Today, we resurrect a medieval engine of war -- and
try not to kill anyone with it. 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 trebuchet was once a
terrible weapon of war. The Chinese invented it,
and the West picked it up in the 12th century. It's
a gigantic counterweighted arm that slings missiles
at the enemy.
You don't see many trebuchets around anymore today.
But now we stand in a pasture in Shropshire,
England. A piano flies overhead and lands with a
terrible crash a few hundred feet away. A few
minutes later an automobile follows it.
We're on Hew Kennedy's estate. Kennedy and a
neighbor have built their own 30-ton trebuchet.
"Why?" a reporter asks Kennedy. "Well, why not?
It's bloody good fun!" he answers.
Okay, forget rhyme and reason. Let's look at
performance. The range for a grand piano is 125
yards. They can throw an upright 150 yards. They
can throw a dead hog 175 yards and a 112-pound iron
weight over 235 yards.
Kennedy built his first trebuchet for a county fair
many years ago. It was smaller. He threw toilets
soaked in gasoline and set afire. The local paper
praised "Those Magnificent Men and Their Flaming
Latrines."
Now local sportsmen want to don parachutes and ride
Kennedy's trebuchet into the sky. The idea is
seductive. He's made experiments with
accelerometers. It seems that the trebuchet
subjects its missile to about 20 Gs.
Kennedy muses over the possibility. "It'd be
splendid to throw a bloke -- really splendid," he
says. Then, sadly, "He'd float down fine. But he'd
float down dead."
Kennedy's not the first post-medieval trebuchet
maker. Cortez tried to build one for his siege of
Mexico City. The first boulder he fired went
straight up. It fell back to earth and destroyed
the machine. Napoleon had one built as an academic
exercise. It threw rocks backward. The technology
sounds simple enough, but it's more complex than it
seems.
Kennedy succeeded where Cortez and Napoleon failed
because he studied medieval sketches before he
began. A sketch of a trebuchet throwing a stone
gives you little sense of proportion. But Kennedy
found a few sketches that showed trebuchets
throwing dead horses. The rotting corpse of a horse
in a castle under siege made a fine medieval form
of biological warfare.
So Kennedy scaled his trebuchet on the weight of a
dead horse, and he got it right. And because he
did, we finally get to watch this terrible medieval
weapon -- flinging automobiles across a Shropshire
meadow.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
Mapes, G., A Scud it's Not, But the Trebuchet Hurls a
Mean Piano: Giant Medieval War Machine is Wowing
British Farmers and Scaring the Sheep. The Wall
Street Journal, Tuesday, July 30, 1991, pp. A1
& A10.
For more on the history of the trebuchet, see also
Needham, J.H., China's Trebuchets, Manned and
Counterweighted. Humana Civilitas: Sources
and Studies Relating to the Middle Ages and the
Renaissance. Vol. I, On Pre-Modern
Technology and Science (B.S. Hall, D.C. West,
eds.). Malibu: Undena Publications, 1976. (I am
grateful to Pat Bozeman, Head of Special
Collections, UH Library for making this uncataloged
source available to me.)
Since I did this episode, there has been a huge
resurgence of interest in trebuchet building. The
image below, for example, is that of a medieval
trebuchet found on the Trebuchet web page http://www.iinet.net.au/%7Ermine/gctrebs.html:
Trebuchets that throw humans have also been built
since then. One is shown at http://trebuchet.com/.
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.
Lienhard.
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