Orbiting bob toy with bobs having pellet-filled equatorial bags

摘要

A toy having three bobs on a string where the middle bob slides. A low moment of inertia of the middle bob is desirable because it minimizes tangling of the string about the middle bob and produces smooth, tactile-appealing orbits. Each bob has a pair of mated throughbore pieces sandwiching a central metal weight and an equatorial bag stuffed with low-density pellets. Concave sections (in profile on a plane along the polar axis) of the throughbore occupy a substantial portion of the length of the throughbore to take best advantage of the torques produced by the string by focusing the tension of the string at the mouths of the throughbore. The concave sections also reduce the volume occupied by the bag, thereby reducing moment of inertia. Additionally, hollows in the concave regions of the throughbore pieces further reduce the moment of inertia.