In addition to Steve's cautions, I would add that crank ups depend on
the hoist cable strength to stay elevated (unless a locking tower which
is designed to be guyed when locked). Guys add a lot of downforce on
the hoist cable, both from the preload, and then several times more at
max wind velocity. So check out the design calcs for all cable loads
against its rated break strength. Sheave and winch winding diameters
also affect the break strength as do the sheave axles.
All together, the PE calcs I have would strongly advise against adding
guys to my HDX589. If the analysis shows the bottom section or anchor
system is most likely to fail first, then I don't think there is much
downside to adding guys to it, since the ground level wind field
probably won't add a lot of tension to those guys.
Grant KZ1W
On 4/11/2019 8:45 AM, k7lxc--- via TowerTalk wrote:
I made a lot of simulations for various wind conditions and found out that
my tower, unguyed, was going to safe sustain wind up to 85 mph with a surface area
of 20 sqft. As the wind, frequently, reaches that value where I live, on a hilltop
in Southern Vermont, I simulated the possibility of adding guy wires. That increased
the safe sustained value to 135 mph. So, against all advice, I have a guyed tower
that can be unguyed.
I don't have a problem with guying a self-supporting tower IF the guys
have very little tension on them (less than 40 or so pounds). Tower strength comes from
the legs - the more tension you put on the guy wires, the more compression you put on the
legs thus decreasing the capacity of the legs to support the tower. With a small amount
of tension, you're not trying to hold up the tower - just restrain it from wind forces.
With little or no tension, you could be subject to wind slamming - a violent and
potentially fatal condition.
What is a guyed tower that can be unguyed per your comments above? I'm not
sure what that means.
I don't know where this misnomer comes from that a self-supported should be
weaker if you added guy wires. Maybe somebody can tell me. I understand if the guy
wires have a very steep angle the load on the tower will increase but that is not
the case with mine.
It's not weaker - it just has potentially less capacity.
Cheers,Steve K7LXCTOWER TECH -Professional tower services for amateur and
commercial
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