group 6 casey ligrano hampton brown nicholas johnson xuan nguyen
TRANSCRIPT
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
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
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
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
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
Prototype Performance
• Weight: 0.638 lbs
• Held: 478 lbs
• Efficiency: 749.2
• Break Points– Top of bridge– Cross-brace cuts
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
• 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
Results of Bridge Improvements
• Weight: 0.531 lbs
• Held: 622 lbs
• Efficiency: 1171.4
• Break Points– Cross-bracing– Walls (warped under weight)
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
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
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