[TowerTalk] Thrust Bearing

[Gary - AB9M]

The reality is that a "thrust bearing" like the ones sold by Rohn really 
don't need lubrication for one RPM and typical downward antenna loads.  As 
long as there is a downward load on a "dry" TB3 or TB4 and it is rotated 
periodically, the balls will stay round enough and the upper and lower races 
will stay clean enough to provide years of service. Its when you add grease, 
dirt, and water, then park the rotor / beam at one heading for months that 
you shorten the life or destroy a Rohn type thrust bearing.

You can use more expensive greased trust bearings designed for other 
applications, but they typically need additional protection from the 
elements in order to prevent premature failures. If you are providing radial 
force bearing protection, that can be accomplished with a hard wood split 
board.

73 & DX,

Gary - AB9M

-----Original Message----- 
From: Wilson
Sent: Monday, June 08, 2015 1:43 PM
To: towertalk
Subject: [TowerTalk] Thrust Bearing

There are lots of kinds of thrust bearings, including the ones on the front 
wheels of cars, which are for a combination thrust/radial loads.
The pillow blocks with ball bearings are for minimal thrust loads and will 
wear rapidly.

http://www.bearingson.com/Category/4-bolt_flanges/cast_iron_4-bolt_flanges/ucf_series/default.asp?page=2&SortType=0


Here are some true thrust bearings:
http://www.timken.com/en-Us/products/bearings/productlist/roller/thrust/Cylindrical/Pages/TP.aspx#

You can quickly recognize a ball thrust bearing, at least many of them, 
because their outer circumference is split, so you see the balls when you 
look in radially.
Think of two big washers, with balls between, like the ball race in your 
rotator.

http://en.wikipedia.org/wiki/Thrust_bearing

I think the term “thrust bearing” is widely misused.  Thrust is parallel to 
the axis of the mast.  A thrust bearing carries the weight of the mast and 
antenna.
Many top bearings are just for radial force, the side loads caused by wind, 
unbalance.

WL
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