Abstract
Azimuth thruster, a kind of marine vessels' thruster, is divided into two versions generally. Motors for thrust are installed on ship's hull, and propellers are driven by mechanical transmission gears in case of one version of azimuth thruster. This type of thruster has a perpendicular middle driving shat, the reaction torque acts on the pod because of the driving torque of the perpendicular middle driving shat. When the single perpendicular middle shat is modified to contra-rotating system and the driving torque of outer perpendicular middle shat is equal to that of inner perpendicular middle shat, it is possible to cancel the reaction torque acting on the pod and to prevent the interference between rotation of motor and gyration of pod in principle.
