Ram type steering gear is one of the commonly used steering gear construction and is quite expensive in construction. The basic principle is same as that of a hydraulically-driven motor engine or lift. There are four hydraulic cylinders attached to the two arms of the actuator disc, on both sides. These cylinders are directly coupled to electrically driven hydraulic pumps which generate hydraulic pressure through pipes.  This hydraulic pressure field present in the pumps imparts motion to the hydraulic cylinders, which in turn corresponds with the actuator to act upon the rudder stock. As we know, rudder stock is an indispensable part of the entire steering gear arrangement of ships and dictates the exact behaviour of the rudder response. The sense of turning the rudder is guided by the action of the hydraulic pump. 

In rotary vane steering gear, there is a fixed housing in which two vanes rotate. The housing along with the vanes form four chambers. The physics behind its operation is similar to the ram type with a small difference. A rotary vane type arrangement is used when the pressure requirement is 60 to 100 bar for producing the required torque. This is the main advantage of rotary vane type steering gear, requiring lesser hydraulic pressure and thus power for producing the same amount of torque as ram type. There are 3 fixed and 3 moving vanes, which can make rudder angles up to 70 degrees, i.e 35 degrees on each side. This arrangement has several other advantages like lower installation cost, less weight and smaller space required. The fixed and rotating vanes are of spheroidal graphite cast iron. Keys are often provided in the rotary vanes for proper strength and orientation.


Modifié le: lundi 1 juillet 2024, 12:17