[TowerTalk] Thrust bearings

[K8RI]

On 3/2/2013 10:14 PM, Grant Saviers wrote:
> One of the worst wear environments for a ball bearing is for it to have
> small oscillatory motions.  As in a rotator infrequently used and
> subject to wind oscillations.  This breaks down the oil film and starts
> fretting corrosion/wear.

Except ROHN TB bearings run dry

As the aluminum appears to be a soft, cast nodular material, it wears a 
bit differently.  The race material is far softer than the  steel balls 
and forms, flat and very thin aluminum flakes. It looks like a dull 
white powder, that is quite slippery to the touch.

Due to the shape of the races and difference in material hardness, once 
you reach the load limit this flaking action proceeds rapidly.  With my 
badly overloaded installation I could only get a couple of years out of 
TB 3's and 4's.

73

Roger  (K8RI)


  When you see the dimples in the races or flat
> spots on the balls it is time for a major fix.  The rotary actuator disk
> drive guys have struggled with this problem forever and use $$$
> lubricants to reduce the problem (and the drive micro code now and then
> runs the actuator full stroke).
>
> If it is possible have occasional rotation to mostly rotate each ball,
> then the oil film is re-established.  That means running the rotator end
> to end  a few times a month.
>
> A race weld filling plus lathe work is a tough project, I got by in
> rebuilding a used Yaseu 2800 with dimples by wet sanding the races and
> replacing the balls with stainless ones and it seems to work ok so far
> (1.5 years).
>
> Grant KZ1W
>
>
> On 3/2/2013 9:40 AM, Ro Grrr wrote:
>> Jim Lux wrote about:
>> Re:Thrust bearings
>> There's no wear without motion.
>>
>>
>> I write:
>> Jim, while I agree with you on this item, I had a tower up years ago
>> that had a TH3 on top of a KR2000 rotor. I was qrt for several years
>> and never gave it any thought. Eventually the tower was taken down in
>> a storm and I simply saved the usable remnants until I moved to my new
>> qth.
>> I decided to put up the tower at the new place and noticed that the
>> TB3 did not turn. I disassembled it to find that the little motion
>> over the years had ground the bearings into the races.
>> I agree with you about no movement = no wear but how many rotors,
>> other than some worm-driven rotors or prop pitch rotors have no movement.
>> I had the races of the aluminum bearing welded, filling the races
>> completely up and planned to recut the races in my lathe. In the
>> interim, I have picked up a different thrust bearing, a FAFNIR that is
>> steel so with grease and a enclosure/seal to keep the weather out, I
>> doubt I'll ever have to worry about it again.
>>
>> Roger
>> aka RoGrrr
>> KC8HZ
>>
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