Abstract: A tree harvester includes a wheeled and articulated frame, a horizontally disposed first elongated beam member, an extendable beam member that is longitudinally extendable from the first beam member, a carriage that is longitudinally movable on the extendable beam member, delimber knives that are mounted on the carriage, and topping knives that are mounted on the carriage.The carriage is longitudinally reciprocated by first and second flexible tension mechanisms. One of the flexible tension mechanisms actuates the carriage in one longitudinal direction and also actuates the delimber knives. The other flexible tension mechanism actuates the carriage in the other direction and also actuates topping knives.The tree harvester is powered by a hydraulic system; and a hydraulic pilot system cooperates with a snowflake cam mechanism to provide automatic control of the delimbing operations.