[TowerTalk] TB3 Thrust Bearing

[W2RU - Bud Hippisley]

Bruce Ferratt wrote:
> Hello and thank you for letting me post a few questions.
> Can someone tell me if a Rohn TB-3 thrust bearing will close/clamp down on a 1 1/4" aluminum mast pipe?

Well, I would never use an aluminum mast for rotating ANYthing, but 
that's your choice.

I don't think the TB-3 will go down to 1-1/4" mast with the stock set 
screws.  When the ends of my set screws are flush with the 2" interior 
wall of the thrust bearing, they have no more than another 1/4" of 
possible travel before the head of the set screw hits the exterior 
wall.  If  I drew my picture of your mast in a TB-3 properly, you will 
need an absolute minimum of 3/8" travel for all three set screws, which 
is 50% more than the set screws on my TB-3 will allow.

Now, it's possible that Rohn has changed the length of the set screws 
over the years, but that's the size of the ones on my old TB-3.

In addition, since you specified aluminum, you'll need even longer set 
screws because your set screws will probably go INTO the mast a little 
bit....and a little bit....and a little bit....

Bud, W2RU