I will pass along my understanding of this. This is
basically a top. A top stays up by precessing, or slowly changing the
orientation of the rotor about the vertical axis. The top or the rotor, or wheel, moves faster than the bottom because of the precession. The difference in rotational speed between the top and bottom leads to a difference in the centrifugal force, which leads to a net upward force on the rotor, supporting it against gravity.
The guy twists the rotor in the precessing direction, increasing the net upward force, causing the top to rise. There is still a force of 40 pounds downward on his hand but its easier to support a bar horizontally than it is to support it vertically.
