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[Towertalk] Wood Mast Bearing

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Subject: [Towertalk] Wood Mast Bearing
From: (Zivney, Terry L.)
Date: Tue, 17 Sep 2002 10:30:25 -0500
I have been told by Mike at M2 that I should have an
additional bearing, or bushing, above my Orion rotor.
I have the flat beacon plate with a thrust bearing at
the top of the tower.  According to Mike, the sideways
thrust created at the rotor probably caused the seal
to fail in the top of the rotor, letting lots of "crud"
into the rotor.  When I replace the rotor, I intend
to take the manufacturer's advice and add a wood
bushing above the rotor.  

My questions are:

The mast is 2.5" OD.  If I use a 2.5" hole saw to
cut a hole in a board, will the wood swell and bind
on the mast?  It seems that the thicker the board,
the more likely this is to be a problem. How thick
should the board be?

What diamter hole saw should I use?  Is pressure treated
lumber (like for outdoor decks) more or less likely
to swell than, say, oak?  

The heavy-duty mast clamps actually bite into the
heavy-walled aluminum mast.   Still, perhaps due
to temperature cycling, over time torsional play
develops at the clamp-mast interface.  The owner's
manual says that the warranty is voided if I pin
the mast.  Of course, the rotor is out of warranty.
Should I pin the mast?  The Orion 2800 is turning
5 elements on 20 with 2 Cushcraft shorty 40 elements
on a 48' boom, plus 5 elements on 10 and 5 on 15 on
a 38' boom.


Terry Zivney, N4TZ/9

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