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[Towertalk] GS-065: how to center the mast?

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Subject: [Towertalk] GS-065: how to center the mast?
From: (Paul Playford)
Date: Fri, 3 Jan 2003 05:01:58 -0000
I use a similar thrust bearing.  I adjusted mine by loosening the mast clamp
on the rotator and turning the antenna back and forth by hand while
adjusting the centering bolts until the mast rotated around it's own axis.
It helped to mark the 4 bolts, 1,2,3 & 4, so I knew which bolt needed
adjustment.  I started with bolts 1 & 3 slightly loose and adjust 2 & 4,
when I had 2 & 4 right I set the lock nut on 2 and loosened 4 slightly and
then adjusted 1 & 3.  After I had 1 & 3 set I tightened the locknut on 1 and
then snugged up bolts 3 and 4 and then tightened their lock nuts.  Then a
final check to make sure the mast rotated around it's own center and if all
is well tighten the mast clamp on the rotator.  And don't forget the shim in
the rotator so the mast is centered there also.

Now when I have to lower the mast I only loosen bolts 3 & 4 and when I
retighten them the mast is back to it's own center.

de Paul, W8AEF

----- Original Message -----
From: "Roger" <>
To: "towerTalk" <>
Sent: Friday, January 03, 2003 4:37 AM
Subject: [Towertalk] GS-065: how to center the mast?

> TTians,
> Is there any practical way to exactly center a 1 1/2 mast inside an YAESU
> GS-065 thrust bearing while we are unconfortable installing the mast on
> of the tower (65 feet high...)?
> The mast is 1 1/2" (OD is 1.89"), 13 feet long and is pretty straigh. The
> rotor is a HAM-M inside the tower, 6.0 feet below the top plate, which is
> flat 3/16" steel plate.
> I've done some tests on the ground and found that any minor error
> the retaining bolts of the GS-065 causes the mast to turn eccentrically,
> severely forcing the rotor and the thrust bearing.
> Precisely adjusting the retaining bolts has been difficult because:
> - there are two sets of them;
> - the GS-065 has an internal diameter of 2.75" and the mast here is OD
> 1.89" - a big difference in diameters;
> - the adjustment must provide good alignment both on the vertical and
> horizontal planes.
> I think that I will not be able to make a good centering while I am at the
> top of the tower without some kind of tool like a bushing for filling the
> empty space between the mast and the bearing.
> Such a bushing should have to fill all the space (from the top to the
> bottom of the bearing), in order to avoid misalignements both on the
> horizontal plane as well as on the vertical plane. Besides, the bushing
> should have to be sliced in four pieces, to avoid the retaining bolts...
> I took the measures with a caliper rule, made a sketch and ordered the
> bushing from a lathe shop... it came pretty well done... but, to my
> surprise, when I forced down the slices into the clear slots (between mast
> and bearing, between the bolts), they only penetrated half an inch! Then I
> discovered that the GS-065 inside cilindrical surface is irregular. Its
> internal diameter VARIES and has some other irregularities.
> Now what? I've never read anything on this subject, so your advice will be
> very wellcome. To see pictures of the bearing, top plate and bushing,
> please go to
> TIA,
> Roger PY1OL
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