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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