Group 6 Casey Ligrano Hampton Brown Nicholas Johnson Xuan Nguyen

2. Group 6 Casey Ligrano Hampton Brown Nicholas Johnson Xuan Nguyen

3. Presentation Outline • Introduction • Prototype Design • Design Process • Reasoning for A-frame design • Prototype bridge discussion • Final Design • Design presentation with changes made • Results of bridge improvements • Recommendations for the future • Conclusion

4. Introduction • Project Restrictions • Design a bridge solely out of tongue depressors and fishing line • Must span a 16” gap and be 2.5” to 3.5” wide • Use no more than 125 depressors and 60 ft of fishing line • The bridge must be as efficient as possible

5. Design Process • Three original choices: Suspension, Arch, A-Frame • Suspension: Makes use of fish line anchors • Can’t anchor them far enough away from bridge • Arch: Strong design, but hard to build • A-Frame: Strong like arch, easy to build

6. A-Frame Reasoning • Easy to build • Less likely to be built wrong (keystone) • Very efficient in holding center weight • Makes good use of materials • Able to make solid walls

7. Prototype Bridge

8. Construction Difficulties • Lack of time to work caused: • Poorly placed cross-braces • Warping in walls due to glue not drying • No pre-drawn design • Time was not managed well • Cross-bracing not predetermined

10. Prototype Performance • Weight: 0.638 lbs • Held: 478 lbs • Efficiency: 749.2 • Break Points • Top of bridge • Cross-brace cuts

12. Changes Made for Final Bridge • Go from 4 depressor tall walls to 3 tall • 4 depressors weren’t adding additional support • Using 3 depressors cut weight significantly • Cross-bracing changed • Went from slots cut into walls to slots cut into cross-braces • Hoped to decrease stress on bridge walls

13. Top of bridge heavily reinforced • Top was the part that gave out first • Reinforcement of top would add to the weight holding ability of the overall bridge

14. Final Bridge

16. Results of Bridge Improvements • Weight: 0.531 lbs • Held: 622 lbs • Efficiency: 1171.4 • Break Points • Cross-bracing • Walls (warped under weight)

18. Bridge Discussion • New design improvements over prototype • Top of bridge held completely • Shorter walls did not break • Prototype points that were stronger • Cutting into the cross-braces made them next to useless

20. Future Recommendations • A-Frame bridge is a good design • Possibly use a 50-50 ratio of cuts into side walls to cuts into cross-braces • More reinforcement of cross-bracing

21. Conclusion • Project Restrictions • Design a bridge solely out of tongue depressors and fishing line • Must span a 16” gap and be 2.5” to 3.5” wide • Use no more than 125 depressors and 60 ft of fishing line • The bridge must be as efficient as possible • Prototype-weight, held, efficiency: 0.638lbs, 478lbs 749.2 • Final-weight, held, efficiency: 0.531 lbs, 622 lbs, 1171.4 • Differences-weight, held, efficiency: -0.107 lbs, +144 lbs, +422.2