Richard Hull's nemesis

From:  richard hull [SMTP:rhull-at-richmond.infi-dot-net]
Sent:  Thursday, January 22, 1998 8:33 PM
To:  Tesla List
Subject:  Re: Richard Hull's nemesis

At 05:34 PM 1/22/98 -0600, you wrote:
>From:  John H. Couture [SMTP:couturejh-at-worldnet.att-dot-net]
>Sent:  Thursday, January 22, 1998 4:25 PM
>To:  Tesla List
>Subject:  Re: Richard Hull's nemesis
>At 06:24 AM 1/22/98 +0000, you wrote:
>>From:  richard hull [SMTP:rhull-at-richmond.infi-dot-net]
>>Sent:  Tuesday, January 20, 1998 6:50 PM
>>To:  Tesla List
>>Subject:  Re: Richard Hull's nemesis
>> what power levels was he running?
>>>Jeff Corr
>>Nemesis ran at a wide range of powers as it was developed and as new and
>>larger terminal capacities were attached.  It started at around 5 KW with
>>.03ufd of capacitince and the same system with only top hat and capacitor
>>changes ended up running 12-13KW with a maximum capacitance of .09ufd.
>>Richard Hull, TCBOR
>  Richard -
>  Your Nemesis coil apparently was well tested with powers from 5 to 13 KW.
>The Tesla List at present is interested in secondary voltage vs spark
>length. Can you give us some comments on spark lengths, pri and sec
>capacitance, primary voltages, etc.? 
>  Forget about the secondary voltage unless you want to comment.
>  John Couture

My knowledge is largely based on emperical experiment from the doing.  What
I am speaking of now is regarding classic Tesla coils only.  Magnifiers are
different beasts.

  Big coils, at high powers, generally benefit from very large primary
inductances.  A small inductance on a big coil might be 50uh, at tune.
Coils in the 10KW and above range might best be designed from the stand
point of starting with a 100uh primary inductance.  This naturally means a
small primary capacitance by the standards of many builders at these powers
and frequencies. I have never had a Tesla coil system run with more than the
.09ufd used in Nemesis at its acme of performance. Current systems in the
7KW class run .03ufd total primary capacitance.

There is no substitute for primary input voltage.  15,000 volts is a very
low voltage for a system of 8KW or more.

Regarding frequency,  I shoot for the absoute lowest frequency I can get!
This means spark length no matter how one slices it.  100Khz is a very high
frequency system for me.

The terminal capacitance's size should dwarf the coil at all times, if spark
length is what one is after.  For a 10KW system I would hope for a 100pf
toroidial terminal.  I now try to aim for a resonator winding length to
toroid diameter of at least 1:2.


All of the above assumes a concommitent step up in power.  I would would
also say that the above advice kicks in at above 3KW.  But really only comes
into its own above 6KW.  As I have never run a conventional system over
13.5KW I can offer little in that rarified range.

I see the power requirements for doubling spark lengths beyond 15 feet going
up in some geometric manner.  I once tried to relate the whole matter of
power input to the ionizing potential of the hemispherical volume of air for
a given straight line sparking circle.  This was based on the fact that the
ionization potential of a volume of air to support spark falls off in some
cubic fashion as the volume of large sparking circles grows dramatically.
Thus, much more power would have to be forced in to support the higher
capacitive loadings of larger ionized air volumes.  I had no real data to
develop this idea on a firm scientific basis however.  Again, the quantity
of variables is staggering in such an effort if the results are to be accurate.

To sum up, there are a lot of shifting variables in a high power system
under design.

1.  Plan on real low frequency operation. 
2.  Short resonator lengths and ratios of L:D of 2:1-3:1 MAX!!!!
3.  Massive resonator terminal capacitances will drop the small resonator's
rather high frequency like a stone into the sweet spot operating range.
4.  Use large primary inductances but hold it to under 15 turns.
6.  Couple to a minimum of K=.25 and pray you can gap the system well.
5.  To keep the primary capacitor value low and still be able to ram in many
KW     of power, use huge primary input voltages. >>12,000 volts.

Gap design is a serious issue and a separate story altogether.
Capacitors for these monster systems must be custom made pulse units!

On the issue of spark length/unit voltage,  I have posted on this literally
til I am blue in the face and won't even discuss the matter any more.  Bill
Wysock was reiterating what I have said all along... the whole issue is a
moot point.  I feel no one will ever be able to pin the values down to
within +/- 50%! Period!

I would think that for a "single specific system", measured by a team of
scientists to exhaustion, in rigidly contolled conditions, at a single
frequency,  the value might be obtained to within 10%.  It would have almost
no meaning for the average Teslaphile, dinkin' around in his damp basement
with Neon transformers and nail gaps.  And these are the real tesla coilers
not the stinkin' egg heads who did the measurement.

Richard Hull, TCBOR