Today, the first locomotive. The University of
Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
created them.
Children called the old
steam locomotives "choo-choo trains." Choo-choo was
the noise made by steam leaving the cylinders down
by the wheels. If you've never seen it in real
life, you've seen it in movies: A conductor shouts,
"All aboard!," there's a great gush of steam around
the wheels, and the train starts moving.
All this was the result of two great ideas that
converged around 1800, after steam engines had been
around for a hundred years -- the idea of running
steam engines at high pressure and the idea of
using them for transportation.
The first steam car was made by the French military
engineer Nicholas Cugnot in 1769. Steam engines
were huge two-story structures then; so it's not
surprising that Cugnot's car was a big brute. It
carried 4 people at about 2 mph. It was meant to
pull field artillery, but it wasn't really
practical.
In 1784 William Murdoch, who worked for Watt, used
a Watt engine to produce a better car -- lighter
and faster. The problem was that Watt didn't like
the idea of using steam engines in vehicles. He
patented the idea so he could put it on ice.
Watt didn't like high-pressure steam, either; and
that's the other thing that was needed to make a
vehicle. You see, the early steam power plants all
depended on condensing steam in a vacuum -- they
worked by sucking the piston in, more than by
pushing it out. Low-pressure steam takes up space,
and that made engines large. When the pressure was
run up to 50 or 100 psi, the engines could be made
a lot smaller. Watt wanted no part of that game,
because high-pressure steam could be dangerous.
The improved boring and machining equipment of the
late 18th century finally made high-pressure
engines realistic. The Cornishman Richard
Trevithick and the American Oliver Evans both made
good high-pressure, non-condensing engines about
1802. They had small, well-machined cylinders, and
they'd fit in a vehicle.
Trevithick and Evans both used their engines in
steam cars -- without much success. But then
Trevithick saw that steam could replace the horses
that drew carts on England's rail system. He was
clever in selling the idea. First, he made a
successful locomotive in 1804. Then, in 1808, he
built a little closed-circuit demonstration
railroad in London -- like a carnival ride. The
train -- called the Catch-me-who-can -- went 12
mph.
From then on, steam trains really caught on. The
high-pressure steam engine opened up Western
America. That familiar "choo-choo" is the sound of
spent high-pressure steam. It's a sound that tells
how two good ideas finally came together.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
