# [TCML] Toroid question

futuret at aol.com futuret at aol.com
Sat May 30 19:25:22 MDT 2009

```Dex,

In my formula, I use the total power drawn from the mains.  But
the formula is only a rough guide anyway.  Many folks use the formula
in different ways for example they might use the input kVA instead
of watts, etc.  The formula still tends to work reasonably well and is
only intended for rather efficient coils.  Inefficient coils will tend
to
produce much shorter sparks.  Small static gap coils with small
tank caps often produce much shorter sparks than the formula
would suggest.

It's not true that I developed the formula based on SRSG, 120 PPS,
equal bangs, although that is a popular myth.  I actually based it on
a variety of coils both 120 PPS and higher async break-rates such
as 280, 340, 420 PPS, but not specifically those break-rates, but
similar
break-rates.   Apparently, larger coils tend to be more efficient so
they
have less trouble meeting the "prediction" given by the formula.  Small
coils have trouble reaching such efficiencies at times.  Because of
this,
small coils seem to require 120 bps SRSG operation to fit the formula.
Larger coils seem to get by well at higher breakrates at least up to
some (unknown) PPS point.  I don't have space to run large coils,
so I had to depend on reports by others regarding their coil's
efficiencies,
when analyzing the larger coils.

Cheers,
John

-----Original Message-----
From: Dex Dexter <dexterlabs at dcemail.com>
To: Tesla Coil Mailing List <tesla at pupman.com>
Sent: Sat, 30 May 2009 3:12 pm
Subject: Re: [TCML] Toroid question

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.

Dex

--- futuret at aol.com wrote:

From: futuret at aol.com
To: tesla at pupman.com
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