Re: The dowel of death - SAFETY

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Tesla729-at-cs-dot-com>

In a message dated 9/10/01 10:59:25 PM Central Daylight Time, tesla-at-pupman-dot-com
writes: 

Justin Hays wrote: 

>
> Bottom line, my main massive point: when you ground the end of an arc rod, it
>
> puts the end at ZERO volts. This shorts any arc that hits it to ground. That 
> means there is no potential difference (voltage) from you to the end of the 
> arc rod, therefore there's no danger. 
>
> This is the way I have made my arc rods for years. I've drawn pig arcs -at- 
> 25kVA. Tesla coil arcs 6 feet long. Neon arcs, MOT arcs, ignition coil arcs, 
> flybacks, everything. 
>
> A PVC pipe section with a bolt on one end, the bolt is solidly grounded to 
> earth. 


I have to agree with Justin on this. IMHO, PVC makes an excellent HV 
discharge probe. 

<I see no safety issues here whatsoever, UNLESS you're dealing with tesla coil 
<arcs that are many times longer than the arc rod itself. This situation is 
<one in where an arc could bypass the grounded bolt at the end, and hit in the 
<middle of the arc rod and find a path to ground THROUGH YOU. 

Again, I'm in full agreement. As a matter of fact, I have personal 
experience with using a discharge probe that was too short to use 
for the length of the sparks that the coil I was playing with was 
throwing out! I did this little stunt back in the days when I didn't 
know better. I had a METAL curtain rod that I had grounded at 
the end that I was holding and I was using it as  "Jesus stick" to 
draw sparks from an inefficient, but still effective 4 ft spark throw- 
er. The rod piece was only about 30" long and I was drawing sparks 
to the end of it. Well, it finally happened! One train of sparks de- 
cided that my well grounded forearm was a more attractive target 
than the end of the rod, even thow the end of the rod was consi- 
derably closer to the makeshft toroid. Fortunately, the electricity 
went straight through my forearm to the palm of my hand of the 
same arm to the well-grounded rod instead of through my vital organs. 

<The danger comes from the ground wire falling off the end of the rod, then 
<there's a LOT of voltage at the end, it jumps across the arc rod to your 
<hand, then you're gone. 

Well, as I stated in the above paragraph, this is kind of what happened 
to me although the ground wire didn't fall off. I defintely had no desire to 
play with a "Jesus stick" any more after this incident! I was ok, just shook 
up with little red dots on my forearm where the sparks hit it. Thankfully, 
no descernable flesh burns. 

<In my humble opinion, I think that high frequency resonances/effects are 
<insignificant when the end is grounded. Your whole body offers a lot more 
<capacitance (HF coupling) to the coil, than your hand does to the (grounded) 
<end of the arc rod. 

Yep. BTW, my current coil system is a drievn by a 10 kVA pole 
pig, so drawing sparks with a hand-held discharge probe from this 
10 ft spark throwing monster is out of the question. I'd need a 15 
ft. "Jesus stick" to safely do this, too long to hold out with one 
hand and not enough room in my cramped shop. This coil is 
for observation only :-) 

<Have a good one, 

<Justin Hays 
<KC5PNP 
<G-3 #1150 
<Email: pyrotrons-at-aol-dot-com 
<Website: www.hvguy-dot-com 

Sparkin' in Memphis, TN, 
David Rieben