The rotor shaft is a central component of the electric motor. The rotor shaft is the carrier shaft for the laminated core of the rotor and thus transmits the electrically induced torque via a corresponding positive connection in the transmission. In addition to the requirement for bearing the rotor and a variety of attachments, the design of the rotor shaft is very much dependent on the chosen cooling concept of the electric motor. Especially with larger electric motors and thus larger and longer rotor shafts, a hollow shaft enables new design aspects both for the cooling system and for lightweight construction. However, the most important function remains the transmission of torque from electrical to kinetic energy in the transmission and thus to move the vehicle. Due to the high rotation speed of up to more than 20.000 rpm and the high torques, the rotor shafts are exposed to very high loads. This requires high-strength components that still have to meet high demands on lightweight design.