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