RE: (spacing of windings)RE: Need Secondary wire source

["David Dean" <deano-at-corridor-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Chris,

I believe that someone, Jeff Behary http://www.lvstrings-dot-com/quack.htm, has
done that. (pre thread the former) If you have a lathe, why not just use it
to do the winding? I have wound two 4.25" dia. secondarys on thin wall PVC
with 26AWG wire at 40 TPI that way. I just set a bent piece of all thread in
the tool holder using the turned up part as a spindle to hold the spool. I
put a couple of nuts jammed together and put a large washer on top. Then a
felt washer to give some drag and keep tension on the wire. The other end of
the all thread was set close to the former with a small piece of
polyethylene tubing as a guide ty-wrapped to the all thread. Worked like a
champ.

Be careful of heating the epoxy resin though, I did that on the first sec. I
wound because it was very cold that day and it was taking a long time to set
up. I got the heat gun and started to warm the rotating cylinder to help the
epoxy along. Well it worked. When the reaction went off, the heat from the
exothermic reaction added to the heat I had put in with the gun resulted in
half of the PVC form melting enough to ruin half of the coil. So I repeated
the process, this time I did not use the heat gun though. I just went to
bed. The next morning the coil was done.

I did not loose all of the first coil, however. Many moons later I cut the
damaged section off with a band saw and used the now short (4.25" X 12") for
a small table top coil that is powered by a 6.5KV 7.5mA current limited
transformer from a small copier power supply. It is not for long sparks, but
does have its uses.

BTW no special prep was done to the PVC other than a light sanding before
winding, then the resin poured on while rotating in the lathe. Have had no
problems with either coil. The 20" winding length coil has Plexiglas ends
epoxied in pace and two more disks inside. No sealing was done to the inside
of the PVC. I have gotten many sparks or arcs, as you prefer, of three times
the winding length, and at least one that was four times the winding length
from that coil. The smaller coil has no end disks but with a 12" winding
length and 5" arcs to a grounded target I don't figure it needs any.

later
deano

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, August 03, 2000 12:48 PM
To: tesla-at-pupman-dot-com
Subject: (spacing of windings)RE: Need Secondary wire source


Original poster: "LOCKWOOD, Chris J." <clockwood-at-orbeng-dot-com.au>

Has anybody tried winding a secondary using threaded PVC?

Its pretty easy to cut a thread into a piece of pipe using a lathe. It
wouldn't take that long, and would give an accurate wire spacing. It might
be an advantage to provide a small spacing, to allow the insulation coating
to flow between the windings- providing better insulation between turns, and
greater mechanical strength.

It would also be less likely for the wire to get messed up during winding-
since they fall into guide slots.

I was thinking of making a new coil with a very small spacing between the
windings (using #26 wire, and a < 0.1mm gap) -coating with a thickish layer
of epoxy resin. This would hopefully provide a superior layer of insulation
compared to enamel, and the epoxy would run freely into the thin gaps
(especially when heated)...

Is the PVC pipe form likely to break down if I dont pre-coat it?

Should I bother?

Chris

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, August 03, 2000 8:38 AM
To: tesla-at-pupman-dot-com
Subject: Re: Need Secondary wire source


Original poster: "Ed Phillips" <evp-at-pacbell-dot-net>

I've wound coils with both monofilament spacing and very heavy woven
cotton thread spacing.  I forget the name of the latter, but left it in
place.  After winding the coils (by hand, mounted on very very crude
centers) I gave them a very light coat of thinned urethane varnish.
When that had dried I pulled the monofilament out and had a very neat
space-wound coil.  Diameter was 4", winding length 18", and wire sas #28
single formvar. Bottom line was that, in accordance with the comment
below, it certainly wasn't worth the bother, and the lower secondary
inductance ran the resonant frequency higher and the things didn't work
as well as close wound.  Don't bother!
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