No. 267:
Early Dynamos

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.