[TowerTalk] Best mast location? now muliple thrust bearings

[K7LXC at aol.com]

In a message dated 5/15/2010 12:01:22 P.M. Pacific Daylight Time,  
towertalk-request at contesting.com writes:

>  For various reasons (some inherent in bearing  manufacturing tolerances) 
three spaced bearings are almost never done in  machinery - it's just too 
hard to get them/keep them aligned.   

And this is in more precision machinery  than you'll ever find in tower 
components. The purpose of the middle "bearing"  is to capture the mast so that 
you can do a rotator swap on a top-heavy mast  and antenna array. A simple 
plate with a hole in the middle (e.g. AS25G, 45G,  Trylon, etc.) is PLENTY. 
It's not going to go anywhere. Lacking a middle  plate, you can still 
capture the mast with some angle iron and U-bolts. It's  not difficult to 
fabricate and use. 
 
    And I still think that top mounted thrust  bearings are a ham radio old 
wive's tale and not necessary. All you want  to do is hold the mast against 
horizontal wind forces - the vertical forces  can go to the rotator in most 
cases with no problem. 
 
Cheers,
Steve     K7LXC
TOWER TECH -
Professional tower services for hams
and author of UP THE TOWER - The Complete Guide To Tower  Construction
available from _www.championradio.com_ (http://www.championradio.com)  
Cell: 206-890--4188