Editing Curve of constant width (section)

==Applications==
[[File:Reuleaux triangle 54.JPG|thumb|Rollers of constant width]]
Because of the ability of curves of constant width to roll between parallel lines, any [[cylinder]] with a curve of constant width as its cross-section can act as a [[Bearing (mechanical)#History|"roller"]], supporting a level plane and keeping it flat as it rolls along any level surface. However, the center of the roller moves up and down as it rolls, so this construction would not work for wheels in this shape attached to fixed axles.{{r|gardner|bs|rt}}

Some [[coinage shapes]] are non-circular bodies of constant width. For instance the British [[British coin Twenty Pence|20p]] and [[British coin Fifty Pence|50p]] coins are Reuleaux heptagons, and the Canadian [[loonie]] is a Reuleaux 11-gon.{{r|chamberland}} These shapes allow automated coin machines to recognize these coins from their widths, regardless of the orientation of the coin in the machine.{{r|gardner|bs}} On the other hand, testing the width is inadequate to determine the [[Roundness (object)|roundness of an object]], because such tests cannot distinguish circles from other curves of constant width.{{r|gardner|bs}} Overlooking this fact may have played a role in the [[Space Shuttle Challenger disaster]], as the roundness of sections of the rocket in that launch was tested only by measuring widths, and off-round shapes may cause unusually high stresses that could have been one of the factors causing the disaster.{{r|moore}}