Abstract: A centrifugal grinding mill including a grinding chamber of substantially circular cross-section with respect to an axis of symmetry and constrained to have nutating motion about a relatively stationary axis, a support for supporting the grinding chamber, a feed passage in communication with the grinding chamber, a driving assembly for driving the grinding chamber about the relatively stationary axis, and a constraint assembly for determining the form of nutating motion of the axis symmetry of the grinding chamber. The nutating motion of the grinding chamber during operation of the grinding mill causes a grinding charge carried in the grinding chamber to dilate and perform a tumbling motion within the grinding chamber. Further, the grinding chamber has a surface configured to exert pressure on the grinding charge so as to limit its dilation and provide effective containment of the grinding charge.

Abstract: A constructional toy having a plurality of nodal elements and a plurality of co-operating rod elements with each nodal element being substantially spherical and having a plurality of channels formed on its peripheral surface, including a first channel encircling said nodal element so as to pass through the poles thereof. At least four other channels are spaced about the peripheral surface so as to be intercepted by said first channel adjacent the poles of the nodal element, the lips of each said channel having inwardly projecting beads thereon. The rod element has a shank with a connecting portion at each end with a cross-section of a shape which can be "push-fitted" into a co-operating channel and held so that the longitudinal axis of the rod element is in substantial alignment with the geometrical center of the nodal element.