Re: New Coil

To: tesla-at-pupman-dot-com
Subject: Re: New Coil
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
Date: Thu, 31 Oct 1996 19:32:59 -0800
Tesla List wrote:
> 
> >From MALCOLM-at-directorate.wnp.ac.nzMon Oct 28 22:37:09 1996
> Date: Tue, 29 Oct 1996 18:38:34 +1200
> From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
> To: tesla-at-pupman-dot-com
> Subject: New Coil
> 
> G'day all,
>             I've just this day wound my new resonator (after a false
> start last week). It'll be a week or two before I characterize it as
> several coats of varnish have to go on to hold the windings steady.
> Winding length about 39"
> Turns about 1000
> Copper diameter = 0.9mm
> Diameter = a little over 16"
> Projected Fo without topload around 87kHz ( you can calculate Cs and
> Ls)
> 
>     The ribbed former turned out to be a bit too flexible and I had
> to buy a 1/8" or so thick sheet of LDPE to wrap around it. Welding
> the seam was an interesting exercise (all hot-melt). It was either
> that or get bogged down in a lot more plastic work. It may be
> possible to remove the central ribbed former from the coil if enough
> varnish is applied. That would be a nice touch but unnecessary. I will
> be using this resonator for a number of different coil configurations
> including : standard spark excited, CW MOSFET driven, an extra coil
> and a special one that I'm keeping under wraps until it's done or I'm
> done.
>      After varnishing and some initial tests, I will be constructing
> a compact general purpose primary system for driving down to 50kHz
> (about 45pF topload for resonator). Main cost there is the copper pipe
> but I am reducing that by use of mutual induction in the primary
> system. Max inductance will be around 200uH all turns in.
>      I hope the results from CP will be reported before I do any
> serious firing as the caps will be used up to 20kV peak.
> 
> FYI,
> Malcolm

Malcolm,

Sounds like you'll have a nice multi-purpose resonator! One suggestion -
you might want to consider using one thick coat of clear epoxy,
especially if you're going to run with high k's and high primary
energies (20 KV). I'm running at about k=0.21 and there's not a hint of
any corona. My earlier 6" coil used 6 coats of Polyurethane and couldn't
go much above k=0.153 without interturn flashovers.. I'm a convert!

PS: I can't wait to hear about your experiments and results!

Safe coilin' to ya!

-- Bert --