George Stephenson is another one of those tinkerers whose genius is improving an existing invention. Like Trevithick, he worked in a coal mine. Stephenson took the steam locomotive to its next level, making it more powerful.
The basic principle of a steam engine is: fire heats water in a boiler; the water turns to steam; the steam expands and creates pressure; the steam escapes into a cylinder to push a piston. The cylinder has 2 openings to let in steam so that the piston is pushed back and forth as steam fills one side and then the other. The piston is attached to a wheel, so the piston’s back-and-forth motion is changed into circular motion.
How to improve that? One way was to run copper pipes from the fire through the boiler so water gets hotter. Then you could mix the smoke from those pipes with the steam exhaust (from the cylinder) in a smoke box. The super-hot smoke and steam want to quickly escape up through a blast pipe (chimney). That in turn pulls more air into the firebox and makes the fire burn hotter. That means more steam, more pressure—so the piston moves faster with more power.
Stephenson designed the cylinders/pistons closer to horizontal, so they lost less energy. He also attached them directly to the driving wheels. Trevithick’s design had pistons that turned great gears that turned the driving wheels. It transferred energy from a piston to a gear to another gear, losing a little energy with each step. Remember how concerned Harrison was with friction between moving parts of a clock?
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