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The Workings of a Trebuchet

The Workings of a Trebuchet. Tara Dougherty, Oscar Esqueda, Lawrence Willis, Tri Phan School of Engineering and Computer Science University of the Pacific Thursday, December 4, 2003. Outline. Introduction Materials Theoretical Energy/Distance Equations and Graphs Proposed Design

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The Workings of a Trebuchet

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  1. The Workings of a Trebuchet Tara Dougherty, Oscar Esqueda, Lawrence Willis, Tri Phan School of Engineering and Computer Science University of the Pacific Thursday, December 4, 2003 University of the Pacific

  2. Outline • Introduction • Materials • Theoretical Energy/Distance Equations and Graphs • Proposed Design • Construction • Competition Results • Performance • Conclusions and Recommendations University of the Pacific

  3. Introduction • Recreate medieval weapon to launch a hacky sack • Distance and accuracy • Dimensions: 3 x 4 x 2.5 feet • Light weight, accurate, and long hurl distance • Counterweight is about 12 pounds • Safety, Teamwork, Communication • GOOD TIMES.....FUN!!!!!! University of the Pacific

  4. Materials • Three, 2 x 2 x 10 pieces of wood • Eight 2 x 1 x 10 pieces of wood • Liquid Nails, Screws, Wood Glue • Screw Drivers, Table Saw, Electric Drill • ¾ inch drill bit • Chain, Jean Pocket, Rope • Cement, 12 pound counterweight (milk jug) • Four UOP students and the workshop University of the Pacific

  5. Effects of Pivot Height Theoretical Pivot Height: 2.4 feet University of the Pacific

  6. Effects of Counterweight Length Theoretical Counterweight Length: 1.75 feet University of the Pacific

  7. Effects of Sling Length Theoretical Sling Length: 2.75 feet University of the Pacific

  8. Theoretical Optimum Geometry L1 = 0.75 ft L2 = 3.0 ft L3 = 2.75 ft L4 = 1.75 ft L5 = 2.5 ft M1 = 12 lbs M2 = 0.0625 lb Mb = .5 lb University of the Pacific

  9. Construction • Started on the project early!!!!!! • Hacky sack went backwards on the first trial • Liquid Nails is very messy!!!! • Original axle: 1.5 feet x ½ inch • we made it shorter and thicker University of the Pacific

  10. Construction Cont. • Difficult to neatly put together the joints • The balsa wood trough saved on weight! • Test trials greatly improved after designed a new pouch shape! • Use a triangle sling-pouch instead of a square one! • Special way to attach sling worked wonders! University of the Pacific

  11. Final Design Dimensions L1 = 0.75 ft L2 = 3.0 ft L3 = 2.25 ft L4 = 1.3 ft L5 = 2.5 ft M1 = 12 lbs M2 = 0.0625 lb Mb = .5 lb University of the Pacific

  12. Competition Results • Weight (lbs): 14.45 • Distance (ft): 70 • Offset (ft): 2.4 • Score: 0.94 • Rank: 8th University of the Pacific

  13. Conclusions and Recommendations • Overall, we are pleased with the results!!! • Test using 12 lb counterweight (we used 10 lbs) • Should have used the soccer ball hacky sack in both trials • Use Powdered Graphite Lubricant on swing axle • Construct joints neatly • Monitor the trebuchet weight closely • Use a camera that works because we lost all the pictures in the beginning stages of the construction!! University of the Pacific

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