Science Behind Catapults

1. Science Behind Catapults Science Olympiad

2. Catapult • Non-handheld mechanical device used to throw a projectile a great distance without the aid of an explosive substance. • 399 BC in the city of Syracuse (ancient Greece) • winched-down bucket • Work by storing tension either in twisted ropes or in a flexed piece of wood (in the same way an archery bow does, but on a larger scale). • Used during Medieval Times, then replaced with cannons

3. Ballista • Relied upon different mechanics using instead of a prod - two levers with torsion springs, consisting of several loops of twisted skeins. • Early versions ejected heavy darts or spherical stone projectiles of various sizes for siege warfare. • The advantage was the fast relaxation time of this system - possible to shoot lighter projectiles with higher velocities over a longer distance.

4. Ballista in Roman Empire • Romans developed it even further, especially into much smaller versions, that could easily be carried. • Proved its worth many times, in sieges and battles, on ships and on the land. It was even used to quell riots. • Replaced the wooden parts of the machine with metal - smaller and lighter - capable of even more power than the wooden version, since the metal was not liable to snap like the wood, and which required less maintenance. • video

5. Trebuchet • A pivoting beam and a counterweight that rotates the beam through an arc. • Used in the Middle Ages either to smash masonrywalls or to throw projectiles over them. • Much more accurate than catapults. • China in about the 4th century BC and in Europe in the 6th century AD, and did not become obsolete until the 16th century, well after the introduction of gunpowder • First use of biological warfare – threw diseased bodies on enemy.

6. Mechanics • Catapults/ballistas use a twisted rope or twine to provide power • Trebuchet uses a counterweight on a fulcrum, usually much closer to the fulcrum than the payload for mechanical advantage • A trebuchet also usually has a sling holding the projectile, which provides a larger arc without having to have a taller trebuchet, because it can be tucked underneath.

8. Tension • Used a long flexible arm, so that when the basket was bent backwards to give the weapon its throwing power, the arm wouldn't break making the weapon useless in battle. • Basket was tied or hooked in some way when bent backwards, so that large stones or other types projectiles could be loaded into the basket. • The tension powered catapult was often used for destruction of castle walls, but sometimes it was used as a defense weapon from the castle itself. • The tension catapult was able to throw and shoot farther than most other types.

9. Torsion • Ballista - used cranks to pull back the basket that held the projectile. • Torsion power created when the rope of the Ballista was twisted to generate the force. • Rope would get tighter and when released, the force would propel the projectile forward from the basket. • Missile was propelled with such force that it could take out several armored men in one shot or do serious damage to a castle wall.

10. Traction • Trebuchets - used people as the power source. • The men would bring down the shorter end of the long beam or arm, causing the longer end of the arm to flip up, causing the basket to lose it's projectile towards the intended target.

11. Gravity • A lever that uses centrifugal force to its advantage. • modified seesaw - when two people are on the seesaw and both are of close weight, the see saw balances it's self. If another person came up and jumped on one end of the seesaw with one of the people, the single person on the opposite end is likely to become airborne. • Like the seesaw, a gravity powered catapult is also pivoted in the middle. • Counter-weight built onto one end of the catapult and a basket or sling on the other. The projectile end was pulled down forcing the counter weighted end to rise. Once the projectile basket was released, gravity would pull the weighted end of the arm down, causing the projectile to hurl through the air.

12. Operation Junkyard: Catapult