Re: High Voltage Potting

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

Original poster: "marc metlicka by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mystuffs-at-orwell-dot-net>



Tesla list wrote:
> 
> Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<evp-at-pacbell-dot-net>
> 
> 
> 
>         If you try this be very, very carefull!  The molten paraffin can
ignite
> at a pretty low temperature.  I've found that dripping the hot glue out
> of a gun works better than just dropping the sticks in and waiting until
> the melt.  Seems to work with lower paraffin temperatures too.  I've
> tried the cut up bottle route, that that also took  higher temperatures
> and longer as well.  The glue stick approach is best.
> 
>         By the way, this stuff looks cool and is nice and solid, but it DOES
> shrink on cooling and, at least in my experience, tends to have tiny air
> bubbles in it.
> 
> Ed


Hi Ed,
This is strange because i found that a double boiler would melt the glue
sticks in the wax very nicely? maybe it depends on the "hardness" of the
sticks, not sure?
 And to be perfectly honest, I think the straight polyethylene strips
made a much better potting mix, It just requires much more patients to
smooth out.
 I found that a small "wisp" moved in a very slow figure 8 pattern
worked best for smoothing the poly\wax mix without air introduced. I
also found that when trying to fill complex shapes or a block that has
many free items in it, It works best if melted straight wax is poured in
and on the (diodes or whatever) then rolled around to give a thin coat
over everything. Then when the poly\wax mix is poured in, It seems to
displace the straight wax giving a total coverage without air pockets.

You are correct that there is some shrinkage, I was mistaken by saying
that there was "none", But i usually "TOP" off the mold while the mix is
hot yet solid. This bonds together as a one pour unit.
 Thanks for the correction because it has been a while and my memory
needed a jolt to get the facts. 
 Either way, this (80% poly\20%wax) mix is the best potting mix i have
tried.
Now there are high voltage potting mixes on the market that claim higher
yields then this mix. I have seen adds of silicone or epoxy mixes in my
tech. magazines that sound very promising, but i have yet to try any.
Take care all,
Marc M.