Abstract: A flexible cutterbar header for an agricultural plant cutting machine, includes a plurality of elongate, telescoping support arms pivotally connected to a floor of the header and supporting a flexible cutterbar for upward and downward, and fore and aft movements relative thereto, apparatus extending between at least some of the support arms configured and operable for controlling the telescoping thereof substantially uniformly, and a preload adjusting system configured and operable for applying a preload force against the cutterbar through the support arms in a manner to automatically increase as the support arms telescopically increase in length, and automatically decrease as the support arms telescopically decrease in length.

Abstract: A system for supporting a cutterbar of a crop harvesting header includes a first arm pivotably secured to the header. The first arm includes a first portion configured to support the cutterbar. The first arm includes a second portion including a torsion device having a mass of elastic material connected to an adjustment assembly. The second portion is configured to be pivotably rotatable about an axis by the adjustment assembly to selectably increase or decrease a force appliable to the first portion in order to raise or lower the first portion with respect to the header.

Abstract: A flexible cutterbar support apparatus with integral adjustable torsional preload mechanism for connecting a cutterbar support arm to a header frame for upward and downward movement. The mechanism includes a first element connected to the support arm and extending about a second element configured for connection to the frame, and at least one resilient biasing element disposed between the first element and the second element and biasable by generation of a torsional loading condition between the first and second elements for applying a preload force therebetween. A preload adjusting mechanism in connection with at least one of the first element and the second element is operable for selectably adjusting the biasing of the at least one resilient biasing element in a manner for adjusting the preload force. The preload mechanism is also operable for damping vibrations emanating from the cutterbar, and can be used in cooperation with apparatus for damping the up and down movements thereof.