Date: Tue, 15 Mar 2016 21:03:45 -0500
From: "Jeff AC0C" <keepwalking188@ac0c.com>
To: <TexasRF@aol.com>, <towertalk@contesting.com>, "Grant Saviers"
<grants2@pacbell.net>
Subject: Re: [TowerTalk] [Bulk] Re: MASTS
What is possible in the worst case and what is likely seem two different
things. I've not seen EMT do anything other than just bend (which it does
pretty easily) and buckle (if you really really abuse it).
So while I can imagine a scenario where the beam is bent back and forth by
alternativing massive blasts of wind resulting in a buckle being introduced
on both sides of the mast - eventually causing it to break and the thing
flying off, that seems pretty bizarre. The more likely case is that it will
just bend - and a guy will look out his window and wonder why his beam has a
big tilt that was not there before last night's storm.
73/jeff/ac0c
## Rigid EMT, whether steel or AL, is designed to be bent, in a bender !
The smaller diameter EMT is bent using a hand bender, which is just a
3-4 ft long steel tube with a radius arc trough welded to the end of it.
## On the bigger OD EMT tubing, like the 2-3-4-5 inch OD stuff, we used
hydraulic benders. Even the bigger OD EMT is thin wall material. Its
thin,
so its easily bent into a 45 to 90 deg angle.
## I would not be using EMT for either a mast nor a gin pole. Its paper
thin wall, and low ksi to begin with. Galvanized sched 40 or sched 80
35 ksi water pipe is a helluva lot stronger...and heavier.
## You can ‘test’ the pipe by strapping it to your deck, with a mile of it
hanging off the deck, then applying more and more weight to the far end.
## UST uses sched 80, 46-48 ksi pipe for their tower legs. However,
on mine, they also inserted a 7 ft, 2 inch long machined piece of steel tube
into
the bottom of each section leg, to increase wall thickness.
## Use the correct material for the job, whether gin pole or mast. If the
yagi is
only within 3 ft of the top of the tower, you can use almost anything. The
mast calculator
will tell you at a glance, if you have it correct.
## Local tower installer uses a 2.375 OD, sched 80 Al pipe, for his gin
pole, its
20 ft long. Aprx .202 thick.
Jim VE7RF
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