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The Spirit of Zubbly flies again
SparWeb:
After a couple of months, mostly normal operation to report.
Winds have been cooperative, but temperatures way too cold for me to be outside tinkering in the shed.
Now that we've had some nights below -30C (-22F) there seems to be one noise problem not yet fixed: the bearings.
I used to have "FAG" bearings on the shaft, your basic 6206 and 6204 types. At -35C, those used to have an annoying skidding sound that had a beat to it. The noise made me think the 9 balls were skidding around at some fraction less than half the inner race frequency. The math from the smart people at FAG bears out that hypothesis, so I suspected damage in a bearing. After taking the turbine down this summer, removing the bearings, I found not damage (other than breaking the races apart, I mean).
The turbine is up now with different bearings. This set of bearings is from NSK, identical in size, similar in style, and the materials appear to be equivalent (hardness etc). One night it was cold enough that these bearings TOO started making an awful scraping noise. No pulse or beat in the sound, just a constant noise. I shut it down until it got warmer, and the noise went away.
So my theory now is that it could be the grease in these bearings: could it be hardening up so much in the cold that it locks one of (maybe many of) the balls up? Then the ball-race just goes around and around without all of the balls actually turning? Does that make any sense?
I guess I should find out what grease is in them, for starters. Shell/Exxon/Mobil grease of some sort...
DamonHD:
You should get some of the grease that lubricates the cold clammy hands of senior politicians: that stuff must work down to near 0K...
Rgds
Damon
SparWeb:
Thanks Damon, but the ones I worry the most about are the ones who seem so warm in person, but when seated in their parliament offices, show their cold hearts.
Anyway...
It seems I've made the same mistake twice. Shoulda coulda woulda. I found the boxes the new bearings came in (normally would have thrown them away) and so I looked up the manufacturer's part numbers. It turns out the grease in them is Shell Alvania (now called Gadus), which is recommended only above -20C. It's lithium-based, not hydrocarbon based. Which would explain the problem nicely.
tecker:
Some ceramic will do the trick if you want to pop for them . There are also stainless races with ceramic rollers / ball ,a little cheaper and non ferrous .
Bruce S:
During my ARMY years, we had a white grease used for bearings in the wheels for mil-spec vehicles.
This stuff was slick even in temps down to -30C, the coldest I could work in and still function.
I'll get in touch with friends still serving and let you know the name brand or mixture of it.
We used to hand pack them with Lithium grease for normal use, then clean and repack using the white grease for the winter months.
Cheers
Bruce S
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