Re: More THOR Expts

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

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 



We should also be asking "what is the best break rate to generate the best
spark appearance"?

The long "stringy" spark appearance generated by a high break rate on a
classic design coil don't have as much character is sparks produced by a
synchro RSG.

Unfortunately, the tradeoff requires Cres * 3.2 for a synchro system.  This
requires more capacitance and hence more $$$ spent.

A non-synchro system, kept at a reasonable break rate in the 375-450 pps
range produces nice thick sparks without the "stringly" appearance.  A
synchro system produces nice bushy appearing sparks at 120 pps but usually
they are not as long as a higher charge pumping system in the 375-450 pps.
We prefer to run around 400-450 pps for most of our systems operating in the
5-15 kVA range.  Slightly longer sparks than synchro with a nice appearance
before going "stringy".

The beauty aspect of the pps should also be considered when searching for
the best looking sparks with a good length.

This range seems to work well for both medium, and large coil systems.  With
small systems we usually run a stationary 2 or 3 gap sparkgap.  Using 1/2
dia. tungsten electrodes and 1/2 dia brass rod fitted to 1.25 x 1.25 inch
square brass blocks as a heatsink, good quenching and efficient operation is
the result with nice looking spark on the output.  A mistake many small
coilers make is not using a large enough dia. heatsink and electrodes for
good cooling and quenching.  Even carriage bolt heads are an improvement
over small 1/8th and 1/16th inch dia. tunsten rod.  It works but the
electrode ends quickly heat to near red hot and the output spark diminishes
as a result of poor quenching.

Dr. Resonance

Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo   WI   53913


 >                 A question that needs to be answered is "what
 > determines what the useful maximum breakrate is?", "useful" being
 > defined as the breakrate beyond which no further increase in spark
 > length results. Some thought led to the hypothesis that the useful
 > breakrate will scale with secondary charge storage (i.e. capacitance).
 > I devised some expts which will hopefully prove or disprove this.
 > There is weak evidence already that supports this hypothesis, mainly
 > the results obtained by Richard Hull in his extensive work. My own
 > observations with a range of coil sizes also suggests this might be
 > true.
 >
 > Noting the highest useful breakrate for the current THOR
 > configuration:
 >
 > #1 - increase Ctop while maintaining the same ROC, and maintain the
 > same theoretical Vout by suitably increasing Cp or Vp (i.e. Ep). An
 > increased useful BPS would indicate a charge-available dependence.
 >
 > #2 - decrease Ctop while maintaining the same ROC and same Vout
 > (reducing Ep to maintain this). If the useful BPS increases, that
 > would throw my hypothesis out. If useful BPS decreases, there is
 > supporting evidence for the hypothesis.
 >
 > #3 - decrease Ctop while maintaining Ep to increase Vout (at this
 > point, I am not sure whether increasing or maintaining the same ROC
 > is the way to go - for completeness' sake it would be worth doing
 > both). Does the useful BPS change and if so, higher or lower?
 > If higher, it again negates the hypothesis.
 >
 > #4 - increase Ctop while maintaining Ep to reduce Vout (ROC may have
 > to be reduced to allow breakout). If useful BPS remains the same, it
 > would provide more support for the hypothesis.
 >
 > This list is by no means complete but should be a useful guide to
 > devising a complete set of tests. Some of these questions may already
 > have been answered but what I would like to see is the full gamut of
 > tests and results presented all at once. A key question I would like
 > to see answered is the degree to which sparklength depends on output
 > voltage and, separately, charge availability. My guess is that there
 > is a dependence on both but that charge availability is the more
 > dominant of the two. The enormous discharge from the 5MV Russian Marx
 > bank plus the behaviour of lightning seems to indicate this also.
 >
 >      The purpose of all this is to refine the design criteria for a
 > spark-producing coil, a goal I'm sure we'd all welcome being reached.
 > The general approach at present seems to be equivalent to grabbing
 > whatever components one has available and building something that
 > works. In the engineering world however, one does as much as is
 > needed to fulfil a design goal and no more (safety margins
 > nothwithstanding), size, weight and economics being the arbiters.
 >      This is also what I'd consider to be a rigorous (scientific if
 > you like) approach to coil building. Why throw a 20 x 5" toroid on
 > top of a coil just because it happens to be lying around if it makes
 > the finished product bulkier and heavier without actually
 > contributing to the performance? I think anyone building coils for
 > commercial gain (I am NOT one of them) would appreciate this way of
 > doing things.
 >
 > Malcolm
 >
 >
 >
 >
 >
 >