[TowerTalk] Roof top towers

[K7LXC@aol.com]

In a message dated 00-01-13 10:14:27 EST, DAVED@ctilidar.com writes:

> The GME tower I've got doesn't even have a round hole at the top. It's a
>  square formed by the inside edges of four pieces of 1/8" aluminum angle
>  stock. 

      Which model do you have? I've mostly worked with the 9-footers that 
have a TB plate so you must have a smaller tower.

> The hole is also relatively wide so I'd thought I'd put a thrust
>  bearing there even though the vertical load isn't all that much. My 
question
>  is: what's the best value in thrust bearings? GME want's $90 for the unit
>  that rusted out on John in 18 months. The one I got from Universal towers
>  was $130 and ultra heavy duty. Are there any cheaper ones of decent quality
>  available?

       IMO a TB is superfluous in this scenario. Unless you've got a pretty 
aggressive antenna mast and load, I personally would skip the TB.

     If you really want the best one, the Rohn TB-3 is the only real outdoor 
TB I've seen. The TB-3 is for up to 2"; the TB-4 is for up to 3". The TB-3 
may have too big of a footprint to be mounted on your tower though. I think 
the TB-3 is in the $80 range (I'm guessing).

      Some tower manufacturers provide a machine shop pillow block bearing. 
These are indoor application bearings and have an Allen screw (usually just 
one!) to pin the mast. It rusts and you have to drill it out in order to 
extract the mast. These are NOT suitable for outdoor TB applications. 

Cheers,   Steve   K7LXC

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