Re: Castor Oil - (was: Paper/Oil Capacitors)

["Jim Lux" <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Castor oil is what Maxwell Labs uses in their caps.

As I recall, the epsilon (dielectric constant) is around 5, roughly double
that of mineral oil, and comparable to askarel (PCB).

Contaminants would be a significant concern (as with any oil).  Very small
particles, bubbles, etc, can lead to field concentrations which then lead to
failure.  I don't know that I would trust the stuff at the model store used
in model airplane engines....

Filtering through a millipore filter and vacuum degassing would be the order
of the day for ultimate performance.



-----Original Message-----
From: Tesla list <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Friday, August 25, 2000 11:57 AM
Subject: Re: Paper/Oil Capacitors


>Original poster: "Steve" <Steve-at-g8cyerichmond.freeserve.co.uk>
>
>I've been looking through some of my old books to try and find out what
used
>to be used in the old days. Unfortunately I haven't found what I was
looking
>for, but if memory serves me correctly, castor oil was commonly used rather
>than mineral oil. In fact I have an oil.and paper cap that is at least
fifty
>years old, and it still works, and its value is pretty well what it says on
>the label. Unfrotunately it is part of an old induction coil, and I don't
>want to dismantle it to check out what's inside. I would also like to find
>out about the electrical properties of castor oil, if anyone can help, I
>rather fancy the idea of trying it myself.
>Steve
>----- Original Message -----
>From: Tesla list <tesla-at-pupman-dot-com>
>To: <tesla-at-pupman-dot-com>
>Sent: Thursday, August 24, 2000 6:28 PM
>Subject: Re: Paper/Oil Capacitors
>
>
>> Original poster: "Duke, Ronn (CCI-San Diego CCC)" <Ron.Duke-at-cox-dot-com>
>>
>> >>Snip <<
>> >>I thought it would be a good idea to make a rolled poly cap with
>> paper-poly-paper layers. I figure >>this would help keep the heat and
>corona
>> away from the poly that would prompt premature failure, >>and also
improve
>> the voltage rating and dielectric properties.
>>
>> >> Reply Snip <<
>> >your idea of using paper, poly, paper is a very good one. I wish I would
>> >have thought of it a year ago.
>> >One thing though, wood pulp dissolves in oil after a time. that is why
>> >you use paper towels to clean the inside of an engine block before
>> >rebuilding, not a rag.
>> >but when I was in drafting at V.O. Tech (back before cad), we used a lot
>> >of velum, I'm not sure what it was made out of but it seemed to be some
>> >kind of impregnated paper?
>>
>> I wouldn't be surprised that wood doesn't last long in motor oil.
>Petroleum
>> based oils you add detergents, ashless dipersants,(keeps carbon particles
>in
>> suspension), anti-foaming agents, acid neutralizers, flash suppression
>> agents, etc.  You get the picture. I would think that paper would fare
>much
>> better in pure mineral oil or transformer oil because of lack of chemical
>> additives.
>>
>> Comments?
>>
>>
>> Thank you,
>>
>> Ronn Duke
>> Cox  Communications
>> Customer  Care  Center
>> Ex. 3485
>>
>>
>>
>>
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>
>
>