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Registered Member #4074
Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
Chris Maness wrote ...
Here they are:
I used 5 in parallel.
Thanks, Chris
Ahhhh, there's your problem. Those polystyrene capacitors aren't really suitable as SGTC tank capacitors. After a brief search I saw a few reports on Instructables stating that the cheap polystyrene capacitors from Chinese ebay stores are hopeless and die quickly. I purchased a couple of them years ago, one has lasted (while being operated at only 10% it's max voltage rating), but the other died within minutes and wasn't even used for pulsed power stuff like a tank capacitor.
Polypropylene film/foil capacitors, like the CD 942C are one of the best choices. The thick foil and low loss dielectric help keep the capacitors from overheating under the large RF currents, and lots of small PP caps are usually cheaper than a couple of giant high voltage RF ceramic/mica capacitors.
Registered Member #55389
Joined: Mon Jul 06 2015, 12:38AM
Location: Grand Terrace, CA
Posts: 29
Back to the beer bottles, and yes the hair dryer in cold air mode through the spark gap makes for a much steadier discharge on top. Man is she loud. I made the mistake of playing with it the first night without hearing protection, and I had tinnitus that night.
I am going to wait on the expensive caps, the bottles will have to do for now as I am already in this thing for a fairly hefty sum. I am brainstorming to figure out a way to make my beer bottles road worthy to take to summer camp. The rangers are going to love me :D
Here is the set up now after the polystyrene caps failed:
Registered Member #79
Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673
Cool! Glad to hear it's working better! I used to keep my bottle caps in something like a coca-cola box, and I would just pull the electrodes out and cap them when they traveled.
Registered Member #55389
Joined: Mon Jul 06 2015, 12:38AM
Location: Grand Terrace, CA
Posts: 29
I am going to change over to a Torroid with a break out on top. I get a lot of leaky corona out of the rims of the two bowls. Although it looks cool in the dark, I think I would rather have longer streamers.
Registered Member #55389
Joined: Mon Jul 06 2015, 12:38AM
Location: Grand Terrace, CA
Posts: 29
I just added the toroid to my bowls, and I am now getting really nice 8-10" streamers. It is working pretty good now. I just need to get a fan that shoots as much air as my cold blast hairdryer that I have rigged up. I am still stuck on salt water caps as I am very much over budget for the month. I will be going to camp with the salt water bottles.
Here is the pic:
Thanks for the help guys, Chris M. GTHS Physics/Chemistry
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
It's good to see an SGTC with saltwater caps for a change.
Please post more details of your capacitors, detailed description of manufacture, etc. When done properly these things rock, and they cost next to nothing
Registered Member #55389
Joined: Mon Jul 06 2015, 12:38AM
Location: Grand Terrace, CA
Posts: 29
I just used regular brown beer bottles. I Elmer glued the tin foil to the outside, and wrapped gaffer's tape around the top to prevent corona. They have a about 3' of #12 solid wire coiled in the bottle. The water is saturated and then some. It topped off with cooking oil.
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Spark Length with Salt Water Caps vs. Factory Made Caps?
