Abstract: A rotary driving apparatus 1 includes a rotary body 5, rotation detecting means 6, six rotary weight devices 7a to 7f on the body 5, and a power generation device 8. The devices 7a to 7f include a rotary arm 10 rotatably mounted to the body 5, the arms 10 at approximately six-fold symmetrical positions around the point O, a motor 11 to rotate the arm 10 at a rotational speed same as the body 5 in a rotation direction opposite to a rotation direction of the body 5, and a weight 12 on a free end side of the arm 10. The devices 7a to 7f are controlled by the motors 11 such that all the arms 10 are oriented laterally on a same side, and the body 5 is rotated by a weight balance of all the weights 12 on all the arms 10 around the point O.

Abstract: A beer frothing device for stably generating froth without degrading beer quality is provided.