The Vehicle that Replaced the Horse
Almost every country in the world has a railroad, one of our most
important means of transportation. Laid end-to-end, the tracks
of the world's railroads would stretch three times the distance
from the earth to the moon. Only ships carry heavier cargoes for
longer distances. Only airplanes transport the public faster
Crude forms of railroads existed in Europe 400 years ago to haul
wagon loads of coal from underground mines. Two wooden rails laid
side-by-side extended from the entrance down onto the floor of the
mine. Men or horses pulled the wagon, which moved more easily on
the rails than on muddy and rutted ground. Gradual improvements
were made over the next two centuries. The rails were extended
to run above as well as below ground. Wood was reinforced, then
entirely replaced, by iron. But the length of these primitive
railroads remained very short, for the means to propel the wagon
continued to require human or animal labor.
The age of the modern railroad dawned with the invention of the
steam engine. In 1804 a high-pressure steam engine was mounted
upon a four-wheeled undercarriage designed to run along a track,
and carried 9 metric tons, 5 wagons and 70 men. In 1830 the
first passenger service was inaugurated. The "iron horse"
A steam engine derives its power by producing heat from the
burning of coal or oil in a firebox. The heat turns the water
in a locomotive's boiler into steam, which is fed into cylinders.
There, the pressure produced by the steam pushes against disks
called pistons. The pistons are connected to rods which move the
But the steam locomotive has several disadvantages. A lot of time
is required to light the fire and heat the boiler so that steam
can be produced. And although speed increased to 50-60 miles per
hour by the end of the 19th century, the steam engine is not fuel
efficient. It requires large amounts of coal to produce and
maintain power, and most of the heat is wasted.
Less than 50 steam locomotives, most of them tourist attractions,
still operate in the United States. Steam power has been replaced
by either the diesel or the electric locomotive.
In comparison with the steam locomotive, the diesel engine has
several advantages. It is more fuel efficient, requires less
servicing, and costs less to maintain. A diesel locomotive can
make longer runs, as well as starting, stopping, and speeding up
faster than the steam locomotive.
The diesel is an internal combustion engine. That is, power is
derived by burning an explosive mixture of gases. The diesel
engine varies from the conventional internal combustion engine
in that the fuel is not detonated by a spark but by the heat
produced when air is compressed in a cylinder. When the air is
compressed, its temperature rises. The resulting heat ignites
fuel that has been injected into the cylinder. The power produced
during this process is transmitted to the driving wheels.
There are three types of diesel locomotives: (1) diesel-electric,
(2) diesel-hydraulic, and (3) diesel-mechanical. Each transmits
power from the engine to the driving wheels in different ways.
Almost all locomotives in the United States today are diesel-electric.
The diesel engine was invented in 1892, and the diesel locomotive
was introduced experimentally in 1923. The first passenger diesel
went into operation in 1925 and the first freight diesels went into
service in 1940. Today there are over 20,000 diesel locomotives
operating in the United States.
Electric locomotives were introduced in the late 19th century.
Unlike diesels, electric locomotives do not generate their own
power - they use power supplied by an electrical power plant that
may be miles away. An electric locomotive, therefore, needs
special wires or rails from which it can get power.
Many electric locomotives use a "third rail" which runs
parallel to the regular rails on which the train travels. A metal
device called a contact shoe is attached to the locomotive. The
shoe slides along the third rail and picks up electricity from it.
Electric locomotives can draw large amounts of power from the
central plant, while diesel locomotives are limited to the power
they can produce from the fuel they carry. Electric locomotives
are also quiet and produce no smoke or exhaust fumes. Electric
locomotives can start and stop more quickly than diesels. Finally,
electricity can be produced from a variety of fuels - coal, gas,
oil, water, or atomic power. Diesel locomotives can only run on
diesel oil, which may become scarce and thus more costly.
Europe's train systems were converted to electricity early in the
20th century. Although only about 100 electric railroads operate
in the United States today, electrification may become widespread
in the next century.
Unlike ships, airplanes and automobiles, trains traveling on
railroads are not steered; they are guided by tracks along a
permanent route - a "rail road."
Most track is made up of two steel rails running parallel and
fastened lengthwise to a series of cross ties. The wheel-and-axle
assemblies of locomotives and cars are specially designed to run
on the track. Each wheel has a flange (rim) around its inner edge.
The flanges on each pair of wheels guide the wheels along the track.
Switches - short movable rails that turn on pivots - are built
into the track where it meets other tracks. By turning a switch,
a train can move from one track onto another.
The roadbed on which tracks are laid is specially prepared to make
the ride as level and smooth as possible, and to hold the ties in
place and keep the track stable. The route of the track is planned
to minimize steep grades and curves, which reduce a train's speed
In many cities the space required of a roadbed has led to its being
elevated above or submerged below ground. Yet the size and weight
of traditional trains make a heavy demand on land, material, labor
The advent of the automobile (and airplane) has reduced reliance
on passenger trains, particularly in the United States. While
people in China, India, Japan, and most of Europe still rely
heavily on trains for transportation, railroads now carry less
than 1% of all U.S. intercity travel.
The automobile's appeal is that it's personal. You travel when
you want and where you want - no timetables, no tracks. But air
pollution, road surface space requirements, and gridlock form the
negative impact of the automobile to the environment and society.
Technical innovations that address these transportation issues are
now being designed, implemented and evaluated. Hybrids that
accentuate the positives of railroad and automobile travel, while
minimizing their negatives, are explored in our "Monorail"
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Last modified: Sat Jun 28 10:10:38 PDT 1997
Copyright © 1997 by Cislunar Aerospace, Inc. All