[TCML] Newbe's First Coil
Weinhold Shannon L
Shannon.L.Weinhold at doc.state.or.us
Mon Feb 1 12:58:04 MST 2010
I wind my primaries "helical" all the time and don't have any problems.
I use heavy gauge monster cable speaker wire (probably 10 ga) with the
thick rubbery insulation and it works great. I run the wire without
spacing, because the insulation alone provides about 1/4" of spacing
between conductors when two layers are stacked.
One plus to doing it this way, other than obviously being much
cheaper/having a much smaller footprint/less labor involved is that you
can use a map tack (basically a long steel tack) to tune your primary.
Just remove 3/4" insulation from your primary circuit lead-out wire and
wrap it tightly around the top of the tack, then push the tack through
the insulation to where its making good contact with the braided wire
inside. Don't mess up here or you'll end up with a loud bang and a free
swinging primary wire bouncing around like a down power line. Make sure
that the tack is pushed in from an angle and has at least 1/2 inch of
its length within the wire, and that its making good contact. (FYI, you
can't do this with solid copper wire. It will heat up and melt the
insulation and then you'll have the downed power line effect again.
Surprising the braided cable is quite resistant to heating.) This makes
for easy tuning, and when you get the tuning perfect you can simply
carve out some of the insulation and easily solder the primary wire to
the now exposed braided cable.
Flat spiral coils look pretty, but they are spendy and take up a lot of
space. Just be sure that your primary coil former is large enough in
diameter to keep from over-coupling the secondary. If you get sparks up
and down your secondary then you're over-coupled. You can always raise
up the secondary a half inch at a time by placing something under it
until you get your coupling right.
Save the flat spiral for later when you know what the heck you're doing
and you want a pretty coil. This works fine for functionality, and tesla
map will tell you what size former you need if you enter in all the rest
of the parameters.
Just my two cents as someone who has some different experience.
My coils can be seen on youtube here:
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From: mddeming at aol.com [mailto:mddeming at aol.com]
Sent: Sunday, January 31, 2010 9:31 PM
To: tesla at pupman.com
Subject: Re: [TCML] Newbe's First Coil
I don't know anyone who uses a close-wound helical primary on a
spark-gap coil. A 3.5 in. coil could easily handle 500-800 watts, but
not with 14 ga wire as the primary coil. 6-10 ga space-wound bare wire,
or copper tubing would allow for higher peak currents for better power
transfer and allow it to function as a heat radiator also. You might
consider replacing the wooden rods with pvc pipe notched on the outer
edge to hold the wire in place. The alternative is a flat spiral coil
with 0.25 in spacing between turns. That should work up to 1 KW.
It sounds like your new toroid may be a little large for your 230W OBIT
to give consistant breakout without a point and ground rod. Be aware now
that once you start making improvements, you will never be satisfied to
the point of not wanting to change something ;^))
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