[TowerTalk] Trust Bearings

[Chris Pedder]

At 01:56 30/12/2003, K4OJ wrote:


>The rotator is capable of withstanding a LOT of downward force - there is 
>a listing of that spec in their manual I guarantee... you probably can put 
>a compact car on it for cripe sake (note seasonal integrity)
>
>The kind of thrust you want to control with the thrust bearing is NOT 
>downward thrust it is lateral (sideways) thrust...
>
>If thrust bearings can keep you antenna mast vertical then all your 
>rotator needs to deal with is providing rotation of it and its antennas...

snip

>To those who use those screws on the side of the Rohn thrust bearing to 
>support the weight of the antenna system while they are changing out a 
>mast - I think you are very much so playing with fire.  the tiny surface 
>area at the end of those three bolts should not be asked to handle support 
>of this heavy mast and its antennas and you could risk losing some fingers 
>or worse.


This does seem to be at odds with the prevailing orthodoxy on the other 
(US) side of the pond, so I am pleased to see so much sense in print. 
Previous posts, from people who should know better, gave me the impression 
that everyone over there tightened the bearing bolts to the extent that the 
entire weight of the mast and antennas was supported by the thrust bearing.

As Jim says, the function of the bearing is to provide lateral support and 
NOT downwards support. It is worth adding that unless you have perfect 
alignment, in practice almost impossible to achieve, attempting to provide 
downward support will increase the likelihood of binding and damage to the 
rotator.

Can we put this to rest once and for all?

Happy New Year.

Chris