The epicyclical drive incorporates a dual flywheel (78,80) carrying a pinion (88) in a balanced axially compact assembly. The assembly includes a counterweight for the pinion nested between the flywheels, which also connects the flywheels and transfers loading conditions therebetween, to reduce and distribute torsional and eccentric loading conditions and reduce vibrations. The use of a second flywheel also provides an improved rotary seal capability for keeping out dust, debris and moisture. The drive is adapted for incorporation into a floor of a header of an agricultural harvesting machine for reciprocatingly driving a sickle (30) thereof, advantageously jointly with a mirror image companion drive in a side by side relationship and timed such that forces generated by the reciprocating actions are cancelled.
