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The Smoke Stack

Our Railyard: The Science of Steam

Posted on February 10, 2017

The Valley Railroad Company, operator of the Essex Steam Train & Riverboat (ESTR), owns three steam locomotives, one of which (No. 40) was built in 1920 by ALCO/Brooks. No. 40 is one of less than 200 steam locomotives in the United States which remain in operable condition. Most steam locomotives were retired from regular service by the 1980s, though several continue to run on tourist and heritage lines like the ESTR. Why don’t we use steam locomotives anymore?


A steam locomotive produces its pulling power through a steam engine. Water is heated by a burning, combustible material (coal, wood or oil) and the outcome is steam which is collected in a boiler. The steam then moves reciprocating pistons which are connected to the locomotive’s main wheels and thus makes the wheels turn. Both fuel and water supplies are carried with the locomotive either on board (such as tank engines, like Essex’s #2) or on tender cars which are semi-permanently connected behind the locomotive (such as Essex’s #40).


Steam locomotives were first used in the very early 1800s, and they were instrumental in the Industrial Revolution movement. It wasn’t until the invention of the internal combustion engine at the end of the 19th century that oil replaced coal. By the middle of the 20th century, internal combustion engines were sufficiently developed to replace steam engines. One obvious example of how much more efficient a diesel locomotive was to steam was the fact that, if you needed a locomotive right away, all you had to do was push a button and the diesel engine was running and ready, whereas we need a full day and a half to fire up a steam engine from cold.

Essex’s No. 40 steam locomotive burns about 2 tons of low sulfur coal for fuel each day and evaporates about 6000 gallons of water pulling a 400 ton train a total of 50 miles. It takes two people to operate a steam locomotive: an “engineer” to run it and a “fireman” to shovel coal into the firebox and maintain the proper level of water in the boiler. Read more about the equipment at the ESTR.

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