# Re: Tank Capacitance: what is the limit (Q)

```Subject:  Re: Tank Capacitance: what is the limit (Q)
Date:   Tue, 29 Apr 1997 19:23:47 -0400 (EDT)
From:   richard hull <rhull-at-richmond.infi-dot-net>
To:   Tesla List <tesla-at-pupman-dot-com>

At 09:52 AM 4/28/97 -0500, you wrote:
>Subject:       Re: Tank Capacitance: what is the limit
>       Date:   Mon, 28 Apr 1997 16:29:46 +1200
>       From:   "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
>Organization:  Wellington Polytechnic, NZ
>         To:   tesla-at-pupman-dot-com
>
>
>Hi all,
>        A comment on Fr McGahee's post:
>
>> While it is generally true that the primary is more than one turn of
>> wire,
>> as the secondary becomes LARGER in DIAMETER, it is often advantageous to
>> use larger capacitors and fewer turns in the primary.
>
>I usually run at lower frequencies and keep primary Q up by keeping
>Lp large. I hear things like "lower frequency implies lower Q" a lot.
>That no doubt comes from observing that Q = X/R. Let's have a closer
>look at that:
>                  Q = (2 x PI x f x L)/R
>
>and we know that f = 1/(2 x PI x SQRT(L x C))
>
>     Let's halve f in three ways, first by making C four times larger.
>That leaves L unaffected which indeed causes Q to dive in half since
>f has halved.
>     Now lets achieve the same thing by doubling L and doubling C. Q
>is now the same (as it should be because the L/C ratio is preserved.
>     Finally, let's quadruple L. Despite f having halved, Q is
>actually doubled.
>
>     With reference to the primary, we know that "R" is a non-linear
>resistance. In fact I maintain it goes down as gap current goes up.
>If the voltage across the gap when it is conducting is reasonably
>constant, then gap losses double as the current is doubled. Despite
>gap resistance doubling as current is halved, it loses less power
>because it roughly follows a VxI dissipation law.
>
>Malcolm

Malcolm, all,

This is exactly what we in the TCBOR discovered way back in 1989!  We
found
it first by empericism and then we worked the math, backwards.  All this
really made us laugh at the, then, "big boys" with their .2mfd caps and
3-4
turn primaries and smallish toroids.  We constantly run huge primary L's
and
moderate to smallish caps and still pump in up to 10KW.

At that time, a really big monster coil's secondary was almost always
space
wound (yuk) and if it had 40 mh of inductance, people cringed,  The
toroids
of that period, if used at all, were rarely over 1.5 times the diameter
of
the secondary. 6" cross sections on toroids in the biggest systems were
considered ungodly large.  Primary L's on even the largest systems were
30uh
or so. It seemed the primary cap was selected first and the primary L
was
wound to suit as needed to resonate with the secondary.

All this was to change rapidly.

Nemesis was a classic example.  With a 110uh 13 turn 4 foot diameter
primary and a .088 capacitor and with about 10kVA, we hit the 15-16 foot
mark with white hot bolts on occassion from a 46" secondary winding of
.130
henry.  Lotsa' folks from 1990 to 1994 witnessed Nemesis in person at
our
Telsathons.  A lot more than the primary tank played a role here, but
the
cap ran as cool as a cucumber.

Once we found this "little secret", we blasted it out on our first
report
tape in 1989 and re-iterated it on many succeding reports to alert
others to
it.  To my knowledge this was the first real mention of this in the
tesla
coil building community.  Since then, we have never looked back at this
issue, but it is refreshing to see the math wizzed out over the net once
more.

The final blast came for us in late 1989 and early 1990 as we enlarged
the
toroid diameters and cross sections to huge proportions on very small
systems.  This artifice allowed 3-4 times the winding length in spark to
be
achieve with a two coil system.  The first use of the toroid on Tesla
coils
is probably a shared honor between Dick Aurandt and Bill Wysock.
Niether,
however,  experimented with obscene sized toroids.  Probably because
they
would never hand make a monster toroid from inner tubes or sewer flex
drain
pipe covered in reynolds wrap or giant corrugated ducting.  They seemed
to
use those items which were commonly machine spun and appeared pretty.
Those
common machine spun units were of very small size and on a 36" diameter
6
foot tall coil a 36 X 6 toroid was considered "state of the art".

60"X12" toroidial structures were the norm on 4 foot coils here by early
1991. in 1992/93 Richard Quick had seen Nemesis in person and on a
number of
our tapes.  Those of you who have his tape will note his immediate use
and
acceptance of the huge primary L's and large toroids.  Thus within a few
months of his first tiny system he was punching out 10 foot bolts with
no
problems.

The bottom line is, if it works, use it. But, if you care to experiment,
it
can always be improved upon.  See what the other guy has and copy it
only
better.  In some cases, strike out on a seemingly impossible tangent,
There
may be a new concept to discover.

