Science Moment: Steam Locomotive

Discover the machine that changed the course of American history! Today we fire up the boiler and ride the tracks through the last two centuries at the Henry Ford, exploring how a steam locomotive works.

* The image of steam trains traversing the American West is enduring, but this story begins long before man first put on the steel wheel – and was certainly not an American invention per se . The first “steam engine” was technically invented in 200 BC: a ball with angled jets was filled with water, and rotated while heated…a fun party trick, but not very practical. Fast forward several centuries, and James Watt’s steam engine helped start the Industrial Revolution… and it didn’t take long for this innovation to be applied to transportation.

*Richard Trevithick patented a “high pressure engine” with (almost literally) all the bells and whistles in 1802, the first real step towards what we recognize on rails today. Years later, George and Robert Stevenson created the Rocket, which ripped down the slopes at almost 30 miles per hour. The father-son team proved to the world that steam was the way to go. Around the same time in the United States, the first American locomotive was forged and it was steaming down both sides of the pond. The transcontinental railroad was considered one of America’s greatest achievements, but the “iron horses” that ran on these tracks paled in comparison to others on the line.

*Here’s the real science behind steam: when water becomes water vapor, its volume increases approximately 1600x…and to get there, those coals in the combustion chamber can peak at around 2500 degrees Fahrenheit , nearly 1000 degrees hotter than your summer campfire. This steam is guided through pipes along the length of the engine, and the engineer uses the throttle to regulate the amount of steam that is pushed to these cylinders. The steam expands, pushing the piston forward, with an exhaust port opening to reverse the process, and so on. The rods connected to the piston turn these driving wheels.

*That characteristic hiss you hear is also a by-product of venting steam from a separate pipe, and the hissing sound is coming from the exhaust of steam from the chimney. This actually has the effect of creating a vacuum to further feed the coals below and maintain combustion.

Sure, today’s modern engines are much more efficient and faster, but there’s nothing quite like those blowing marvels of engineering that roll down the rails all day.

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Jose P. Rogers