Epitrochoids and Hypotrochoids by mattmoses

Description

This is a Public Domain OpenSCAD file with epitrochoids and hypotrochoids.

These shapes are useful for making mechanisms like Roots Blowers and Wankel Engines.

An EPITROCHOID is a curve traced by a point
fixed at a distance "d"
to the center of a circle of radius "r"
as the circle rolls
outside another circle of radius "R".

An HYPOTROCHOID is a curve traced by a point
fixed at a distance "d"
to the center of a circle of radius "r"
as the circle rolls
inside another circle of radius "R".

An EPICYCLOID is an epitrochoid with d = r.

An HYPOCYCLOID is an hypotrochoid with d = r.

See en.wikipedia.org/wiki/Epitrochoid
and en.wikipedia.org/wiki/Hypotrochoid