Re: A challenge

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Ed,

At 08:40 AM 7/11/2002 -0700, you wrote:
>Tesla list wrote:
>> 
>> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>> 
>> Hi,
>> 
>> I should note that there are three known Tesla coiling deaths:
>> 
>> Henry L Transtrom - Electrocuted while working on a stage and using a large
>> Tesla coil. He inadvertently allowed a power arc to go from his body to
>> some metal framing that was part of the stage backdrop. He authored the
>> following book:
>> 
>> "ELECTRICITY AT HIGH PRESSURES AND FREQUENCIES"
>> Henry L. Transtrom, originally published: 1913, second edition 1921, Joseph
>> G. Branch Publishing, Chicago; Reprinted 1990, ISBN 1-55918-054-4, Lindsay
>> Publications, Bradley, Illinois, 60915. Paperback, 247pp, Lindsay # 20544.
>> 
>> 1992 - Graduate student intern working at McDonnell Douglas in St. Louis. A
>> Tesla coil was being used to test aircraft parts against the effects of
>> lightening. The person got too close to the tank circuit and either bushed
>> up against it or a spark left the circuit and struck him. He never regained
>> a heartbeat despite excellent CPR and paramedic responses.
>> 
>> March 29,1998 - An unsupervised 14 month old boy wandered into the poorly
>> made AC line wiring of a Tesla coil. He was found some time later but could
>> not be resuscitated.
>> 
>> A master, a bystander, and a small child have been killed by Tesla coils.
>> It is always a number one priority to keep that list from growing...
>> 
>> Terry
>
>	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.

Of course, not too much hard fact here since it is hard to test ;-)  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.

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 ;-)

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 ;-)  

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

Cheers,

	Terry