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Re: Hurray, I destroyed my homemade cap!


From: 	Benson_Barry%PAX5-at-mr.nawcad.navy.mil[SMTP:Benson_Barry%PAX5-at-mr.nawcad.navy.mil]
Sent: 	Sunday, November 30, 1997 4:43 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Hurray, I destroyed my homemade cap!


Hi Terry, Adam, All,
     The newer flyback transformers are potted in some kind of silicon 
rubber.  If a vacuum pump were available thin it might make a very nice dry 
capacitor.  Some of the plastics dealers sell silicon rubber in two part 
cans that cure upon mixing.  If the mixture were poured over a flat plate 
capacitor and then pumped on to remove air bubbles the corona from the 
resulting capacitor should be very minimal.  The unknown is whether silicon 
rubber can conduct heat away sufficiently to prevent the capacitor from 
overheating.  The cure time for thick molds is also a problem as the full 
dielectric strength is unavailable until fully cured.  Anybody tried this?

                         Barry

 ----------
From: "tesla"-at-pupman-dot-com-at-PMDF-at-PAXMB1
To: Benson Barry; "tesla"-at-poodle.pupman-dot-com-at-PMDF-at-PAXMB1
Subject: Re: Hurray, I destroyed my homemade cap!
Date: Sunday, November 30, 1997 4:50AM

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From:     terryf-at-verinet-dot-com[SMTP:terryf-at-verinet-dot-com]
Sent:     Sunday, November 30, 1997 12:25 AM
To:  Tesla List
Subject:  Re: Hurray, I destroyed my homemade cap!  But beware wax!

Adam,

        I tried to insulate a small Tesla coil with paraffin wax once.  It
was a disaster.  The wax shrinks as it cools which causes big problems.
When cool, it has a tendency to crack in the cold.  The coil arced and has
made an excellent door stop in my garage for the last five years.  Perhaps
the addition of bee's wax will solve this????  I once had a recipe for
vacuum grease that involved adding Vaseline and a few other ingredients to
wax when it was warmed (beware, it is very flammable!).  It made the wax
stay soft and fairly pliable.  I don't have the formula anymore but perhaps
wax mixed with something like that would make a good durable insulating
material?

I am in full support of eliminating that nasty mineral oil!  In an
experiment before the wax, I was using oil to insulate the coil.  It arced
through the oil, the side of the container, and oiled my patio.  Detergent,
cat litter, and sunlight removed the mess but it made me hate that damn oil! 


        Terry


At 08:38 PM 11/29/97 -0600, you wrote:
>
>From:    Alfred A. Skrocki[SMTP:alfred.skrocki-at-cybernetworking-dot-com]

>Subject:      RE: Hurray, I destroyed my homemade cap!
>
>On Thursday, November 27, 1997 12:56 PM Adam
>[SMTP:absmith-at-tiac-dot-net] wrote;
>
>> ... So then, how about solid corona protection, like paraffin wax?  I
could
>> get this cheaply at the grocery store, melt it in a double boiler and pot 

>> the cap.  This would make the cap a lot more difficult to repair, but if
>> I over engineered it in the first place it should survive a few years of
>> Tesla use, right?.  I am using 120mil of very high quality LDPE (4 x
>> 30mil) and operating at 9kV, so my cap is not likely to blow anytime
>> soon.  Mostly I just want to make something without that horrible oil!!!
>
>With mineral oil's dielectric constant being 2.2 - 2.7 and it's dielectric
>strength being about 200 volts per mill and with paraffin's dielectric
>constant being 2.1 - 2.5 and it's dielectric strength being 250 - 450 volts
>per mill, it would seem that paraffin may be a possible good choice
>ASSUMING you can keep out any bubbles when pouring in the paraffin. BTW
>paraffin and mineral oil can be mixed to change the viscosity to anything
>from solid to liquid and everything in between! I would suggest that after
>you pour in the paraffin that you keep the capacitor at the melting point
>for the parafin for a while (like several hours) to let any bubbles rise
>out.
>