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# salt water caps

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From:  Thomas McGahee [SMTP:tom_mcgahee-at-sigmais-dot-com]
Sent:  Monday, January 26, 1998 10:06 AM
To:  Tesla List
Subject:  Re: salt water caps

> From:  Ben McMillen [SMTP:sammac-at-cobweb-dot-net]
> Sent:  Saturday, January 24, 1998 7:31 PM
> To:  tesla-at-pupman-dot-com
> Subject:  salt water caps
>
> I have some questions about saltwater caps. I've read that they can be made
> out of wine cooler bottles. Would it be possible to substitute the wine
> cooler bottles with larger 1 gallon wine bottles(with metal screw-on caps)?
> If so, are there any percautions that should be taken and/or design changes?
> How many would I need for one coil? Finally, would the larger size have any
> affect on the discharge performance of the cap? Thanks for any help.
>
> Ben McMillen
> sammac-at-cobweb-dot-net
>
>

Ben,
You want a fairly thick glass wall so you can withstand the voltage.
In this respect most beer and wine bottle work fine. The large gallon
jugs will work, but they are not as good for the following reason:

We want CAPACITANCE. Now, if you determine the capacitace of a 1 gallon
jug and compare it to the capacitance of the several wine bottles
that would fit in the same physical space, you would find that the
1 gallon jug was not as high a value. Let's assume that the HEIGHT
and thickness of each was the same. OK, then capacitance value would
then be a function of total circumference. Draw a BIG circle representing
the gallon jug. Now draw just TWO circles inside, with their
outsides JUST touching. Assume the BIG circle has a diameter of 2.
The circumference is therefore 2*3.14=6.28     Each of the other circles
has a diameter of 1, so 1*3.14=3.14  but there are two of them, so
2*3.14=6.28  Exactly the same value as the big circle by itself. Now
fill in the empty area with two more little circles. Obviously the
total circumferential distance is now greater than 6.28   Hmmm,
maybe this is telling us something.

Now draw another big circle and inside of it fill it with as many SMALL
circles as you can. As the circles become smaller and more numerous, the
product of number*diameter*3.14 will approach infinity. Of course, in the
real world our glass bottles have a finite thickness that would
limit how thin the bottle could be.

Bottom line is that you will get more capacitance in a given space if
you use smaller bottles of the same height. SO lots of small wine
bottles is better (at least in some ways) to one big gallon jug.
But if you have the room for it, use all the gallon jugs you want.
Roll the bottles out flat and you have a stacked flat cap which has
minimum wasted (non-capacitance producing) space. You also will have
a major problem with the heat, and that is why stacked flat glass plate
caps are not really a very good idea. There are MANY things that will
*work*. Not all are cost-effective, efficient, or long-lasting.
Salt water caps are a cheap way to get started. Once you outgrow
them, move on to a poly cap.

Hope this helps.
Fr. Tom McGahee

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