RE: Barts Flat Coil Dimensions Was: Dimensions of my flat spiral coil

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

Original poster: "David Thomson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

Hi Paul,

>Incidentally, I'm looking forward to calculating the current profile for a
flat spiral, as the radial coupling due to internal capacitance might well
be as dominant in the flat spiral as it is in a small H/D solenoid.   If so,
then at resonance, the effective inductance might well be considerably
higher (my guess: 30% higher?) than the DC inductance - with consequent
potential advantage for reduced gap loss.

For my flat spiral secondary wye coil, if it resonated at 325KHz, and
assuming that the inductance is in fact 56.07mH, it could only reach the
resonant frequency if the self-capacitance were 2pF or less.  But certainly
the self-capacitance is 50 times that amount or more.

This is the problem I ran into the first time I tried to get the coil
working.  So I just randomly used different capacitances until it would
work.  The .026 capacitor I ultimately found, just happened to work for both
the single wound coil and the wye coil.  I later found the single wound
required a .035uF capacitor and the wye coil required a .02uF capacitor.
The .026 just happened to fall in between and close enough to make them both
work.

The wye coil is resonating non-stop now that I have built two .04pF caps and
balanced them in series on either side of the spark gap.  I'm also getting
large arcs between the secondary outer lead and the terminal.  The corona is
also much more pronounced than before.  I've got to start thinking of
immersing the coils in oil soon.

I've tried running the coil with the windings oriented vertical and the
poles horizontal.  At least on the surface, nothing stood out as being
different.

Dave