This Demonstration simulates a mechanism used to convert rotary motion into rectilinear motion.[more]
A planet gear rolls inside a static ring tracing an epicyclic trajectory. The trajectory reduces to a straight line when the planet (green) is half the diameter of the ring (red).[less]
The parametric equation of the hypocycloid formed by rolling a circle of radius inside a circle of radius is:
With and , the right-hand side becomes , which is the parametric equation of a line segment between the points and .