er throwing power than the tension device, in ancient catapults. The figure below illustrates the torsion device.
The twisted rope is commonly referred to as a torsion bundle. It consists of several lengths of rope with the arm inserted in between them. The rope is then twisted manually on both sides of the arm using levers. Upon release, the torsion bundle rotates the arm at high speed, launching the payload. The figure below illustrates how a torsion bundle is twisted.
The video below shows how to wrap the rope on a torsion catapult.
The fact that a mangonel uses an energy storage device that consists of a deforming material, like wood or rope, means that its throwing distance will not be as consistent as a trebuchet. This is because these materials (unlike more modern materials), naturally wear and lose elasticity during their use. This is something that needs to be constantly monitored during a battle, with replacement materials made readily available, if necessary.
In the next section we will briefly discuss the onager.
Catapult Physics – The Onager
The onager catapult is almost identical to the trebuchet, but instead of a falling counterweight, it uses a torsion bundle to rotate the arm (similar to the mangonel, described previously). Because of its design, it allowed for greater throwing distance than the mangonel (comparable to that of a trebuchet). But the throwing distance wasn't as consistent as the trebuchet since it relied on deformable materials as the energy source, which naturally wear and lose elasticity during their use.
Lastly, we will look at the ballista.
Catapult Physics – The Ballista
Source: http://en.wikipedia.org/wiki/Ballista. Author: Scigeek
The ballista is similar in principle to a crossbow, but much larger. Like the torsion powered mangonel, it used twisted rope as the energy source. The picture above shows the torsion mechanism consisting of twisted rope, located at the pivot location of the two side arms.
In the ballista, the bow string would be winched back and the tension set. It would be used to launch darts, bolts and spears with deadly force and accuracy. It could also be used to launch stone projectiles of various sizes.
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