Hi Jack

That is probably true and the reason the project was abandoned!

Step Leaders can form and reach up from almost any grounded source,
but more often than not, the eventual discharge causes no appreciable
harm.

The small study I helped with was some 25 or 30 years ago and I really
don't remember too much of the details about it, other than apparent
physical damage was almost always within our red zones.

I don't think the spheres we were using were anywhere near 300 feet in
diameter, if I recall they were like 36 feet, 72 feet and 108 feet.
Regardless of the size of the ball, on most structures the red zone
was in the same place. Only on very tall structures would the red
zones be more than one zone at varying heights along the structure.

I do remember our accuracy for the town we modeled was very high over
90%, but then too, we had a LOT of red zones as well since we were
using like 5 different sizes of balls to mark these zones.

You also have to remember, back when I was in Skewl, the correct
answer to a question was considered WRONG. And the wrong answer
correct. EG: Number of Elements, the WRONG answer the skewl demanded
as correct was 45 Elements NO MORE NO LESS, and you had better not
forget the NO MORE NO LESS phrase!
There are 92 Natural Elements and about 114 Elements Maybe More.
But if you put that on your exam, you were graded as the answer being
WRONG.

MOST of the stuff I learned in skewl was Erroneous in Real Life, I
don't doubt that our lightning experiments were also!

TTUL
Gary

"Gary V. Deutschmann, Sr." wrote
Hi Jack

That is probably true and the reason the project was abandoned!

Step Leaders can form and reach up from almost any grounded source,
but more often than not, the eventual discharge causes no appreciable
harm.
TTUL
Gary

Hi Gary, I understand completely. Lightning attaching to an object is not
where the damage comes from, it's the way the damn stuff *leaves* that
causes the problems! ;-)

Notwithstanding your hopefully unique experience where water in a tower leg
was superheated. Some private company specifications call for an air
terminal and grounding electrode conductors on all their towers, including
at each fixture (antenna) attachment point.. Even most tower manufacturers
call this unnecessary, recommending bonding of air terminals (if used) to
the tower legs only. But I suppose that a grounding electrode conductor from
tower-top to ground *could* have prevented your loss, by reducing some of
the current in the tower legs in favor of the heavy GEC coming down
alongside them.

Best regards,

Jack

Hi Jack

The damage to my tower was directly my own fault.

It was of tubular aluminum construction and DID have drain holes in
the legs so they could not readily fill with water.

I made two very dumb mistakes that contributed to the damage.
The first was using one of these holes for attaching the ground rod
strap to the tower, instead of the clamp that WAS provided for the
purpose.
And the second was backfilling over these holes when a new air
conditioner was installed, and a small retaining wall placed between
the steps, tower and A/C unit.

Had there not been water in the leg of the tower, it would have taken
the hit unscathed.

There was a grounding strap on each leg of the tower at the unions
between sections, these were installed properly or should I say, per
the instructions, hi hi.....

Ironic, I was way overboard on everything else as far as protection
from lightning. Had a copper bulkhead on the house, grounded of
course. All coax shields were grounded first to the bulkhead and then
through gas bottles which were also grounded. The station equipment
was ground, even equipment in plastic cases I installed a ground to
the chassis and they were grounded too.

I did everything right except I forgot about one old abandoned rotor
cable that was coiled up behind 4 file cabinets, out of sight out of
mind. Luck of the Irish, the day I took the hit, I had sparks flying
all over my shack. My pooch who was young then, terrified of thunder,
came to my office to be by me for protection, just when the sparks
began to fly. He never came into my office ever again!
The only damage from this rotor wire was a few burn marks on the back
of the file cabinets. The tower obviously took the main hit.

As an aside. A tree outside my mothers home was struck by lighting.
Split that sucker almost all the way to the ground. Dad bolted it
back together with threaded rods and it survived, it's still living
too.
But the reason I brought it up is that INSIDE the house, sparks danced
all over my mothers stainless steel kitchen sink, made burn marks and
pits all over it. We later discovered the aerator on her faucet spout
was fused to the spout and it too was severely burned and pitted.

Back then all the waste lines to the sink were metal, not PVC as used
today and all the water lines are copper. So I assume both the sink
and the faucet were grounded.

Makes one wonder how lightning got inside the house and bounced around
in her sink and did enough damage that the sink and faucet had to be
replaced.

TTUL
Gary

Hi Gary,

I did everything right except I forgot about one old abandoned rotor
cable that was coiled up behind 4 file cabinets, out of sight out of
mind. Luck of the Irish, the day I took the hit, I had sparks flying
all over my shack. My pooch who was young then, terrified of thunder,
came to my office to be by me for protection, just when the sparks
began to fly. He never came into my office ever again!
The only damage from this rotor wire was a few burn marks on the back
of the file cabinets. The tower obviously took the main hit.

