THE PROJECT
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What We Did
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The Stirling Engine
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The Science
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My Thoughts
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We went in to the project with a very high expectation of what we could do. After bouncing around ideas ranging anywhere from blimps to a steam powered car, we settled with the design of a Stirling Engine (explained at right). This worked in tandem with the building of the chassis of the car, which was not attached to the enigne. The reason for this, beside logistical issuses, was that we feared the engine not working. This fear came to be realized, when we found the deadline bearing down upon us and no finished product in sight. Thereafter, we started work on our gravity powered car, as shown in the timeline in our presentation. As presenation day came, tested our car and tried out numerous pully systems. As none of them worked, we went with a simple single pulley system, and refined the wheels. Overall, our group produced a satisfactory car in a fraction of the time alloted, as well as investigating a highly intruiging design.
The more complex of our designs warrents an explenation. The idea of a Stirling Engine is simple in concept, taking advantage of the principle that hot air expands. We confined the air in a chamber, that, when heated, pushed on a piston. This piston lead to a wheel that forced another peice of wood upwards, forcing a piston down on the other side by means of a lever. This piston forced air into a chamber ajoining the hot chamber, therefore pushing the first piston back into place and starting the process over again. For a visual, refer to the presentation above.
An aspect of our presentation that may appear confusing is our graphs. The first of which is a time vs. distance graph, which is self-explanatory. The next graph, of time vs. velocity, shows how the car accelerated quickly, then had a constant acceleration, and finally tapered off. This reflects how the car's weight constantly turned the axle before hitting the base of the car and stopping it. The final graph is one of energy. All of the car's energy started out as potential energy (Energy equals mass times acceleration (9.8 m/s squared) times hieght) when the weight was raised. Over time, the weight dropped and converted potential energy into kinetic energy (which equals 0.5 times mass times velocity squared). However, you can see that the amount of kinetic energy is reletivley low. This is due to the fact that the energy was lost as heat (thermal energy). Note that the total energy stayed constant, reflecting the law that energy cannot be created nor destroyed.
Everbody in my group had high expectations for this project. We had a satisfactory amount of time, acsess to materials, and good tools. However, this project is case number one in examples of overambition. Starting with our first design, we opted not to use a step-by-step plan we had found, instead going for our own design. Afterwards, we also alloted too little time for the finessing of the engine, leading to delays and the ultimate cancellation of that engine. However, we had planned for this, showing that we did have some foresight. Using a blueprint we had made at the begininng of the build period, we quickly built and attached the necessary parts for the gravity powered car. Numerous meetings outside of class were necessary to see this project to frutation, showing our commitment to each other. This is highlighted in our grading of each other, resulting, on average, with the highest grades that I have ever given and recieved, as well as the highest group average that I have witnessed. However, one thing that still irks me about this project is the quality of construction. Although the level was not the worst in the class, I felt this greatly contributed to our problems. "Flat" wooden wheels, or axles not correctly secured, or many other problems plauged our group. That being said, we overcame those problems and produced a vehicle that was asthetically pleasing, as well as practical in our enviroment.
View Our Presentation
An overview of the project, including descriptions, timelines, costs, and much more.