[TowerTalk] TB3 Postmortem

[K9MA]

True, but the rotator distributes the load among a much larger number of 
ball bearings. The shape of the races in the TB3 make it clear it was 
designed primarily for radial loads, not axial.  Also, an "in tower" 
rotator can be removed without taking the whole antenna system down.

Another thought occurred to me: With the thrust bearing bolts tightened 
down, the system is overconstrained. That means that very high stresses 
could occur if the two bearings systems aren't perfectly true as they 
fight each other.

73,
Scott K9MA


On 5/5/2019 06:46, mike repinski via TowerTalk wrote:
>   Then the rotator gets the little marks. Can't win.
>   
>   
> -----Original Message-----
> From: K9MA <k9ma at sdellington.us>
> To: towertalk <towertalk at contesting.com>
> Sent: Sat, May 4, 2019 9:39 pm
> Subject: [TowerTalk] TB3 Postmortem
>
> After nearly 30 years of holding up my TH7 and D40, the thrust bearing
> was pretty rough. The T2X never had any trouble turning it, but I took
> it apart to see what was going on. I found the surfaces of the two
> aluminum pieces deeply indented by the ball bearings. It's scrap metal
> now, but I wonder if the long periods I left the antenna in one position
> might have made things worse. Would it have helped to just turn it once
> a week or so? Or is such failure inevitable? After all, once the
> bearings create the slightest indentation, they're going to always
> settle into those positions, making them worse. I suppose one could
> periodically take it down and smooth out the surfaces, but who is going
> to bother with that? It lasted almost 30 years, so I got my money's worth.
>
> Another possibility: Would it be better to leave the bearing set screws
> slightly loose, so the rotator takes the vertical load?
>
> 73,
>
> Scott K9MA
>

-- 
Scott  K9MA

k9ma at sdellington.us