Re: Winding Secondary

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "B2 by way of Terry Fritz <twftesla-at-uswest-dot-net>" <bensonbd-at-erols-dot-com>

> I finally got some magnetic wire, but I need to create some sort of jig to 
> wind my secondary.   Any tips will be appreciated.
>                                                Justin
Hi Justin,
    Go into the plumbing section of the hardware store and look for
something called a "test plug" made by the oatley company in Cleveland,
Ohio.  It looks like two metal disks with a rubber piece in between them.
A bolt runs through the assembly.  When the bolt is tightened the rubber
ring expands and plugs (or holds) the pipe.  When I was at Lowes hardware a
few months ago I saw some of these for 2", 4", and 6" pipe.

    Also look for something called a "Knock out plug" manufactured by a
company called Charlotte (don't know where they are).  I trim the edges
with a tin snip so that they just slide into the coil form tube.  I epoxied
3 inside of my coil form.  One was in the middle and the other two were
about 2 inches from the ends.  This keeps the tube from turning oval shaped
during winding.  It also prevents streamers from propagating down the
inside of the coil form.  With proper coupling, field shaping, and limited
power, these baffles are unnecessary.  I decided to build a conservative
coil until I gain more experience.

    For my winding fixture I used two 4" "test plugs", 2 big "L" brackets,
and four "C" clamps.  The "test plugs" mount to the "L" brackets via holes
that I drilled near the ends to keep the coil up off of the winding bench.
The other ends of the "L" brackets were clamped to a bench with the "C"
clamps.  For a winding handle I used a screen door handle with a set screw.
 The 4" "test plugs" used 3/8" bolts.  The bolts need to be held to the "L"
brackets with jam nuts and washers.  This should be tight enough to keep
the assembly from wobbling but loose enough to not drag down the motor.  3
in 1 oil or grease helps also.

    To mount the coil form slide it over the "test plugs" and then move the
brackets closer together (helps minimize wobble).  Tighten up the plugs and
rotate the coil form at the same until it becomes centered and secure.
Don't tighten excessively or the coil form may bulge and then later shrink
when it is removed, leaving loose turns or a cracked coating.

    The whole thing was driven by a very nice 90 Volt DC gear motor that I
bought from Chuck Curran.  I put four 3/8" nuts and a fender washer on the
end of the "test plug" to be driven.  I covered the nuts with a short piece
of  tygon tubing (this is hard to do).  I covered the gear motor shaft with
a similar piece of tygon tubing.  A vacuum cleaner belt was used to drive
the "test plug" assembly with the DC gear motor.  The motor speed was
controlled with an adjustable DC power supply.  I only needed about 20
Volts to get a good winding speed from the motor.

    (Tentatively, I am using 1" wide strips of copper tape wraped around
the coil form with a 1/2" rounded gap.  The coil ends are soldered to the
copper tape.  Connection to the ground or toroid is via soldered wire.
When the coil form was coated with 2 part epoxy, the copper tape was
included by coating all but a 1/2" round spot on the end opposite the
winding connecting.  This is an experiment to be tried out this summer.)
Does this answer some of your question?

Cheers,
Barry