Today, we find the technology we need, out on the
farm. 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.
The first practical electric
generator, or dynamo, was built in Paris in 1870.
It was the fruit of years of theoretical thinking,
and it was a terribly important milestone. When
Edison and Westinghouse got their hands on it, a
few years later, they transformed American life.
But electric generators also transformed the steam
engines that drove them, and there hangs a tale.
Dynamos are ill-matched to mechanical engines
because electricity, unlike steam, moves at the
speed of light -- without any delay. Generators
naturally run faster than steam engines do.
Stationary power plants were large slow-moving
affairs during most of the 19th century. They ran
at around 60 rpm -- one stroke a second. In that
sense they were still kin to the engines of James
Watt, 100 years before. A Dynamo turned much faster
-- maybe 900 rpm. It had to be coupled to the
lumbering steam engine with complicated gears and
belts.
A new breed of high-speed steam engines did exist
in the outback. Rural sawmills and threshing
machines used small high- speed engines that went
as fast as 600 rpm -- 10 strokes a second. They
were made by little companies far from the
mainstream of the big industrial steam engines.
Edison's first generators were driven by those
conventional monsters. But he soon found his way to
the little companies that were making high-speed
engines. And they saw the light. Maybe fast-moving
engines developed out on the farm, but now the
little companies took over. By 1890, you could buy
an engine-generator set whose engine turned fast
enough to drive the generator on a straight-through
shaft -- with no gear-box at all.
Oddly enough, the day of these new high-speed steam
engines was rather brief. They quickly replaced
their slow forbears; but reciprocating engines
weren't the long-term answer. Just after Edison
installed his first power station, a man named
Parsons built a practical steam turbine. He saw how
to blow steam through fan blades that spun a shaft
in steady rotation.
Parson's steam turbine quickly made reciprocating
steam engines obsolete. And so, the dynamo finally
ended the era that James Watt had begun. Today,
even modern nuclear plants use steam turbines to
drive their generators.
And that whole transition completed itself within a
just a few decades, because the right technology
had grown up while we weren't looking.
I'm John Lienhard at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
Bowditch, J., Driving the Dynamos. Mechanical
Engineering, April 1989, pp. 80-89.
From The Steam Turbine,
1905
Parsons Parallel-Flow Steam Turbine
From The Steam Turbine,
1905
Parsons Turbine driving a 500 kW generator
From The Steam Turbine,
1905
Turbinia, the first ship powered by a steam
turbine. It was built ca. 1894, just a few years
after Parsons began manufacturing turbines.
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.
Lienhard.
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