The compact sickle drive mechanism (66) comprises at least one and preferably two epicyclic drives (76, 78) adapted to be incorporated into or beneath a floor (28) or pan of a header (22) at a location between and spaced from the sides or ends (40, 42) of the header (22). The two drives can be configured for reciprocatingly driving two knife assemblies (60) disposed in end to end relation, in opposite directions, such that potentially vibratory forces, including those generated by the moving masses of the knife assemblies, at least substantially cancel one another and thus are not transferred to structure of the header (22). As a result, the overall width of the header (22) and structure thereof can also be reduced.
