Magus' Memories

KEY WORDS: STEM PROJECT, 4TH GRADE MATH AND SCIENCE, TRIANGLES, BUILDING TRUSS BRIDGE MODELS WITH PLASTIC STRAWS, TENSION AND COMPRESSION, BRIDGE DESIGN COMPETITION.

TRUSS-BRIDGE DESIGN, BUILD, TEST

A proud future engineer showing his design

DISTANCE EDUCATION ACTIVITY

SCIENCE: STATIC FORCES: TENSION AND COMPRESSION

In class we had already studied push-pull as they relate to motion. We also studied the internal forces that develop when materials are pushed or pulled. In math we studied the geometry of triangles, and all the important applications that we can do with them. We studied trusses in engineering.

1. Review online truss designs, and photos of truss bridges.

2. Review online uploaded videos of the different models built by students in preparation of the college and high school competitions: spaghetti bridges, popsicle bridges, toothpick bridges…and plastic straws. We will NOT use hot glue-guns, nor superglue.

3. Create your own truss design to span clear 15 ", and extra for supports.

Sample design sketck

4. The materials to be used are: standard plastic straws without elbow (One packet of 150), masking or blue tape, scissors and a ruler. Before cutting anything, you must prepare a drawing (plan) that you will follow. Remember the engineering challenge: no wasted materials, use as little as possible, maximize the result.

Basic materials and tools tested

5. The straws and their particular nature (tubes) are the main material. Tape is to be used only to join and secure. We are not testing the tape. Bridges that are all wrapped in tape will not count. Tape is not magic. Your brain has more magic than that.

Prefabrication of repetitive units by using a "tool" or template with three nails on a board.

Blue straws inserted into each other, for the road

6. The model you will build is in 3D, with an internal “road” of 3 inches wide. The clear span between supports is 15 inches, and leave an extra edge of 1.5 inches at each end. The model has to be resting by gravity, without being attached, on the two supporting sides.

Assembled elements using three trusses. Two for the sides, one for the "road"

8. THIS IS A SCIENCE EXPERIMENT. YOU MUST TAKE NOTES IN YOUR LOG. Set aside some pages for these notes. Use this page to describe: objective, materials, and procedure. Make a neat drawing that you will follow to build your design. The drawing is your hypothesis. After testing, complete the results , comments and reflections.

WE WILL DO THE TESTING ONLINE, IN FRONT OF EVERYBODY.

9. TESTING: Find stable supports and separate them 15". Sit by simple gravity the model on the supports. Place a ruler, or any flat small piece of wood, across in the center of the model. Hang a shopping bag, slowly load the bag with weights determined, observe deformations and weak points, keep a tally of weights in the bag until you stop the test.