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RE: Capacitor construction?
David,
Why construct your capacitor twice?
If you make the higher value capacitor initially you can use it without
the topload by just tapping to fewer turns on the primary.
I'd use all available copper tubing to make as much primary inductance
as possible for future experiments/versions/secondaries.
You may want to consider a larger i.d. for the primary to allow later
experiments with larger secondaries, compensate for larger i.d. and
number of turns by reducing the space between turns, the space is only
required to allow a moveable tap without short-circuiting turns as the
turn to turn voltage can be insulated with 1/10" air only.
Also consider a larger value for your primary capacitor, 0.006 to 0.010
uF.
my two cents worth ... Sulaiman
> ----------
> From: Tesla List[SMTP:tesla-at-pupman-dot-com]
> Sent: Monday, November 09, 1998 7:53 AM
> To: tesla-at-pupman-dot-com
> Subject: Capacitor construction?
>
> Original Poster: "David Knaack" <dknaack-at-idworld-dot-net>
>
>
> Greetings!
>
> I recently obtained a 12kv 30ma NST to use for my TC.
> Before I started putting things together I wanted to post
> the specs I am currently planning on using, to see if anyone
> notices any obvious problems or miscalculations.
>
> Here are the details:
>
> Transformer: 12kV 30mA NST (no power factor correction)
>
> Primary: 1/4 copper tubing, 21" od, 6.75" id, 8 turns
>
> Secondary: 4" x 10.75" ~54 TPI ~0.014" wire (75% spacing?)
> Calc. Freq: 660kHz (currently no top capacitance)
> Planned Toriod 4" id, 8"od, ~3pF (drops frequency to about 530kHz)
>
> Tank Cap: (Until I have a toroid)
> 90 mil poly (20 layers 4.5 mil stock)
> 105 in^2, 6 plates, ~0.0029uF 13kV rating
>
> Tank Cap: (After I get the toroid)
> 90 mil poly(20 layers 4.5 mil stock)
> 105 in^2, 9 plates ~0.0046uf 13kv rating
>
> Spark gap: 1/2"x4"(x2) steel ground rod, ends ground flat
> spacing unknown
>
> Safty gap: dunno yet
>
>
> Questions:
>
> On the primary I only have 8 turns, I have enough tubing for a few
> more,
> shall I go ahead and inish off the coil with the remaining tubing?
> (just
> have to buy some new wood to mount it on).
>
> For the tank cap I only have some 4.5 mil black construciton type
> plastic
> (but I have LOTS of it). I figured a voltage rating of 450v/mil, with
> 20
> layers
> to get to 90 mils (and help to protect defects), and a voltage rating
> safty
> factor of 3 would give me a cap that could handle about 13kV total.
> Six plates should give me about 0.0029uF, and later, after I get the
> toroid I can add three more plates to get to 0.0046uF.
> Anybody see any problems with this?
> When I have some money I may buy some clear plastic, but for now
> I'm stuck with this stuff.
>
> There is a web page out there somewhere that offers smooth copper
> spheres up to several inches in diameter for pretty reasonable prices.
> I can make a toroid up to about 8 inches in diameter, but its surface
> won't be as smooth as the copper sphere. Which would be a better
> option for this size coil?
>
> What should I set the spark gap to initally?
>
> What should I set the safty gap to?
>
> Thanks!
>
> David Knaack
>