Rotational Motions Excited by Vertical Harmonic Motions

Rotation of a pair of wings was driven by the vertical harmonic motion of a pin inserted into the center hole of the wings.To elucidate the mechanism by which the rotational motion of the wings was excited,the relationship between the wings and the pin was examined by tracking their motions using both displacement measurements and high-speed photography.The motion modes occurred in this study were categorized into five types:slipping,rolling,jumping(without eccentricity),jumping(with eccentricity),and non-rotation.In the case that the hole of the wings was located at a distance from the center of the wings,referred to as″with eccentricity,″the slipping,jumping(with eccentricity),and non-rotation modes resulted.The experimental results showed that the mechanism of the jumping(with eccentricity)was different from that of the other modes(slipping,rolling,jumping(without eccentricity)),which are well known to be driven by the periodical reaction of the wings against the vertical vibration of the pin.It was found that the jumping(with eccentricity)was driven by the non-periodical force with the collision between the wing hole and the pin.