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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: (Roger)
Date: Fri, 03 Jan 2003 04:37:08 +0000
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 top 
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 a 
flat 3/16" steel plate.

I've done some tests on the ground and found that any minor error adjusting 
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

Roger PY1OL

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