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Re: Polyethylene
At 11:19 PM 11/15/96 -0700, you wrote:
>>From Esondrmn-at-aol-dot-comFri Nov 15 22:57:04 1996
>Date: Fri, 15 Nov 1996 18:43:13 -0500
>From: Esondrmn-at-aol-dot-com
>To: tesla-at-pupman-dot-com
>Subject: Re: Polyethylene
>
>In a message dated 96-11-15 01:29:05 EST, you write:
>
><< Hello everyone,
> Thank you all for your ideas and advice. What a
> wonderful resource this list is. Bert (Pool), I would be delighted to
> read your recipe. So the molecule chains in HDPE are considerably
> longer than LDPE. That explains a good deal. The reason I am opting
> not to use glue sticks is the number I would have to use to do the
> job. The reason for filling the tube is to suppress corona and boost
> the voltage rating so a shield may be placed around the outside
> (shunt C allowed for). Robert, sounds like the Dow-Corning filler
> might be a bit expensive. I will consider wax, but will wait until
> the recipes are all in. Plastic has the advantage of also assisting
> to glue the thing a bit more solidly.
>
> Malcolm
> >>
Well, I dug out the original post that has the poly/wax recipe that I had.
I'm posting it in it's entirety below:
Message 5107 DATE/TIME: 02/27/94 17:03
>From : GERALD O'DOCHARTY
To : BERT POOL
Subject: Bolt Barrier compound
Folder : A, "Public Mail"
Hi Bert! Here's the recipe just like Pete wrote it. I have not tried it
yet but plan to do so soon. I am also uploading this as a file.
.
------------------------------------------------------------
Excerpted from "The Tesla Phile" newsletter of May 1985
written by the late Peter Lefferts.
Provided by Gerald O'Docharty Feb. 1994
------------------------------------------------------------
.
.
BOLT BARRIER, compound for Tesla coils
.
PURPOSE: To have an easily castable compound for insulation
that is tough yet slightly resilient so that stress cracks
will not occur. Available kitchen materials and low melting
point are very important. My primary use will be to cast
insulation between the primary and secondary using cardboard
molds. The object is to wind the primary closer to the
secondary, depending on the insulation to prevent flashovers
between the two windings.
.
MATERIALS: Paraffin, shredded soft polyethylene (old,
translucent, coffee can lids etc.)
(maybe clean clear polyethylene sheeting commonly
available. G.O')
, salt, & two large pots... one of which will sit easily
inside the other. These pots should be stainless steel or
good uncracked glass-porcelain covered.
.
PREPARATION: First step is to make up a high temperature
double boiler where the inner pot sits in the water. Some
sort of support is needed so the inner pot doesn't sit on
the bottom. Put enough paraffin blocks in the inner pot to
supply the expected need. The inner pot will have to be
weighted down because the outer pot should have enough water
added to come about an inch above the melted wax level. Boil
the water while adding salt to it until no more salt will
dissolve. this raises the boiling point for a better
product, yet greatly decreases the chance of flames.
.
COMPOUNDING: When the water is at a medium boil with most
salt dissolved and the wax melted, start adding the slivers
of flexible polyethylene (avoiding other plastics that are
stiffer or make a white line when creased). Stir every few
minutes to prevent the poly from sticking to the bottom and
browning the wax. When about 1/2 the poly appears melted,
add some more. Add water slowly to the outside pot to keep
the level an inch higher than the plastic level of the inner
pot. As soon as a hint of cloudiness appears in the mixture,
or the consistency of thin oil appears, stop adding poly,
and heat and stir a little longer.
.
CASTING: A mold of good dense cardboard, glued watertight
sides and bottom with ample epoxy should be prepared well
ahead of time. also seal any wire joints likewise. Do not
use other plastics such as Acrylics as molds. practically
all epoxies and hard magnet wire insulations will stand up
to the heat and solvent characteristics of this compound.
Pre-heat the mold cavity using an oven for small objects, or
hair drier for larger ones. If oven, pre-heat it 250 deg.F.
and wait until well stabilized before putting object in. If
hair drier, heat until a metal part will sizzle slightly
when touched by a wet finger. Be sure that if a Tesla
primary is being molded that several taps for tuning are
brought out through the mold. Also if you want to take the
cardboard off later, smear the inside with silicone grease (
easier to paint the cardboard though).
Pour rapidly without splashing; this stuff burns skin worse
than boiling water. Shake gently to bring up bubbles. If a
small leak appears, patch with magic tape and blow with hair
drier on cold setting until the plastic in the leak has well
solidified.
.
FEATURES: Bolt barrier is at least an 8 times better
insulator than air. It can be carved quite easily and very
smoothly, and in fact may make an excellent amateur's
sculpture media. If done slowly, the material can be drilled
and sawed with ease. It makes good light duty custom
bearings for models etc. Almost any household solvent may
be used for short term cleaning without effect...turpentine
has some polishing action.
.
-----------------------------------------------------------
Well, that's it. If you try it soon let me know how it turns
out. -Gerald
----------------------------------------
Malcom, everone, I hope this helps out those of you who need castable HV
materials.
Bert Pool