Groundhog Day...

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...is as good a day as any to bring my blog-vacation to a close. Today Punxsutawney Phil failed to see his shadow -- predicting an early spring -- but Ruffles the Porcupine in Duluth's Lake Superior Zoo predicts six more weeks of winter. Which sounds about right to me, seeing as tomorrow's high is supposed to be around -5°F.

Needless to say, there was no public observing tonight. Heck, the grease we use on the refractor's clock drive gears is only rated down to about 10°F. And observing on the roof would be out of the question; we're under a wind chill advisory until Monday. 25 to 40 below clear through the weekend. Hope the Loppet racers dress warmly!

Anyhow, blog-vacation over.

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Welcome back. But too cold for refractor grease? For whatever reason, when I came to Chicago the only grease at Ryerson was a high-temperature brake grease. I have no idea why we had it. Anyways, it didn't work at low temps either. Later I discovered what oils and greases are all about, learned the difference between them, and now it's white lithium grease all the way for load bearing surfaces--works down well, down as far as Chicago gets.

P.S. Now I see you are talking about clock drive gears. For the clock mechanism (that was renovated a few years ago by a clocksmith), no oiling was needed for years according to the guy, and then only a light oil of a particular name. Once the clock mechanism turns into the worm part, we use white lithium for that.

Howdy, Dean!

We just use Li grease on all the drive clockwork, which seems to work fine. Our grease is labelled as working down to about 10 F, but we haven't really tested that rigorously. Two reasons: first, that's also about the temperature where the (ancient, creaky) dome starts getting really hard to rotate; second, much below that and we start running out of public night volunteers.

However, since our refractor is far too large to dismantle, we can't get at the load-bearing surfaces to grease them. Instead, the thing has capillary oil-pots, in which we do use a low-temp machine oil (only seems to lose a few mL a year, anyway). So far we've never had a problem there.

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This page contains a single entry by Milligan published on February 2, 2007 10:35 PM.

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