A threshing system for an agricultural combine comprising: a fixed structure; a rotor and an adjustable concave; and a concave adjust assembly comprising: - an elongate torsion axle defining a longitudinal direction and being connected to the concave; and - a drive connected in rotatably driving relation to the torsion axle and including a motor mounted to fixed structure of the combine, such that operation of the motor will rotate the torsion axle in a manner for moving the concave relative to the fixed structure, characterised in that: the torsion axle includes an inner element having an angular sectional shape and opposite longitudinal ends (70, 72), a tubular outer element disposed about the inner element along at least a substantial portion of length thereof, the outer element having an angular sectional shape having a larger sectional extent than a sectional extent of the inner element and being oriented relative thereto such that corner portions of an inner surface of the outer element are disposed in generally opposing relation to flat portions of an outer surface of the inner element and define spaces therebetween and such that the outer element and the inner element are relatively rotatable, and elongate resilient damping elements disposed in the spaces, respectively, such that forces exerted (FW, FI) urging the lateral relative rotation of the outer element and the inner element will load the damping elements compressively, respectively; and the drive is connected to one of the inner element and the outer element and the other of the inner element and the outer element is connected to the concave, the damping elements being configured for damping impulse forces exerted thereagainst by the concave to limit or reduce transmission of the loads to the drive. a fixed structure; a rotor and an adjustable concave; and a concave adjust assembly comprising: - an elongate torsion axle defining a longitudinal direction and being connected to the concave; and - a drive connected in rotatably driving relation to the torsion axle and including a motor mounted to fixed structure of the combine, such that operation of the motor will rotate the torsion axle in a manner for moving the concave relative to the fixed structure, - an elongate torsion axle defining a longitudinal direction and being connected to the concave; and - a drive connected in rotatably driving relation to the torsion axle and including a motor mounted to fixed structure of the combine, such that operation of the motor will rotate the torsion axle in a manner for moving the concave relative to the fixed structure, the torsion axle includes an inner element having an angular sectional shape and opposite longitudinal ends (70, 72), a tubular outer element disposed about the inner element along at least a substantial portion of length thereof, the outer element having an angular sectional shape having a larger sectional extent than a sectional extent of the inner element and being oriented relative thereto such that corner portions of an inner surface of the outer element are disposed in generally opposing relation to flat portions of an outer surface of the inner element and define spaces therebetween and such that the outer element and the inner element are relatively rotatable, and elongate resilient damping elements disposed in the spaces, respectively, such that forces exerted (FW, FI) urging the lateral relative rotation of the outer element and the inner element will load the damping elements compressively, respectively; and the drive is connected to one of the inner element and the outer element and the other of the inner element and the outer element is connected to the concave, the damping elements being configured for damping impulse forces exerted thereagainst by the concave to limit or reduce transmission of the loads to the drive.