# Pythagoras Coffee Cup

Create a coffee cup that regulates the amount of coffee you serve yourself

Created: February 13th, 2019

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I personally do not have a daily drink routine. However, I have always secretly believed that people drink too much coffee and rely on it too much. (Sh. Don't tell anyone.) Therefore, for my project I decided to take advantage of a fascinating fluid dynamics phenomenon: the automatic Bell siphon. See from 2:24 to 3:15 of the video below for an explanation that is much clearer than anything I could provide.

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Automatic Bell Siphon Explained
Practical Engineering
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This is the mechanism behind the famous Pythagoras cup, one of the oldest known practical jokes. I decided to move forward with creating a "kit" that could turn any cup into a Pythagoras cup, thus limiting the amount of coffee a person could pour themselves at a time. Initial sketches from my brainstorming phase are below.

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From there, I made a rough prototype out of a Solo cup, a straw from Chipotle, a random plastic cover I found in my desk, and honestly far too much effort for what the final result was.

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But it worked! So, I could move forward with designing a better version. A mechanical engineer through and through, I started with a Solidworks model. I did some initial refinements, and the final CAD is shown below, along with each component individually.

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Cutaway view of the design, showing each of the components of a Bell siphon.
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Each individual component of the Pythagoras cup kit.
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I was initially going to create the riser and bell by folding a single piece of acrylic into a tube shape. However, my first test made me rethink this idea. An image of my first test below shows why I had to pivot.

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The piece warped, I couldn't get a tight enough radius, and making the edges meet cleanly enough to be watertight would be downright impossible. So, I decided instead to glue together four rectangular pieces of acrylic using acrylic glue, which when done correctly is extremely strong and nearly invisible. This process made a much more robust and watertight tube. My first effort is shown below.

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This worked quite well, although spots can be seen where I was a little sloppy and glue spilled onto the plates themselves. Finally, I made my final product and it worked great! It can be seen in the images below.

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My mood board for this project is below. I wanted to express the intersection of personal opinions, ancient physics, practical jokes, and modern manufacturing and materials that created this project.