> I'm not worried about the vibration because it is steel. I did know of
> a fellow with an aluminum tower who lost the whole top 30 feet or
> so of the tower in a mild breeze, because it vibrated and cracked.
Material has nothing to do with it. Steel will fail too, it is the matter of
time, or better to say number of cycles.
To underline the mechanism of failure, it is not from say vibration exceeding
the material strength, it is from cyclical stress, aggravated by grooves,
scratches and it is microscopic failure. In aluminum, material hardens,
crystallizes, fracture starts at the point of surface scratch (or not) and
starts slowly propagating across the cross section of element. Eventually
breaks with clean, sometimes even shiny cut.
The point is, anything mechanical has some resonances somewhere, question is
how and where it is mounted. It starts with tower foundation, tower, guys,
masts, plays in the system, other antennas, rain droplets, owls, lawyers,
etc. Just picture tuning fork and see what affects the tone, same goes for
antenna installation, it is a giant tuning fork, as soon as you hear, see or
feel vibrations or thing singing, go and kill it by dampening (ropes, things)
because sooner or later fracture will come. The thing is that you can't even
see the fatigue fracture in progress, unless you use ultrasonic testing. The
result is piiiinggg... and part just breaks.
Things can vibrate in slight breeze or strong winds, it is just a matter of
finding "happy" resonance point. Just like antenna modeling software, the
mechanical vibration calculation software is not capable of encompassing ALL
variables participating, and therefore fools would rely on it for absolute
answers (I tried and got "burned").
Be suspicious if someone claims that their stuff is vibration free. It ain't
So don't let it zing or vibrate, kill the vibrations and you will have long
lasting antennas. It also does not mean that just sticking rope in the
element fixes everything, you better make sure that that rope in that element
dampens the vibrations, if it doesn't, try different rope (diameter, length,
mass), just remember rope needs room inside of the element to jump and
counteract the vibration of the element.
As far as Force 12 warranty thing with ropes, I don't understand it.