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Re: Large Plasma Globe Calculations

Original poster: "Scott Bogard" <teslas-intern@xxxxxxxxxxx>
I don't think it would be possible to build a glass globe that large, at least not out of one piece. I suppose you could weld smaller pieces together, but glass is not steel, it would need to be wicked thick to support its own weight (and it is very difficult to weld anything, and get good penetration, more than a few inches deep like that, not to mention you would need a frame to support the thing during construction, or else it would break). I am not going to do the stress analysis on such a structure, as I have way too much to do right now, but my initial impression is it would be impossible to build such a structure without a metal frame of some kind, which might still look cool. Probably the best option to get the HV to the middle would be to use a tiny top load, and run a long, well insulated wire to the center and leave the coil outside (or, just have an isolated middle, like in real plasma globes, so the toroid is the only part touching the glass). If you were to consider building such a large globe, my advise would be this, build a structure 10 feet diameter (instead of 125), and use a small coil, and fill the thing with atmospheric pressure argon. It would look like a normal (larger) TC, but in a globe-like structure, and the lightning would be very bright and a really cool blue color, instead of purple. Once again our reach seems to exceed our grasp! 
Scott Bogard.



From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: Large Plasma Globe Calculations
Date: Mon, 30 Apr 2007 22:29:16 -0600

Original poster: "resonance" <resonance@xxxxxxxxxxxx>
You need an oven large enough to bake out the globe --- to remove all the residuals. We also blast ours with argon at 50 kV for 2 hrs to do the final removal after baking.
The oven large enough to bake a 125 ft dia sphere should only cost a million $$$ or so. Our oven for up to 40 inch dia. globes, used, cost us $9,500.00, and we got a "good deal" on it. 

Dr. Resonance
Hi everyone, just wondering if these calculations I made seem to be close to correct? I remember hearing someone say that a 6" plasma globe would probably send 4mm streamers in the air instead of the gas filled sphere. So if that is not correct then these calculations would be way off. 



Standard Six Inch Plasma Globe
& Spark Gap Tesla Coil;

Compare Chart

************************
S_IG = Spark In Gas
S_IA = Spark In Air
************************

------------------------
Six Inch Plasma Globe;

( 76.20mm ) 3.00in S_IG

( 04.00mm ) 0.16in S_IA
------------------------

************************
76/4 = 19 (?)
711.2 x 19 = 13,512.80
************************

------------------------
Medium/Small 9/30 SG Coil;

( 13512.80mm ) 532.00in 44.30ft S_IG

( 711.20mm ) 28.00in 2.30ft S_IA

Sphere Diameter 88.60ft
------------------------

------------------------
Medium Sized 9/60 SG Coil;

( 19304.00mm ) 760.00in 63.30ft S_IG

( 1016.00mm ) 40.00in 3.30ft S_IA

Sphere Diameter 126.60ft
------------------------

------------------------
Medium/Large 15/60 SG Coil;

( 26790.00mm ) 1055.00in 87.90ft S_IG

( 1410.00mm ) 51.50in 4.60ft S_IA

Sphere Diameter 175.80ft
-------------------------
If the calculations are correct, that would be one amazingly huge Plasma Globe to see. Would it even be possible to build one that large? I was thinking and the coil would need to be elevated to the exact center of the sphere to work correctly. I would think the primary would need to be heavily insulated if the coil was in the sphere. Something special for the spark gap would have to be thought up, or just use a VTTC, maybe. Of course a Glass sphere that large would cost thousands of dollars to make though, if not more. I doubt this is something any of us on the list could build. 

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