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6th Grade Social Studies Ancient Engineering

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6th Grade Social Studies Ancient Engineering

  1. 1. Let’s Build a...Catapult!
  2. 2. Need a blank piece of paper
  3. 3. So what's a catapult? The goal of a catapult is to fling a mass into the air - mainly to inflict damage.
  4. 4. What is a Catapult? ● A catapult is a mechanical device used to store potential energy, then release it as kinetic energy as it throws a projectile a great distance.This is done without the aid of explosives. ● The word 'Catapult' comes from the two Greek words: kata: downward and pultos: a small circular battle shield. ● Katapultos (Catapult) then means “shield piercer”
  5. 5. History
  6. 6. History of Catapults Humans have limitations! We can only lift so much, can only throw so high...
  7. 7. History of Catapults By increasing the energy stored in projectiles, you can increase the amount of damage they will inflict.
  8. 8. History of Catapults War has always been a motivating force in development of new technologies. This helped engineering advance in many areas, not just weaponry.
  9. 9. History of Catapults Engineers researched ways to increase these forms of energy storage in weapons in order to increase their damage.
  10. 10. History of the catapult In 399 BC Dionysius of Syracuse created a think tank to design and build weapons for his campaign against Carthage. The goal was to overcome limitations of the basic bow and arrow - how could they increase the energy stored?
  11. 11. Who Invented the Catapult? (3rd c. BCE) ● Ancient Greek mathematician Archimedes (b. 287 BCE) is credited with inventing the catapult along with other “war machines” (Death Ray, the Iron Claw, and Steam Cannon). ● Archimedes developed the fundamental principles of mechanics; and methods for finding the center of gravity, surface area, and volume of geometric figures. He also derived an estimate for the value of Pi. (Can we say, genius?!)
  12. 12. Catapult Development ● War has always been a motivating force in development of new technologies. ● An interesting thing about catapults is that they developed over time from smaller weapons. ● The Catapult is a derivative and direct result of the Bow. ● The catapult is the end result of the desire to make weapons that are bigger, more powerful, and can hurl bigger objects longer distances.
  13. 13. Types of Catapults Catapults can be split into three categories: ● Traditional Catapult ● Ballista ● Trebuchet
  14. 14. ‘Traditional’ Catapult A traditional catapult looks like a bucket on a long arm being held down by some form of tension. These were used into medieval times.
  15. 15. Engineering
  16. 16. Traditional catapult The traditional catapult uses stored elastic energy (potential energy) by twisting and stretching ropes and in the bent wooden arm used to vault its mass into the air. Think about bending a spoon back to launch peas across the table!
  17. 17. Forms of Energy ● Potential energy (stored) is energy when matter is still. ● Kinetic energy is matter in motion.
  18. 18. Winch A traditional catapult can store more energy to send their projectile further by using a winch. The winch is a wheel and axle simple machine
  19. 19. Winch A winch allows a person to store a great amount of energy (in this case, tension) over a period of time
  20. 20. Ballista Ballistas and other arrow-shooting machines were the first catapults. A ballista looks like a giant crossbow.
  21. 21. So to increase the potential energy... ● Heft the projectile higher off the ground ● Make the projectile heavier
  22. 22. Strain How do these forces store energy? Imagine a loose rubberband vs. a taut one.
  23. 23. Potential energy Potential energy is stored in rubberband, just like how potential energy is stored in bow when bow is drawn.
  24. 24. Bow and arrow As you pull the string of a bow, your arm does work. The energy that it takes you to pull that string is stored in the bow as tension.
  25. 25. Bow and arrow When arrow is released, elastic energy transfers to the kinetic energy of the arrow
  26. 26. Compound bow Bow makers discovered they could strengthen the bow even more if they combined: ● Wood ● Animal horn ● & Animal sinew
  27. 27. Compound bow Horn holds up better to compression so was added to the inside of a wooden bow while sinew holds up better to tension so was added to the outside
  28. 28. Compound bow Now limitations are physiological - meaning humans were limited by their own bodies Can you think of what they might be?
  29. 29. Compound bow ● Length of an archer’s arms ● Strength of arm, chest, & shoulder muscles ● Strength and dexterity of fingers
  30. 30. Compound bow Because of these limitations, the best possible bow required 45 pounds to pull with a 28 inch draw range.
  31. 31. Back to the think tank... So how was the group going to advance bow and arrow technology? Their first solution was the gastraphetes or “belly bow”
  32. 32. Gastraphetes
  33. 33. Increased draw force
  34. 34. Increased draw length
  35. 35. Increased control
  36. 36. Increased control
  37. 37. Advancement and Progress Weapon makers continued improving the gastraphetes. What did they do to make it better?
  38. 38. Advancement and Progress Made it BIGGER of course! This development led to technological advancements that made the first true catapult possible.
  39. 39. The 1st Catapults
  40. 40. Zopyrus’s Bow-machine Stiffer bows made cocking the weapon more difficult. A windlass was added to the back of the weapon to draw the arrow back.
