A rotor assembly, comprising: a rotor core barrel comprising a wall extending between lateral ends, and at least two compression bridges each formed in the wall proximate one of the lateral ends and separated by a distance; an array of a plurality of magnets positioned on and spaced along the wall between the compression bridges and about a circumference of the rotor core barrel; and one or more pre-stress wraps wrapped over the plurality of magnets and about the rotor core barrel along at least a portion of a length of the rotor core barrel between the compression bridges at sufficient force to cause an inward radial compressive pre-stress of the wall of the rotor core barrel causing a reduction of the diameter of the rotor core barrel at least along a portion of the length of the rotor core barrel, wherein the compression bridges are radially flexible structural elements configured to flex in response to the radial compression deflection of the portion of the rotor core barrel under the pre-stress, while preventing rotational and axial misalignment between lateral ends and maintaining the bending stiffness of the rotor assembly, wherein the compression bridges are formed in the wall at least in part through a reduced first thickness of the wall of at least a portion of the compression bridge relative to a second thickness of the wall adjacent to each compression bridge and between the compression bridges in the at least the portion of a length of the rotor core barrel where the magnets are positioned and relative to a third thickness proximate the lateral ends, wherein the third thickness is separated from the second thickness by the compression bridges, wherein the reduced first thickness provides for increased flexibility along the compression bridges, wherein the compression bridges enable radial compression deflection, induced by the radial compression of the rotor core barrel by the one or more pre-stress wraps, of the wall of the rotor core barrel at the compression bridges along at least the portion of the length of the rotor core barrel induced by the one or more pre-stress wraps relative to the wall of the rotor core barrel proximate the lateral ends while reducing the radial expansion deflection at the lateral ends. a rotor core barrel comprising a wall extending between lateral ends, and at least two compression bridges each formed in the wall proximate one of the lateral ends and separated by a distance; an array of a plurality of magnets positioned on and spaced along the wall between the compression bridges and about a circumference of the rotor core barrel; and one or more pre-stress wraps wrapped over the plurality of magnets and about the rotor core barrel along at least a portion of a length of the rotor core barrel between the compression bridges at sufficient force to cause an inward radial compressive pre-stress of the wall of the rotor core barrel causing a reduction of the diameter of the rotor core barrel at least along a portion of the length of the rotor core barrel, wherein the compression bridges are radially flexible structural elements configured to flex in response to the radial compression deflection of the portion of the rotor core barrel under the pre-stress, while preventing rotational and axial misalignment between lateral ends and maintaining the bending stiffness of the rotor assembly, wherein the compression bridges are formed in the wall at least in part through a reduced first thickness of the wall of at least a portion of the compression bridge relative to a second thickness of the wall adjacent to each compression bridge and between the compression bridges in the at least the portion of a length of the rotor core barrel where the magnets are positioned and relative to a third thickness proximate the lateral ends, wherein the third thickness is separated from the second thickness by the compression bridges, wherein the reduced first thickness provides for increased flexibility along the compression bridges, wherein the compression bridges enable radial compression deflection, induced by the radial compression of the rotor core barrel by the one or more pre-stress wraps, of the wall of the rotor core barrel at the compression bridges along at least the portion of the length of the rotor core barrel induced by the one or more pre-stress wraps relative to the wall of the rotor core barrel proximate the lateral ends while reducing the radial expansion deflection at the lateral ends.