Re: Help with first coil

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Kevin,

The cap is too large. In parallel capacitance adds. In order to tune your
coil, you would end up with
less than 1 turn. With the caps series connected, the capacitance halves to
1.4uF, but still the coil
tunes at about 1 turn. You may want to hook the caps in series and try it
at 1 turn to see how it reacts.
Following that, you should try about 0.01uF which should tune in at about
12 to 13 turns.

Bart A.

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~