RE: Secondary size

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

Original poster: "Luke" <Bluu-at-cox-dot-net> 

Thanx for the insight.  I am beginning to gather the empirical nature of
it.  But it seems if I keep hammering why there sometimes pop up why
this empirical rule was set.  So even though it is empirical someone
finally jumps up and explains where it came from.

You know like old sayings that you say all the time and you know what is
meant by them you have no idea where they came from.  And if you look at
the words literally it makes no sense.  Sometimes you hear where these
saying originated.  So when I keep hammering why sometimes I get answers
that may not be solid but you know why they are there and that is good.

Luke Galyan
Bluu-at-cox-dot-net

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Friday, January 16, 2004 5:05 PM
To: tesla-at-pupman-dot-com
Subject: RE: Secondary size

Original poster: Jim Lux <jimlux-at-earthlink-dot-net>

At 12:00 PM 1/16/2004 -0700, you wrote:
 >Original poster: "Luke" <Bluu-at-cox-dot-net>
 >
 >So telling me to make it tall enough to avoid strikes is good and I
knew
 >that before I ever asked.  But very few seem to actuall tell HOW they
 >figured that tall enough value out in the first place.

HV design is exceedingly empirical.  Spark propagation and HV breakdown
have a lot of inherent variability, which causes all sorts of
aggravation
for people who have to trade off things like physical size and cost.
There
is an incredible amount of what is basically "tribal lore" associated
with
HV design, including such things as rules of thumb about creepage
distances, required free air clearance distances from components, and
all
manner of things.

It's not something that is highly amenable to rigorous analysis,
although
the latest Finite Element models, made possible by cheap computer power,

are helping a lot.  Still, though, when it comes to predicting whether
something will breakdown, most designers include a lot of margin, and
regret it when they can't.

If you want a good introduction to practical HV design in the theory
sense
(as opposed to building things and trying it for yourself), the Los
Alamos
report by William North titled "High Powered Microwave Transmitters" is
a
great starting point.  There are several copies on the web (including
one
at Terry's site:
http://hot-streamer-dot-com/TeslaCoils/OtherPapers/NorthReport/
) Lots of empiricism tied to theory in that report.

North is talking about systems where you have a "real budget".  For the
usual coiler, where you're looking for scrounged materials and so forth,

it's even more empirical.  It's not like you can call up the
manufacturers
of QwikForms or Sonotube and get the HV breakdown or RF loss
characteristics datasheet.  Relatively few coilers have the resources to
do
a systematic investigation and publish the results, so you have to
synthesize your design from a large number of point designs and their
reported results, recognizing that a goodly part of performance is
construction technique and workmanship.