[saspinski (OP)]

I bought a gyroscopic toy, and realized that it can start precessing badly (I put it inclined on the ground), but before fall, it gets still, completely vertical for a while.
I always thought that it would precessing more and more until the RPM become too low and it fall.
Why does it happen?

link:https://youtu.be/UZYlW6ErqdI

[saspinski (OP)]

I have a physic book (Alonso&Finn) that explains and derives a formula for the angular precession speed, given the angular momentum, the couple, and the angle of the rotation axis to the vertical.

But that is valid for a constant rotation speed (no bearing or air drag friction). Even so, the authors warn that it is an approximation when the angular momentum due to the precession is much smaller than that due to the rotation of the gyroscope around its axis. In the real situation the angle to the vertical is not constant and another movement called nutation arises.

But I could not find an explanation why the gyroscope raises its own center of gravity as shown in the video.