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Re: SISG New Cap Construction

Original poster: "Scott Hanson" <huil888@xxxxxxxxxxxx>

Terry -

As I'm just at the point of soldering up my SISG MMC, what's the new target capacitance value?

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, August 09, 2006 9:07 PM
Subject: SISG New Cap Construction

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Bart,

At 08:06 PM 8/8/2006, you wrote:
....Low and behold, you now throw this new cap containment system in front of me!!!! I'm back to being "p***** off" at myself - again!!!

Just to tease you more :o)))

With my SISG computer model finally working, I was able to run a bunch of numbers today and decided my present cap value was too high and should be reduced just a little for optimal performance from one MOT (but the present one has a much wider BPS range!!). So I found I had the parts on hand to make the new MMC!!! This time, I took pictures...

First I wired up the caps with solder, bleed resistors, Kapton tape, G-11 insulator sheet wire terminals...


It does not matter how it "looks" as long as it is sound electrically. You are never going to see it again ;-)) All connections are heavily soldered and the ring lugs are soldered to the brass bolts. Then, I took the plastic gutter pipe and cut it to 8 inches and made holes for the bolt terminals. You then install the guts...



The bolts are held with loctite 271 and are D*** Tight!! They should never come loose, but if they do, the foam holds the other side so they can be re-tightened anyway.

Then I masked off the pretty parts and covered the bench with plastic and tape getting ready for the foam fill.


Then you just blast the inside with foam from the inside out trying to avoid big air spaces:


After a few hours it expands and does its thing as it pleases:


The Dow foam really does not expand super much which is good.

Later tomorrow, I will cut off all the dried excess gushing from the ends. Then let it dry for about a week to be sure all the foam inside is totally dry (but it can be used right away) If there are any big gaps, I can always re-foam them again...

After about a week, I will cut out shallows in the foam ends and fill them with two layers of epoxy. Then just mask off and paint the ends with white paint. It should then look just as good as any commercial cap. I may add mounting tabs too with the epoxy step above.

This cap will be used right at all its ratings. But if it blows up, all the caps will be dead anyway so no need to worry about "fixing it". But it should do find and having the cap part rock solid is simple and cheap with this method!!

The gutter pipe was $9 for like teen feet. The can of foam was $6. You can pick out the dry foam from the can tip, applicator, and ream the tube very easily to use it again. It does seem to expand a little less with many uses. Maybe I did not shake it enough though... Be sure to read all the instructions for the foam since it can be nasty if misused...