Unfortunately, this experience was about 12 years ago and all
the plans and papers have long since disappeared. The only things remaining
are the photographs on this web site and the broken remains of the machine.
However, I still remember some of the specifics.
The throwing arm was 16 feet long and two feet wide,
constructed of four 2x12s,
two on each side of the arm. The axle was two steel pipes of different
size, so that one fit inside the other. They were also well greased. The
axle was positioned
4 feet from the short end of the throwing arm so that the arm sat on top
of the axle. It was held in place by several boards bolted to the arm,
protruding below it, with a hole drilled through for the axle.
The fulcrum base was constructed of 2x4s oil-derrick style
so that the axle was 9 feet above the ground. The seat on the long end
of the arm swivels on one end of a parallelogram so that the rider stays
in the same attitude throughout the ride.
In the final version that I rode, there were four 55 gallon drums filled
with water. Three hung off the short end of the arm by cables, providing
about 1500-1800 pounds of counterweight. The three drums would all hit the
ground at the same
time that the arm hit its stops. The fourth barrel sat on the back to prevent
the machine from tipping over from the inertia of the arm. The arm was
stopped at about 50 degrees from horizontal. At the time I weighed about
160 pounds, so a 10-to-1 counterweight to payload was the ratio. The whole
thing was designed to disassemble into three pieces
(base, arm, and seat assembly) which could easily be
reassembled on-site by two men. It's weakness turned out to be at the axle.
the assembly that connected to the fulcrum was too weak
and the arm literally ripped
off the base after about a dozen firings. The trigger was a system of cables,
a crowbar, and three carabeeners so that when one carabeener was slid off
the crowbar, the tension on the cables would spin the crowbar around and
it would slip off the other two carabeeners and fling away. Thus releasing
the arm. The flying crowbar was dangerous, but dramatic and somewhat
predictable. We used a "come-along" hand winch to cock it.
Before I built the big one, I built several small models. The models did
not perform anything like the big one.
It turns out that trebuchets don't scale very well.
What was it like?
It was amazing. If you've ever jumped out of a tree or off a cliff
30 feet or so over water, that was about half the experience. In addition
to falling 30 feet, I was also tossed up 30 feet and 40 feet forward,
so I was in the air twice
as long. Once I left the catapult I was decelerating.
Sounds obvious, but at the top
of the arc when my acceleration went to zero, the experience was something I
It only lasted for an instant, but hanging there in mid-air, 30 feet up
looking down at everything with nothing but air anywhere near me was an
ethereal experience. Speed is easy to achieve in a ride, but complete
detachment was a whole different thing.
After the calm of the momentary hang in space, I continued to fall.
It was quiet, long, and thouroughly enjoyable. The ride up gives you time
to become accustomed to the experience, then you get to come down in a
clearer frame of mind. Everone who rode it came up laughing after they
hit the water. It was more fun than any roller coaster I've ever ridden.
Where can I get more information?
When I built mine, the only information I had came from the
encyclopedias in the school library. My design was based on a few
sketches I saw and my own mechanical intuition. Today there is a lot
more information. I've seen lots of it over the years, but haven't
kept track of any of it. If you have any information you'd like to
share, or questions you'd like to ask, try the
Catapults Bulletin Board! Or you can send e-mail to me at
How can I build one?
You're on your own here. Anything that has enough force to toss
a person 40 feet is very dangerous (just imagine a traffic accident).
I don't want anyone to get hurt. Several professors of physics and
mechanical engineering warned me not to do it, and my machine shattered
while I was riding it. I was lucky I didn't get hurt. If you want to
build a smaller one, you'll be better off starting from scratch. Trebuchet
architecture is complex and doesn't scale very well.
If you do build one, I'd love to hear about it, whatever size
it is. Send your story (and pictures if possible) to