This final thesis elaborates are the performance of steering gear on modern ships with an emphasis on the rotary vane steering gear. In the first part, hydraulics is defined and basic hydraulic schemes are shown, which find their application in hydraulically powered steering gears. During this thesis, the reader is also referred to the basic concepts of a steering gear extending during this work. In addition, the manner of steering machine control and their advantages and disadvantages in the field of their application are described in detail. In addition, other parts of steering gear which have effect to the machine's performance are described. Power pump, rudder, bearings and special control devices are some of them. The calculations of the rotary vane steering gear have been analyzed with a conical clamping joint between the rudder shaft and the rotor of the machine and the necessary dimensions of the machine are obtained. Calculation of the obtained values served for the drawing of the machine in attachment of this work. The regulations of the classification societies and state institutions emphasize the safety and working measures that the steering machines should fulfil.