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Mechanics books always highlight that the main advantage of bearings is to reduce friction, especially when we talk about them in rotational motion applications. The example of ball bearings is always mentioned. The balls prevent and regulate the contact between the inner and the outer rings in which they reduce the friction between the two.

Would that be the main philosophy behind bearings? If that is true, then would not be better off just to remove the whole setup and have the axis of rotation free from bearings so that there are not any inner or outers rings and therefore the friction problem would be removed from the beginning?

However, I always see that the friction treatment is secondary to a main purpose of bearings ( that I have not realized yet ). Should not be there a more fundamental reason of bearings?

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  • $\begingroup$ It would be to support lubrication between relative motions. $\endgroup$
    – Pandya
    Nov 30 '19 at 14:03
  • $\begingroup$ To reduce wear... $\endgroup$
    – Solar Mike
    Nov 30 '19 at 21:00
  • $\begingroup$ Bearings, bears, load. $\endgroup$ Nov 30 '19 at 22:13
  • $\begingroup$ @Pandya what do you mean by relative motion? what are you referring to? $\endgroup$
    – Gold_Sky
    Dec 2 '19 at 18:42
  • $\begingroup$ @SolarMike How can a circle shaped element reduce the wear? and wear of what? $\endgroup$
    – Gold_Sky
    Dec 2 '19 at 18:43
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If that is true, then would not be better off just to remove the whole setup and have the axis of rotation free from bearings ...

  • Ball bearings change a system from sliding friction (as in a journal bearing) to rolling friction which is usually considerably less.
  • Ball bearings prevent wear in one place as would occur with a horizontal rotating axis at the the point of support.
  • Ball bearings can provide holding force in the axial direction - a drill-press for example - while providing lower rotational resistance than a plain bearing.

The term "bearing" is derived from the verb "to bear"; a bearing being a machine element that allows one part to support another. Source: Wikipedia, Bearing (mechanical).

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  • $\begingroup$ I tried to approach learning bearings with examples like ball bearings, journal bearings and others. However, as I use them, I get confused more. I thought that realzing the concept of bearings from philisophical point of view might help in understanding it better than using examples. $\endgroup$
    – Gold_Sky
    Dec 2 '19 at 18:49
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so that there are not any inner or outers rings and therefore the friction problem would be removed from the beginning

The axis needs to be supported somehow (i.e. in direct contact with the support) or it would be "floating in space". As the later is impossible, you are forced to have the first. Usually you provide a lubricant between axis and support surfaces, but that lubricant won't be there in all possible operating scenarios, particularly during starting and stopping stages, effectively increasing friction. There's also the problem of having a lubricant pressure big enough to overcome the forces at play, so the film of lubricant is as thick as needed (under dynamic loads).

So bearings are there to reduce friction wear to the axis or its support. The fact that they have their own friction is unavoidable, but something you can mitigate through careful design.

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  • $\begingroup$ do you mean by your example of support surface as something like a wheel of car during accelerating or deaccelerating ? $\endgroup$
    – Gold_Sky
    Dec 2 '19 at 18:52

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