A roller is a fragment of rock to the aspect rounded, smooth.

The rollers are products of erosion which are transported by Rivière S or Fleuve S: by friction with the other fragments, the rocks become smooth; rolled, the rollers take their round form (rollers Fluviatile S). They accumulate in the beds of the rivers and in the delta S. There exist also marine, formed rollers of fragments of rocks ballotés by the currents and the waves, thus undergoing a wear similar to that of the fluviatile rollers. These are rollers that one finds on the beaches, often mixed with fluviatile rollers.

Mechanical engineering

In mechanical engineering, a roller is a cylindrical or conical part interposed between two parts moving relative substituent thus the Frottement of slip by rolling friction.

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