Trebuchet Project
By AM and CS
Introduction
▪ Inquiry Statement:
▪ Historical technical innovation has contributed to
advances in modern day human progress.
▪ Global Concepts:
▪ Scientific and technical innovation.
▪ Design Specification: Students will design and build a
trebuchet that is capable of throwing an object with
repeated accuracy.
IB Design
Cycle
Investigation
Pros and Cons
▪ The swinging counter weight
▪ The fixed counterweight on a
floating frame
▪ Pros:
▪ Pros:
▪ Vertical counterweight
▪ Wheels
▪ Easy to adjust
▪ More vertical fall
▪ Cons:
▪ Easy to move and adjust
▪ Possibly difficult to move?
▪ Cons:
▪ The fixed counterweight on a fixed frame
▪ Counterweight may be
▪ Pros
difficult to attach
▪ Easiest to build
▪ The floating arm trebuchet
▪ Cons
▪ Pros:
▪ most accurate
▪ Shakes frame
▪ Vertical counterweight
▪ Non-vertical fall
▪ Cons:
▪ Not as efficient
▪ Difficult to build
▪ Difficult to adjust
Planning Process
Choosing the arm:
▪ We chose the swinging counterweight trebuchet because it
was the easiest for us to build with limited resources. Easily
adjustable for distance by adding or removing weight. The
vertical counterweight fall adds more power to the trebuchet
we built.
Guiding Questions
These questions were to illustrate the many number of choices
we were faced with on this project. A different answer could
have completely changed the outcome.
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How big will the base be?
How will we attach the wood together?
What will we use as a counterweight?
What type of axel will we use?
What will the sling be made of?
Roles
▪ ALEX: Designing (drawings), Arm (cutting, sanding,
construction) , sling, track construction
▪ CHLOE: base construction (cutting, gluing, stapling, sanding)
track support (cutting, sanding, gluing, stapling)
▪ Throughout the trebuchet process we would consult each
other for opinions or assistance.
Materials Given
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Wood
Nails
Eyehooks
Metal rod
Ready rod
Bolts
Washers
String
Twine
Glue
Fabric
Designing
We drew out the rough design to scale and recorded the measurements.
(Unfortunately we didn’t see that the base was too wide and too short.)
Creation
Measurements and
rough sketch
Planning the cuts
Building and Sanding the
pieces
The Final Product
Goal
To have the trebuchet fire a tennis ball
25 feet into a plastic recycling bucket.
Testing
▪ Attempt #1:
▪ 10 lbs. of weight.
▪ Traveled roughly 3 feet.
▪ Ball went higher up than further. This may have been because of the weights hitting the
track when going downward. So, we decided to shorten the loop attaching the weight to the
arm.
▪ Attempt #2
▪ Traveled roughly 4 feet.
▪ The ball went slightly further. In an attempt to make it travel even further, we added 1.5 lbs.
of weight and shortened the sling length.
▪ Attempt #3
▪ Travel about 6 feet.
▪ The ball went quite a bit further but still nowhere near the box. We decided to change the
twine attaching the sling to a thin green string hoping it would change the tension.
▪ Attempt #4
▪ Traveled around 8 feet.
▪ We used a ten pound weight, and loosened the sling loop. We also slightly adjusted the
sling rod.
▪ It was our most successful trial, and it traveled more than twice the distance of our first try.
Evaluation
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Unfortunately, our trebuchet didn’t complete our intended
goal.
This is probably because our base was too long, and so
the angle between the supports was far too wide, thus
shortening the base itself.
With such a short base, we had to make our arm much
shorter than we intended, so it would fit inside the base.
Because of this, our throwing distance suffered, and we
weren’t able to come close to our target.
If we were to redo this project, we would pay closer
attention to the measurements and see if they fit together,
and also model the base measurements for optimal arm
length.