Center fed coil

cc: tesla-at-grendel.objinc-dot-com


I have been trying to help David Lawrence design a coil that is best
described as an Ouden (can't remember how to spell it) or center fed Tesla
coil.  He wants to experiment with intense electric fields created between
two plates connected to the ends of the coil.  He has ordered one of the
Condenser Products .025 mfd capacitors so I thought we shoot for a frequency
that would allow him to use that.  He has a 4.0 ft x 12" form.

I did some rough calculations today and came up with some numbers.  For a
normal 1/4 wave Tesla coil we want about 900 turns of wire.  With this type
of coil I think we want 1/2 wave - or twice the amount of wire.  Using 1800
turns of wire (he has #25) we come up with a self resonate frequency of about
69 khz.  In order to use his capacitor, we come up with a primary that is
about 20 turns of 3/8" copper tubing on .75 centers wound on a 24" form about
15 inches long.  It appears there will be no way to adjust the coupling once
he gets this thing built.  Have you ever built one of these?  Dave was
thinking about allowing 6" of clearance between the primary and the
secondary.  Do you have any ideas?

Thanks, Ed Sonderman