Parametric bearing

The bearing has an internal rail which helps to keep rolls straight.
When a roll angles to one side, its internal cut scrapes on the rail which makes angling in the opposite direction and straightening.
It works well even with significant perpendicular forces.

Parameters:
r1 - internal ray,
r2 - external ray,
height - height (thickness of bearing),
minThickness - minimal thickness of walls,
coverRatio - height of rolls' cover as a fraction of their delimeter,
coverThicknessRatio - thickness of rolls' cover,
rollLiner - liner (fill) of rolls - to minimize usage of filament,
railWidthRatio - width (as a fraction of rolls' height) of internal rail which helps to keep rolls straight,
railHeightRatio - height (as a fraction of rolls' ray) of internal rail which helps to keep rolls straight,
epsilon_xy - space between parts in X and Y axis,
epsilon_z - space between parts in Z axis.