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Re: Primary/sec'y spacing for my big coil. (fwd)





---------- Forwarded message ----------
Date: Tue, 4 Aug 1998 20:59:51 -0500
From: Chuck Curran <ccurran-at-execpc-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Primary/sec'y spacing for my big coil. (fwd)

Clay:

Last year I completed and ran a coil similar to the one you have described.
I used a piece of PVC sewer pipe that was 15 1/4" O.D. for the secondary and
wound it with #15 magnet wire over a 56" length.  I used two caps with a
combined capacitance of .075 mfd and a 14,400 VAC pole transformer.  On this
coil I have 2 1/2" spacing from primary to secondary at the closest point,
with the primary slightly below the bottom turn of the secondary--I don't
have an exact dimension sitting here.

The Maxwell caps that Surplus Sales are selling look interesting, but they
can't offer any pulse per second specs on these, at least they couldn't
earlier this year when I tried to find out.  They might not handle Tesla
service.  I would suggest you run through some calculations for your primary
inductance and cap size--right now the values you mention do not appear to
match with your secondary + toroid resonant frequency "estimate" I've done.
I'd be happy to share some of the items with you that I worked through
resulting in 13' max sparks at 15-16 Kw input.  Just let me know if your
interested.

Chuck


-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Monday, August 03, 1998 1:27 AM
Subject: Primary/sec'y spacing for my big coil. (fwd)


>
>
>---------- Forwarded message ----------
>Date: Sun, 2 Aug 1998 17:11:59 -0500 (CDT)
>From: Larry Bud Melman <gasman-at-althea.a-line-dot-net>
>To: Tesla List <tesla-at-pupman-dot-com>
>Subject: Primary/sec'y spacing for my big coil.
>
> Hi all...
>
> Finally got my coilform for my coil - using a 16 inch sonotube,
>sealed with urethane varnish, and going to reinforce with fiberglass cloth
>and resin, since I suspect 3500 ft of 14 gauge wire is *pretty heavy*...
>
> Thinking about overall design, and when I was planning the primary,
>I realized that I wasn't sure how large I should make the space between
primary
>and secondary.  Don't wanna make it too small, but obviously will get more
>spark from coil if I can minimize it... (I was planning a flat, archimedes
>spiral - sound good??)
>
> I'm thinking about 2 inches space.  Whaddya all think??
>
> Tentative specs of coil:  using 10 kVA PP, 23 kV (27 if using 280v
>input)
>
> --height of windings 54 inches (800 turns) - sec'y inductance 73.01 mH
>
> --Approx resonant freq 110.8 kHz
>
> --Tank cap: 50 kV 0.05 uF ($375 at SurplusSales-dot-com - OUCH!!!!)
>   (geez - only gave $250 for my reconditioned
>    pig with non-PCB oil)
>
> --Primary: using 1/2" (12.7 mm) copper tubing, 8 turns, should tune
>between 5 and 6.
>
> --Sparkgap:  I'm blazing the trail with a Terry Fritz gap on this
>relatively high-power coil, planning 5 thousandths gaps times 50 or 60.
>I will do most anything to avoid the dreaded and feared RSG.
>
> --Topload: beats the hell outta me.  I figure this thing will take a
>toroid in the 48-inch range.  I have no idea where to get one.  Try some
>muffler shops maybe - I remember that thread.  They'd be awful skinny
though.
>Need a bigger X-section.  Probably end up with heating duct.
>
> I'll be mighty disappointed if I can't get 10 - 15 foot sparks from
>this one...time to start wining and dining the neighbors...
>
>
> Clay   8-}
>