Marine Engineering

Steering Gears
The direction of the ship is controlled by the steering gear. As the ship moves through the water, the angle of the rudder at the stern determines the direction it will move. Modern ships are so big that moving the rudder necessitates the use of hydraulics or electrical power.

The steering starts at the Bridge. The required rudder angle is transmitted hydraulically or electrically from the steering wheel at the Bridge to the telemotor at the steering gear, just above the rudder.
There are a few common arrangements for using hydraulic power. There are the 4-rams, 2-rams, and rotary vane types. The heart of these hydraulic systems is the variable delivery pump. This type of pump can be controlled by just moving a spindle. The pump is driven by an electrical motor at constant speed. By moving the control spindle away from the central point, the pump stroke increases, and the hydraulic fluid is pumped in one direction. Moving the spindle more from the central point will cause more fluid to be pumped and consequently more pressure is generated to drive the rams. Moving the control spindle back to the original position and then away in the opposite direction causes the hydraulic fluid to be pumped in the reversed direction. The rams will also move in the reversed direction.

By using a floating lever feedback mechanism, when the rudder stock has reached the desired angle, the pump control lever moves back to the original position, and the pumping action stops. The rudder is stopped at the required angle. Moving the steering wheel to the opposite direction will cause the rudder to come back to the original zero position.