Concave transparent acrylic body with spherical curvature. A rolling ball oscillates
inside the concavity about its rest position like a mathematical pendulum does.
The radius of curvature is equivalent to the length of a normal pendulum.

Diameter of balls: 16 mm

Radius of curvature: 200 mm

Diameter: 140 mm

A rolling ball bearing moves inside a concave acrylic body of spherical curvature. The radius of curvature of the acrylic body corresponds to the length of the pendulum. One special case is a circular motion of the ball around the vertical where it acts like a conical pendulum. Mathematically speaking, the way the location of the oscillating ball changes over time is described by the space vector in spherical coordinates.