Bottle Balance, Water Bottle, Wine Bottle

####Bottle Balance, Water, Soda, or “Wine” Bottle: Whatever You Are Allowed to Bring to the Classroom

Please adjust the amount of water in the bottle to balance or play with the STEM behind it. It is a worthwhile project.

The Bottle Balance is one of the simplest math-science devices one can design. Yet, it is mind-boggling at first sight. Just sketch a parallelogram and play with the variables—length, width, thickness, angles, and position of holes. I was able to make my first design to work with a soda bottle at hand (500 ml) which has a 30mm cap. Then, I played with the variables and added a second hole. With a soda bottle, one can try to balance one full bottle or a bottle with whatever is left as one drinks it. And that is fun! If it does not work well, you can just drink some or if you drink too much, add more water. And water bottles work just as well as, if they fit into the holes (30mm or 28mm). The board can be printed in a small home printer.

Question: As you drink from the bottle, should the bottle be moved up or down and why?

I printed mine at 0.32mm at 10% infill using PLA. You could experiment with other printing parameters. Please try some tape, if needed, to help the bottom cap stay in the hole. A slight adjustment of the bottom neck might make a big difference.

Now the angle of the bottom wedge plays an important role, too. The 45-degree piece works well in most cases. To save filament and time, I decided to make some “shoes” (adapters) with various angles, just to allow more experimentation. They work well, converting 45 degrees to 48/50/55 degrees.

It takes a while to figure out all the math and physical gems behind the simple mechanism. The Millerville reference has a pretty good elaboration of the physics.

####Among the Files
1. Balancing boards with two different hole diameters (30mm & 28mm)
2. Three shoes/adapters with different angles (48, 50, 55 degrees)

####References
1. https://www.millersville.edu/physics/experiments/030/index.php
2. http://hyperphysics.phy-astr.gsu.edu/hbase/torcon.html

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