Today, let's place bets on a perpetual motion
machine. 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.
In 1812 Charles Redheffer
showed up in Philadelphia with a perpetual motion
machine. He set it up and charged a viewing fee.
The public was fascinated. We didn't yet have
physical laws to deny perpetual motion, but common
sense ran against it. So Redheffer's machine drew
people in. A confederate stirred things up in the
Philadelphia Gazette. He offered a
huge bet that no one could debunk the machine.
Redheffer also asked the state of Pennsylvania for
money to develop his device. When state inspectors
arrived, they found they had to view the machine
through a barred window.
What they saw was a gravity-driven pendulum affair.
The output gear drove a vertical shaft. Then a
member of the team noticed something very small and
very subtle. The gear teeth were worn on the wrong
side. Apparently the output shaft drove the
machine. The machine didn't drive the shaft.
So the inspector went back and made his own
perpetual motion machine. He used hidden clockwork
to drive it. It looked like Redheffer's machine,
but you could walk right up to it. Next he arranged
a showing, and he invited Redheffer.
Redheffer took the bait, the hook, the line, and
the sinker. He was so astonished that he cornered
the fellow and offered to buy the secret for a huge
And so Redheffer was unmasked in Philadelphia. He
had to take his scam to New York. This time some
friends of Robert Fulton took him to see it. Fulton
noticed the motion wasn't steady -- the speed kept
varying. Redheffer surely didn't use hidden
clockwork, but Fulton realized what was driving it.
Encouraged by the crowd, Fulton knocked away some
structure behind the table. Sure enough, there was
a hidden catgut belt. He traced it back to where an
old man was locked in an upper room. Redheffer was
feeding the poor fellow bread and water and forcing
him to turn the crank drive all day long.
Back in Philly, newspapers kept the issue alive.
Had the city missed a chance to drive its water
pumps free of charge? Redheffer was far from the
last to waken dreams of something for nothing. The
public likes to be fooled, but only for a little
while. How often have you read about impossibly
efficient engines suppressed by dark forces of "the
The game goes on today -- sometimes deliberate, but
more often sincere. The will-o-the-wisp of cold
fusion draws us in just as surely as ESP and UFO's
do. We drink in the magic that invention promises,
because it's so exciting when invention actually
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
Ord-Hume, A.W.J.G., Perpetual Motion, The
History of an Obsession. London: George Allen
& Unwin, LTD, 1977, Chapter 8.
For more on perpetual motion, see Episodes 33, 527,
528, and 614.
Smithsonian Institution photo
provided by Charles Redheffer's descendent, Nancy
Redheffer Perpetual Motion Machine replica at the
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.