain 
energy from the coil system at any frequency, which is why it is avoided.

The only math that I used for the strike rail was Pi * D to get the length
of wire to make the rail.