Re: Improved coil and questions

to: Andy

If you are running a NST keep your total gap around 0.2 inches --- this will
save the xmfr.

Use approx 24-26 turns of scrap #12 AWG house wiring until you find correct
resonance, then discard and make a nice primary.  Having extra for initial
testing never hurts --- having too little and your coil never will run


Dr. Resonance

-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Tuesday, August 31, 1999 11:06 PM
Subject: RE: Improved coil and questions

>Original Poster: "Andy Cleary" <gemware2-at-dreamscape-dot-com>
>Thank you for the suggestions, I think I might try using #12 awg wire for
>the primary.  I did forget to mention the cap.  When I posted that message
>the cap was a .009 uf saltwater bottle cap.  Since then I added 2 more
>bottles, which I believe would bring the capacitance up to about .01.  I
>don't have a meter that will test capacitance that low, so I can't provide
>an accurate measure.  As to the spark gap, I tried making a roundish gap
>around the inside of a 4" PVC pipe, so that I could hook it directly to the
>output of a powerful blower.  I planned to put 7 segments, adding up to
>about 1/2".  As it turns out, due to poor workmanship and even poorer
>I put 5, 1/4" x 2" pipe segments adding up to about 1/2".  I have the wires
>movable to select any number of segments.  When I try to cross three gaps
>with four segments, the spark gap doesn't fire, I am guessing not enough
>capacitance, or the gap is too large (although it would be less than 1/2").
>The gap only fires with three pipe segments = two gaps.  I am not sure what
>the total gap space is, the gaps are all different.  At least the blower
>works well.  Again, thanks for the suggestion.  Perhaps the #12 wire will
>cheaper to buy than the copper tubing as well.
>-Andy C.
>> -----Original Message-----
>> From: Tesla List [mailto:tesla-at-pupman-dot-com]
>> Sent: Monday, August 30, 1999 8:58 PM
>> To: tesla-at-pupman-dot-com
>> Subject: Re: Improved coil and questions
>> Original Poster: FutureT-at-aol-dot-com
>> In a message dated 99-08-30 06:27:45 EDT, you write:
>> <<  I just recently improved my small 4", 12000 60ma Tesla coil, which
>> > previously giving off only 9" streamers.  My previous coil had
>> about 1300
>> > turns of 28 gauge magnet wire on the 4" pipe.  My primary coil
>> was getting
>> > extremely large and expensive, about 17 turns of 1/4 inch
>> tubing, so I tried
>> > to find how I could limit it.  What I found was that my coil
>> had too many
>> > turns, and too small of a primary capacitance to have a smaller primary
>> > coil.
>> Andy,
>> I use 1300 turns or more of #28 wire on my 4" secondary, but I use
>> #12 insulated wire on my primary.  This wire can be close wound and
>> gives a compact primary, I'm using 22 turns at the moment, but at times
>> I've used up to 34 turns.  I'm using a .0147uF cap, and I get 42" sparks
>> from a 12kV, 30ma NST.
>> I suspect that your coil is not tuned correctly, you probably still need
>> a lot more inductance in your primary.  Why don't you just add some
>> turns of #  12 wire to the outside of your existing primary as a test to
>> see where it tunes?  Or build a simple scrap wire primary using #12 wire.
>> The tune point at 5 turns you tried is most likely incorrect.  The reason
>> your coil doesn't work well with a large top terminal is because a large
>> top terminal demands even more primary inductance (more turns).  Add
>> more turns, and the fire and brimstone will pour forth from your coil (if
>> your gap is OK, and if your cap size is reasonable).  NST's work well
>> with sync gaps (if the cap is the right size), async gaps are
>> generally NG for an NST based TC.  I don't think you mentioned your
>> cap size?
>> Another thing you could do is keep your copper tubing primary, but
>> make a new secondary wound with #22 wire or so, which will give the
>> coil a much lower inductance and make it more likely to tune correctly
>> with your primary.  It's best to do some calcs, or use a TC computer
>> program to calc the number of turns needed so it will tune OK, etc.
>> Cheers,
>> John Freau
>> > -Andy >>