# Re: [TCML] Toroid question

```John,in your formula
Spark lenght = 1.7*SQRT(P)
is P in watts power delivered to Tesla coil circuit or total power drawn from the mains?
Also,I heard that you developed the formula on the basis of SRSG , 120 PPS,and equal bang sizes coils.
Does that mean  it is not so accurate for static gap coils,ARSG coils,and higher PPS coils.

Gary,there is surely a possiblity of a too big toroid for a power level.Let say ,if you put 48"x12" (with a braekout point on it) toroid on 360 W coil.That would probably decrease a spark lenght output,right?That size of the toroid is optimum for a 1 kW+ range coil.

Dex

--- futuret@xxxxxxx wrote:

From: futuret@xxxxxxx
To: tesla@xxxxxxxxxx
Cc:
Subject: Re: [TCML] Toroid question
Date: Fri, 29 May 2009 18:18:23 -0400

Andrew,

at my website, I show my TT-42 coil with a 4" x 13" spun toroid.  The
coil
produces 42" sparks using a robust 12/30 NST.  An ordinary 12/30 gives

http://futuret.110mb.com

Cheers,
John

-----Original Message-----
From: Lau, Gary <Gary.Lau@xxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Fri, 29 May 2009 9:13 am
Subject: RE: [TCML] Toroid question

Hi Andrew,

As you noted, bigger toroid equals bigger streamers but fewer of them.

Personally, between the two choices you gave, I would choose the larger
4.5x18
toroid.  I haven't personally built a coil powered by a 12/30 so I
can't say how
much larger than that one could go.  Do you already own both of those
toroids?
If so, try stacking both of them and see how that performs, assuming
that you
have sufficient primary turns to accommodate the lower frequency.

The final answer will depend upon how much time and cash you have
available.
Big spun toroids are expensive.  If cash is limited, you may want to
try the
http://www.laushaus.com/tesla/foamtoroid.htm

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Andrew Robinson
> Sent: Friday, May 29, 2009 3:23 AM
> To: tesla@xxxxxxxxxx
> Subject: [TCML] Toroid question
>
> I asked this once before but dont remember getting a very clear
>
> With a 4" x aprox 22" secondary. 12/30 NST what would be an
appropriate
> sized toroid? I've heard bigger toroid equals bigger streamers but
fewer
> of them. I guess looking at it from the physics point of view, bigger
> toroid = more capacitance = bigger streamer but longer charge times.
>
> Basically we're looking at either a 3" x 12" spun toroid or a 4.5" x
18"
> spun toroid. Also is there a better place to get these other than
ebay.
> Can someone out there sell us one?

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