I have some pictures of students creations.
Trebuchets are seige weapons from Medieval times.
Trebuchets were extremely efficient, accurate, easy to build, and much more stable than their simple catapult cousins. In the right circumstances, one man could operate a trebuchet freeing others for the battle. When released, the throwing arm would carry the load for a distance until abruptly stopped by a bar. Inertia would carry the load to its intended target. Although not as well known as catapults, trebuchets were the seige weapon of choice.