Electric motor shaft including inner helix pattern

A method of manufacturing an induction motor rotor shaft assembly for an induction motor, the method comprising:

• providing an induction motor rotor shaft rotatable about a center axis and including a hollow cylindrical base including an outer circumferential surface, an inner circumferential surface, a first axial end annular surface extending radially from the inner circumferential surface to the outer circumferential surface, and a second axial end annular surface extending radially from the inner circumferential surface to the outer circumferential surface
• forming a helical structure extending about the center axis on or in the inner circumferential surface;
• and
• providing a coolant supply for providing coolant inside of the hollow cylindrical base onto the helical structure for flow axially inside the hollow cylindrical base along the helical structure as the induction motor rotor shaft as the induction motor rotor shaft rotates about the center axis.