RE: Primary and Secondary winding direction

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <paul-at-abelian.demon.co.uk>

John Couture wrote:

> Am I taking too much for granted?

Maybe. I just don't see any physical justification for invoking the
original straight line resonance of the winding's wire. I'm not aware
of any research which establishes such a connection.

When it comes to choosing an optimum toroid size I'm sure that our
previous discussion on the subject did at least introduce criteria
which could be reasonably justified. For other's benefit we discussed
a toroid choice based on an equilibrium between voltage gain and
breakout. Too small a toroid gives a voltage limited by breakout, and
too large a toroid gives a voltage limited by the total capacitance of
the resonator. Plot reasonable estimates of these two factors and
the curves intersect at a proposed optimum toroid (in the sense of max
output voltage). Alternatively, for maximum corona display, the choice
of toroid may amount to achieving the optimum power transferring
impedance match from the top of the bare coil to the absorbing load of
the 'corona sphere' in which the toroid acts as a shunt matching
capacitance.

> It also gives a capacitance that agrees with the intersection of
> the two curve graph we discussed last October.

I seem to recall that one of the factors which established the point
of intersection was the power level or bang energy involved - a lower
powered system requires a smaller toroid to achieve its maximum
voltage than does the same coil driven at higher power. This important
aspect does not enter into your wire length based alternative, so I
have to question whether the two methods can really be said to give
the same answer.

> If the secondary is made smaller the wire length will be shorter,
> the frequency will be greater, and the capacitance will be smaller
> according to the equations. The opposite will happen if the
> secondary is made larger.

I could accept the use of wire length as an empirical gauge of the
coil size, in the same sense that you might also have used area or
volume, but for the fact that it is proportional to turns, and the
output voltage for a given energy does not depend on turns, so it
would seem to be a poor measure.

> I read about this optimum toroid many years ago but I do not 
> remember where.  However, I do not believe it is a myth because this
> design method will give a workable TC. It actually gives a secondary
> topload capacitance which may or may not be an optimum.

It sounds like you're not too sure or convinced yourself of the origin
or basis for the use of wire length. I agree that the formula you
give will generate some sort of reasonable toroid size, but see no
justification for the claim that it is optimum. Surely it would be
more beneficial to persue more recently discussed ideas and perhaps to
reconsider things from the point of view of impedance matching between
coil and corona load?  Choice of toroid is an interesting and it seems
under developed topic which should not be allowed to rest on an
ancient and potentially naive recipe - to do so risks papering over a
wealth of interesting Tesla physics.

Cheers
--
Paul Nicholson,
Manchester, UK.
--