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Re: secondary winding
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