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Re: New Coil



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

Malcom:
	Glad to hear about your new coil project and the success with the
secondary winding efforts.  What really caught my attention is the fact
that your design specifications are quite similar to what I am currently
involved with at the moment.  
	I spent last night in the basement with my new treasure, the same one I
mentioned about a week ago, which happens to be a 59" length of 15 1/4 "
PVC sewer pipe.  I will wind 50" of it's length.  This appears to be
very close to what you have selected for your secondary form.  This one
won't be as flexible as what you indicated yours was, it has 1/2" thick
walls.  I originally thought that PVC was not a reasonable material
choice, but since I believe Richard Hull indicated that all his big
coils used PVC forms, I jumped at the chance to get this chunk out of a
scrap heap with 8 or 9 other pieces laying beside it.  I had to clean
off the mud and use some 220 grit emery cloth to remove some minor
surface flaws.  I am intending to use IEC R-40 series 1.40mm wire, or
AWG #15 for us in the U.S.A.!  Expected resonant frequency will be down
around 60 Khz with the toroid I am presently using, or about 117 Khz
without the toroid.  The next step will be to calculate the primary
copper tube requirements and get that going too.  I really don't need a
new truck this year, so I'll just build another coil!  Keep your
progress posts coming, they'll be read with great interest.

Chuck