Building Big

LESSON 1: TWIST, PULL AND PUSH: The best way to learn the terms Compression, Tension and Torsion is by experiencing them. You can experience compression by teams pushing their hands against each other's; tension by pulling against each other's curved fingers and torsion by hold each other's wrists with hands and twisting in opposite directions.

Then start testing materials for these three qualities. The materials we used were all household items (such as cloth, aluminum foil, clay, a rubber band and a drinking straw) that the boys had found the day before by way of a scavenger hunt.

Sometimes it was hard to decide how to rank the different materials in terms of tension, compression and torsion, but we did make a chart of the results of our testing, ranking the items from 1 (weak) to 4 (strong) in the different areas. We will use this information when we later build various structures.

LESSON 2: CREATING SHAPES
I started this lesson by printing out templates to build 3-D shapes. I asked them to predict what 3-dimensional shape might be formed when a 2-dimensional pattern was cut out and folded along dotted lines.This activity helped them learn the names and attributes of 3-dimensional shapes and explore the number of faces and vertices's they have. They discovered that both the tetrahedron and the pyramid have four triangular faces but that the pyramid also has a square base as its fifth face. These shapes serve as introductory concrete models as they continue to develop 3-dimensional geometric vocabulary and understanding.

LESSON 3: TOOTHPICK TRUSSES Making structures out of toothpicks and gumdrops is so much fun.

They learned that triangles made structures more stable because they formed a truss, which is a skeleton-like structure composed of struts, some of which are in compression and some in tension, which are joined to form a series of triangles. We looked at pictures of bridges which had trusses, which connected what they were learning to real-life situations. They had a wonderful time being creative and their structures just kept on growing!

LESSON 4: DOWEL DESIGNS: This task is to build a structure that would stand out of newspaper and tape only. The dowels are just made from newspapers rolled up and taped together.

LESSON 5: PAPER BRIDGES How many tiles do you think a bridge made out of a sheet of paper can hold?
What can you do to the paper to make it stronger?

Your task is to make a bridge out of one sheet of paper.

You can also use up to 5 paperclips, but nothing else.

The sides of the bridge must rest on two equal materials such as books, or as in our case, two storage containers, with about 8 inches between the sides.

You cannot use tape to tape down the sides.

Quentin used the paperclips to weight and support the sides and was able to hold a few more tiles.

Katie folded hers into an accordion and it held many more -about 20.

James folded his paper for added stability and reinforced the edges with the paperclips -and it held nearly 40.

The strategies were combined for the toughest of all bridges and we could pile on it as many as we could fit on the bridge and it could still hold more.

LESSON 6: SUSPENSION BRIDGES: In this lesson, you look at the differences between suspension and beam bridges.

The tension in the cables leading up from the bridge deck is balanced by the tension in the cables leading up to the anchor blocks as well as the compression in the towers.We made a model of a beam bridge by taping two straws together at one end and at the other end taping them together with a small piece of st aw as a spacer, making a tall triangle out of straws. We made two sets of these and these were the two towers of the bridge. The towers were taped to chairs and another straw was placed on top of the spacers to form a beam bridge. We made a load tester by hanging a cup from the beam, and they took turns putting coins in the cup. It held a fair amount (about 15 coins) before the beam bent, dropping its load.The next step was to make a suspension bridge and compare how much it could hold. We tied the center of a length of thread around the middle of a new straw and placed the straw between the towers. We passed each end of the thread or "cable" over a tower and down the other side. The cable then was pulled tight and anchored on the table. The cup of the suspension bridge filled with over 25 coins, but the bridge could have held more weight if the cup could have held more. We need to devise a system with a larger cup! After we finished with this activity, Quentin and James continued to use the materials to make structures to test.

LESSON 7:COLUMNS

When I think of a cylindrical shape, I think of columns. What could we use as a model of a column so we can experiment with it? Columns are often used to hold up heavy loads such as the roofs of buildings. The heavy load pushes on the column, putting it in compression. A good column, then has to be very strong in compression. Can a toilet paper tube then support your weight? First we experimented with an empty toilet paper tube and because the tube is round it was able to distribute the compression all around evenly, both James and Quentin could stand on the tube without it collapsing! Sam's weight, however, was too much and collapsed the tube. Then we taped the ends of the tube and filled it with sand. The tube now could distribute the compression of the weight outward from each sand grain and could now hold the weight, not only of Sam, but of Mom as well without collapsing. Wonder how much weight it would hold before it collapsed?