Re: Toroid Recommendations?

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

Original poster: "sundog by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sundog-at-timeship-dot-net>

Hi All,

Usually, I don't base my toroid sizes on aesthetics, though I generally 
make the minor diameter about the same size as the form diameter, and the 
major diameter about 1/2 to 3/4 of the coil's height.

   When I get "sophisticated", I choose a tune point about 3/4 of the way 
in on the primary, pick an LTR cap for the power supply, and size the minor 
diameter so that it's just below what would hold off the spark, then adjust 
the major diameter so that Fres of the coil is just above what the tank 
circuit is tuned at.  Example,

  For my 2.5" coil I wanted to tune it at ~7 turns on a 10 turn primary, 
and use an LTR 12/30 NST tank supply, on a 120bps sync gap.  So I figured 
the resonant size cap, make it 1.5x larger, and figured what freq the 
primary would oscillate at.  The secondary's Fres is 1.2mhz-ish, so I 
figured a 3" minor diameter, and increased major diameter till I got it 
where I wanted it.  That was too freakishly huge, so I added a 1.5x6" 
toroid underneath it, and re-sized the big topload appropriately.  Works 
for me, but be prepared, the toploads can get big like that.  With a 
different tank cap, the 2.5" coil was using the 1.5x6 toroid and a 3x17" 
toroid on a 9/60 NST, and threw constant 30" sparks, and I got a few hits 
out to 35" or so. Not too shabby.

Hope it helps!

Shad G3-1203

At 09:49 AM 4/11/02, you wrote:
>Original poster: "Barton B. Anderson by way of Terry Fritz 
><twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>
>
>Hi ALL,
>
>I know everyone is busy with one thread or another, but could some of you
>reply to Marks request for
>toroid recommendations (see below for coil specs). I asked Mark to ask the
>List so he could get an idea of
>what sizes some of you are using, but haven't seen any replys come through 
>yet.
>
>Thanks,
>Bart
>
>Tesla list wrote:
>
> > Original poster: "Mark W. Stolz by way of Terry Fritz
><twftesla-at-qwest-dot-net>" <mark_w_stolz-at-hotmail-dot-com>
> >
> > Hi All!
> >
> > I'm working on my new coil and wanted to get some input regarding the
> > toroid.  Here's the specs:
> >
> > Primary
> > 19 turn 20 degree inverse cone
> > 3/8" tubing, 3/8" turn to turn spacing.
> >
> > Seconday
> > 9" diameter 38" winding length 22 AWG single build
> >
> > Tank
> > 15/60 NST, 7 segment RQ/TCBOR fan cooled static gap, 20 nF MMC
> >
> > I was think about using my existing 4" x 15.5" toroid from my previous 
> coil,
> > except that ETesla 6 indicates a drop in the free space capacitance from
> > 17.2 pF to 5.2 pF.  I'm now thinking more towards a 4" x 30".
> >
> > What are your recommendations for minor/major diameters and why (i.e.
> > testing, taste, experience)?
> >
> > Thanks in advance,
> >
> > Mark Stolz
> > Houston, TX
> >

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Shad (Sundog)
G-3 #1203
"Ever stop to think, and forget to start again?"
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