Re: Tesla Coil Firehazards (Exploding paint cans) (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Mon, 13 Aug 2007 05:22:12 EDT
From: FIFTYGUY@xxxxxxx
To: tesla@xxxxxxxxxx
Subject: Re: Tesla Coil Firehazards (Exploding paint cans) (fwd)

 
 
In a message dated 8/12/07 8:43:09 P.M. Eastern Daylight Time,  
tesla@xxxxxxxxxx writes:

>It's not a temperature of the streamer thing, it's a energy carried  

>in the streamer, which would then be transferred to the can,  heating 




>it up.  I would be somewhat suprised if a streamer carried  more than 

>5% of the coil's input power to whatever it hits. Not only is there  a 

>fair amount of input energy dissipated in the spark gap and the  

>series resistance of the secondary, but there are probably many  

>smaller streamers dissipating some power, and, of course, you have  to 

>keep the streamer hitting the can hot enough to be ionized, which  

>takes a fair amount of energy.
>
>
>That said, if  one had a small NST powered coil with, say, 450 W 

>feeding it (the usual 15kV 30mA), and you got, say, 20 Watts into  the 

>target, and the target was a low melting alloy solder, it might  

>melt.  Think of using a soldering iron.  Pretty iffy,  though... 

>you've got that big can sitting there as a heat sink.  Heating  the 

>valve might be more productive as a means of destruction: low  thermal 

>conductivity, low melting point.


[snip]  

>

>An easier test... get a cheap soldering iron in the tens of watts  

>range, rig up a jig to hold it in contact with the  can.

    All good thoughts, Jim, but still comparing apples  and oranges on *rate* 
of energy transfer. A laser beam can deliver even less  energy than a 20 watt 
soldering iron would, and still perforate metal. A 5  Joule pulse from a ruby 
(etc.) laser would be capable, but that's a fourth of  the energy delivered 
from the soldering iron in only one second. Energy transfer  efficiencies 
aside, that can *is* a pretty big heatsink (as you have noted). You  guys who also 
do laser stuff please correct me... Anybody have a conversion  factor between 
Joules and "Gillettes"?
    This is Tesla coil topical, because I suspect the  energy density in a 
streamer is pretty high, and we want to know if it's capable  of causing damage. 
As an aside, a high-voltage transmission line cable can have  more energy 
density than a laser beam (100 MW/cm^2 vs. 20 MW/cm^2). I  imagine natural 
lightning has a pretty high energy density.
    We could be empirical WRT the question of streamers  burning metal. I'll 
throw this observation out there: we usually don't burn  holes in the sheet 
metal or foil that comprises our toroids! So unless the outer  end of a hot 
streamer has a significantly different cross-sectional area, it's  gonna be 
incapable of doing damage to a similarly-constructed target.
    I *have* seen pic on various sites of CW or  high-powered TC's burning 
metal electrodes. IIRC, Peter Terrens' Youtube vid  showed sparks (of hot metal) 
falling from his toroid. I imagine at the 10kVA+  level, the streamer can do 
some real localized damage to low-melting-point  metals. We know they can burn 
wood and plastic, and melt glass bulbs, so I'd say  long-term exposure of 
metal to a streamer could burn it.
 
 
-Phil LaBudde
 
Center for the Advanced Study of Ballistic  Improbabilities



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