A swinging bob toy having three bobs constrained to a string with at least the center bob being slideable along the string. Each bob is modular and consists of two hemispheric elastomeric mantle pieces, a three-component throughbore sheath, and one or two hex nuts mounted on a threaded central component of the throughbore sheath. The two end components of the throughbore sheath are flared and are non-elastomeric, while the threaded central component is elastomeric. The outside ends of the flared end components of the sheath are recessed relative to the mouths of the throughbore so that all exterior impact surfaces of the bob are elastomeric. The string has a circular cross-section and has a width greater than 50% of the width of the narrowest diameter of the throughbore.