yeot spring 2015 webinar 5: catapults and trebuchets
TRANSCRIPT
So what's a catapult? Review
Catapults can be split into three categories:
● Traditional Catapult● Ballista● Trebuchet
HistoryThe 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.
History
Descendents of the first Chinese trebuchets, these siege weapons resulted from advancement by the Islam and Byzantium civilizations and further developmentin Western Europe.
TrebuchetThe 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
Major factors to consider
● Counterweight Mass● Counterweight Height● Projectile Mass● Sling Length● Launch Angle● Wheels vs. hinged counterweight
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.
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
Gravitational Potential EnergyEnergy stored by trebuchet is determined by:
● Weight of Counter Weight
● Height Counter Weight is hoisted
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.
Energy
Gravitational energy stored by hoisted counter weight is translated into rotational kinetic energy of the sling on the arm
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
**
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.
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.