Re: secondary winding

Tesla List wrote:
> Original Poster: Bob Misiura <misiura-at-nccoast-dot-net>
> Ian
> If your only winding one coil . . . support the ends with end caps on
> the form and add a nail through a couple of uprights as a bearing.  Turn
> the form with one hand and feed wire with the other.  Keep a roll of
> masking tape handy to keep it from unraveling if you have to stop.
> Hot melt adhesive works well to secure the end turns.  You can also lay
> a loop of dental floss or strong thread parallel to the form and put the
> first turn through the loop and wind about an inch of windings (over the
> thread) then pull the free ends of the dental floss to secure the first
> turn.  (its neater than hot melt)
> If you are using PVC pipe, wipe it with acetone before you begin.
> Acetone is a mild solvent for PVC and takes away the gloss, as well as
> any markings.
> Don't apply a layer of varnish and try to wind the coil on a tacky
> surface.  It will hold the turns in place, but will also hold the gaps
> in the winding and every bit of dirt it comes in contact with.
> I like to coat coils with polyurethane or epoxy to hold the wire down
> after the coil is wound.  I have a motorized winder that spins the coil
> while the coating dries (so it doesn't run).  (if you sand between
> coats, avoid emery cloth abrasives, the particles are conductive, use
> sand paper).
> Uncoated coils work a little better, but are not as rugged.
> I mounted a DC motor horizontally and drove a block of wood onto the
> motor shaft.  I can turn the wood using a chisel until it supports the
> form.  I make another mandrel for the form, for the opposite side end,
> and support it with a live center.  The whole contraption took about two
> hours to build and can wind up to a seven inch diameter and 30" length.
> The hardest way to wind a coil is to try to hold it, and wind it,
> without using any form of jig.  It takes less time to build a jig or
> winding machine, and wind a coil, than it takes to wind a coil without
> one.
> good luck
> bob

        Winding by hand has a big advantage!  You can stop whenever you want,
and for whatever reason.  It helps to have a roll of 1" masking tape,
with narrow pieces precut and stuck to it.  Even a coil of 100o turns
can easily be done in a few hours.  By the way, feeding the wire over
the END of the spool is preferred, because there is no inertia of the
rotating reel to worry about.  That's the way the "big boys" do it when
winding most coils, at least from small wire.

        As for turns counting, there is no need to do that accurately so just
keeping the turns close together and measuring the length of the winding
will give you a good idea of what you have wound.  Assume that the
winding is around 95% "tight " and use turns/inch from the wire tables. 
Exquisite accuracy isn't warranted for any reason I can think of, and if
you count the turns with an accuracy of +/- 10% you will almost
certainly be close enough.