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Coil Form Preparation

 * Original msg to: usa-tesla-at-usa-dot-net

Quoting tweagan-at-maind.dnet.dupont-dot-com:

> Question:

> How would someone go about drying a PVC or similarly hygro-
> scopic material before it was to be sealed? In the oven? What 
> temp? Is the interior of the form sealed as well?

Before I get to the drying stage, I go ahead and wet sand the
coil form with abrasive paper or emory cloth. I use a #150 grade
of abrasive and sand with water until all printing, oxidation,
and major dings (cuts and scratches) are removed.

One of the best ways to dry this plastic is to get a large
cardboard box. Cut a few small vent holes in the top and bottom
of the box. Thread some string or light cord through the top of
the box to form a sling to hold the coil form. You will need two
or three loops of cord inside the box to securely suspend the
coil form near the top vent holes.

Place a light bulb on a heat resistant insulator inside the box
directly below the coil form. Depending on the ambient
temperature, the wattage (or number) of bulbs may be varied. 

The heat from the bulbs will produce a warm air convection inside
of the box that will effectively dry the coil form over a period
of about three days. The temperature does not need to be very
high, temperatures between 120 - 150 degrees F are just fine.

Once removed from the drying box, the outside of the coil form
should be sealed immediately, then wound with wire. Once the coil
form is wound, the ends of the coil form are capped with plastic
disks glued down with epoxy to form a hermetic seal. 

However, if the coil form is removed from the drying box and
winding is delayed for some reason, one coat of sealer should be
applied to the inside of the coil form to prevent moisture from
reabsorbing. If the winding proceeds at an orderly pace without
delays, then the end caps will prevent air exchanges which
removes the need to seal the inside surface of the coil form.

Richard Quick


... If all else fails... Throw another megavolt across it!
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