Stable pendulum uprights itself due to gyroscopic precession

This is very interesting interaction I saw while playing with fast rotating objects in Gmod.

Note: The video is playing approximately 12 times faster than the original speed of the events.

Description of the experiment:

A powered, spinning disk and a sphere are connected to one another, with the sphere colliding with a horizontal plane. Initially, Both are placed in a stable attitude, with the disk bellow the sphere, forming a pendulum. The disk is not perfectly bellow the sphere but offset slightly to side. This induces a precession of the disk. The precession grows over time and to such an extent, that the disk is flung upwards and dragged vertically, forming an inverted pendulum. The precision of the disk tends to zero over time once it is in a vertical attitude.

Parameters of the experiment:

  • The disk is spun at 1583 rpm ( aprox. 9500 degs/s ) and held that at by a governor (the disk is powered).

  • The disk can pass through the plane without collision.

  • The disk is attached to the sphere, free to rotate in the direction parallel to it’s radius. (The disk is axised to the sphere).

  • The sphere sits on a horizontal plane. The coefficient of friction between both surfaces contacting surfaces is very small (0.01).

  • The Disk has slightly high mass than the sphere ( approx. 1.5 times the mass )

  • Both bodies feel an acceleration due to gravity in the downwards (negative Z) direction.

  • The path taken by the center of mass, of both the sphere and the disk, are highlighted by a white line.

Constrain diagram of the two bodies:


Music: Vangelis - Tears in the rain