"(A)What are the forces that the wind exerts on a tower and
(B)are these forces evenly distributed?"

A. More than you might think!
B. No. Depends on the particular configuration of the tower's load,
and the strength/speed of the wind. Infinitely variable.

You already know that there's no 'good' solution for one set of
guywires. The 'best' solution I've heard so far is an excess of
insurance and a gulible claims adjuster.
'Doc

Thank you all for the information. I knew I could find good"stuff" out
there.
The wind generator (not an antenna) I was planning has limited
information available as to loads. ie. No Flat Plate or FPE numbers.
The only statement is that the tower must take a 200 pound lateral
thrust and not deflect more than six inches with winds of 200 mph. The
Trylon T-200 tower specs. for my maximum wind speed area (from the
chart at their web site),
shows that the T-200 will take a 42 pound lateral thrust at winds of 85
mph.
If 120 mph winds cause the wind generator to exert 200 pounds of
lateral thrust, what speed of the wind will yield the 42 pound maximum
lateral thrust that the tower will hold? Please show your work.

fcrumpler,
Figured as a simple ratio, about 25-30 mph. No idea if
that's accurate...
'Doc

Dear "fcrumpler" no call, no location:

Theoretically, the force produced by moving air impacting on a flat
plate is proportionally to the square of the air's velocity. However, in
the real world where one should appropriately deal with wind gusts and
variability of materials, things are not so simple. Safety factors should
be used. Accommodation for the significant vibration to be caused by your
proposed "wind generator" must be made.

Numbers supplied by some vendors involve no safety factors.

You need to retain a Professional Engineer licensed in your state or
province who is experienced with vertical wind structures. This is
certainly the case if the proposed structure is able to damage other
property or endanger living things.

It is not safe for you to scale the numbers that you have. Too little
information. Too much risk.
Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:

Cecil, !5DXP wrote:
"According to Rohn, a single set of guy wires limits the tower to 40 -
feet maximum height - sorry about that."

Well, it depends on the Model No. and how you will load the tower. It is
best to follow thw manufacturer`s recommendations to the letter.

There is a length that you can stack which will endure without guys in
most cases. Towers usually come in 20-ft. sections. Often one or two
sections is all it is safe to use without guys. Windloading the tower is
expected to withstand, often determines space between guy points.

Wind exerts force on the tower and its appurtences, often expressed in a
sum of pounds per square foot on the area facing the wind.. Resistance
(drag) produces a differential pressure on items in the wind. Force is
proportional to the projected area in the wind, and varies with the
shape and roughness of the item in the wind. Windload on a tower is not
uniform. The wind usually blows harder at higher altitudes. Wind tries
to turn the tower over but until something yields, it is in equilibrium
and the summation of of forces about the base of the tower is zero. The
summation of torques is zero.

Guywires exert force in yje only way they can. They have tension in the
direction of the wire. This may be resolved into vertical and horizontal
components. This prevents movement and increases base loading when the
wind blows.

Pressure on items in the wind (pounds per square feet) is a function of
the square of the wind velocity (miles per jour).

One formula considered useful is named "Ensewiler" which is said to
give:
22.5 psf = 85 MPH
45 psf = 134MPH
60 psf = 155MPH
75 psf = 173MPH

Best regards, Richard Harrison, KB5WZI