Subject: RE: TESLA
From: jim.oliver-at-welcom.gen.nz (Jim Oliver)
Date: Wed, 28 Jun 1995 06:22:00 GMT
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TE>From: richard.quick-at-slug-dot-org (Richard Quick)
TE> MM> I came up with two 9kv .030 amp neon xformers and two 12kv
TE> MM> 1.5kva PTs (don't ask)... I bought a length of 6" HDPE from
TE> MM> the local plumbing supply... wound 25" of 22 AWG on it and
TE> MM> put about a quart a polyurethane on top. Looks nice but I
TE> MM> think if I ever wind another I'll use figerglass resin or
TE> MM> epoxy paint...
TE>Use the epoxy paint over the polyester resin. I agree with you on
TE>the problems of polyurethane sealer applications, but it has
TE>generally been more available and less expensive than a high
TE>quality two-part epoxy paint. Both types of sealers perform well
TE>when properly applied.
I have played around with epoxy and PU paints on PVC secondaries.
They can be tricky. I used to use a slowly turning lathe to
create smooth coatings. I have found a better way (I reckon).
I bought a few kilos of paraffin wax. The grade is a low melting
type ( 120 degrees F) and is rather tacky and soft to the touch.
These types of wax vary and it's important to get the right one.
The hard high melting types ( > 212 Degrees F) are no good. I
think the type I used is the sort used to make old fashioned
capacitors, the ones that go all gooey on the outside when it
oozes out. This type were also used to fill transformers. I think
the wax type can rightly be described as a paraffin /
microcrystaline blend to get the right properties.
One could use bitumen, but it's smelly, too sticky, very black
and very, very messy. The stuff thats inside neons would be Ok.
Carefully clean and dry the PVC. Preheat it to about 100 F or so,
then dip it into a narrow high sided vessel filled with molten
wax. Hold it in for a few seconds and pull out carefully and
allow to cool and set. The coating weight is adjusted to be
fairly thin ( < 1 mm) by having the tube the right temperature
before dipping. Cooler = thicker coating. Keeping it immersed for
longer creates a thinner coat. If you get it wrong it can be
placed vertically in an oven and the wax melted off and then be
When you wind the wire onto the wax it stays in place and
insulates it also. When you've finished winding, then re-dip into
the molten wax. This time don't preheat the coil. By dipping cold
and the mass of metal creates a rather thick coating on the wire.
I then wrapped it in thin polyethylene to prevent too much
sticking to the wax. The second coating is about 3 mm or more
thick. If you allow the coil to cool then redip the wax can be
built up even thicker like they make candles.
The heating and cooling should produce some variation in winding
neatness with the movement of copper wire. In practice it didn't
seem to be a problem with a close wound coil.
A coil produced this way has higher and more reliable output then
a badly coated epoxy coil. I have been using one on a small
benchtop Tesla coil for many years with no deterioration at all.
Jim Oliver <jim.oliver-at-welcom.gen.nz>
* SLMR 2.1a *