Re: Hello from a new coiler.
From: Chip Atkinson[SMTP:chip-at-XiG-dot-com]
Reply To: Chip Atkinson
Sent: Tuesday, August 05, 1997 7:05 AM
To: Tesla List
Subject: Re: Hello from a new coiler.
On Mon, 4 Aug 1997, Tesla List wrote:
> From: Sulaiman Abdullah[SMTP:sulabd-at-hotmail-dot-com]
> Sent: Monday, August 04, 1997 8:25 PM
> To: tesla-at-pupman-dot-com
> Subject: Hello from a new coiler.
> Hello Coilers !
> I'm a virgin coiler just about to join you all.
> I started winding my main coil before I was aware of the expertise
> available here, so it's less than optimum and I'd like some help.
> I've loads of questions so I'd really appreciate some help.
> 1 My coil is wound on a nominal 4" uPVC pipe
> 0.7mm magnet wire, 33 turns per inch
> 108mm actual winding diameter (4.25")
> 576mm actual winding length (22.67")
> 753 turns total
> 11mH measured
> 14ohm measured
> Heavily coated with polyurethane varnish
> Warmed to 60 C (140 F) for one week to reduce moisture
> Is this workable or do I REALLY need to start again with a larger
> diameter former ?
This sounds like an excellent secondary, and you should do well with this
one. The general trend is towards about 900 to 1000 turns, but yours is
> 2 I intend to use a Neon Transformer rated as follows:
> Primary 240 v 1.9 A a.c. (Malaysian a.c. like U.K.)
> Secondary 15 kV 30 mA a.c. centre-tapped.
> The secondary measured at 21 k ohm.
> I intend to make two 10 nF capacitors to use in series (0.005 uF).
> What is the largest value capacitance I can use with the above
> transformer WITHOUT cooking it ?
>From what I've heard and learned, it's not so much the size of the cap,
but the size of the gap. For my 4" coil, I used a 0.0177 (measured) cap.
This is a rolled cap using a sandwich of LDPE and Al flashing. The LDPE
is 16 inches wide by 8 feet long, and the Al flashing is 14 inches wide by
7 feet 8 inches long (8 feet, less 2 inches on each end). This is all
rolled up into a bundle and put in a 6" pvc pipe and filled with oil.
There should be information on my website, www.pupman-dot-com. See the
howto section for making caps.
> 3 Could someone explain spark-gap quenching to me ?
> I'd REALLY appreciate a photo, .gif, .jpg etc. or even a
> description of waveforms and voltages.
Here's a moderately non-technical explanation that I've managed to come up
with that is certainly subject to correction (hint hint).
The spark gap serves as an on/off switch that is capable of switching
large currents at high voltages. The spark gap allows the primary to
efficiently transfer the energy to the secondary. The problem occurs when
the frequency of the primary does not exactly match that of the secondary.
By exact, I mean really close, so close that it's virtually impossible to
achieve. When the frequencies don't match, the secondary is soon out of
phase, and no longer gets energy from the primary. In fact, once the
secondary and primary are enough out of phase, the secondary is feeding
what energy it has back into the secondary, causing kickback, and damaging
things such as the capacitor. By switching the current off quickly, you
can dump a whole lot of energy into the secondary before the primary and
secondary are out of phase. By the time the secondary is out of energy,
the capacitor has been charged again and is ready to discharge into the
Quenching quickly means that the switch that is the spark gap opens up and
stops the transfer of energy from the primary to the secondary, and allows
the secondary to "ring" (oscillate electrically) unimpeded by any out of
phase energy in the primary.
> 4 I'd like to operate at low-frequency / high top-capacitance,
> is it necessary to operate at the quarter-wavelength frequency ?
You are pretty much restricted to either half wave, or quarter wave,
depending on the design of the coil. You could make a coil a 3/4 wave,
but then you'd get all sorts of sparks breaking out from the 1/4 wave
point. Think of the voltage following a sine wave up the length of the
coil. It will peak at the 1/4 wave point, and again at the 3/4 point.
However, with a 3/4 wave coil, there will still be a peak at the 1/4 wave
point, and a node at the 1/2 wave point. Sparks will break out from the
1/4 point, and there will be zero voltage at the 1/2 point. Why bother?
It's a waste of wire anyway.
> 5 I just saw a photo in July's National Geographic of Christian
> Ristow's 1.8 MV TC launching great bolts from what looks like the
> last few turns spaced-out and strengthened, which brings me to my
> last question,
> Don't toroids and guard-rails form an effective shorted-turn ?
No, yes. Toroids haven't been shown to be a shorted turn, but the guard
rails have. The solution is easy enough. Just make a guard rail with a
gap in it and overlap the ends. Think of it as a little more than one
turn from a spring.
> Thanks for your endurance reading this long e-mail !
> I will really appreciate all your responses.
> Get Your Private, Free Email at http://www.hotmail-dot-com
If I can't fix it, I can fix it so it can't be fixed
Chip Atkinson; Xi Graphics 1801 Broadway, Denver CO 80202
(303)298-7478voice (303)298-1406fax (800)946-7433sales