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Re: Gas Properties and Gap Cooling

Tesla List wrote:
> 
> Original Poster: "Dr. John W. Gudenas" <jgudenas-at-admin.aurora.edu>
> 
> OK John, by your request:
> Big Tube CW Coil initial specification.
> Plate Transformer:  6KV -at- 300ma
> Rectification: Full Wave Bridge with four 35KV stacks ,10 henery inductance
> choke
> and 2mfd filter cap -at- 18KV
> Circuit Protection: 20KV 12 mmfd vacuum caps, rf chokes, safety gaps.
> Oscillator: Likely plate tuned Armstrong...now experimenting with different
> grid feedback.
> Tube: One large ceramic used eimac # 8239/3cx3000f1, plate dissipation 3000
> watts
> Secondary Form: 8" by 32" Lucite cylinder with .125" wall.
> Primary: not as yet determined
> Frequency: not as yet determined
> I want to keep the frequency reasonably low and am using modeling to
> check various resonance combinations. I believe I can use a smaller tank cap
> than you sparkers with the CW operation and my power supply...but still
in the
> design stage.
> 
> "Old Faithful" my empirical test coil uses three 811A in parallel at 1.2KV
> -at-500 ma.
> All suggestions are welcome. I have been discussing issues with list
> members on
> an individual basis. When I get something significant done (probably
winter )
> I'll let ya know.
> John
> 
> John W. Gudenas, Ph.D.
> Department Chair of Computer Science and Mathematics
> Aurora University, Aurora IL 60506
> Office: 630-844-5539     Fax: 630-844-7830
> 
> -----Original Message-----
> From:   Tesla List [SMTP:tesla-at-pupman-dot-com]
> Sent:   Monday, September 07, 1998 3:40 PM
> To:     tesla-at-pupman-dot-com
> Subject:        Re: Gas Properties and Gap Cooling
> 
> Original Poster: FutureT-at-aol-dot-com
> 
> John,
> 
> Can you tell us something about your large tube coil project, power input,
> circuit, type and number of tubes, expected spark length, etc?  Thanks,
> 
> Yes, this list is the greatest!
> 
> John Freau

John W. Gudenas,

Sounds like a worthwhile project.  Don't expect a streamer out of this
baby, it will be more like a gas burner flame.  You will likely get
longer ultimate discharges if you nix the DC filtered power supply in
favour of just running this oscillator straight off the plate
transformer.  The oscillator will be cutoff half the time on negative
excursions of the plate transformer (and the toob will be resting!) and
then on the positive swings it can work twice as hard for the same
average power input.  Connecting streamers are scarry and a real burn
hazzard on the pure DC supplied CW mode.  The 60 Hz interrupted
operation helps then detach and makes for a much safer coil if you are
planning to do body contact parlour tricks.

At ~1800 watts I'd suggest 1/4 inch refrigeration copper tubing for your
primary plate tank coil.  Circulating currents in the plate tank and
secondary resonator of a vac tube TC with any kind of a topload are
significant.  I squared R heating effects can be very significant
compared to disruptive discharge coils of considerably higher peak
power.
If you plan on a topload, I'd suggest winding the secondary with at
least #14 AWG polythermalese magnet wire. At that power level even this
wire gauge can become overly warm for a PVC form very quickly with a
topload.

I built a large vac toob TC based on three EEV BR1160 transmitting
triodes rated at 5000 watts each plate dissipation in parallel. This
beast is affectionately known as the 'Coronatron'. Because of inadequate
funding I used the two layers of silvered copper outer braid of RG-214
coax in a large plate tank 20 inches in diameter.  At just 6500 watts DC
plate input, ~5 kW output RMS, this coil overheats in just 4 minutes. I
plan to completely re-do this coil using 1/2 inch or 5/8 inch copper
tubing.  The Coronatron is still under development, but is a back burner
project receiving little attention in its two year existence so far.  It
shows promise as being a good barbeque on which to cook Tesla dogs at my
first proposed teslathon.

Have fun, good luck with your project, and be safe.

Robert W. Stephens