status report etc.
Subject: status report etc.
From: chip (Chip Atkinson)
Date: Wed, 30 Aug 1995 13:48:03 +0700
I finally have a few minutes to do more than scrutinize and redistribute
the tesla mail!
I was reading about the variable inductance ideas and thought that magnetite
may make a suitable core material. I believe that ferrite is some form of
magnetite (Fe3O4). The next question is where to get it? That I don't know.
Perhaps some chemical supply houses or some geological/mineral supply places.
Any way, my tesla coil is coming along well. I have the secondary virtually
done except for mounting the toroid. The primary forms are done and half of
the primary is wound. It turns out that I'll need well over 50' for this
thing. That means that I will indeed have to do some creative soldering
to smoothly butt-join the two 50' pieces of 3/8" tubing.
The details of the secondary are:
4"x20" winding of 24ga wire. 950 turns. I initially coated the wire with
PU (minwax urethane). However, that wasn't going on well/thick enough
for me, so I got this stuff called "Build 50" by Behr. It is an epoxy
that is used to make thick one coat finishes on things. I put the wound
secondary on the lathe (or winding device) and turned it at about 20 rpm.
Then I slathered the stuff on and let it turn for about 4 hours. This stuff
worked quite well. I have a thick insulating (I hope :-)) layer that is
as hard as epoxy gets. I also put solid end caps on the pvc pipe so that
the interior is entirely sealed. Unfortunately I missed the reason
for using epoxy and used PVC cement to seal it. (I read the reason after
it was too late). (The reason is exploding fumes in the secondary form)
I used Ed Sonderman's great idea for the toroid attachment and glued a
pvc pipe cap to the top end of the secondary.
The details of the primary winding are:
30degree banked spiral of 3/8" copper tubing separated by 3/8". 16 turns.
I used plywood for the base and triangular forms. On the plywood triangles
I put some plexiglass "combs" that hold the tubing. I used a drill press and
set up a jig to allow me to use a 3/8" milling cutter to drill C shaped notches
in the edge of the plexiglass. The notches are ever so slightly more than
half so that the tubing snaps into place. The combs are held in place by
nylon screws that slide in slots in the triangles. The reason for the
slots is so that I can have a little slop and so that the tubing can smoothly
spiral out rather than having to make jumps between circular tracks.
I have some pictures that I'll send when I get them scanned in.