Hang tough & enjoy your tower Charlie!
If it breaks, fix it. Otherwise enjoy it!

Some day I may get brave and post the pictures of my fold over-crank
up mast with the CushCraft A3 beam on it. It waves around in the wind
like a sailboat mast and flexes the I-beam gantry enough to scare the
clueless when it is time to do antenna work.

When mine breaks, I will either fix or replace, just as I have always
done...

My current worries are lightning and ice.

It has only been up about five years, time will tell.

On Wed, 13 Jul 2005 03:43:15 -0700, "Ed Price"
wrote:


"Charlie" wrote in message
...
The images are the same yeah...DUH!!
Since there was no damage.....except perhaps your brain damage.
You don't catch on too fast do you?

--

Charlie
Ham Radio - AD5TH
www.ad5th.com
Deep South 2 Meter SSB Net
www.deepsouthnet.net


Well, this will be my last post on this thread. I think Charlie has burnt
his last shred of credibility by using identical images for "before" and
"after" evidence. I'm sure everyone noted that not even a single tree leaf
was lost during that disaster, so I suppose Charlie could also claim that
his tower is as strong as a leaf, maybe even stronger!

Since Charlie doesn't seem to worry too much about factual evidence, his
request for technical comments must have been posted for entertainment
value, and in that, he certainly has succeeded. Can we look forward to
annual updates posting the same original image, thereby proving that Chuckie
has not only built a strong, but an eternal tower?

"John Ferrell" bravely wrote to "All" (13 Jul 05 14:47:06)
--- on the heady topic of " AD5TH Tower - Storm Damage Photos"

JF From: John Ferrell
JF Xref: aeinews alt.ham-radio.vhf-uhf:8238

JF Hang tough & enjoy your tower Charlie!
JF If it breaks, fix it. Otherwise enjoy it!

JF Some day I may get brave and post the pictures of my fold over-crank
JF up mast with the CushCraft A3 beam on it. It waves around in the wind
JF like a sailboat mast and flexes the I-beam gantry enough to scare the
JF clueless when it is time to do antenna work.

JF When mine breaks, I will either fix or replace, just as I have always
JF done...

JF My current worries are lightning and ice.

JF It has only been up about five years, time will tell.


There is a thing called metal fatigue of which I was abruptly reminded
of this spring. I was raking the lawn as I usually do and the aluminum
handle just snapped in half without any provocation. No way I could
have casually seen it but the rake was some decades old and probably
flexed all it would flex. So there you go, time is against us!

A*s*i*m*o*v

.... Give me that old time religion. Hail, Zeus!

Asimov wrote:
"There is a thing called metal fatigue of which I was strongly reminded
this spring."

Yes. It usually begins with a microscopic crack. The greater the stress,
the shorter the life. Damage is cumulative. It is affected by
temperature and surface finish.

Some metals such as steel and titanium have lower stress limits below
which they are mostlly im,mune to failure from repeated flexing. Other
metals such as aluminum and its alloys have no such immunity and
eventually fail under repeated flexing. In these, designs are kept below
the fatigue threshold for the number of stress cycles expected within
their lives. Or, a lifetime is specified and replacement is required.
Another technique is non-destructive testing to find cracks and the
piece is retired for cause.

Best regards, Richard Harrison, KB5WZI

I rarely get caught with the antenna fully extended when the wind is
gusting.Thank goodness for electric winches!

Crank up masts are an entirely different kind of antenna mount. I
would not bet on it withstanding 110 mph winds in the up position, but
I am betting it will do more than that retracted!

Wednesday, 13 Jul 2005 23:14:08 -500, "Asimov"
wrote:

"John Ferrell" bravely wrote to "All" (13 Jul 05 14:47:06)
--- on the heady topic of " AD5TH Tower - Storm Damage Photos"

JF From: John Ferrell
JF Xref: aeinews alt.ham-radio.vhf-uhf:8238

JF Hang tough & enjoy your tower Charlie!
JF If it breaks, fix it. Otherwise enjoy it!

JF Some day I may get brave and post the pictures of my fold over-crank
JF up mast with the CushCraft A3 beam on it. It waves around in the wind
JF like a sailboat mast and flexes the I-beam gantry enough to scare the
JF clueless when it is time to do antenna work.

JF When mine breaks, I will either fix or replace, just as I have always
JF done...

JF My current worries are lightning and ice.

JF It has only been up about five years, time will tell.


There is a thing called metal fatigue of which I was abruptly reminded
of this spring. I was raking the lawn as I usually do and the aluminum
handle just snapped in half without any provocation. No way I could
have casually seen it but the rake was some decades old and probably
flexed all it would flex. So there you go, time is against us!

A*s*i*m*o*v

... Give me that old time religion. Hail, Zeus!

In all honesty to those that ridiculed the tower and it's associated
riggings etc...I have posted photos of the damage incurred from the
category 4 hurricane Dennis.


According to my map you weren't hit by hurricane Dennis..... maybe a
bit of tropical storm.... maybe.



