[TowerTalk] TB3 Postmortem

[Grant Saviers]

"Thrust" bearing or rotator, the problem is the same.  Steel bearing 
balls on aluminum are a bad combination for causing fretting corrosion 
and wear.  When there are small motions, the oil film is penetrated and 
the metal to metal contact and electro-chemical forces cause pitting, 
and wear particles, ultimately making the divots.

There are specialty greases made to reduce the problem.  White lithium 
or auto store wheel bearing greases aren't.  At one time HyGain sold an 
ounce container of Rheolube xxx  (Nye lubricants).  The sourcing problem 
I've found is only large package sizes are available and some are fairly 
expensive.

With any grease, the best idea is to move the rotator often enough to 
replenish the oil film between the ball and race.  Each ball should make 
a full rotation.   Generally, all synthetic grease is a better choice as 
it is more stable over time and temperature and doesn't separate.  My 
favorite is Super Lube 21030 PTFE augmented and is widely available.

Grant KZ1W

On 5/4/2019 18:38 PM, K9MA wrote:
> 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
>