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When looking at various small fans (like those found in a computer or the bathroom) you often see in their specifications the type of bearings they use. And the typical values there are either "sleeve bearing", "1 ball bearing" and "2 ball bearing".

Now I can imagine what a "sleeve bearing" is - it just means that the axis of the fan is stuck in a hole, maybe with a bit of lubricant, and that's that. In essence, it means "no bearing". But what are "1 ball" and "2 ball" bearings? I know what a "ball bearing" is in general, but how do you make that with just 1 or 2 balls? I think that the very minimum theoretical amount would be 3 balls but in practice I don't think I've seen anything less than 6 or so.

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    $\begingroup$ A sleeve bearing does not mean "no bearing", it is a separate machine part. In its own way just as complex as roller bearings, except that it has no rolling elements. $\endgroup$
    – OpticalResonator
    Commented Jul 8, 2020 at 8:19
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    $\begingroup$ This implies 1 or two rows of ball bearings $\endgroup$
    – Jonathan R Swift
    Commented Jul 8, 2020 at 8:45
  • $\begingroup$ Many of the biggest,fastest machines have sleeve bearings. $\endgroup$
    – blacksmith37
    Commented Jul 8, 2020 at 14:41
  • $\begingroup$ Ok, I'm no mechanic, I don't really know the pros and cons of different bearing types. :) I wonder - are there frictionless bearings based on magnets? And if yes, why haven't I heard of them? Are they too expensive? $\endgroup$
    – Vilx-
    Commented Jul 8, 2020 at 15:33
  • $\begingroup$ @Vilx- they still have some friction (though very low), but they're expensive and relatively large en.wikipedia.org/wiki/Magnetic_bearing. Hydrostatic bearings have similar properties, with different advantages and disadvantages $\endgroup$
    – llama
    Commented Jul 8, 2020 at 19:15

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A "1 ball bearing" does not mean the bearing has 1 ball. Or 2...

It means that the motor / fan has been designed with one ball bearing assembly - which may contain 6, 8, 10 or 12 balls depending on the size and design. For example a caged bearing will have fewer balls to allow for the cage and this reduces inter-ball friction. Otherwise, the balls can touch each other when rotating which adds to the wear rate, but this is also heavily influenced by the other loads on thee bearing.

So, when the fan / motor assembly says "2 ball bearings", that tends to mean that there will be a ball bearing at each end of the shaft, but in some situations there can be 2 ball bearings at one end of the shaft to support the offset load.

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    $\begingroup$ @Vilx- no, some of those labels are so poorly printed that they could mean just about anything. $\endgroup$
    – Solar Mike
    Commented Jul 8, 2020 at 8:53

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