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I have lubricated the ball-bearings of two hand spinners (the anti-stress toys) and contrarily to my expectation the time they keep on spinning has been divided by four.

One fact I have noticed, the rolling bearings now makes almost no more noise at all: they were really noisy before.

I am trying to explain myself why/how the energy in the two hand-spinners would dissipate so much faster ? It is contrary to my intuition.

Any idea ?

When I say divided by 4, it is an estimation:

I have an anti-smoking anti-stress technique that involves a short meditation, and I was using two hand-spinners, one in each hand for a duration of roughy 2 minutes, a bit more, (repeated numerous time for one year or so).

But after lubricating them this afternoon with WD-40, the duration falls to 30 seconds at most.

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The lubricant you put into the spinner bearings has both viscosity and surface tension, and it coats the rotating parts inside the bearing. Therefore, as the spinner bearing revolves, it churns the lube and makes and breaks air/lube interfaces- which dissipates energy and makes the spinner slow down.

This energy dissipation mode is absent in the case of a dry bearing, in which case the main energy dissipation mode will be radiating away the noise generated when the bearing parts rattle around as the bearing spins.

This illustrates the fact that in a roller- or ball-bearing, the purpose of the lubricant inside them is not to reduce friction (the rolling elements do that) but to inhibit wear caused when the balls or rollers skid against the bearing races instead of rolling smoothly. The lubricant adds a little bit of frictional drag but the tradeoff is worth it.

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  • $\begingroup$ Agreed, that's what happens, and when bearings are under load the lubrication also helps transfer heat... $\endgroup$
    – Solar Mike
    Sep 5, 2019 at 6:56
  • $\begingroup$ @SolarMike, yes indeed- my old brush-cutter had a bevel gear box between the PTO shaft and the mow deck, that box dissipated a lot of heat! $\endgroup$
    – niels nielsen
    Sep 5, 2019 at 7:09
  • $\begingroup$ @nielsnielsen nice answer. I'm already trying to wash the WD40 with a mix of white spirit and terebentine. $\endgroup$
    – Stephane Rolland
    Sep 5, 2019 at 11:12
  • $\begingroup$ @StephaneRolland, best to use liquid cigarette lighter fluid if you can get some, this is the classic "degreaser" compound. Another thing that works well is aerosol starting fluid, used to get gasoline engines to start, but it is violently flammable! $\endgroup$
    – niels nielsen
    Sep 5, 2019 at 17:14

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