displacement is resisted by the guys as the vector summation
of the forces in the guys. Equal and opposite total
reaction. The tower section is in equilibrium and will not
translate in its plane. Remeber guys only resist tension and
cannot resist a lateral load to their line of action.>>
....but eventually the tower twists enough that guy tenison
tries to pull it back. I KNOW this happens because when
moron's improperly install or guy a tower and the anchors
are not aligned with the point of the tower, the tower gets
all shaky and twisty no matter how tight the guylines are.
This is because the tension of the guylines is trying to
twist the tower, rather than hold it in position.
As the guyline is moved out on torque arm the effective
radius of the tower increases, and rotational movement
decreases enough that it is VERY easy to feel.
It isn't quite true to say guylines don't help keep the
tower from turning. Anyone who has climber a tall tower
with a point base that allows rotation, like an insulated
tower, knows the guylines greatly contribute to rotational
stability. When those needless do-nothing torque arms are
added, the tower becomes much more stable.
The only question I have is if the increase in resistance to
twist translates into higher wind survival ratings, or if
the tower can "twist" so much without contributing to
failure the rating does not change. Of copurse even if the
survival remains the same, I still prefer to NOT have my
tower twist more than necessary.
> In this case the farther away from the center the guy
attachment point is really doesn't help with the torsional
strength the angle between the guy and the line of force of
the torque is what matters.
I don't agree. While the angle remains the same, the lever
distance from center is increased. If you double that
distance, it is a two-fold increase in resistance to twist
for the same increase in guyline tension caused by the
> When you star guy or 6 point guy a tower with a torque arm
mechanism then you have guys that are better aligned to
initally resist the twist from the onset. Therefore this
type of system is better able to resist torsional loadings.
That's certainly true, and you don't need a six point guy.
You can use a three guy anchors and split each guyline into
two ends some distance from the tower. If you keep the angle
small, there is almost no difference at all between six guy
points and three.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
TowerTalk mailing list