Rotation exercising ball structure swinging smoothly

A rotation exercising ball structure comprising:

• two shells, two pivot seats, two holding members, a weight unit, and two handle protecting members;
• wherein:
• the two shells are combined together to construct a hollow ball;
• each of the two shells has an interior provided with a space;
• the space has a bottom provided with a fixing hole;
• the fixing hole is located at a center of the bottom of the space and penetrates each of the two shells;
• each of the two pivot seats is formed on the bottom of the space and directed toward an opening of one of the two shells;
• each of the two pivot seats is provided with a pivot pillar;
• the pivot pillar has a center provided with a through hole;
• the through hole penetrates each of the two pivot seats and extends to the fixing hole;
• the two holding members are mounted on the two shells respectively;
• each of the two holding members covers the fixing hole of one of the two shells;
• each of the two holding members has an inner side and an outer side;
• the weight unit includes a mandrel, a rotation member, two bearings, a weight, and at least one auxiliary weight;
• the mandrel has two ends each of which extends through the through hole of one of the two pivot seats;
• each of the two ends of the mandrel is secured in the through hole of one of the two pivot seats;
• the rotation member has a first end provided with a mounting hole;
• the two bearings are mounted in the mounting hole of the rotation member;
• the rotation member is radially mounted on a central position of the mandrel through the mounting hole;
• the weight connects a second end of the rotation member and is located opposite to the mandrel;
• the rotation member and the weight are rotated in the hollow ball radially and centrifugally with the mandrel served as an axis;
• the at least one auxiliary weight is removably mounted on the weight;
• and
• the two handle protecting members are mounted on the two shells of the hollow ball respectively and align with the two holding members respectively.