Re: DArN CAPACITORS!--The Geek Group Bucket Cap

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Christopher Boden by way of Terry Fritz <twftesla-at-uswest-dot-net>" <chrisboden-at-hotmail-dot-com>

>Original poster: "Gregory Hunter by way of Terry Fritz 
><twftesla-at-uswest-dot-net>" <ghunter31014-at-yahoo-dot-com>
>
>Hi Drew,
>
>--- Tesla list <tesla-at-pupman-dot-com> wrote:
> > Original poster: "Drew Murray by way of Terry Fritz
> > <twftesla-at-uswest-dot-net>" <drewallmighty-at-hotmail-dot-com>
> >
> > OK people,
> > I'm sick of getting dry, crusty, stinging, bleeding
> > hands from salt water
>

Drew, we've built just about every type of SW cap that can be made over tha 
past 4 years. Mason Jars, Beer Bottles (with clear, brown  and Green glass), 
plastic water bottles (the big 5 gal ones), and even household glasses. Just 
about anything that can be wrapped with Al-foil has been wrapped here. If I 
thought I could get arcs from a saltwater aquarium I'd try it, fish and all 
(no worse than that chicken :) ). We've made every possible mistake that CAN 
be made and had some serious messes in the shop from it. And never, has any 
member of the group had the problems you're having, you have to be doing 
something horribly wrong.

I highly reccomend you do two things right away.....

1. Hold this wire......

2. Go to this URL, follow the instructions on the Bucket Cap, it should take 
a whole $20 and an afternoon. And I swear, if you follow the instructions, 
and built it carefully...you WILL have a safe, working, reliable cap that 
will match wonderfully to a 15/60 NST, and can be adjusted down to whatever 
size NST you want.

http://www.thegeekgroup-dot-org/Projects/Tesla/capacitors.htm

I've even copied it all here for you, with spelling corrections :).

The Geek Group Bucket Cap:
Though terribly lossy, a decent cap can be made for tesla coil service for 
under $50 in a couple hours that is easily repaired and will give you years 
of service if properly maintained. Tesla himself used SW (Saltwater) caps, 
but Cap technology has progressed a bit in the past hundred years and the 
current choice is Metalised film polypropylene. But if cost is a serious 
issue, and performance isn't, SW caps are the way to go.

Materials Required:
1 clean new 5 gallon bucket. This should be made from HDPE and MUST NOT BE 
METAL! It should also be white, not black or Grey.

1 well sealing lid (preferably airtight) for the bucket

12 longneck beer bottles, preferably Corona brand, these must be washed and 
clean

3 quarts of new synthetic motor oil

25' of 10AWG bare solid copper wire

1 rubber stopper, about .5" or so, no smaller than .25"

2 "5-Way" binding posts (these must be separate, not the kind that come as 
an attached pair) panel-mount.

2 of the 5"dia X 7" tall cardboard containers of Morton's Salt (or 
equivalent). ANY salt will do, iodized or not, even Epsom salts would work.

1 glass pitcher with a good pour lip. You must be able to pour from this 
into a bottle without spilling everything all over. It must be glass if you 
ever plan on using it again, plastic is OK but getting the salt taste out is 
rather difficult. 2 quarts is the best size.



Construction Technique:
1. Fill the pitcher about 75% full of the hottest water you can stand. Add 
one container of salt and stir for a full 2 minutes. There will be a LOT of 
salt on the bottom, this is alright. Let it sit for about 5 minutes. If 
there isn't a good layer of salt on the bottom, keep adding and stirring 
until there is. If you stir it enough, then there will only be salt on the 
bottom when the water won't accept any more. You want it as saturated as 
possible.

2. Fill as many bottles as you can to the base of the neck with the salt 
water from the pitcher. Be careful not to pour out all the water. Do NOT 
POUR OUT THE SALT IN  the bottom of the pitcher. When the pitcher starts 
getting low just add more hot water and stir. When the salt in the bottom 
starts to get low, add another container of salt. It's alright if you get a 
little salt in the bottles, it won't hurt anything. It just wastes salt. 
Fill all the bottles to the same level, where the base of the neck just 
starts. If you have an extra, fill a 13th glass bottle and set it aside.

3. Place all 12 bottles in the bucket, they will *just* fit. Fill the area 
around the bottles with Saltwater to the same level as the bottles are 
filled.

4.  Now you have to make the jumper wires to connect the bottles. You want 
to cut and bend piece of copper wire so that they form an inverted "U" 
shape. Each wire should go from inside 1 bottle, about 1" from the bottom, 
out, over, and into the bottle next to it down to the same level in the 
second bottle. This is a LOT easier than it sounds. Connect each bottle to 
the one next to it, most bottle will have 2 or 3 wires going into them.  
Just make sure they are all connected. Make sure you make gentle bends, NO 
SHARP BENDS they contribute to corona losses, about a .5" radius is fine.

5. Mount one of the Binding posts in the center of the lid. And another one 
as high up on the side of the bucket as you can without interfering with the 
lid. These will be your terminals.

6. Connect a piece of wire from the side terminal (on the inside) extending 
down into the water jacket around the bottles. This wire should go straight 
down and stop about an inch from the bottom of the bucket. Bend a 2" 
vertical loop in the end of the wire.

7. Connect a piece of wire about 1' long to the inside of the top terminal. 
This will be threaded into a bottle (any one should work) when you put the 
top on. You may have to trim it a bit, but make the wire as long as you can 
without it hitting the bottom of a bottle.

8. Fill each bottle all the way up with motor oil, don't worry about 
spilling any into the water jacket. Once all the bottles are filled, pour 
the remainder of the oil into the water jacket, this is your corona 
suppression. It should take about 1 quart to fill the bottles.

9. Check your connections, make sure everything is tight. Before mounting 
the top onto the bucket, drill a hole for your stopper. Plug the hole TIGHT 
with the stopper. You might even want to use a mallet to hammer it in. If it 
leaks you have a mess you won't soon forget.

10. Mount the lid, and seal everything tight. You now have a .0125uF 80KV 
capacitor.

Check everything with a meter to make sure. The value of the cap will take a 
week to finally settle as the oil absorbs a LOT of water. If you look at the 
extra bottle you made, you will see salt settle on the bottom. This is fine, 
and actually helps to make sure that the SW is as concentrated as it can be. 
If the salt content were to lower it would just absorb salt from the bottom. 
If you put a layer of oil on top of the water in your extra bottle you will 
see it drop over a couple days, this is the oil absorbing the water.

Remember to short out your cap after use and during storage. This is a good 
practice for ALL caps as ALL caps can kill, even though the Bucket cap is 
inherantly safe, it will self-discharge in a couple minutes at most. ALL 
CAPS CAN KILL, we still use SW caps for blowing CD's. If you want a generig 
cap for HV tinkering SW's are better than MMCs because if you kill a SW it's 
a 5 minute thing to repair it....MMCs take $$$$$ and HOURS of work.


1 Bucket cap is perfect for a 15/60 NST, if you have more NST's, just add 
more buckets. We have 4. If you are running 15/30NST's then just use 2 NST's 
to a bucket. For a single 15/30 NST, just open it and only connect 6 
bottles. (you can actually add another binding post on top and have 2 caps 
in one with 2 groups of 6 bottles wired separately, one to each binding 
post. The side terminal is the negative for both.





Christopher A. Boden Geek#1
President / C.E.O. / Alpha Geek
The Geek Group
www.thegeekgroup-dot-org
Because the Geek shall inherit the Earth!


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