[TowerTalk] Re: Long mast, intermediate bearing

[nm9h@ctnet.net (Matt Kolb)]

Robert Hummel wrote:

> Matt -- Are you confusing the plane of revolution with the axis of
> revolution? The axis of revolution is coincident with and (hopefully)
> concentric with the mast. Same for the thrust bearing. The axis that the
> ball bearings revolve around runs through the center of the bearing,
> perpendicular to the plane of its revolution.


Oh so obviously correct!!  My error exactly. Pardon my tunnel vision on
this subject as I really meant to express that IMHO the primary forces
that I am trying to counteract with the use of the bearing is the
lateral forces presented by the wind pushing my mast to one side in
whatever I use to support it at the top.  This binding effect that would
occur on, for instance, a pointy top tube are limited (yes not
eliminated) by the smoother surface of ball bearings in the bearing.
These are the forces that are indeed perpendicular to the axis of
rotation that I so crudely misinterpreted. Even your smaller rotators (I
am looking at the Yaesu G-800 manual as I speak) will easily handle 400
lbs of vertical load while they will handle very little in lateral
binding on the mast before they crap out.  The centering effect as well
as the ball bearings make sure that the only pressures seen by the
rotator are those of a purely vertical load....something that they
appear to be designed to handle, hence the vertical load rating.

Thanks to all who nicely pointed to my geometrical error.  What worries
me is a couple direct messages I received that were nothing short of
insulting and purely bad natured. I sure hope these guys are not sending
messages like this to those guys coming here asking about such things as
20 foot water pipe masts and 40m beams on their TV towers.  Messages of
this type are counterproductive to the exchange of quality information 
and investigative thought.  Those who are made to fear bringing forth a
though or idea are not likely to be back and learn that their plans for
the 70 foot of self supporting 20G is a bad idea.

I think my geometry skills were clouded by the lactic acid buildup from
the last two days of sunup to sundown work on my tower! HI!

73 de Matt NM9H



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