How do roller-element bearings work?

 

To appreciate how roller-element bearings function, first, it would be best to understand their design. A bearing may contain balls, ball rollers, tapered rollers, or needle rollers. They feature an inner and outer ring with raceways for the caged parts. They also include a lubricant to reduce friction and seals to prevent the entry of particles that might contaminate the oil.

The pockets within the cages separate the rolling elements and maintain constant spacing as the apparatuses roll in the race tracks. As aforementioned, roller bearings come in different configurations, including single- and double-row elements.

The cylinders between the inner and outer races enable the caged elements to roll in the raceways along a single axis. The rolling elements would slide out of position under operation without the cages, causing bearing failure. The cages don't handle any loads, and their purpose is to hold the rollers in place. There are also cage-free bearings called full complementary bearings (FCB). Usually, FCBs have more rolling elements, handling heavier loads. Another upside is that they can withstand sudden shock loads as the rollers evenly distribute the load throughout the raceway.

There's also a need to lubricate roller bearings. Whether or not to grease depends on the product you buy. Sealed roller bearings typically come pre-lubricated, and no additional greasing is required. Non-sealed ones need a lubrication plan called elastohydrodynamic lubrication and must adhere to the manufacturer's specifications.

In this greasing regimen, a lubricant, usually less than one micron, is applied with pressure levels reaching up to 34,500 bar (500,000 psi). The grease partially solidifies and elastically deforms the rolling elements and the contact surface. Any contamination of the oil can lead to significant degradation of the mating surface and can result in the build-up of more wear particles.




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