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Vertical Mast

To: <>
Subject: Vertical Mast
From: (
Date: Wed, 9 Oct 1996 12:35:28 -0400
In a message dated 96-10-04 13:27:47 EDT, you write:

>What's the best way to ensure a mast is vertical?  My plan is to use a
>level and go around the mast, tweaking for the vertical position by
>adjusting the thrust bearing.  The manual for the rotator talks about the
>"eccentricity tolerance" but does not address how to minimize the
>eccentricity. The manual for the thrust bearing is in Japanese! (?)
Hi, Jay --

    I didn't see any posts come across addressing you question so I'll shoot
you out something.  I wouldn't worry too much about having the mast vertical.
 What you really want is to have the rotator/mast/thrust bearing aligned with
each other.  If your tower is out of plumb and you make the mast vertical,
you could be causing a binding problem.  Assuming of course that your tower
is plumb (spec is + or - 3 inches in 100 feet) and you're using factory
supplied and pre-drilled tower shelves and plates and THEY'RE plumb, I think
the only thing you have to worry about is having the mast centered on the
rotator.  With a Hy-Gain, you just use a 2 inch mast and tighten it up.  For
a Japanese rotator or one using a 2-piece mast clamp, you can use the marks
on the top of the rotator.  You want each clamp to be on the same mark.  A
way you can check this is to see if the clamp bolt slots are in approximately
the same relative position.  If one is way off, it won't be in the same
position as the others.  You can also get a good idea by running your fingers
over the ends of the mast clamp-rotator plate junction; they should have the
same proportion for each clamp.  Do you have to re-drill the tower plate for
the JA thrust bearing mounting holes?  That could produce some eccentricity
if it is off-center.

     When you think you're done and you're still on the tower, have someone
on the ground with the control box turn it through a couple of 360 degree
rotations.  Watch the installation as it turns and you'll be able to see and
hear how good or bad it is.  A little eccentricity is normal and as long as
the rotator doesn't slow down or bind too badly, it should be okay.
 Sometimes you take out bind in one area and it shows up someplace else.

73 and I hope this helps,  Steve  K7LXC

   TOWER TECH -- professional tower supplies and services for amateurs

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