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HELP: I'm Trying to achieve a larger streamer length

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fatboyslim

Thu Nov 20 2008, 10:02AM

Registered Member #1779 Joined: Sat Oct 25 2008, 11:05AM
Location:
Posts: 32

Hi, I have been building my coil for quite a while and here are my specifications

Power Source: 12kv 30ma
Secondary: 3.5 inch wrapped 10 inches
Primary: 12AWG wire with multiple tap points
Spark Gap: Multiple Copper pipes with various tap points
Primary Capacitor: 8 30kv doorknob capacitors giving me 8nF total capacitance
Toroid: Two metal bowls welded together and then later wrapped with aluminum to give more capacitance.

The longest spark i am able to get out of this tesla coil is about 7-8 inches from a breakout point to a copper pipe.

Is there any way of increasing the spark length further more. Should i set back the spark gap a couple more copper pipes so theres more of a gap. If i do that, do i have to change the primary tap point as well. Do i need more capacitance?. Also i dont want to spend more money on capacitors so can i possible make a salt water capacitor that can link up to the existing doorknob capacitors? Im taking this to school again next year, cause school finished for me, and im trying to make the spark as BIG as i can. Would buying a larger secondary make a difference?

ALSO. I currently have 8 30kv 1nf capacitors which i mounted in parallel to get the 8nf capacitance. Is it OK to put a 30kv 2.7nf capacitor in parallel with those 1 nF capacitors. to give me 10.7 nF?!?

Hope some can help me

Fatboyslim

Arcstarter

Thu Nov 20 2008, 05:32PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

fatboyslim wrote ...

ALSO. I currently have 8 30kv 1nf capacitors which i mounted in parallel to get the 8nf capacitance. Is it OK to put a 30kv 2.7nf capacitor in parallel with those 1 nF capacitors. to give me 10.7 nF?!?

Yes, you can put a different capacitance in parallel, just not series. For your transformer, 10.7nf would be about right, as 7.9nf(just say it is 8nf) is resonant, so 10.7nf would be around what you want cause you want above resonant, to insure longer transformer and cap life. Teslamap says 8.0nf is resonant and 11.1 is LTR(larger than resonant)assuming you are using 50hz. So it is just something you are going to have to play around with. Remember, any change in tank capacitance will need a retune, as well as terminal capacitance(topload). You should be getting more than 7-8 inches, estimated spark output is 32.8 inches with teslamap, and 32 inches with deepfriedneon. But those numbers are onl based on power input, not the coil itself, so you are just going to have to mess with different primaries and secondaries. I got small sparks with my 4 inch coil because at the bottom the wires overlapped cause i was stupid when i made it, and shorted and heated really bad on my vttc. So make sure that didn't happen.

TheBoozer

Thu Nov 20 2008, 10:05PM

Registered Member #1535 Joined: Wed Jun 11 2008, 11:37PM
Location: Northeastern Pennsylvania - USA
Posts: 117

Check out what I did with my 12kv 30ma transformer... The specs are listed there... I started out with smaller diameter coils, and during the course used a 3.5" secondary. In the end I stuck to a 4.5" secondary. When I was using a static gap, I was getting 15". A rotary gap improved things. It's really hard to tell you how to improve yours without more info. You don't mention how the coils are coupled. What style primary? Pancake, vertical helix.... I'm certainly not qualified to tell you what to do to improve yours, I can only tell you what I did to mine.

I've made a new, smaller coil, and I also am having difficulty achieving expected arc length with the new one. I don't ask for help, because it's too difficult to explain. :( Kinda like calling up a car dealer and saying your car doesn't work right, but giving no more info...

I'm certainly not happy about using 12awg wire though. 1/4" tubing will offer far less losses though!!!!

8nf certainly sounds like enough bang energy... Mine uses less...

P.S. When my coil started out, all I could get was 7" to 8" and that was only with a breakout point. A year later, it's sweet!

fatboyslim

Thu Nov 20 2008, 10:37PM

Registered Member #1779 Joined: Sat Oct 25 2008, 11:05AM
Location:
Posts: 32

Thanks, I originally had 1/4 inch copper piping bit i had wound it once and then unwound it and winded it again. The end result was soo bad i trashed it. some parts were touching or overlapping. I can never wind a primary nicely, and i dont know how. Instead of spending 40 for a new copper pipe i bought some 12wag wire. The spark length stayed the same though

TheBoozer

Thu Nov 20 2008, 11:40PM

Registered Member #1535 Joined: Wed Jun 11 2008, 11:37PM
Location: Northeastern Pennsylvania - USA
Posts: 117

When I began, I couldn't figure out how to wind up a perfect pancake. So, I took an 8" coooking pot and wound my tubing on that. It was easy to space the gaps between windings. My first secondary winding sits just above the last of the primary winding. Easy to adjust coupling, from poor to severe. I think my only drawback is that it made my whole assembly quite tall...

Hazmatt_(The Underdog)

Sat Nov 22 2008, 04:34AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

1. I suggest making a vacuum type sucker gap so you can really charge your caps up. I think what you're experiencing is power arcing, which is why you can't achieve best results right now.

2. Go with the 10.7nF. More power = longer arcs. If you want to kick things up a notch in the future you could get a 12/60 or another 12/30 for your system, and more doorknobs. Of course that's all a matter of budget.

3. Ditch the bowls. Get some ducting and make a 4" x 18" toroid.

4. Use a breakout point to intensify the charge to a singular point, this way you can control the breakout and prevent multiple breakouts stealing your overall length.

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