The invention relates to a reciprocating drive assembly comprising: a housing; a flywheel mounted for rotation about a rotational axis ; a crank member; a yoke supported by the housing for movement along a yoke axis, the yoke being connected to the shaft and having a linear race formed therein for receiving the crank member; first and second guide assemblies connected to the housing, and to the yoke for sliding engagement therewith along a pair of guide axes extending parallel to the yoke axis, the pair of guide means being spaced from each other with the yoke disposed therebetween. According to the invention, when the flywheel is driven, the crank member is caused to translate within the race thereby urging the yoke to engage the guide assemblies and move along the yoke axis to effect reciprocating movement of the shaft and the mixing head.