On 5/17/2010 11:05 PM, Brahmangou@aol.com wrote:
> 1. Remove the allen screw
> 2. remove the ball bearings one by one through the hole left by the screw.
> 3. Now the bearing halves will come apart.
> 4. clean the races and ball bearings with brake clean.
>
What are you going to clean out other than powdered Aluminum?
> 5. Apply grease to the races.
>
Not recommended by ROHN who said to run them dry in the old catalog.
> 6. reassemble the halves.
> 7. reinsert the ball bearings.
> 8. Reinsert the allen screw.
> have a beer, all done.
>
> You have to disassemble it. The clunking is the dried out grease in the
> races and has to be cleaned out.
>
There is no grease in the TB-3. They are run dry unless some one other
than the factory put grease in them. I've had many apart. They are
rough to begin. You have steel ball bearings in a cast Aluminum race
which is granular. Were they machined from a billet of good alloy they
would be much smoother but you'd still have steel balls running on soft
Aluminum. Under pressure the balls will cause the Aluminum to flake, or
peel off thin, flat pieces of Aluminum. Far better to have steel on
steel or better yet, use one of the many forms of pillow blocks, or
sleeve bearings.
When you grease one of these, like greasing bolts it reduces the torque
to get a given force. As the balls can move to the side with wind
creating side pressure (which is what thrust bearings are for) the point
contact pressure increases greatly.
I have no proof, but theory tells me a greased thrust bearing with a
hefty wind load will not last as long as one run dry.
The array here has completely destroyed two TB-3's in just a few years.
Imagine how much side thrust this array
http://www.rogerhalstead.com/ham_files/Tower29.htm puts on a bearing at
the top of the tower. The tribander is 2' above the top of the tower,
the 7L 6-meter yagi with 30' boom is about 15 feet above that and the
cross boom with the 144 and 440 stacked pairs is 30' above the top of
the tower.
It's far too much load for the TB-3's so it's going to sleeve bearings
made of DOM and lubricated with Molybdenum Disulphide (BR-2) Grease
(That's Molybdenum Disulphide suspended in a White Lithium base
grease/soap) . That and the top array will be removed so it'll be a 3L
40M3 125 M^2
2' above the top of the tower and then the 7L 6-meter Yagi about 12-15
feet above that. Even with the larger antenna in place of the tribander,
without the VHF/UHF array 30 feet up the side load will be less.
When I finish up the system I'll put up some photos of the bearings and
installation.
>
> 73,
> Marty AB5GU
>
> In a message dated 5/17/2010 7:48:07 P.M. Central Daylight Time,
> wb2aio@yahoo.com writes:
>
> Hi TTers,
> I got that Rohn 45 tilt-over down and home last week. In remarkably good
> condition. Only thing I wondering about is the TB3 thrust bearing and how to
> lubricate it. It turns freely but has a notable rumbling sound and feel to
> it. I notice at the bottom of the inside shaft area where to mast passes
> through, is a recessed Allan head fitting/plug. Would this be the place to
> remove and squirt in some white grease? And then replace the plug?
No, that is the disassemble plug that lets you take the ball bearings out.
73
Roger (K8RI)
>
> Thanks for your guidance,
> Kathy
>
>
>
>
>
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