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First Coil Design (fwd)





---------- Forwarded message ----------
Date: Sat, 28 Mar 1998 06:31:18 -0800
From: djQuecke <djQuecke-at-worldnet.att-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: First Coil Design

Well, I've spent a couple of months collecting most of what I need for my
first coil.  I've tried several of the Tesla programs (and generally come
close to the same answers <g>).  I thought I'd float my plans (and
questions) for this first coil and see if I'm close.

I have one 15k, 30ma, 115v, 60hz neon transformer and intend to add a second
soon.

With one tranny, I'll need .0053uf and with two, .0106uf for the tank
capacitors?  I'll try saltwater, poly/flash in oil and I'm working on an
experimental design (aren't they all <g>) using a product called ALPOLIC
I've mentioned on the list several months ago.

Secondary is approx. 4.2" diameter and I'm figuring 21" tall (5 to 1).  I
haven't wrapped it yet, though I've built a crude motorized "lathe" (PVC
<g>) and have started sanding on a 36" PVC pipe.  I've got 1000' of 22 gauge
magnet wire and a gallon of oil based polyurethane.  I'm figuring about 790
turns of wire at 37.5 turns an inch and about 840' of wire used.

Primary is 1/4" copper fridge tubing, inverted saucer, 1/4" spacing, 15
turns (or however far 50' gets me <g>).  I'm not certain about lateral
spacing of primary and secondary.  I'm taking a shot at 5/8" space between
secondary and inner coil of primary??  Inductance figures don't seem to add
up??  Best spot to start tap?

Secondary base is easily adjusted vertically to optimize coupling.

I've built a safety gap using 3/4" x 1.5" brass rod on 3/8" threaded brass
rod in a nylon base.

I've built a similar spark gap with attached airblast for main spark gap.
I'll also try a couple of 6" RQ cylinder gaps.  I've acquired a motor, (a
1/2hp Dayton with a variable speed drive, 705-4230rpm), bearings, etc for a
rotating sparkgap but have had trouble locating the G-10 (same as GAROLITE?)
material for a disk.  The locals don't have a clue so far.  I've seen it in
McMaster's.  Any other (cheaper) mail-order sources for a 10" - 12" disk or
a 10" x 10" - 12" x 12" sheet?  Best thickness??

Toroid constructed from 4" aluminum flex, pizza pans and aluminum tape.  I
have yet figured diameter.  Would seem that the goal for me would be to try
to get secondary freq. down from approx. 515kHz range to the 250kHz area??

I have a 5a STACO variable transformer. (Large enough?)  I have access to a
10a if necessary.

Four 8' ground rods.  Any problem with cutting them in half and going with
eight 4' rods?? (Hardpan about 5' below surface)

I still need to figure PFC??  Seems to be contrasting arguments over the
need for this?

I need to build chokes.  I saw a thread on using the cores from flybacks.  I
have several such cores at 4" square by 1/2" diameter.  Is this viable?

What changes will be necessary when going from 30ma to 60ma with a second
(or third) tranny? (Besides capacitance of the tank circuit...)

Cheap source for high voltage wire?

Sorry this is so long but I tried to include all necessary info (as well as
fish for some answers <g>).

As my first coil, I want to try as many different methods in constructing
each part, hence the different capacitor types, spark gaps etc.  My thought
is to try and keep as many parameters as possible variable for optimization
later (variable speed motor, secondary height, primary length, etc).

Anything obvious I'm missing here?

Thanks for your time,

dj