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
Scott Reed wrote:
Yep, found that mount. Couple bucks less and Electro-Comm, too.
I am looking at Schedule 40 steel pipe, 21' from a local guy. Almost
$100. Where do you find aluminum, and about how much for 20'?
Scott Reed
Owner
NewWays
Wireless Networking
Network Design, Installation and Administration
www.nwwnet.net <http://www.nwwnet.net/>
The season is Christmas, not X-mas, not the holiday, but Christmas,
because
Christ was born to provide salvation to all who will believe!
*---------- Original Message -----------*
From: Bob Moldashel <[EMAIL PROTECTED]>
To: WISPA General List <[email protected]>
Sent: Wed, 28 Dec 2005 21:51:26 -0500
Subject: Re: [WISPA] Utility pole mount
> Scott Reed wrote:
>
> > I like that. Is 2 ft enough space to hold the other 18 ft? I would
> > have expected 3ft or more, but the more pipe in the air the better.
> >
> > Scott Reed
> > Owner
> > NewWays
> > Wireless Networking
> > Network Design, Installation and Administration
> > www.nwwnet.net <http://www.nwwnet.net/> <http://www.nwwnet.net/>
> >
>
> Ahhh...No. 2' is not enough. My rule of thumb is 15-20%.
>
> I know the discussion is on pole mounts......Here is my suggestion.....
>
> First you need a mount:
>
http://www.tessco.com/products/displayProductInfo.do?sku=15433&eventPage=1
<http://www.tessco.com/products/displayProductInfo.do?sku=15433&eventPage=1>
>
> Then you can get a length of thick wall aluminum pipe 2" x ? This
> comes in 20', 24' and 40' lengths here.
>
> Mount and smile. Ready to go. About $ 225 total... Real
mounting...No
> game playing. No "making it work".
>
> -B-
>
> --
> Bob Moldashel
> Lakeland Communications, Inc.
> Broadband Deployment Group
> 1350 Lincoln Avenue
> Holbrook, New York 11741 USA
> 800-479-9195 Toll Free US & Canada
> 631-585-5558 Fax
> 516-551-1131 Cell
>
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