Re: Help with first coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>

Hi Kevin,

Congratulations on first light! The main difficulty appears to be that your
coil is far out of tune. This is primarily do to your tank capacitors being
about 1000 times too large... or did you mean that your caps were 2.8 nF
instead of 2,8 uF? 

For proper operation, the primary and secondary must be tuned such that
they resonate at the same frequency - this appears not to be the case in
your coil, and this likely the main reason why your output is poor. There
are also considerations of tank capacitor size versus the size of the HV
transformer - again your tank caps are much too large for your transformer.
The main gap setting of 1/2" is much too wide for a 10 KV NST, and can lead
to overvolting (once you get the right sized tank cap). And finally, it
also sounds as though the RF ground may not be making good contact with the
soil due to the heavy paint coating. Sounds like you have some work (fun!)
ahead to get the system whipped into optimal running order. 

But you may need some additional knowledge, and some design aids might also
be useful. Fortunately, you've come to the right source by joining the
Tesla Coil Builders List.

First, you'll need to read up on Tesla Coil Theory. Some very good web
sites for beginner and intermediate theory include the following:
   http://home.earthlink-dot-net/~electronxlc/
   http://www.staff.ncl.ac.uk/r.e.burnett/
   http://hot-streamer-dot-com/TeslaCoils/TeslaCoils.htm

A variety of Tesla Coil design aids are also out there. Some of the better
ones include:
   http://members.aol-dot-com/rscopper/index.htm      (WinTesla V4.0)
   http://home.mmcable-dot-com/surplus/               (WinTesla V3.2)
   http://home.att-dot-net/~couturejh/                (JHCTES V3.1 and 3.2)
   http://www.classictesla-dot-com/java/javatc.html   (JavaTC 7.07)
   http://users.better-dot-org/roverstreet/resources/measure.htm   (Ed
Sonderman and Ross Overstreet)

Printed references that you may find useful include:
TESLA COIL CONSTRUCTION GUIDE by J. H. Couture
Contains theory plus a number of proven coil designs from a few watts to
several kilowatts. Excellent source for the beginning Tesla Coiler.
1994, 70pp, $18.00

MODERN TESLA COIL DESIGN THEORY by Duane Bylund
The author shares excellent information and his own experimentation in
this 129 page GBC bound book. His research includes: RLC circuits,
transmission lines, the Tesla coil secondary, capacitor discharge,
vacuum tube, and solid state Tesla coils. 1991 8 1/2 x 11 GBC, 129pp,
$19.95

THE TESLA COIL BOOK by Brent Turner, 1996, 146pp. Available for $23.95
directly from the author at: 
   http://www.apc-dot-net/bturner/t-page.htm
This is one of the best written, technically accurate, modern day Tesla
Coil building texts around. Compiles some of the best information from
the Tesla Coil Builder's List and personal experiences of the author.
Written by a professional coiler.

Most of the above published books (except for Brent Turner's book) can
be obtained from Twenty First Century Books: 
   http://www.tfcbooks-dot-com/

The above sources should get you started along the right track! Good luck
and keep us posted of your progress or if you have any questions.

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "Kevin Wampler by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <wamplerk-at-u.arizona.edu>
> 
> I have completed the construction of my first coil and have ran into a
> problem.  As far as I can tell, everything is working, but I can't seem
> to get a spark length to a grounded object of any more than about 10".
> When tuning the coil, there is a range of about 2-3 turns on the primary
> where the spark length is at a maximum, but within that range I don't
> see much of a difference.  The toroid also has little or no effect on
> the spark length.  Does anybody have any ideas for what could be wrong,
> or at least have some suggestions for things I could try that might get
> it working?
> 
> Here is the info on my coil:
> NST:            10kV at 30mA
> 
> Spark gap:      Air blast gap set at about 1/2"
> 
> Caps:           2 2.8uF 30kV caps wired in parallel, I bought them online.
> 
> Primary:        30 degree saucer shape of 1/4" copper tubing spaced 3/8"
apart.
> 
> RF ground:      3 metal stakes hammered ~2' into the ground, the top part of
> each where I attach the grounding cable has been sanded clean, but the
> part in the ground has a fairly heavy coat of paint left. The soil here
> is also very dry, though I did try wetting it, which didn't seem to
> help.
> 
> Secondary:      6.5" outside diameter white PVC pipe, with 1/4" thick walls.
> It was sanded clean and dried for several days in a low temperature
> oven, then varnished with polyurethane and capped with plexiglass.  It
> is 27 1/2" long, the middle 24" of which is wound with 22 AWG enamel
> coated magnet wire.
> 
> Toroid:         4" minor diameter, ~12" major diameter, made from corrugated
> aluminum duct.  A metal rod about 4" in length has been attached as a
> point to arc off of.
> 
>         ~Kevin Wampler~