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1. Ancient Engineering
Trebuchet

2. So what's a catapult? Review
Catapults can be split into three categories:
● Traditional Catapult
● Ballista
● Trebuchet

3. Trebuchet
A trebuchet launches a projectile from a sling
on a pivoting beam.

4. History
The 1st catapults, designed by
the Greeks and Romans, date
back to the 4th century BC.
Traction trebuchets originated
in China and date back to
around the same time.

5. History
We will be focusing on
counterweight
trebuchets, first designed
in the 12th century.

6. History
Descendents of the first
Chinese trebuchets, these
siege weapons resulted
from advancement by the
Islam and Byzantium
civilizations and further
development
in Western Europe.

7. How they work
A counterweight
rotates the beam
through an arc
that releases the
projectile.

8. Trebuchet
The counter weight is hoisted into air and is held in
place, usually by a release system attached to the
opposite end of the arm.
Counter weight
Release system

9. Trebuchet
Release system activated.
Counter weight drops, swinging arm with sling
attached.

10. Trebuchet
As sling follows its arc, one end is released

11. Trebuchet

12. Trebuchet
Can you guess some of the main factors that
affect trebuchet performance?

13. Major factors to consider
● Counterweight Mass
● Counterweight Height
● Projectile Mass
● Sling Length
● Launch Angle
● Wheels vs. hinged counterweight

14. Simulation
Let’s see how some of these factors affect performance!
www.globalspec.com/trebuchet/

15. How they work
● It is powered by gravity.
● Generally, its force is equal to “4 to 6 times
of the counterweight arm’s length”
● The sling acts as a secondary fulcrum.

16. Review: Gravitational Potential Energy
The gravitational potential
energy of an object can be
found by multiplying the
weight of the object by how
high it is off the ground.
PEGravitational
= weight *
height

17. Gravitational Potential Energy
Energy stored by
trebuchet is determined
by:
● Weight of Counter
Weight
● Height Counter Weight
is hoisted

18. How they work
● It is powered by gravity.
● Generally, its force is equal to “4 to 6
times of the counterweight arm’s length”
● The sling acts as a secondary fulcrum.

19. Energy
Gravitational energy stored by hoisted counter
weight is translated into rotational kinetic energy of
the sling on the arm

20. Rotational Kinetic Energy
The rotational kinetic
energy is dependent on the
length of the arm and the
weight of the counterweight.
This is because of torque,
or rotation around a fulcrum
**In this case, the force is the weight of the falling counter weight
**

21. Rotational Kinetic Energy
Force: the weight of the
falling counter weight
Fulcrum
Distance

22. How they work
● It is powered by gravity.
● Generally, its force is equal to “4 to 6 times
of the counterweight arm’s length”
● The sling acts as a secondary fulcrum.

23. Sling
The sling releases
when a certain angle α
is reached. At this point
the ring connected to
the sling slips off and
the projectile is
launched.

24. Sling
Here we get the
second fulcrum.

26. Virtual Trebuchet
http://www.virtualtrebuchet.com
A much more intricate simulator

27. Cd Trebuchet
You will get a chance to build this during lab.