A method of fabricating a rotor assembly for an electric motor, comprising: Assembling a lamination stack, wherein said lamination stack is comprised of plurality of lamination discs, wherein each of said lamination discs is comprised of a first plurality of slots, and wherein each of said lamination discs is further comprised of a central bore; inserting a plurality of oxygen-free electrolytic, OFE, copper rotor bars into said first plurality of slots corresponding to said lamination stack, wherein a first end portion of each of said plurality of OFE copper rotor bars extends beyond a first end surface of said lamination stack, and wherein a second end portion of each of said plurality of OFE copper rotor bars extends beyond a second end surface of said lamination stack; locating a shaft within said central bore of said lamination stack; locating a first member adjacent to said first end surface of said lamination stack, wherein at least a portion of said first member is encircled by said first end portion of each of said plurality of OFE copper rotor bars, and wherein said first member at least partially defines a first end ring of said rotor assembly; locating a second member adjacent to said second end surface of said lamination stack, wherein at least a portion of said second member is encircled by said second end portion of each of said plurality of OFE copper rotor bars, and wherein said second member at least partially defines a second end ring of said rotor assembly; characterised by die casting said first end ring and said second end ring of said rotor assembly, wherein said first end ring is comprised of said first end portion of each of said plurality of OFE copper rotor bars, and wherein said second end ring is comprised of said second end portion of each of said plurality of OFE copper rotor bars; and removing said shaft, said first member and said second member from said rotor assembly. Assembling a lamination stack, wherein said lamination stack is comprised of plurality of lamination discs, wherein each of said lamination discs is comprised of a first plurality of slots, and wherein each of said lamination discs is further comprised of a central bore; inserting a plurality of oxygen-free electrolytic, OFE, copper rotor bars into said first plurality of slots corresponding to said lamination stack, wherein a first end portion of each of said plurality of OFE copper rotor bars extends beyond a first end surface of said lamination stack, and wherein a second end portion of each of said plurality of OFE copper rotor bars extends beyond a second end surface of said lamination stack; locating a shaft within said central bore of said lamination stack; locating a first member adjacent to said first end surface of said lamination stack, wherein at least a portion of said first member is encircled by said first end portion of each of said plurality of OFE copper rotor bars, and wherein said first member at least partially defines a first end ring of said rotor assembly; locating a second member adjacent to said second end surface of said lamination stack, wherein at least a portion of said second member is encircled by said second end portion of each of said plurality of OFE copper rotor bars, and wherein said second member at least partially defines a second end ring of said rotor assembly; characterised by die casting said first end ring and said second end ring of said rotor assembly, wherein said first end ring is comprised of said first end portion of each of said plurality of OFE copper rotor bars, and wherein said second end ring is comprised of said second end portion of each of said plurality of OFE copper rotor bars; and removing said shaft, said first member and said second member from said rotor assembly.