An approach for managing addition or deletion of nodes in a multicast or broadcast group, which avoids introducing a single point of failure at a group controller, certificate authority, or key distribution center, is disclosed. The rotor disk is arranged at one end of the shaft, in overhung manner, and the electric rotor is connected with the shaft of the turborotor. Each roller is preferably a conventional paint roller with an inner sleeve and an outer tubular roll made of an absorbent, compressible, resilient foam material. In some embodiments, the word lines of the plurality of blocks define gaps separating each block of the string from neighboring blocks of the string. A screw threads into the inserting nut and into a recess in the main supporter to fix the top case to the main supporter. Specifically, this invention discloses shredder motor gears and belts which are coated with a dampening material to reduce noise.