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Re: new coil

Original poster: FutureT@xxxxxxx

In a message dated 12/13/04 12:49:24 AM Eastern Standard Time, tesla@xxxxxxxxxx writes:


Hello, my name is Blake Hartley, and I am a new member to this group and I
have finished my first coil. The specs are as follows: 9kv 30mA NST,
.0075mF party cup capacitor, 6 turn flat primary (ID 3" OD 9", .25" soft
copper tubing, .25 inch spacing), 1.86" secondary wound with 785 turns 29
AWG magnet wire (coating), and 1.5" radius spherical topload. I could get
2.5" sparks from it tapped at the end of the primary. I built a new 8 turn
primary, same as last but 11" OD, so I could get the correct resonance.
Right when I finished the primary, my secondary came apart somewhere, so I
must make a new one, which I plan on coating with polypropylene so it
doesn't fall apart. I was wondering if I should make the same secondary
again or if I should redesign it. Any suggestions would be much appreciated.

Thanks
Blake Hartley



Blake,

Congratulations on first light of your coil.  A 9/30 NST can
give about 20" sparks or so in a somewhat near optimal design.
I'd suggest using a 3.5" or 4" dia secondary about 15" or 19"
tall, using 1200 - 1400 turns of 29awg magnet wire.  The capacitor
should be an LTR value such as 0.02uF.  A small synchronous
rotary gap will get the best results from the system.  In any
case a good spark gap is very important even it's a fixed
multiple type gap.  Use a safety gap and Terry filter to protect
the NST.  The toroid should be 3" x 10" or so.  A 2" x 8" toroid
would be OK too, and should give multiple streamers.  For a
small coil like this, 10 or 12awg insulated wire can be used for
the primary, or the copper tubing can be used, but will need
quite a few turns.  You can calculate the number of primary turns
needed by using Bart's JavaTC program.  You can see my
TT-42 coil which gives 42" sparks from a 12/30 NST at;

  http://hometown.aol.com/futuret/page3.html

Click on the link for spark gap coils.  There's also information
on tube coils, rotary gaps, a SRSG phase shifter, toroids, etc.

John