Fan bearing lubricant was Re: WD-40 (again)

Noel Chiappa jnc at
Sun Apr 17 21:28:12 CDT 2016

    > From: drlegendre

    > Ok, so there's an annular groove cut mid-way along the length of the
    > shaft. That might well be for retention of lubricant.

Yeah, that was my guess too.

    > I took these to be the typical 'Muffin' type fans, that run about 600
    > RPM.

For comparison, one of my desktops has a thing that reports the fan speeds in
that machine; it says the case fan there is doing 1.5K RPM, and the CPU fan
5K. Going by that, since these are going considerably faster than that case
fan, I'm going to say these are doing roughly 3K-4K or so.

Since they are 120VAC fans, i.e. 60Hz AC input, if I had remembered enough
EE, I should have been able to work out the speed from the number of poles on
the rotor, etc, but alas that's beyond me.

    > This is a long-shot, but does the groove in the shaft communicate with
    > a passage in the bearing

Nope, the cylindrical (outer part of the) bearing is a plain cylinder. But
looking at it closely, it's probably not copper, so it might be that Oilite

    > What's the diameter of the shaft, btw? 1/4" or less?

Pretty much about 1/4".

    > I'd stick with the suggestion to use a light-bodied grease like Phil's

I'm just worried a bit about a grease, given the high speed.

For comparison, a car wheel is about 2' in diameter, or about 6' in
circumference, so at 60 MPH, which is 5280 FPM, it's going to be doing about
880 RPM, somewhat slower. Hence my thinking a fluid lubricant might be the
way to go, although of course fluids can migrate.

    > But again, there's no harm in using a medium-body motor oil, like 30W
    > or 10W-40. It's not as if it's going to be in 24/7/365 service, eh?

No, it's not, which is exactly the problem, though - I want something that
won't coagulate if left to sit for a long period.

Actually, now that I think of it, my son is a Mech E - I should ask
_him_! :-) They probably know about all this stuff!


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