Or you could take someone's word for it that has done it probably 40+
times without issue....
:-)
-B-
Jason wrote:
List,
As a Mechanical Engineer (non-PE), there are 2 obvious failure
modes. First, there is the folding of the mast at the top bolt/mount.
This is affected by the length of unsupported mast above the pole, the
ridigity of the mast material, and the size of the hole you drill into
it to mount it against the pole (so use a mount and don't drill a hole
through it). This failure mode is not affected by the amount of
overlap. The other failure mode is that the bolts/mounts are
broken/torn from the pole. This IS affected by the amount of
overlap. As long as your hardware is strong, the most likely failure
will be the buckling one. Once the strength of the mount setup
exceeds the strength that it takes to fold the mast over, it will
always fail by folding over. So at this point increasing the amount
of overlap does nothing. This is especially true for very long,
slender masts, and even more true for light gauge aluminum tube.
Because there are so many variables, I propose that you do a quick
test. Take a piece of your mast material and mount it to a section of
a power pole, cross tie, tree stump - whatever you think is a
reasonable model of the final version. Then try to bend the pole over
with a come-along, drive your car/tractor over it, jump up and down on
it - any reasonable contraption that mimics the bending effect of the
wind. Don't brace or otherwise touch the mount area of the setup to
avoid skewing the test. Also, do this in a direction that pulls or
pushes the mast away from the pole to stress the mounts to the max.
Then you should clearly see what the weak point in your system is and
have a qualitative idea of what it can handle. If it folds the mast
over, your hardware and overlap are probably fine. Disclaimer: I can
not be held responsible for your execution of this concept/test.
Maybe execution is not a good way to put it...
Jason Wallace
--
Bob Moldashel
Lakeland Communications, Inc.
Broadband Deployment Group
1350 Lincoln Avenue
Holbrook, New York 11741 USA
800-479-9195 Toll Free US & Canada
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516-551-1131 Cell
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