One of most common thrust bearings is the Rohn TB-3
http://www.texastowers.com/rohntb.htm
You can see that it has three "set" screws.
Without three (or four) the mast would, by definition,
not be centered - how much depends on the diameter of
the mast versus the bearing's inside diameter.
Whether the TB carries any weight depends on how you
set it up. Lots of folks like to "suspend" (via the
TB) the mast just above the point at which it
would "bottom out" on the rotator. This way, should
the rotator need servicing, it can be easily removed.
Often they employ a second rotator shelf with a second
TB between the rotator and the top TB to stabilize the
mast laterally (important when the rotator is pulled).
Others have suggested that the rotator is better off
with some weight on it so that the bearings inside the
rotator operate the way they were designed. In fact,
inside a Tailtwister there are three complete sets of
bearings, each set alone with seemingly more bearing
surface area than that of the TB-3 suggesting it needs
little help in that regard. IMO, it is wrong to
think, from a system perspective, that it is somehow
better that the TB bear all (or nearly all) the
weight, while the rotator bears little or none. But
it probably matters little for durability's sake...
Mike N2MG
K3BZ wrote:
My thrust bearing has only two setscrews... at 90 deg
to each other. That's what led me to think that the
thrust bearing is a weight-carrying device, to take
vertical load off the rotator. Many have told me the
setscrews are for centering the mast.... wouldn't that
take 4 setscrews spaced 90 deg? or 3 at 120 deg?
________________________________________________
PeoplePC: It's for people. And it's just smart.
http://www.peoplepc.com
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|