Ed

http://www.wunderground.com/history/...2/MonthlyHisto
ry.html#calendar

DATE High Avg Gusts Events
9 24 3 59 Rain , Thunderstorm
10 37 8 28 Rain
11 21 13 20 Rain
12 16 2 30 Thunderstorm


Damn! gusts to 59 and they get Federal disaster assistance? Hell, we
had gusts that high in the past couple months on the Oregon coast. Maybe
we ought to appy too?



Ed K7AAT

"Richard Harrison" bravely wrote to "All" (14 Jul 05 12:04:53)
--- on the heady topic of " AD5TH Tower - Storm Damage Photos"

RH From: (Richard Harrison)
RH Xref: aeinews rec.radio.amateur.antenna:34153

RH Some metals such as steel and titanium have lower stress limits below
RH which they are mostlly im,mune to failure from repeated flexing. Other
RH metals such as aluminum and its alloys have no such immunity and
RH eventually fail under repeated flexing. In these, designs are kept
RH below the fatigue threshold for the number of stress cycles expected
RH within their lives. Or, a lifetime is specified and replacement is
RH required. Another technique is non-destructive testing to find cracks
RH and the piece is retired for cause.


How can one estimate stress cycles from a wind load?

A*s*i*m*o*v

.... All the tea in china: 356,000 metric tons.

Asimov wrote:
"Richard Harrison" bravely wrote to "All" (14 Jul 05 12:04:53)
--- on the heady topic of " AD5TH Tower - Storm Damage Photos"

RH From: (Richard Harrison)
RH Xref: aeinews rec.radio.amateur.antenna:34153

RH Some metals such as steel and titanium have lower stress limits below
RH which they are mostlly im,mune to failure from repeated flexing. Other
RH metals such as aluminum and its alloys have no such immunity and
RH eventually fail under repeated flexing. In these, designs are kept
RH below the fatigue threshold for the number of stress cycles expected
RH within their lives. Or, a lifetime is specified and replacement is
RH required. Another technique is non-destructive testing to find cracks
RH and the piece is retired for cause.


How can one estimate stress cycles from a wind load?

A*s*i*m*o*v
Believe it or not, but from historical weather data. Historical wind
profiles do exist. Statistical analysis will yield an 80 percentile, 90
percentile or even 99 percentile probability of all wind being below the
profile limit.

Asimov wrote:
"How can one estimate stress cycles from a wind load?"

Tower failure usually results from a single event or cycle of
overstress.

Radio towers are rated according to the mph or wind load ( pounds per
square foot) they will withstand while carrying all their other loads,
dead or live.

Towers do vibrate in a breeze as any tower climber can affirm. Resonant
frequency depends on construction.

Wind vibration has brought down structures. A famous example is
"Galloping Gertie", a suspension bridge in the western U.S.A.

Deflection is limited in radio towers and elastic limits are not
exceeded. The tower section returns to its original form after each
flexing.

Stress cycles enlarge certain microscopic cracks. Examples are the Comet
airliner. Three aircraft flew apart in mid-air. It was determined that
stress cracks in the angular corners of its windows were enlarged by
pressurization / depressurization cycles. This was fixed by rounded
corners but it was too late. The first jet airliner was scrubbed.

Another example is found in high pressurre gas pipelines. Their internal
pressure cycles and this tends to enlarge microscopic cracks, if any, in
the pipe. Pipes are hydrostatically tested before placed in service (no
energy storage in water as it is incompressible) so a pipe blow out of
water won`t likely hurt a bystander. After the pipe is put in service it
is retested each year.

Radio towers are not usually flexed beyond limits by vibration but come
down due to an accident and / or extreme wind.

Best regards, Richard Harrison, KB5WZI

Yes, the Tacoma Narrows Bridge !

They forgot to design it for torsional forces.
Expensive lesson to learn.

It was rebuilt without the solid sides,
this allows the winds to pass between the
steel members instead of against them.

jake

Richard wrote:

Asimov wrote:
"How can one estimate stress cycles from a wind load?"

Tower failure usually results from a single event or cycle of
overstress.

Radio towers are rated according to the mph or wind load ( pounds per
square foot) they will withstand while carrying all their other loads,
dead or live.

Towers do vibrate in a breeze as any tower climber can affirm. Resonant
frequency depends on construction.

Wind vibration has brought down structures. A famous example is
"Galloping Gertie", a suspension bridge in the western U.S.A.

Deflection is limited in radio towers and elastic limits are not
exceeded. The tower section returns to its original form after each
flexing.

Stress cycles enlarge certain microscopic cracks. Examples are the Comet
airliner. Three aircraft flew apart in mid-air. It was determined that
stress cracks in the angular corners of its windows were enlarged by
pressurization / depressurization cycles. This was fixed by rounded
corners but it was too late. The first jet airliner was scrubbed.

Another example is found in high pressurre gas pipelines. Their internal
pressure cycles and this tends to enlarge microscopic cracks, if any, in
the pipe. Pipes are hydrostatically tested before placed in service (no
energy storage in water as it is incompressible) so a pipe blow out of
water won`t likely hurt a bystander. After the pipe is put in service it
is retested each year.

Radio towers are not usually flexed beyond limits by vibration but come
down due to an accident and / or extreme wind.

Best regards, Richard Harrison, KB5WZI