Crop harvesting machine with variable header float

A rotary mower comprising:

• a self-propelled support vehicle for running over ground carrying a crop to be harvested;
• a crop cutting header having a plurality of transversely spaced cutting disks and at least one ground engaging component for providing a supporting force from the ground as the header runs over the ground;
• a support apparatus providing a lifting force for supporting the header from the vehicle for upward and downward floating movement of the header;
• a control system configured to provide a value of the lifting force so that a predetermined proportion of a supporting force is supplied by the support apparatus and a remaining portion is supplied by the at least one ground engaging component in engagement with the ground;
• a sensor providing ground speed signals indicative of different ground speeds of the vehicle;
• the control system being configured to 1) temporarily vary the lifting force in response to detected acceleration of the header relative to the vehicle, 2) decrease the lifting force upon detection of an end of the acceleration in an upward floating movement of the header, and 3) control the value of the lifting force such that the lifting force has a first value at a first ground speed and a second value at a second ground speed higher than the first ground speed where the second value of the lifting force at the second higher ground speed is less than the first value of the lifting force at the first ground speed.