[TowerTalk] Where to get thrust bearing?

[Stan Griffiths]

>My question, when I get the rotor back, I want to get a thrust bearing
>bracket to help handle the weight of my Cushcraft A3S in the HD73.  Where is
>best place to obtain a ready made thrust bearing bracket for Rohn 20G?
>
>73 
>Harvey KM4JA

If it is really Rohn 20G, it is already overloaded since that tower is for
TV antennas and that's about all.  A thrust bearing won't help you make the
tower stronger which is a serious problem for you.

On the other hand, if you meant 25G instead of 20G, maybe there is hope.
There is a flat top section already drilled for a thrust bearing (25AG4).
There is also a "Bearing/Accessory Shelf" (BAS25G) which is a short (about 2
feet) top section that has a flat plate on top (like the 25AG4) for a
bearing and a rotator plate welded in 18 inches or so below the top bearing
plate.  There is also a Short flat top (BPL25G) Which is a top plate for a
bearing for a regular tower section.

If you want to put the thrust bearing any place on 25G tower other than on a
flat plate on the very top, there is no ready-made shelf for that, that I am
aware of.  You can always drill a rotator shelf with the correct hole
pattern for the thrust bearing you want to use, but you may still have a
problem installing it since Rohn rotator shelves will only go into a 25G
section where there are no diagonal braces and this is where you generally
have to install your rotator.

On one of my towers (25G), I have a pipe top with a rotator shelf drilled
for a thrust bearing and mounted a couple of feet below the top where the
rotator usually goes.  The rotator is mounted on another shelf about 8 feet
further down where the top section joins the section below it and there are
no diagonals for about 5 inches.  I have a 6 element 15 meter beam at the
tower top and a 5 element 10 meter beam about 10 feet above the the 15.  My
mast is 18.5 feet long.

Stan  w7ni@teleport.com


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