- STM TOOTHPICK BRIDGE PROJECT
- Special Thanks to Mount Notre Dame Physics Department - http://home.cinci.rr.com/waynep/Project_Bridges.htm
- OBJECTIVES
Research actual bridge designs
Design a model bridge based on research
Submit construction drawings for approval
Build a bridge with toothpicks that can be tested for structural strength
Round or flat wooden toothpicks
Elmer's white glue
Paper for the roadbed (optional)
String (for suspension designs only) 3 meters max.; string must be procured from Mr. Throm.
- RESEARCH AND APPROVAL DRAWINGS
Each student will research bridge designs from literature or actual structures noting bracing points and reinforcements and how each design takes into account gravitational and load forces and the materials used. Each student will then create a bridge design and submit a drawing for approval. A simple force analysis (discussion) should be included (refer to the load testing procedure below). Approved drawings will be returned and used to construct the bridge.
As you begin to construct your bridge, you will undoubtedly want to make improvements (changes) to your design. Design changes are allowed. However, you must revise your drawings showing the changes you intend to make and submit them for approval prior to proceeding with construction. Once change approval has been secured, construction can continue (be aware that I may make minor adjustments to your requested changes).
Any design can be used as long as the roadbed is flat and unobstructed to allow a matchbox car to travel its length. The roadbed does not actually have to support the car; the car is used only to check clearance (i.e. the roadbed can be made of paper to save on weight). The bridge must be free standing and allow for a 2 cm. high x 30 cm. wide board to pass under the bridge while the bridge rests on a flat surface. Only the materials listed may be used to build the bridge. Excessive amounts of glue may not be used as part of the structure, i.e. the bridge or bridge joints may not be completely covered with glue.
Each bridge will be placed on two support structures. An 8" long, 1/2" diameter wooden dowel will be set across the center of the bridge on top of the road surface (set perpendicular to and on top of the road). Heavy-duty cord is looped over each end of the dowel which supports hanging weights below the bridge. 1 kg weights are added until all the weights are used up (total of 11 kg. / 25 lbs.) or the bridge structurally fails (breaks).
Each bridge will be graded using a ratio of supported load weight to total bridge weight i.e. heavier bridges must support more weight to achieve an equal grade.
Wayne M. Peppercorn © 2004
http://home.cinci.rr.com/waynep
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