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[TowerTalk] Re: Long mast, intermediate bearing

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Subject: [TowerTalk] Re: Long mast, intermediate bearing
From: (Matt Kolb)
Date: Mon, 06 Apr 1998 13:31:34 -0700
> Webster sez:
>   thrust bearing, Mach. a bearing designed to absorb thrusts parallel to
>   the axis of revolution.
> I interpret this to mean the "weight" of the mast/antenna.
> 73,
> Jon
The weight of the antenna/mast is perpendicular to the axis of
revolution, not parallel.  The parallel forces are those left to right
or "lateral" in nature.  Thus I believe that Webster has it right in
this case in indicating that the thrust bearing's purpose is to limit
the sideways thrust (better known as slop) thus eliminating the binding
effects of the mast on members it must pass through.  If you have a long
mast sticking out of a pointy top, imagine the friction as your rotor
tries to turn the antenna in high winds to where the mast is rubbing the
inside of the pointy pipe.  The flattop with thrust bearing was designed
to eliminate such a binding situation.  Unless you are looking at huge
arrays of 40m beams or greater, the odds of you overloading your
rotator's vertical weight capacity is pretty slim. Let the rotator and
the bearing both do their respective jobs for which they were designed.

Matt Kolb, NM9H

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