A friend in Mobile, AL had several station equipments damaged this summer
when protection was presumed to be "complete". Old cabling on the floor
behind equipment racks was inductively charged and arced over to the
equipment and computers, defeating the extensive surge protection installed.
I had considered this a serious enugh problem to include it in a warning on
my web page, and he was of course furious with himself about this since we
had previously talked about it. This is also what I mean by the statement
that lightning finds and exploits the weak parts of a system.

As an aside. A tree outside my mothers home was struck by lighting.
Split that sucker almost all the way to the ground. Dad bolted it
back together with threaded rods and it survived, it's still living
too.
But the reason I brought it up is that INSIDE the house, sparks danced
all over my mothers stainless steel kitchen sink, made burn marks and
pits all over it. We later discovered the aerator on her faucet spout
was fused to the spout and it too was severely burned and pitted.

Back then all the waste lines to the sink were metal, not PVC as used
today and all the water lines are copper. So I assume both the sink
and the faucet were grounded.

Makes one wonder how lightning got inside the house and bounced around
in her sink and did enough damage that the sink and faucet had to be
replaced.

Could be either from an older home's cold water pipe grounding, or EMI from
the nearby strike. The former is more likely, when ground becomes saturated
with HV from a nearby strike, it raises the potential of everything
connected to it. Nowadays this is called "GPR" or Ground Potental Rise.
Possibly one of the biggest causes of damage to stations that are otherwise
"protected".


TTUL
Gary


Cheers,

Jack

Hi Jack

That was probably the cause!

I figured the sink itself was at one ground potential and the faucet
at another which caused the arcing.

Of course, the way mom described it, one would think the whole sink
was ablaze.
Even back then I thought of possibly a single drop of hot metal
(probably from the aerator) and how that is what probably bounced
around in the sink sparking all over the place. Like dropped hot
metal when your welding goes all over the place.

Speaking of differing ground potentials. I think the wierdest thing I
ever saw was when my step-son was taking me through the automated
welding section of a body assembly plant for cars.

A line of steel platforms bolted to a steel floor framework, between
two of the platforms (about 2 to 3 inches apart) there was an
occasional arc that occurred when the machines on each both stopped at
the same time.

Don't know if you remember the old vacuum powered windshield wipers
that operated independent of each other. Every once in awhile they
would be in sync for a few wipes.
When these welders came into sync they hummed really loud and when the
sync broke is when the arc would jump between their two stands.

I thought it was interesting!

TTUL
Gary

On 21 Oct 2004 10:49:37 EDT, am (Gary V.
Deutschmann, Sr.) wrote:

As an aside. A tree outside my mothers home was struck by lighting.
Split that sucker almost all the way to the ground. Dad bolted it
back together with threaded rods and it survived, it's still living
too.

Hi Gary,

Sounds like this was from the 1950s era when fathers were omnipotent.

73's
Richard Clark, KB7QHC

Hi Richard

Are you insinuating that a tree struck by lightning cannot live after
being electrocuted?

Although not logical, since the sap turning to steam is more than
likely what split the tree in the first place. The path to ground
could have been less than 1/4 inch wide on opposing sides of the tree.

Nonetheless, the tree is still standing. It does have some strange
areas of bulging bark where the crack used to be.

I don't remember the exact year of the strike, but it was after 1968
and before 1972 and now this tree is the larger of the pair in moms
backyard. It's immune system must have been damaged, because it has
suffered from galls ever since shortly after it was split.

Now, as far as bolting trees back together using threaded rods, this
is not uncommon at all. The forked maple tree in my own front yard at
my St. Louis QTH was bolted together in two places to keep the two
trunks from spreading further as the tree grew. It worked!
A cedar tree in my backyard that split during an ice storm was mended
the same way at the same QTH. On this tree you can still see a part
of some of the rods that were used.

It only takes about 3 to 4 years for the large washer and nut to be
covered with bark and depending upon the gap where the rods were
placed, they may be visible for decades or covered in short order.

TTUL
Gary

On 22 Oct 2004 09:51:40 EDT, am (Gary V.
Deutschmann, Sr.) wrote:

Are you insinuating that a tree struck by lightning cannot live after
being electrocuted?

C'Mon Gary,

It was a commendation.

73's
Richard Clark, KB7QHC

Hi Richard

OK, I'll take it that way!

YOU didn't know my father though, if it wasn't the way great grandpa
did it, it wasn't done right, hi hi.....

TTUL
Gary