ENGINEERING – In the 19th century, marine engineering applied steam power to the propulsion of ships. In 1786, John Fitch tested his experimental steamer on the Delaware River. It had 12 individual paddles with a system of cranks and levers that mimicked human paddling motion. Robert Fulton began commercial trips of the North River Steamboat in September 1807. He made three round trips between New York and Albany, carrying passengers and light freight. Problems like mechanical difficulties and jealous boatmen who would ram the unprotected paddle wheels of their new rivals, made Fulton redesign the steamship. During the first winter season he stiffened and widened the hull, replaced the cast-iron crankshaft with a forging, fitted guards over the wheels, and improved passenger accommodations. These modifications made it a different boat, which was registered in 1808 as the North River Steamboat of Clermont, soon reduced to Clermont by the press.
Paddle Wheel Propulsion in Marine Engineering
In 1815, the English company Boulton & Watt constructed a beam engine. It consisted of a cylinder whose piston connected with one end of an overhead beam driving a gear wheel that moved the paddle shaft. This engine found extensive use in America. From the early 1820s, Americans used this engine for paddle steamers on rivers. Different engine builders created refinements, but the essential side lever form remained in place until Cunard’s Scotia of 1862. The 4570ihp (indicated horse power) plant installed propelled the 1850-ton ship at 14.5kts (knots – a unit of speed equal to 1 nautical mile per hour), but cost of the coal consumption was around 350 tons per day.
Coal served as the predominant source of fuel powering steam engines in the 1800s and well into the 1900s. Furnaces burned the coal, which fueled water boilers that generated steam. The pressure from the steam turned paddlewheels or propellors. A walking-beam engine, also called a vertical beam, used a pivoted beam to provide the force from a vertical piston to a connecting rod.
Often visible from the top deck of ships, the walking-beam transferred force to a crankshaft that turned the paddlewheels on the side or rear (stearn) of the vessel. The type of engine was common in American coastal and river steamers.
Screw Propelled Ships and Expansion Engines
Early ocean going vessels used paddlewheels, but as larger ships set out, more powerful and safer means of propulsion became necessary. Engines changed in size and orientation. Instead of vertical beams, vertical compound and expansion engines turned propellers at the stern of a vessel instead of paddlewheels. With multiple cylinders, expansion engines reused steam more than once, making them more efficient. These engines also changed the center of gravity, moving the heaviest part of the engine down in the shape of an inverted V. Walking-beams, had the opposite shape, and were much heavier. At this time, many ships moved from coal to oil as a source of fuel. Coal took up a lot of space on ships, so cargo ships, which needed the storage space, looked for alternative energy sources to power their ships. Coal was also expensive and over time, even smaller vessels used oil.
The cost of fuel precipitated the gradual phasing out of steam engines in favor of diesel powered engines. By the 1960s, many vessels changed from SS (steamship) to MV (motor vessel). Today, most vessels use diesel or gas engines and turbines. New hybrid engines use electricity.
Nuclear Power in Marine Engineering
In 1953, Dwight Eisenhower began his Atoms for Peace program, which promoted nuclear power for peaceful purposes. The Nuclear Ship (NS) Savannah launched in 1953, as the first and only nuclear powered passenger ship. George Sharp designed her as an ambassador to Eisenhower’s program rather than as a commercially viable ship. The Savannah was not active long. She carried passengers until 1965 and was deactivated in 1971.
Nuclear power needed little refueling, allowing ships to be out at sea for long periods of time. It make the useful for working vessels like ice-breakers and military aircraft carriers. The NS Savannah today serves as a museum ship and is open to visitors in Baltimore, Maryland.
Questions for Further Thought
- How did the cost of fuel affect changes in marine engineering?
- Why did oil replace coal on ships?
- What new technology was used to recycle and reuse steam?
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