System and method for ground following of a combine header with flexible cutter bar

A harvesting head for a combine, the harvesting head comprising:

• an attachment frame provided at an aft end of the head for attachment with a combine feederhouse;
• a main frame movably connected to the attachment frame to define a roll center therebetween, wherein the main frame has a range of travel about the roll center with respect to the attachment frame;
• at least one resilient float element provided between the attachment frame and the main frame and operable to exert a lifting force on the main frame;
• and
• a cutterbar positioned at a forward edge of the main frame and operable to reciprocate for cutting crop material from the ground, wherein the cutterbar extends across a width of the head and is flexible throughout, and wherein the cutterbar is supported by a plurality of pivoting arms distributed across the width of the head, each pivoting arm being pivotally supported on the main frame and having a pivot range,
• wherein, with the main frame centered in the range of travel, each pivoting arm of the plurality of pivoting arms is supported at a maximum upward position of the pivot range in contact with a corresponding top stop on the main frame so that the cutterbar is in an uppermost position that is configured to follow ground irregularities exclusively in a downward travel direction from the main frame, and
• wherein the main frame and the attachment frame are configured such that during operation the roll center is positioned at or below ground level.