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[TowerTalk] tower mast installation

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Subject: [TowerTalk] tower mast installation
From: (Frank T. Brady)
Date: Fri, 27 Jun 1997 09:07:42 -0700
Dear refwector fwends:

Just to keep from going bonkers waiting for my new QTH Loan Approval - I've
been drawing some pictures of various tower+mast+stacked yagi configurations. 

I noticed something I don't remember reading about as of yet.

If I have a good rotor (husky no-slip worm gear type) and a heavy load of
antennas on the mast with lots of "twisting moment" - wouldn't the amount of
torque transferred to the tower be almost entirely a function of the mast
length from the tower top to the rotator mounting position?

In other words, the longer the mast run inside the tower, the more the
torque is absorbed by the mast rather than the higher (weaker) portions of
the tower.

If true, and you take it to the extreme just for an example - if your tower
was 'H' feet high and your rotator was mounted on a plate on the concrete
foundation of the tower, and a H+2 foot mast was run up through the tower
with couplings like an oil rig through a lateral load thrust bearings every
ten feet or so and at the top - it seems to me that almost all of the dead
load and twisting moment forces would be supported by the concrete
foundation and the mast - leaving only horizontal forces on the tower.

Of course, whatever limit there might be on the length of the mast couplings
will dictate that the rotor be mounted on a plate in the tower at some
height limit - but in all cases the lower you mount the rotor, the stronger
and wider the tower is at that point - and that would be good - right?

Just curious - if these new CM masts can be welded/coupled into long
sections, it seems the tower strength would be mostly to support the points
at which lateral thrust bearings keep the mast in a straight line.

 Frank - W0ECS

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