  41. 41. Zopyrus’s Bow-machine While this allowed for larger arrows, now the entire weapon needed to grow in size, making it unwieldy as a hand held weapon. A base was added.
  42. 42. Zopyrus’s Bow-machine Bows on this first model of catapult were maxing out the size that artisans could make them.
  43. 43. Catapult development Composite bow temporarily meets its limits. Developers must now turn to fundamentally different ways of storing elastic energy. This path led to the Torsion Catapult.
  44. 44. Torsion Catapult Torsion catapult development occurs over a series of discoveries and advancements, starting in mid 4th century B.C.E. By end of that century we have the arrow shooting weapon called the euthyntone and the stone throwing weapon called the palintone.
  45. 45. Euthyntone & Palintone
  46. 46. Torsion springs Much of the hardware looks the same: stock, rachet, trigger, windlass, etc. What’s new are vertically aligned torsion springs.
  47. 47. Torsion Torsion is the twisting of a beam or structural element
  48. 48. Torsion springs Torsion springs in a palintone consisted of bundles of rope with a wooden arm thrust through the center. What material do you think was used for this rope? Think back to when we talked about materials that could withstand compression or tension.
  49. 49. Torsion springs
  50. 50. How powerful were they? Reports of arrow shooters that could shoot 200 yards and Roman ballistas that could throw 200 lb stone balls 400 yards.
  51. 51. Ramifications These torsion catapults were so important for city defense, walls were made thin to support arrow shooters on the inside.
  52. 52. Advances in catapult technology Scorpion Cheiroballistra Hatra ballista
  53. 53. ‘Traditional’ Catapults
  54. 54. 56 Gastraphetes The gastraphetes (`belly-bow´) was invented about 400 BC and is considered the first mechanical weapon. It was cocked by resting the stomach on the stock and pressing down. The military effect of this weapon during the siege of Motya (Sicily) 397 BC encouraged the Greek engineers to develop a larger gastraphetes, mounted on a carriage with a windlass to cock it.
  55. 55. Mangonel ...and we finally get our traditional catapult!
  56. 56. 58 Ballista Physical limits prevented further enlargement of the composite bow. In the mid-fourth century BC torsion springs, made from horse-hair or sinew, replaced the bow. Such a spring could be enlarged indefinitely. Inscriptions on the Acropolis of Athens first mention torsion spring catapults there about 330 BC and Alexander the Great employed them on his campaigns. The Greeks used two types: the euthytonon for shooting arrows and the palintonon for throwing stone balls. These war engines are better known today by their Roman name: the ballista.
  57. 57. 59 Onager The onager (wild donkey), was a torsion engine similar to the ballista but only one arm. This catapult was the largest weapon used by the Roman army, almost exclusively for siege warfare.
  58. 58. 60 Traction Trebuchet In the 6th century AD, the Chinese developed a large- scale stave sling with a crew that pulled the pole. Known today as a traction trebuchet.
  59. 59. 61 Trebuchet Trebuchet was the ultimate achievement in mechanical siege engines. Developed in the Far East and brought west in the 10th century by the Mongol and Muslim armies.
  60. 60. 62 Trebuchet in Europe European armies encounter and adopt the trebuchet during the Crusades of the 12th century. Siege of Jerusalem
  61. 61. 63 Biological Warfare Casting a dead horse into a besieged town (from Il Codice Atlantico, Leonardo da Vinci) During medieval times, siege machines were the first weapons used for biological warfare. The carcasses of diseased animals and those who had perished from the Black Death were thrown over castle walls to infect those barricaded inside.
  62. 62. 64 Mangonel The mangonel is a simplified trebuchet using a fixed counter-weight.
  63. 63. 65 Decline of the Trebuchet In this siege scene, taken from a 14th century document, a trebuchet stands behind the weapon that would ultimately replace it, the cannon.
  64. 64. 66 Return of the Trebuchet Many modern reproductions of trebuchets exist today. The trebuchet in Denmark’s Medieval Center is built of oak and medieval craft techniques were used in its construction. Has a ballast of 15 tons and is designed to throw projectiles of up to 300 kg. Counterweight lifted by human powered “hamster wheels”
  65. 65. 67 Punkin Chunkin Yearly pumpkin throwing contest in Delaware Ballista Trebuchet Onager
  66. 66. 68 Pumpkin-Throwing Trebuchet
  67. 67. Sketch designs
  68. 68. Reminder Bring in a water bottle cap
  69. 69. 1. NEVER launch at people, animals, or things of value 2. ONLY use these with supervision! 3. Ask for help using potentially harmful tools, like a knife, hot glue gun, wire cutter, or electric drill 4. Anyone aiming at others, doing stupid thing will be done! WARNING
  70. 70. Day 2….. Let’s Build An Easy One ● 9 popsicle sticks ● 7 rubber bands ● 1 bottle cap ● 1 marshmallow/pom for ammo ● Hot glue gun
  71. 71. What other version can you make? Restrictions ● Must fit within 8 x 8 inch square ● Use only what you need ● If you don’t plan on keeping item please leave behind to be recycled ● Respectful of space and materials
  72. 72. Catapult simulator http://thred.github.io/xkcd-time-catapult/#0033 Change these factors and see how they affect catapult performance!

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