Capacitors for tesla coil

[skyler]

Hi,

I am working on a tesla coil with my friend, we started it up at school, and are trying to finish it up before summer is complete.

http://www.amsatnet.info/#coil

We finally found an NST and bought it because everyone was telling us MOTS were not going to work. We got a 60ma 15kv NON GFI.

The secondary was tested by the meter, and we measured around 88khz resonant frequency with the top load installed. We also wound 100 feet of copper tubing for the primary around it.

The bucket capacitor is having major problems though (see the picture in the site) , the beer bottles keep breaking when we try to add power, and everyone says they are really inefficient and don't work very well...

So, for the last step in our project before completion, we need some capacitors. The problem is we kinda spent a lot of our money for the coil, and are on a pretty big budget and don't want to be spending hundreds and hundreds on a capacitor bank.

Does anybody have any suggestions and links for good capacitors for my setup? I know it can be really picky when it comes to tesla coil capacitors. 

PS

The primary in the pic is not the one we are using now, we realized that it had way to short of a length and too little inductance and we would need a giant cap to compensate.

We do plan on switching to 4 mots for a total of 8kv in the future, just now we are doing it with the NST for initial testing.

[Stray Electron]

  I made a Tesla coil when I was in high school and I just used a large glass plate and put tin foil on each side (taped on). To connect it I just stripped about 1 1/2" of insulation from the end of the leads and laid the bare wire on the foil and taped it down.  I had to keep the foil about 2 inches away from the edge of the plate to keep it from arcing around the edge.  IIRC I had to use thick (about 5/16") glass because it would arc through and shatter normal window glass.  I powered it off either a 12kV or 27kV neon sign transformer, I had both but don't recall which one I used.  I used a mechanical chopper in the primary of the Tesla coil to generate high frequency current.  It was basically a spinning blade mounted between two contacts in series with the primary. But for the life of me I can remember how I drove the spinning blade!

[Psi]

I used Cornel Dublier (sp?) pulse caps from digikey, from memory it only cost ~$100 nzd for the caps
(  12kv 30ma nst)

I actually got the wrong type. Got high pulse discharge instead of ultra high but the seem to work fine. I have 2 series strings in parallel

[David Hess]

Mine used glass plates as well.  The aluminum foil was attached with spray glue and set back from the edges by more than one inch.  Several plates were installed into a wooden frame and two bus bars with springy music wire fingers attached to alternate sides.

In the dark, the whole inside of the assembled capacitor glowed blue from the corona discharge.  If the humidity was too high, it would short out sporadically with a bang until the voltage was lowered by closing the spark gap spacing.

A fan could be used for cooling but I never ran it long enough for it to get hot.

[calexanian]

Yeah, I think foil and either glass or mica sheets is the de facto standard.

[skyler]

ok, thanks, yeah our bucket beer bottle capacitor does not use foil, it uses salt water and motor oil

This link is the youtube video from the geek group that is the one I used.

[David Hess]

The glass plates we used with aluminum foil on each side were just plate glass and not anything special.  I have been told they will crack if they get hot enough from extended operation but I never ran mine that long because the spark gap was so loud.