On 12/10/01 5:26 PM, David Robbins at k1ttt@arrl.net wrote:
>> You probably don't need it. The tapered top section will do the work that
>> a thrust bearing would.
>>
>
>the tapered top doesn't do what a thrust bearing does, put a plate below
>it with the thrust bearing.
For the installation he specified, he doesn't NEED a thrust bearing.
> a thrust bearing holds up the dead weight of the mast
>and
>antennas,
There's some debate about that -- given the construction of your typical
Rohn thrust bearing. It does more to keep the mast straight and keep the
bending stresses off the rotator. The pointy top is more than capable of
doing that.
In any case, he didn't specify a weighty stack of antennas and masts. The
rotator he is using is more than capable of holding the weight of the
stack.
>it also makes service on the rotor easier since you can just
>pull it
>out without having to lift the weight of the mast and antennas off of it.
Several of the Rohn pointy-tops have set screws which can be used to hold
the weight of the mast and antennas while you swap out the rotator. My
25AG4 top does, I cannot remember if the 25AG2 does or not. In any case,
you can use a muffer clamp at the top of the tower to accomplish the same
end.
It wouldn't hurt to use a thrust bearing, but it would cost more and it
wouldn't really do a lot of good.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
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