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NEW PROJECT STATUS

 > From: Esondrmn-at-aol-dot-com (Ed Sonderman)
 > To: richard.quick-at-slug-dot-org
 > Subject: New project status

 > Richard,

 ES> I finally got everything put together Saturday morning and   
 ES> got his project lit up.  It works great!  This coil makes    
 ES> the first one I built (in high school many years ago) look   
 ES> like a toy. This thing makes serious sparks - and a hell of  
 ES> a lot of noise.  I think I should wear hearing protection -  
 ES> if my hearing wasn't already shot.

Sounds like you are very pleased with the project! Another
satisfied customer :-)

 ES> Here's the details:

 ES> Secondary 27.6" long, 6.0" dia, #22 magnet wire, measures 32
 ES> milliheneries. 

Nice high inductance secondary, aspect ratio is just fine.

 ES> Primary 14 turns 3/8" copper tubing wound at 30 degrees
 ES> on a plastic form. 8.0" dia at base, 27.5" dia at top        
 ES> measures 82 microheneries. 

There you go, nice primary too. Snugly coupling, lots of turns,
lots of surface area to produce a large field flux that completly
envelopes the secondary.

 ES> Discharger is 14" dia x 4.0" thick made of styrofoam
 ES> covered with foil tape. 

This will get you tuned in and firing. Your are going to need a
larger toriod to peak this coil system out.

 ES> Tank capacitor #1 is  .0186 mfd, # 2 is .0178 mfd.
 ES> Bypass cap # 1 is 698 pf, # 2 is 675 pf.
 ES> RF chokes are 650 to 700 microheneries.
 ES> Running at this time with two 12kv 30ma transformers in      
 ES> parallel.

Hey! This looks good!

 ES> I ran it with the two tank capacitors in series tapped at 14 
 ES> turns until Sunday afternoon at increasing power levels.  I  
 ES> did get it up to full power finally.  I never did see more   
 ES> than 4 small air bubbles come up in one capacitor and none   
 ES> in the other.  It seems to tune with the two capacitors in   
 ES> series right at 14 turns.  With one capacitor it seems to    
 ES> tune at 10 turns. I calculate the frequency to be the same   
 ES> at these two points - exactly 185 khz.  


Another nice thing about these large primaries: you can tune with
a wide variety of tank circuit capacitor values. This gives lots
of experimental and power level room.
 
 ES> I don't seem to be able to tune it within a turn (i.e. 9.5   
 ES> or 10.25 turns) although I can tell the difference between   
 ES> say 9 turns and 10 or 11. 

This could be what I call "mushy" tune, or it could be a problem
with just so much overwhelming spark that it is hard to be
objective. Mushy tune in a well designed and built coil system,
such as this one, is mostly likely a ground path problem or a
problem with the RF chokes. Double check your ground and ground
path looking for areas to improve (heavier braid or strap? a good
soak maybe?)> Then look at your RF chokes: are they far enough
back, are they mounted off axis (they should be) are they too
large or too small (experiment a little). Lastly if the display
is just too intense to be objective then try video taping; move
the tap, tape the coil firing, move the tap, tape some more,
etc.. Then sit down in a comfortable chair and be objective. 

 ES> I do seem to get more power out of it with one cap tapped at 
 ES> 10 turns. 

One cap alone will deliver more peak power than two caps in
series. 

 ES> This brings up a point that I have seen discussed.  I        
 ES> calculate the quarter wave frequency of the secondary to be  
 ES> 150 khz.  This must be the frequency that will produce the   
 ES> highest voltage at the top of the coil.  Does the discharger 
 ES> and the loading of the primary actually bring the primary
 ES> frequency down by 35 khz to 150 khz? 

Yes! This is one essential function of the discharger. Lower
frequency = bigger sparks. Bigger toriod = lower frequency.

 ES> I noticed that I can increase the discharge length by        
 ES> sitting a 10.0" dia x 2.0 " tall stainless steel
 ES> pan on top of the discharger.  Which I imagine tells me the  
 ES> discharger is too small, correct?  

Yes. You will want about a 30" diameter discharger or so to
really peak this coil out. Maybe even larger.

 ES> When I do this <add the pan>, it forces all the discharges   
 ES> to go downward - none off the top  -- curious.  Can you tell 
 ES> me why?  

The pan would seem to be disrupting the nice uniform field shape
produced by the toriod discharger alone.

 ES> At full power in this configuration I get strikes down into  
 ES> the primary causing very loud pops which in turn causes the  
 ES> safety gap to fire, and of course I immediately turn the     
 ES> power down.  I assume these pops indicate the primary is     
 ES> being shorted by the ionized air.  

Or the overload from the discharge striking the primary is
causing kickbacks. 

 ES> I can't figure out how the strikes are getting past my       
 ES> strike rail.  It is also copper tubing mounted about .75"    
 ES> above the last turn on the primary.  I only have the strike  
 ES> rail grounded to the RF ground with a #12 copper wire.  Is   
 ES> this the problem?  I can raise the discharger by a few more
 ES> inches but I don't think this will help much.

Start thinking about that larger toriod, and raise your existing
toriod up as high as possible. You may add additional strike
protection by soldering some projections on the strike rail.

 ES> By the way, what do you do with the metal case on the        
 ES> cylindrical spark gaps? Because of its close proximity to    
 ES> the AC line (inside the motor) I did not want to connect it  
 ES> to RF ground and I did not want to connect it to AC line     
 ES> ground either so I finally just built a shield over it and   
 ES> connected it to RF ground.  What do you do?

I do what you did.

 ES> I forgot to mention the discharge length I'm getting with    
 ES> two 12kv 30ma transformers and one cylindrical spark gap     
 ES> (using the whole thing) is about 32 to 36 inches. These      
 ES> discharges are violet, not white like on your video,
 ES> and there are many of them.  Is this because the discharger  
 ES> is too small?  I this about the performance you would        
 ES> expect?

Your performance is very good for this power level. You have
recorded 3 foot strikes with less that 3/4 kVA. Your next step is
learning the ins and out of synergistic tuning. This is the
matching of the power supply to the capacitance, then matching
the toriod to the capacitance, then adjusting the coupling,
toriod heights, strike shields, tweaking and tuning here and
there to really peak the coil out. 

If you put both caps in parallel you are looking at over .036
mfd. in the tank circuit. This will take about 180 mA from a
12 kV power supply to charge and fire synergistically, which
puts you in the 2 kVA range. That's a BIG JUMP in power levels
for a coil that is efficient enough to produce 3 foot strikes at
720 VA. To regain the system tune with .036 mfd. in the tank
circuit you will need a very large toriod, because you want to be
usiing all 14 turns on the primary, so your secondary resonate
frequency will have to go lower (more toriod will drop it.)

Good luck. Excellent project. BTW, what are you using for a
ground again?

Richard Quick

... If all else fails... Put another megavolt across it!
___ Blue Wave/QWK v2.12