Re: [TowerTalk] Thrust Bearing Question

[Phil - KB9CRY <kb9cry@comcast.net>]

Jerry Keller wrote:

> Do I understand correctly....that the thrust bearing (a) takes the weight
> off the rotor, Not Really and (b) allows removal of the rotor while leaving the 
> mast
> and antennas in place?  Not Really again Any other purpose(s)?
>
> I have the good fortune to have a tiltover tower, so I can install
> everything while it's horizontal, with no load on the mast. is 1/2" enough
> of a gap to leave in the mast-to-rotor connection?  That's what I do.

> Do I then just tighten
> the thrust bearing set-screws as tight as I can? The set screws only are used
to center the mast in the bearing, they really can't hold any weight.

> Or is there more to it? (My
> thrust bearing didn't come with instructions, and I've never done this
> before.)
>
> Jerry K3BZ
>
>  

I have a 72 ft. tower with a 10 ft heavy wall mast, 5 ft in the tower 
and 5 ft above.  On the mast is a KT34XA and a Ham IV rotator beneath.  
I set the mast in the rotator, bottoming it out.  The rotator can handle 
the weight and many suggest some weight so the bearings in the rotator 
seat and wear evenly.  The thrust bearing is on the tower top plate and 
the set screws merely center the mast withing the bearing.  This is the 
setup without the antenna attached.  Onto the mast, resting on the top 
of the thrust bearing is a stainless steel pipe clamp from McMaster 
Carr.  This was firmly attached and then the antenna mounted onto the 
mast.  So any additional weight from the antenna is partially borne by 
the thrust bearing.  If I have to remove the rotator, which I have, I 
mount a screw jack on the top plate and use an extension block of wood 
to bear up onto the bottom of the antenna's boom to mast plate.  As the 
mast and antenna are jacked up, I attach another clamp at the top of the 
bearing to hold the assembly up.  I then attach a piece of Uni-strut, 
slotted steel channel to the mast below the top plate and up bolt it to 
the tower leg to hold the bottom of the mast in place.  On my new tower 
I've mounted a second rotator plate beneath the top plate and above the 
rotator plate and this will serve this purpose.  I must say that my 
assembly is rather simple since there is only the one antenna on the 
mast, etc.  Capice?  Phil  KB9CRY
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