Abstract
When the horizontal rotation is given to the toy called rattleback to have the shape of the boat put on the desk, it rotates only to one direction. When the rotation of the opposite direction is given to the toy, the pitching vibration begins stopping rotating like disliking the direction, and it shifts to the rotation in the opposite direction gradually with the given direction. A dynamic feature of the toy is that the inertial roll axis is a little twisted around the vertical axis, i.e. it is not included in the vertical plane that a lower ridge line forms. Putting this shape feature on the mind, this paper tries to give an intuitive explanation about following two items: reason where direction that rotates easily and direction not rotated easily exist, and cause of pitching vibration generation and reverse-rotating torque generation.
