This siege engine is made of two rigidly bound groups of balls - the brown base and the green throwing arm - and is powered by the stretched elastic bond (between the short end of the throwing arm and the middle ball of the base).
Six balls in the base attempt to contain the middle ball of the throwing arm - while allowing it to rotate.
The simulation starts at the moment the throwing arm is released.
The "in action" simulation shows a ball launched at a brick wall (or more accurately - as it's a 2D simulation - a column of bricks). This simulation automatically repeats without needing to press the rewind button.
The "close up" simulation allows a closer look at exactly what happens as the balls is launched.
The "experiment" simulation lets you try out projectiles of different masses and forms.
All three simulations display a graph showing the changes in energy of the whole system (or the kinetic energy of a selected object) with a time control giving the option of slowing events down to observe them in greater detail.
There is no air friction in the simulations, or friction between objects and the ground.
The elastic bond powering the siege engines is not 100% efficient - so that not all the energy put into stretching it can be recovered. Energy is also lost in the inelastic collisions between objects.
Jari Vaarma's trébuchet and onager
Knight's Armory siege engines:
Siege engine blueprints
Siege engine prototypes
Experimental Reconstruction of a Medieval Trébuchet
Trébuchet links and resources
Red arrows show forces on an object. Thin headed arrows show the individual forces that combine together to give the triangle headed resultant force.
Blue arrows show the direction and speed of an object's velocity.
The longer an arrow, the greater the force or velocity it represents.