Re: Dual toroid and efficiency tests

Hi John,
    I am actually as surprised as you about the extra spark length!  I
like your system.  The primary is very interesting.  I had to see it
with my own eyes to believe it!  PVC coated stranded hook up wire with
a needle sticking in it for tuning!!  It has definitely made me
rethink my rethinking on tank circuit dynamics.

    The talking tube Tesla coil is eerie.  I thought I would never see
the day when sparks could talk.

    I once had to measure the maximum voltage an insulated helicopter
could sustain before corona breakout from the blades.  To do that I
needed a way to connect the 400 kV power supply to the helicopter and
to a capacitive voltage divider.  The capacitive voltage divider was
made with a big toroid (like the big ones that you make)  placed above
a ground plane with a probe on the ground plane.  I charged up a piece
of 12 gauge house wire, connected between the 400 volt power supply
and a toroid, to 180 kV before the radio started making noise from the
corona.  A piece of 2 inch diameter corrugated stainless steel muffler
pipe got up to about 350 kv.  Based upon this, I do not think that the
difference between a corrugated toroid and one of your nice smooth
toroids is so much electrostatic as electrothermodynamic.  Kiesev (sp,
Cathode Processes in the Mercury Arc) indicated that the cathode spot
moved very fast over a smooth surface, but took time to reform if it
encountered a discontinuity, such as the surface of a corrugated
toroid.  I observed the streamer roots on your 13 inch smooth toroid.
They moved around the surface with great fluidity and facility.  On
the corrugated toroids that I have observed, the streamers seem to be
restricted to only smooth vertical movements off of the corrugations
or tape edges.  With really big toroids, like on Ed Wingate's giant
magnifier, the streamers are so hot that it doesn't seem to make much
difference.  The smooth toroid makes a nicer streamer.  I think that
it is harder to form a streamer root on a smooth toroid than on a
corrugated one.

    I once had to cut down a steel frame building with an oxyacetylene
torch.  I learned that it was easier to heat up edges, before hitting
the oxygen and cutting through the steel beams, than trying to heat up
a flat spot.  The flat spots took forever to heat up.  Similarly, the
thermal conductivity of a smooth aluminum toroid, at any point on the
surface, is greater than with a corrugated surface.  Any point on a
smooth surface can thermally conduct on four sides.  A corrugated, or
uneven, surface thermally conducts on less than four sides.  It should
take more energy to form a streamer root on a smooth toroid.  By
competitive process, the streamers thus formed should be fewer, have
access to a greater amount of the energy share, and therefore be

    I have noticed that your toroids are built much better than the
Science First (used to be Morris and Lee?) toroids (IMHO).  The two
halves of their toroids are not as symmetric and have a big gap
between where they join.  There is also some glue leakage.  The prices
are pretty steep also.  I bought several of your toroids for the price
of theirs, and yours are smoother!  The 13 inch toroid that you make
is magnificent.  Those extra long, 58 inch, high efficiency, streamers
love it. The price is incredible!  Ross and Hipotronics want at least
twice as much for the same size.  I appreciate your effort.


> Original Poster: FutureT-at-aol-dot-com
> All,
> Lately, I've been running my "42 spark TC" at 950 watts instead of
> 560 watts.  At 950 watts it gives 49" max sparks with a 4" by 13"
> spun aluminum toroid.  Sparks can reach 49" with or without a toroid
> breakout bump, but they reach 49" more consistently with a bump.
> (all power measurements with lab type wattmeter....wallplug power)
> When Barry Benson visited recently, he suggested placing a 3" by10"
> toroid beneath the larger toroid.  I finally got around to trying
that, and
> my spark length increased to 58" max at the same 950 watts input.
> There is 1/2" space between the toroids, this helps to increase the
> capacitance, and besides, I don't want to mar the finish of the
> by letting them rub together.  These latest results obey the square
> law for spark length that I use for my coils:
>  max. spark length (inches) = 1.9*SQRT input power (wallplug watts)
> (I now manufacture high quality spun aluminum toroids.  To order a
> 4" by 13" toroid, send $126 postpaid to:  John Freau, 49 Thiem Ave,
> Rochelle Pk, NJ   07662)  These can be seen at my website at:
>             <  http://members.aol-dot-com/FutureT/index.html  >
> (photos are a little blurry due to cheap digital camera)
> (1.5" by 6" toroids are also available for $32 postpaid.  These are
> for small coils, or as corona shields, etc.)
> Cheers,
> John Freau