Re: Preliminary design... Any suggestions?

Hi Albert,

Thanks for supplying such great information!

E-Tesla3 says the resonant frequency will be about 180kHz instead of
163kHz.  Not a big deal.  The self capacitance of the secondary is around
10.7pF but the top terminal will probably add 15pF instead of 20pF.

The primary will probably be taped at 12.3 turns with a 10nF cap.
Personally, I would use around 17nF and tap at 9.7 turns but you can
experiment with all that.  Your 5.4 turns seems way low.  10nF needs an
80uH primary to hit 180kHz...

I get 2.25 Joules instead of 1.194  The 15000Vrms is really around 21000
volts peak so the energy is about doubled (actually it is exactly doubled).
 A 17nF primary cap would get you to 3.8 Joules but you may not fire as
often....  Long story on all that.  With beer bottles, don't worry too much
about that.  You will probably need around 12 of them.  Be sure to use a
safety gap across the neon.  

With the secondary bottom turn level with the primary, the coupling is
around 0.137  That may be a little low.  You might consider winding the
primary with a little less space between turns.  That would give you a
better coupling which should help performance in this case.  You could
probably use 1/4 inch tubing instead of 3/8 with no noticeable power loss.
An 8 inch I.D. on the primary is also a consideration...  I would avoid
conical primaries as being harder to build and too easily arced to.

A multi gap will probably give the best performance in an easy gap type.
You may want to check my fast and simple one at:


This gap can be varied for firing voltage easily and has a built in safety
gap.  With a small cap value, the current may be a little high for this gap
but the most it will do is burn up ;-)  A fan would be a big help.  A
variac is also very nice to have as opposed to just plugging it in at full
power and seeing what happens. :-O

So, sounds like your real close and you have a good understanding of it
all.  Your coil will work fine.  I would guess sparks in the 24-35 inch
range.  Get a better primary cap (like an MMC) for your first improvement
and you should get to around 40 inches.  A sync gap and 27nF cap could push
that to 50+ where it will be very impressive at 6 Joules.  Be sure to keep
future improvements in mind and build it to be sturdy and tough.  A larger
torroid is always good too.  That tends to produce just one long streamer
as opposed to many smaller ones.  Put the center of the torroid about 6
inches above the top secondary winding.  A protection filter is also nice
but many people sneak by at first without them.  When the streamers start
to get big, a filter is pretty important.  A safety gap is a must at all
times however.



At 12:41 PM 08/25/1999 -0400, you wrote:
>Ok, guy's... I'm sending out my preliminary design for you with experience
>to review and make professional comments on.
>This is my first "bigger" coil. I have only fooled around with Flyback
>derived coils before, so I'm really excited.
>Here goes:
>Source EMF:120VRMS 60Hz (USA)
>Input Transformer for primary: 120VRMS to 15,000VRMS 60mA NST
>Tank capacitance: approx 10nF (Salt Water Capacitors. (Dark glass 40oZ
>Coors) Friends had fun drinking all of them. ;)
>Calculated Joules : approx 1.194
>Secondary stuff:
>	Diameter : 6 inches
>	Length: 27 inches
>	Ratio: 4.5
>      Turns: 950
>	wire: 22AWG
>	Secondary Coil Length: 23.37 in
>	Winding Ratio: 3.895
>	Secondary winding length: 1492 feet
>	Weight: 7.566 lbs
>	Secondary Inductance: 31.161 mH
>	Capacitance of Secondary: 10.82pF
>	Outer Diameter: 18 inches
>	Cross sectional diameter: 4 Inches
>	Torroid Capacitance: 19.61pF
>	Total capacitance of secondary: 30.43pF
>	Calculated secondary resonant frequency: 163.442 Khz
>Primary:(Flat Spiral)
>	Primary coil ID: 10 inches
>	Primary Wire Diameter: .375 inches
>	Spacing: .400 inches
>	Number of turns: 5.4
>	Inductance of the primary: 14.317 uH
>With the above design information, What type of results could I expect under
>"as close to perfect as possible" conditions?? Just want to get a feel for
>what I might get close to achieving....
>Thank you in advance for your suggestions/criticism......
>Albert Race