Re: LC III

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Terry,
          I went through a period of some agonizing back in the 90's
trying to understand exactly what is going on in a TC resonator. I
had to regard the Corum's basic description of disturbance
propagation in a coil as correct since the current is non-uniform
because the speed of light is finite and the coil has spatial
dimensions which means (propagation) time is involved. On reading
their analysis more carefully I realized that all their VSWR voltage
predictions were based on CW drive. It seemed to me that the typical
disruptive coil "looked" lumped because it was driven with finite
shots of energy. Additionally, using lumped parameters (Medhurst's
capacitance formula e.g.) finally meant that one could design a coil
for a nominated resonant frequency (it took the guesswork out of that
aspect of the design). However as Robert Jones has pointed out, the
capacitance Medhurst's formula gives is *not* the static isotropic
capacitance of a conductive cylinder. This is easily measured and I
have done it. For one particular resonator I recal measuring
somewhere in the vicinity of 100pF where Medhurst gives (a la
resonant frequency calculations) somewhere around 25pF. Therefore,
Medhurst (and Wheeler) give us a useful tool for coil design but say
little about the actual working mechanism. To me it is a recipe
approach and nothing more. Extremely useful but limited to coil
building and not to an operational description. I read the latest
paper from the Corum's from (I think it was) Bill Wysock's website
just recently and see at the bottom what I interpret to be a
concession not to the resonator's physics but operational differences
(e.g. output voltage) between the two modes of operation. I may have
that wrong so please don't quote me. I still think the idea of
coherence on the resonator is not an accurate description of coil
operation *unless perhaps* the coil is fed with pulses and not an
oscillator.

I stand to be corrected/flamed etc.
Malcolm

On 27 Mar 2005, at 10:20, Tesla list wrote:

> Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi,
>
> Transmission line theory was popular in the 80's especially with the
> Corums.  But I never saw an example where they actually got the
> analysis to work...  They were on the right track, but the devil was
> in the details...  The true system was too complex...  The Tesla coil
> is a very "non" uniform transmission line and the coefficients one
> comes out with look pretty much like a simple inductor or an
> impossible mess....  It fell apart in the 90's and was replaced buy
> lumped parameter models which are still often used.  Today, computers
> can grind fantastic amounts of data to really get down to the true
> operation of the Tesla coil.
>
> http://www.classictesla.com/fantc/fantc.html
>
> I don't think anyone even tries to study coils with transmission line
> theory anymore even with fancy computers.  All the modern programs and
> techniques either are lumped parameter and Medhurst based or use
> finite element analysis.  There very high accuracy is undeniable!!
>
> I think transmission line theory's last days are summed up in these
> two pieces from five years ago...
>
> http://www.ttr.com/corum/index.htm
>
> http://www.pupman.com/listarchives/1999/October/msg00428.html
>
> So I join with Paul (but perhaps with a bit more gentle tone ;-)) and
> agree that if your still trying to use transmission line theory with
> Tesla coils, your 10 - 20 years behind...
>
> Cheers,
>
>          Terry
>
>
> At 06:22 AM 3/27/2005, you wrote:
> >Jared wrote:
> > > you are misapplying transmission line theory.
> >
> >No I'm not.  You're ignoring all the evidence of measured
> >coils, and apparently can't be bothered to learn any of the
> >relevant theory.
> >
> >Have you measured a coil yet?  Your faulty assumption of light
> >speed propagation along wires will put you around 50-100% out
> >on frequency measurements.  Measure a solenoid and see that you
> >are wrong and EM theory is correct.
> >
> > > This is the likely reason for the accuracy of our model in
> > > predicting node locations in multiple wave length coils.
> >
> >Again we see the bottom line of your argument - the nodes
> >are in the right places.
> >
> >Let me use a rope analogy.  Vibrate a rope between two anchors
> >to form some high resonance with multiple half waves, and note
> >the node positions.  Then, increase the rope tension so that
> >the propagation velocity is increased.  Set the rope oscillating once
> >more in the same mode (now at a higher frequency).  The nodes will be
> >in the same locations.   In the same way, your observations of node
> >locations say nothing about the propagation velocity.  You saw the
> >nodes where you expected them and erroneously concluded that the
> >operating frequency and velocity must therefore be as predicted - an
> >elementary mistake.
> >
> > > it does bother me that you would describe velocity factors of up
> > > to twice the speed of light, pretending that this was some sort of
> > > mainstream science.
> >
> >If you'd bothered to read earlier extensive replies attempting
> >to correct your errors, you would already understand that a
> >velocity factor with respect to the wire of greater than unity
> >doesn't imply that signals are travelling the wire at greater
> >than light speed.   It shows instead that the field disturbances we
> >call "signals propagating through the coil" are guided by the wire
> >into a spiral with a pitch greater than that of the winding.
> >
> >If it makes you happier, define a velocity factor with respect
> >to the solenoid length instead, to get factors around 0.001
> >or so.
> >
> >This is just an example of a much larger class of phenomena in
> >physics in which EM propagation velocity is reduced (sometimes
> >severely) in the presence of charged particles, both free and
> >bound.  Inside a metal like copper, for example, the velocity
> >is down to walking pace!
> >
> > > Richard Quick told you this about 10 years ago, you should have
> > > listened to him.
> >
> >He's never told me anything. What on earth are you talking about?
> >
> > > The rope resonance models we have employed are not jokes.
> >
> >Sure, rope models are handy, sometimes.  But they don't have the
> >properties of an EM field.  For example, each piece of rope only
> >affects its immediate neighbours, via tension, whereas charges in a
> >wire affect each other at a distance via their fields, especially so
> >when they are brought into proximity by coiling.  All those EM
> >effects are missing from the rope model.  They determine the
> >inductance and capacitance and propagation velocity, taking the place
> >of tension and mass in the rope model.
> >
> >If you push the rope analogy too far, you end up with predictions for
> >a rope, not a coil!
> >
> >Please, measure some coil frequencies before you make more of a
> >fool of yourself.  Then go learn the theory that predicts those
> >frequencies.  Otherwise, people will laugh at you for ignoring
> >measurements and rejecting well established theory - all because you
> >are too stubborn to recognise that you made some elementary mistakes.
> >-- Paul Nicholson Manchester, UK. --
>
>
>