Longitudinal sieve compensation

A cleaning shoe for a combine harvester, comprising:

• a frame;
• a sieve;
• at least one reciprocating mechanism attached to the sieve for reciprocating the sieve in a generally forwards and backwards motion, the reciprocating mechanism comprising:
• an eccentric drive housing, pivotably mounted to the frame, said eccentric drive housing arranged so as to rotate around a pivot point and to operably change an angle of the housing to horizontal;
• a support mounted onto the frame comprising an inner aperture and a boss;
• a gear having toothing around an outer circumference, the toothing configured to engage with toothing on an inner circumference of an aperture of the eccentric drive housing, wherein an offset pin is provided on the gear, the boss engages with the offset pin;
• a back cover on the eccentric drive housing comprising a slot, wherein the offset pin is configured to slide along the slot in a reciprocating motion;
• and
• an actuator connected to the eccentric drive housing, wherein the actuator is operable to rotate the eccentric drive housing so as to vary an angle to horizontal of the slot in which the offset pin is configured to slide in order to vary the angle to the horizontal of the reciprocating motion of the sieve.