Sure, just my 2 cents.
Bob Moldashel wrote:
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
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