Re: A challenge

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:

> >       Safety first, for sure.  But this question:  Was it contact with
the RF
> >from the secondary that killed, or was it contact through that arc to
> >the 60 cycle primary HV?  In other words, is anyone ever known to have
> >been electrocuted by RF?  Horribly burned, no doubt, but electrocuted?
> >
> >Ed

 
> >From the accounts of the accidents, Henry L Transtrom may have indeed been
> killed by a streamer arcing to ground with him in the path.  The McDonnell
> Douglas case did seem to be a primary circuit contact and the child was the
> AC line wiring.  I would think high power radio or TV transmitter accidents
> may answer your question.  In may limited knowledge, most transmitter
> accidents involve the high voltage DC circuits.  High power AC does cause
> bad burns that "could" fry a person but not directly stop the heart.
> 
> Tesla coils may be "RF" but when a streamer strikes ground, you are
> basically discharging a big high voltage capacitor to ground in a big
> basically DC pulse.  That is probably easily enough to cause death in some
> cases.  Also remember that the coil can recharge and zap you again at say
> 120BPS+.  So if it does not get you the first time it may have 1000 more
> chances before you fall off (onto the primary...).  So from the daredevil
> side, you may not die from streamers of the fingers to air, but if those
> streamers connect directly to a good ground you are probably in big
> trouble.  A 20kV pig with say a 100pF (person on top) capacitance stores 20
> joules per bang.  The "person" is the load in that case since the coil and
> ground are fairly low impedance.  At 120 BPS you are dissipating 2400 watts
> in high power DC pulses...  I think that could easily kill.

	I think it would be interesting to use a scope to measure the actual
waveform of the current at the "receiving" end of a streamer.   My
question would be as to how much of that power is dissipated "where it
hurts".
 
> Of course, not too much hard fact here since it is hard to test ;-)  

	I can think of a few candidates from "the other Tesla list", but that
isn't too practical!

But
> those are "my" ideas on this.  Perhaps others who have been hit by
> streamers have noted very "bad" shocks that would be an indicator of near
> lethal contacts.  If a streamer has knocked anyone down or something like
> that, then that would show a pure streamer hit could be very dangerous by
> itself.  But I would guess the shock would be mostly a DC pulse rather than
> nice pure RF.

	I've noticed shocks plenty of times, but only as I moved a conductor
toward the coil and streamers first started.  Case of rectification by
asymmetric geometry, I suspect.  The effect is quite noticeable even in
very small coils.  
 
> As far as accidents go, "I" think many more injuries occur building coils
> than operating them from power tools and the like.  Of course, that is true
> if you were building a wooden chair with power tools too.  In general,
> building and moving Tesla coils (backs ripped up pushing pigs around), car
> accident, etc. is probably more dangerous than using them.  But those
> injuries are not as "dramatic" or "unique" just to Tesla coiling.  So as we
> are installing the new super safe dead man switch, try not to drive the
> drill bit through you hand ;-)

	How about sticking a screw driver through your hand while you're
holding something and trying to unscrew a screw from it?  I've done it a
couple of times and immediately wondered what was in my mind just a
moment before......

> I have never been hurt by the discharge from a Tesla coil.  But I have hurt
> my self a number of times with tools building them, slipped badly on ice
> carrying parts, cut the heck out of my self in a junk yard pulling out
> Tesla coil treasures, and pushed the front end of my car in while going to
> get Tesla coil parts...  But these are the risks in doing "anything" fun ;-)

	I personally am super careful when using wood working tools, even
chisels.  It's also easy to get a drill caught in the work on the table
of a drill press, with possibly quite unfortunate results if it's a thin
piece of sheet metal.  There's also the wire scratch brush which can
grab things and through them mighty hard.

 
> Certainly not to at all discount the dangers of Tesla coils and high
> voltage.  The low number of accidents is in no doubt due to our being
> extremely careful!!  But, the person who asked this question originally is
> probably more statistically likely to die from the wife getting mad at him
> spending too much time coiling (or depoting that NST in the oven) and
> shooting him, rather than getting electrocuted ;o))  

	Somewhat of a problem around here, especially when there's house
maintenance or yard work outstanding.

> So while coiling, be
> very careful of the high voltage, and watch your back too :o))
> 
> Cheers,
> 
>         Terry

	The original purpose of my question was really too see if anyone had
any data on the physiological effects of "RF" signals.  I know from
experience that contact with a high power 4800 hertz source (driving a
shake table, of all things) hurts like crazy.  I've always regarded the
primary circuit of a TC as a lethal device, but been more concerned with
burns than electrocution from secondary streamers.

Ed