Richard Hull, TCBOR

Date:
Tue, 29 Apr 1997 19:23:47 -0400 (EDT)
From:
richard hull <rhull-at-richmond.infi-dot-net>
To:
Tesla List <tesla-at-pupman-dot-com>

At 09:52 AM 4/28/97 -0500, you wrote:
>Subject:       Re: Tank Capacitance: what is the limit
>       Date:   Mon, 28 Apr 1997 16:29:46 +1200
>       From:   "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
>Organization:  Wellington Polytechnic, NZ
>         To:   tesla-at-pupman-dot-com
>
>
>Hi all,
>        A comment on Fr McGahee's post:
>
>> While it is generally true that the primary is more than one turn of
>> wire,
>> as the secondary becomes LARGER in DIAMETER, it is often advantageous to
>> use larger capacitors and fewer turns in the primary.
>
>I usually run at lower frequencies and keep primary Q up by keeping
>Lp large. I hear things like "lower frequency implies lower Q" a lot.
>That no doubt comes from observing that Q = X/R. Let's have a closer
>look at that:
>                  Q = (2 x PI x f x L)/R
>
>and we know that f = 1/(2 x PI x SQRT(L x C))
>
>     Let's halve f in three ways, first by making C four times larger.
>That leaves L unaffected which indeed causes Q to dive in half since
>f has halved.
>     Now lets achieve the same thing by doubling L and doubling C. Q
>is now the same (as it should be because the L/C ratio is preserved.
>     Finally, let's quadruple L. Despite f having halved, Q is
>actually doubled.
>
>     With reference to the primary, we know that "R" is a non-linear
>resistance. In fact I maintain it goes down as gap current goes up.
>If the voltage across the gap when it is conducting is reasonably
>constant, then gap losses double as the current is doubled. Despite
>gap resistance doubling as current is halved, it loses less power
>because it roughly follows a VxI dissipation law.
>
>Malcolm

Malcolm, all,

This is exactly what we in the TCBOR discovered way back in 1989!  We
found
it first by empericism and then we worked the math, backwards.  All this
really made us laugh at the, then, "big boys" with their .2mfd caps and
3-4
turn primaries and smallish toroids.  We constantly run huge primary L's
and
moderate to smallish caps and still pump in up to 10KW.

At that time, a really big monster coil's secondary was almost always
space
wound (yuk) and if it had 40 mh of inductance, people cringed,  The
toroids
of that period, if used at all, were rarely over 1.5 times the diameter
of
the secondary. 6" cross sections on toroids in the biggest systems were
considered ungodly large.  Primary L's on even the largest systems were
30uh
or so. It seemed the primary cap was selected first and the primary L
was
wound to suit as needed to resonate with the secondary.

All this was to change rapidly.

Nemesis was a classic example.  With a 110uh 13 turn 4 foot diameter
primary and a .088 capacitor and with about 10kVA, we hit the 15-16 foot
mark with white hot bolts on occassion from a 46" secondary winding of
.130
henry.  Lotsa' folks from 1990 to 1994 witnessed Nemesis in person at
our
Telsathons.  A lot more than the primary tank played a role here, but
the
cap ran as cool as a cucumber.

Once we found this "little secret", we blasted it out on our first
report
tape in 1989 and re-iterated it on many succeding reports to alert
others to
it.  To my knowledge this was the first real mention of this in the
tesla
coil building community.  Since then, we have never looked back at this
issue, but it is refreshing to see the math wizzed out over the net once
more.

The final blast came for us in late 1989 and early 1990 as we enlarged
the
toroid diameters and cross sections to huge proportions on very small
systems.  This artifice allowed 3-4 times the winding length in spark to
be
achieve with a two coil system.  The first use of the toroid on Tesla
coils
is probably a shared honor between Dick Aurandt and Bill Wysock.
Niether,
however,  experimented with obscene sized toroids.  Probably because
they
would never hand make a monster toroid from inner tubes or sewer flex
drain
pipe covered in reynolds wrap or giant corrugated ducting.  They seemed
to
use those items which were commonly machine spun and appeared pretty.
Those
common machine spun units were of very small size and on a 36" diameter
6
foot tall coil a 36 X 6 toroid was considered "state of the art".

60"X12" toroidial structures were the norm on 4 foot coils here by early
1991. in 1992/93 Richard Quick had seen Nemesis in person and on a
number of
our tapes.  Those of you who have his tape will note his immediate use
and
acceptance of the huge primary L's and large toroids.  Thus within a few
months of his first tiny system he was punching out 10 foot bolts with
no
problems.

The bottom line is, if it works, use it. But, if you care to experiment,
it
can always be improved upon.  See what the other guy has and copy it
only
better.  In some cases, strike out on a seemingly impossible tangent,
There
may be a new concept to discover.

Richard Hull, TCBOR

```