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To Ride a Trebuchet
Ron L. Toms
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When I was 12 years old my history teacher in
junior high school asked me to do a project for the upcoming
history fair. She recommended building a model of the famous civil
warships the Monitor and the Merrimac or perhaps a reconstruction of
what Stonehenge looked like around three thousand years ago.
Dissatisfied with these suggestions, I went off the the library to find
something more dynamic to bring to the history fair. As I was flipping
through an encyclopedia, it fell open to a page with a picture of a
catapult on it. I read the article and instantly I knew what my project
would be; a miniature working model of an onager type catapult. With the help
of my father I built that catapult. It could hurl small rocks, tennis
shoes, paperback books and other items across the classroom and made me
the hit of the fair.
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While I was doing research for that project,
I had come across a story about a king
whose castle was under attack. The king needed food for his people and
offered one
of his sons as a hostage to facilitate a cease fire and open
negotiations. When the negotiations fell apart the attackers put the
king's son in a catapult and hurled him against the castle wall. A sad
page in history, but it got me thinking about what it might be like to
ride a catapult.
Fourteen years later I was thinking about that story again, and as a
mechanical engineering student with a short summer break on my hands,
I now had the skill and the time to do something about it. Being
inspired by Walt Disney (He loved trains, and built the first rideable
miniature trains) I set out to build a catapult scaled
to throw me 40 or so feet through the air to land safely in a river. I
set out to build and ride a replica of an ancient throwing machine.
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I settled on a design called a trebuchet. I
made some calculations, drew up a design, and built a small model, but
the model didn't work like I expected. The test loads fell short of the
intended mark, so I took my drawings to a physics professor and tried to
get things figured out. After some calculations, he showed me a number
about twenty digits long and said "This is the centrepital acceleration
that you'll be experiencing. That's enough force to rip your head clean
off!" I sensed that he did not approve of my plan to hurl myself
through the air and into a river. So after modifying my story and
consulting with a mechanical engineering professor (who also told me it
wouldn't work), I went on to build it anyway.
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After two weeks of construction in the hot
Texas sun the trebuchet was complete. I loaded a 160 lb. test load on it (a 55
gallon drum partially filled with water) and pulled the trigger.
The test load went straight up, and came straight down on top of the
catapult. Obviously I had a serious design flaw. I also now had a badly
damaged catapult. After a quick redesign and a rebuild, I fired the
second test load of a 1 foot cube of concrete, a bowling ball, a
punching bag, several bricks and a length of chain. It flew beautifully
through the air and landed a perfect 60 feet from the front of the
catapult. The test load was seriously underweight, but the trajectory
was perfect. I figured I'd just increase the counterweight of the
trebuchet proportionately to get the same trajectory with myself as the
projectile.
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The next day I gathered up some of my
(willing) friends to participate in the event. We loaded the big machine
onto a trailer and moved it to the edge of the Blanco River. After a few
hours of setting up the contraption and gathering some large rocks for
another test launch, a small crowd of picknickers had gathered. They
were interested in seeing just what the hell we were going to do with
this big machine. After the successful test launch, there was much
applause and cheering from the crowd. They were very impressed to see
that big pile of rocks fly into the air and "KAWHUMP", splash into the
river. We recocked the machine, and I climbed into the launch bucket.
there was an audible gasp from the crowd. Women told their children not
to look and men advised me not to do it. I turned to my friend at the
trigger and said "On the count of five, pull it." I started counting
backwards from five. "FIVE..." I never got to four. My literal friend
pulled the trigger right then. Suddenly I was flying. I looked down and
for an instant I was hovering, 30 feet over the river below. When I hit
the water, I was elated! My dream of riding an ancient throwing
machine had come true! I came up laughing. My friends and I spent the
rest of the afternoon riding the trebuchet, until the machine
self-destructed in mid throw. I was the passenger, and luckily I was
thrown clear just as it snapped. The increased counterweight was too
much. I fixed the design, but my money and my time had run out. I couldn't
afford to
rebuild again. Now the broken pieces sit on an empty south Texas ranch,
the cows look at it curiously from time to time. I became busy with
other concerns; school, life, career, etc. I frequently think about
building another one, one that will throw someone a little farther, a
little higher. All I need is the time...
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[ Read the FAQ! ]
Copyright 1994 Ron L. Toms
WARNING!
DON'T TRY THIS AT HOME
Recently there have been attemtps by people in England to hurl people using
a large trebuchet. Several people were badly hurt- one person ruptured his
liver and another person broke her pelvis.
Sadly, and most recently, a student was killed when he missed the landing
zone and hit the ground. People were arrested and there is a criminal case
pending. Worst of all, someone died.
If you endeavor to repeat a similar stunt, YOU COULD BE SERIOUSLY HURT OR
KILLED! DON'T DO IT.
Thank you,
-- Ron L. Toms