Abstract: A mop head assembly having: a base plate member with a generally flat bottom portion adapted to receive a flexible cleaning member; and an electric motor mounted on the base plate member at a laterally centered position thereon and having a rotatable shaft with an asymmetric weight mounted thereon, the shaft projecting downwardly from the electric motor and oriented substantially perpendicular to the base plate bottom portion, wherein rotation of the asymmetric weight on the shaft causes the base plate to vibrate primarily in a plane parallel to the flat bottom portion. A cover member that covers the electric motor and which is positioned over other components mounted on the base plate is also described.