[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [TCML] Extremely LARGE spark. 2

gary350@xxxxxxxxxxxxx wrote:
I grew up on a farm in the planes states everyone had lightning rods
on their house and barn.  The cable from the roof to ground was a
5/8" diameter braided wire.  It looked like about 10 wires each wire
about 1/16" diameter braided into a hollow tube shape.  Lightning
rods were spaced about 10 ft apart on the roof.  The cable ran right
down the center of the roof and down both ends of the house attached
to a ground rod on each end of the house.  Faraday cage is what makes
it work.  The barn also had the same lightning rods setup.  I
remember seeing lightning strike the barn once the cables light up
like a white laser bean for a split second. After the storm had
passed I ran to the barn expecting the cables to be melted or
something but they looked fine no different then before the storm.
The weathered copper was still green looking like before.

I think 1/2" copper plumber tubing will work for lightning rods and
cable grounds. I am going to put copper tubing on my roof with a T
fitting every 10 ft.  I will mount the T straight up with a 3 ft
section of copper tubing sticking straight up from each T.  The 3 ft
pieces will be my lightning rods.  I can run the copper tubing down
the side of the house to an earth ground.

Hi Gary,

I'm sorry to hear your house got hit, but thankfully nobody was injured and your house survived. Many years ago, what was apparently a single "super" bolt of positive lightning hit a house about a block away from ours. It sounded like a bomb going off, with echoes of heavy rumbling thunder lasting for at least 15 seconds afterwards. The occupants were away on a weekend trip at the time, and the bolt apparently ignited numerous simultaneous fires inside the house. The house was fully engulfed by the time the firefighters got there, and it burned to the ground.

Re: your proposed lightning protection system:
When passing high currents (10's - 100's of kA), thin hollow conductors can collapse from magnetic forces. An example of this effect due to an estimated 80+ kA current from a positive lightning strike can be seen in the following report. The strike apparently passed through the metal aileron control hardware of a glider, causing the glider to partially disintegrate and crash. Fortunately the pilot and student both had parachutes and survived. Of interest during an analysis of the wreckage was a 16 mm diam x 1 mm thick aluminum tube that was crushed from the magnetic fields associated with the lightning current (figures 8c-8e):

http://tinyurl.com/3wpjab  (pictures)
http://tinyurl.com/2fymlb  (entire report)

Thick wall (K) "hard" copper tubing will be significantly more resistant to collapse than soft copper tube or thinner (M or L) pipe. However, you may want to reconsider using a "roll your own" lightning protection system, even though it may work in theory and practice. You will likely be violating state and local building codes if your equipment or installation technique do not comply with National Fire Protection Association (NFPA 780) standards. The practical impact is that your home owner's insurance company may refuse to cover ANY future lightning-related damage, effectively leaving you uninsured against future events.

We specialize in UNIQUE items! Coins shrunk by huge
magnetic fields, Lichtenberg Figures (our "Captured
Lightning") and out of print technical Books. Visit
Stoneridge Engineering at http://www.teslamania.com
Tesla mailing list