RE: Over-coupled or under-insulated?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Lau, Gary by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Gary.Lau-at-hp-dot-com>

Your statement about having a "semi-wide spark gap" is concerning.  For any 
given power supply voltage and gap geometry, regardless of current rating 
or capacitor size, there is only one "maximum recommended" static gap 
width.  The distance must be determined experimentally by seeing where the 
gap breaks down with only the power supply across the gap.  Less than this 
distance results in a performance penalty, and greater than this distance 
results in capacitor charging voltages that endanger the cap and power 
supply.  You are absolutely correct however, in that a too-wide gap will 
cause excessive bang size (basically the cap is charged too high), and this 
may result in racing sparks.  Reducing the coupling or the gap width will 
resolve the problem, but setting the gap properly will also prolong the 
life of your hardware.  If you reduce the gap width, you may find that you 
can also lower the secondary to increase the coupling (which will improve 
performance).

The slightly short secondary winding length is probably also contributing 
to promoting racing sparks, and a taller one would help.

Gary Lau
MA, USA

 >Original poster: "Chris Roberts by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <quezacotl_14000000000000-at-yahoo-dot-com>
 >
 >I read that a lower bps coil will require a larger, taller secondary and
 >toroid to handle the larger bang size to prevent racing sparks (!!!!) and
 >premature breakout from the toroid. Having a LTR primary capacitor and a
 >semi-wide static spark gap, I would imagine that I have a low bps, but high
 >bang size each time the gap fires. (If I am missing something somebody
 >please let me know) My secondary is quite short ( 6 inch diameter, 24
 >inches tall, 3.84 H/D aspect with 22 gauge wire) so I suspect this might be
 >the culprit. Am I correct on this? If so, the only real options would be to
 >keep the coil undercoupled (which would mean a wimpy coil =/ ) or wind a
 >much taller secondary (I'm thinking something like 31.25 inches tall, for a
 >H/D aspect of 5?) Any ideas on this? I want to make sure I have the right
 >clue about this before I start trying things =D
 >
 >
 >-Chris