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Why U.S. Tower is the Best
Choice for Small Wind
Turbines |
U.S. Tower, Inc. is the best choice
for small wind turbines. Our towers are designed specifically
for small wind turbines and the needs of wind turbine owners.
Our tower designs have a proven track record and have been installed
throughout the U.S. Following are some specific comparisons
with the our Radian/ROHN SSV (TM).
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Larger Tower Spread Reduces
Stress and
Cost |
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Broader tower sections mean lower tower and
foundation stress. For any given tower height, the greater the
distance between the tower legs at the base, the lower the stress
will be on the legs and foundation attachment points. The
image at the right shows the dimensions for the 120' US Tower,
Inc. Model W and 120' Radian/ROHN SSV Tower. The
larger base dimension of our tower is clearly
visible. In fact, the spread dimension of our tower is larger
than the SSV for the base of each 20' section running up the
tower. These larger dimensions result in a lighter weight and
less expensive tower with no sacrifice in strength.
An
additional benefit of a larger distance between tower legs is that
the tower tends to be stiffer. This means that when the
turbine runs in a strong wind the tower tends to move
less. A stiffer tower can also lead to a higher
natural frequency for the structure which can help to reduce
vibration from turbine rotor excitation. Tower vibration can
cause rattling of the braces and noise.
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| Tower Base Spread - 120'
Tower | | |
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Engineered Brace
Attachment |
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| US Tower Engineered Brace
Attachment | | |
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| SSV Tower Top
Section | | |
The US Tower, Inc. engineered brace
attachment design results in more efficient tower assembly and can
save the installer many hours of labor when installing the
tower. A 120' Radian/ROHN SSV (TM) tower uses approximately 426 brace
bolts. The US Tower. Inc. Model W uses 252 brace
bolts. Because two diagonals are attached using a single brace
bolt the number of bolts is nearly halved. When a single brace
is attached using one bolt an engineer would call this "single
shear". When two braces are attached using a single bolt, an
engineer would call this "double shear". A bolt in double
shear can handle twice the load of a bolt in single shear so there
is virtually no difference in strength between the Radian/ROHN SSV
(TM) method and
our design. However, because only a fraction of the number of
bolts is used, The US Tower, Inc. design can save many hours of
expensive labor when assembling the tower. Each bolt not only requires a
nut, but it also requires a lock nut so reducing the number of bolts
saves a great deal of time. Time reduction results in lower
installation cost to the owner.
Another benefit of our
design is a reduction of leg warping. The above image at the
right shows an SSV top tower section being assembled. The
curve in the tower legs is clearly visible. This curve is
caused when the brace tabs are welded to the pipe leg. When
steel is welded and cooled, the steel in the weld area
contracts. Because the opposite side of the pipe is not heated
nearly as much it retains its original shape. Because of the
differential heating, the metal contraction causes the pipe to
bow. When the tower is assembled it is necessary to remove
this bow and straighten the legs. Because the pipe is very
strong and stiff, it is sometimes necessary to use a "come along" or
winch to pull the legs apart so the braces can be installed.
For sections with short braces such as the top section, this can be
difficult and time consuming. The US Tower, Inc. design
uses short individual brace tabs so there is less welding and
substantially less distortion. This results in time and cost
savings for the owner and installer. |
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| All towers are Made in America (100'
Model W, Taunton,
MA) | | |
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Data Supplied with the
permission of U.S.
Tower, Inc.
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