Re: Super Static Gaps

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: FutureT@xxxxxxx 

In a message dated 6/19/05 2:38:49 PM Eastern Daylight Time, 
tesla@xxxxxxxxxx writes:


> I have compared this gap design on a coil which is a 4 x 17 in using about
> 1200 turns of #28 wire. A 30 ma NST is the power source. So far the super
> gap has outperformed static cylinder gaps (several configurations including
> a 9 gap unit with a vacuum fan), several types of sucker gaps, an
> asynchronous rotary, and a synchronous rotory gap. Not only are the
> streamers longer with the super static gap but there is breakout all over
> the toroid. In addition, I have been able to stack a 6",a 12" and a 16"
> toroid on the coil with spark length growing to 30". For reference, the
> synchronous rotary best has been 24".


Jim,

To properly comment on your results, I'd need to know more details
about your coil.  Details such as the NST voltage rating, the
number of primary turns, and the tank capacitor capacitance value,
would be helpful.

But in any case I'll make some general comments for the readers.
I'll assume your synchronous rotary has a 120 bps break rate
since you didn't mention the break rate.

Unlike static gap systems, sync rotary systems are *fussy*
about the capacitor value for a given NST.  For a fair comparison
of the spark gap types, the NST must be used with the
proper value capacitor when used with a 120 bps sync rotary.
Chip's pupman site has Terry's LTR cap value calculator
there I think.

If the capacitor value is smaller
than optimal, then static gaps will tend to outperform the sync
rotary.  This occurs because the static gap will automatically
run at a higher break rate than 120 bps when a small capacitor is
used.  This higher break rate will to some degree compensate for
the smaller capacitor, and permit more power throughput to
be realized in the system.

Here is the key however.  Although the static gap will to some
degree compensate for the smaller capacitor, the ultimate
spark length will tend to be shorter than for a properly designed
sync rotary system.  Here is an example.  Suppose a 12/30
NST is used.  In this case the optimal capacitor value is at least
0.015uF or somewhat larger.  In this case a sync rotary should
give about 38" sparks or so.  Suppose instead a 0.003uF
capacitor is used.  If this capacitor is used with the 120 bps
sync rotary the break rate will be too low.  The power
throughput will be low and the sparks will be short.  In this
case the sparks might be only 20" or so.  Now if the static
gap is installed in place of the rotary, the breakrate will increase,
power throughput will increase, and the sparks will get longer.
However they may be only 30" or so long, and therefore still
shorter than with the properly designed sync rotary system.

I remember a number of years when I was developing and
reporting on my sync rotary designs.  I would report on my
results then some folks would simply swap out their static
gaps for a 120 bps sync rotary in their coils and report that
they got shorter sparks.  This was because their
static gap coil used small value capacitors.  The 120 bps sync
rotary demands a larger value capacitor before the benefits
of a 120 bps sync rotary can be realized.

The bottom line is that although a sync rotary can get the
most spark length out of an NST, the capacitor value has
to be carefully selected.  If the capacitor value is too small,
then the static gaps will outperform the rotary, but the spark
lengths will be shorter than they will be with a 120 bps
sync rotary and and a proper capacitor value.  I should
mention for the benefit of newbies that a triggered static
gap running at 120 bps will do as well as the sync rotary.

I look forward to the details of your coil design Jim.  If your
capacitor value is optimized for a 120 bps synchronous
rotary, and if the coil is performing to the expected standards
for the particular NST ratings using the 120 bps sync rotary,
and if the static gap then gives such a performance advantage
as you described, then it is truly a breakthrough in static gap
performance.  This static gap sounds like the one Bob built
10 or 15 years ago.

John