A linear motion mixer for mixing fluids within a vessel, the mixer comprising: a mixing shaft having an upper and a lower end and defining a longitudinal axis extending therebetween, with the mixing shaft supporting a mixing head adjacent its lower end for immersion in said fluids; a reciprocating drive assembly connectable to the mixing shaft adjacent its upper end for imparting reciprocating movement to the mixing head in substantially parallel relation to said longitudinal axis, wherein, said drive assembly comprises: a flywheel mounted for rotation about a rotational axis extending substantially normal to said longitudinal axis; a crank assembly projecting from the flywheel in a direction substantially parallel to the rotational axis; first and second column bearing shafts each extending substantially parallel to the longitudinal axis in laterally spaced relation from each other so as to define a pair of guide axes substantially parallel to the longitudinal axis; a yoke assembly positioned between the first and second column bearing shafts and having two or more contoured bearing shaft rollers mounted thereon for respective rolling contact with each of the first and second column bearing shafts so as to provide for rolling movement of the yoke assembly along said column bearing shafts in substantially parallel relation to said guide axes; the yoke assembly having a linear race defined between a lower surface of an upper way shaft and an upper surface of a lower way shaft arranged in opposed relation to each other for operative contact by the crank assembly, the race being disposed within the yoke assembly with each said upper and lower surface being oriented substantially normal to both the rotational axis and the longitudinal axis; said mixing shaft being connected to the yoke assembly adjacent its upper end for movement with the yoke assembly; wherein, when the flywheel is rotated, the crank assembly is caused to linearly translate back and forth within the race, thereby urging the yoke assembly to reciprocatingly roll along the first and second column bearing shafts to impart said reciprocating movement to the mixing head. a mixing shaft having an upper and a lower end and defining a longitudinal axis extending therebetween, with the mixing shaft supporting a mixing head adjacent its lower end for immersion in said fluids; a reciprocating drive assembly connectable to the mixing shaft adjacent its upper end for imparting reciprocating movement to the mixing head in substantially parallel relation to said longitudinal axis, wherein, said drive assembly comprises: a flywheel mounted for rotation about a rotational axis extending substantially normal to said longitudinal axis; a crank assembly projecting from the flywheel in a direction substantially parallel to the rotational axis; first and second column bearing shafts each extending substantially parallel to the longitudinal axis in laterally spaced relation from each other so as to define a pair of guide axes substantially parallel to the longitudinal axis; a yoke assembly positioned between the first and second column bearing shafts and having two or more contoured bearing shaft rollers mounted thereon for respective rolling contact with each of the first and second column bearing shafts so as to provide for rolling movement of the yoke assembly along said column bearing shafts in substantially parallel relation to said guide axes; the yoke assembly having a linear race defined between a lower surface of an upper way shaft and an upper surface of a lower way shaft arranged in opposed relation to each other for operative contact by the crank assembly, the race being disposed within the yoke assembly with each said upper and lower surface being oriented substantially normal to both the rotational axis and the longitudinal axis; said mixing shaft being connected to the yoke assembly adjacent its upper end for movement with the yoke assembly; a flywheel mounted for rotation about a rotational axis extending substantially normal to said longitudinal axis; a crank assembly projecting from the flywheel in a direction substantially parallel to the rotational axis; first and second column bearing shafts each extending substantially parallel to the longitudinal axis in laterally spaced relation from each other so as to define a pair of guide axes substantially parallel to the longitudinal axis; a yoke assembly positioned between the first and second column bearing shafts and having two or more contoured bearing shaft rollers mounted thereon for respective rolling contact with each of the first and second column bearing shafts so as to provide for rolling movement of the yoke assembly along said column bearing shafts in substantially parallel relation to said guide axes; the yoke assembly having a linear race defined between a lower surface of an upper way shaft and an upper surface of a lower way shaft arranged in opposed relation to each other for operative contact by the crank assembly, the race being disposed within the yoke assembly with each said upper and lower surface being oriented substantially normal to both the rotational axis and the longitudinal axis; said mixing shaft being connected to the yoke assembly adjacent its upper end for movement with the yoke assembly; wherein, when the flywheel is rotated, the crank assembly is caused to linearly translate back and forth within the race, thereby urging the yoke assembly to reciprocatingly roll along the first and second column bearing shafts to impart said reciprocating movement to the mixing head.