Types of Engineering

Square vs Triangle Experiment

We created two models to demonstrate how a triangle is better to use in engineering. A triangle has only three joints and it evenly distributes compression force which allows it to stay stable. A square has four joints and a weak point at the center of each side. It doesnt distribute force easily which means it collapses easier than a triangle.

Bridge Made of Straws

With this knowledge, we built a bridge that was designed with triangles. This bridge was strong enough to hold about 80 hex nuts.

The First Day

On the first day of the project, our group split into two groups of three, the first group worked on the straw bridge, while the other bridge worked on the packet. In the packet, we followed each step in order to understand how structure can change the strength of a bridge. The first bridge we built was simply an index car that was placed over a gap between two wood blocks. The bridge was able to hold about 4 nuts before it fell. In the next step, we cut up another index card into strips and formed triangles. Then we added these triangles to the sides of the bridge, to help support the middle. The bridge was then able to hold up to 12 nuts.

Drawing the Scale Model

Once we had a basic design, it was time for us to draw a Scale model of our bridge. In our drawing, we decided that one inch was going to be equal to one foot. The purpose of this exercise was to see if another group could understand our drawing. Once we got our bridge back from another group, we saw that they understood our drawing easily. We also saw that there were little ways that we could improve our structure: like connecting the bottoms of the legs.

Final Bridge

As we built the final bridge, we saw that it would be best to double, triple, and even quadruple the balsawood sticks. Also, as we continued to build, our original design became more complicated because we added support beams where ever we saw weakness. Lastly, once the bridge was completely built, we tested it by placing bricks in every spot to see if there was any buckling.

The Robot

The robot team consisted of Tom, Aidan, and David. Since none of us had worked with Vex robots before, the very first couple of days were spent learning about vex and how to piece each of the parts together. We started like most of the other teams using a simple design with four motors. The wheels were connected directly to the four motors and the programming was relatively simple. However problems soon came. For starters, we thought we would be able to make the robot quite small, less than 6 inches is what we originally planned. The bridge designers were happy with this since the smaller the bridge the better. As time went on however, we realized that we could not make the vex robot under 6 inches, or at least not easily, due to the motor size and the vex pieces themselves. By now the bridge designers were already halfway through building the bridge and there was no turning back. So us robot designers quickly started coming up with crazy new designs for the robot, most of which either had less than 4 motors or had some gears. We also knew we would be needing gears, since without them, the motors were not strong enough. We went through more than 5 designs, with lots of trial and error. At one point, all three of us were designing separate cars, in order to test all of our different designs. Unfortunately, we did not managed to make a working car under 6 inches, and as a result, the car could not turn on the bridge. The main reason the car was more than 6 inches was due to the size of the wheels and motors of vex. In the end, we learned that communication is very important and that building should not take place until all aspects dependent on others are confirmed.

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