Reversing the Engine: Going Astern on a Liberty Ship
How do you reverse the engine, or go ‘astern,’ on a Liberty Ship, as there is no transmission to shift gears? Since the crankshaft is connected directly to the propeller shaft, the only way to go astern is to reverse the rotation of the crankshaft by reversing the main engine.
## The Role of Eccentrics in Steam Engine Valve Mechanisms
Next to each of the main rods is a pair of smaller-diameter ones called eccentrics. They are driven by the crankshaft and move the valve mechanism to send steam to the top or bottom of the cylinder. The eccentrics are out of sync with each other though they are timed, one for forward and one for reverse rotation.
## Reversing the Engine: The Role of Stephenson Linkage in Quick Direction Changes
Reversing is accomplished by changing the valve sequence. The valves to all three cylinders are changed at the same time by a mechanism called a Stephenson linkage; located next to the throttle valve. It only takes about ten seconds to reverse the engine. Engine room operation and the reversing of the engine in the 1997 version of Titanic was filmed in the O’Brien’s engine room.
Explore this Station's Gallery
Step forward into the fire room to view the ship’s boilers. Our friendly engineers on duty can usually be found at this level. Feel free to ask them any questions you may have about the Engine Room.