This is my final product. The picture and the video already appeared in the previous blog post, but they are presented again for convenience. This model is able to adequately convert elastic potential energy into kinetic energy to power a propeller. However, it does not work due to the high mass of the whole model. The kinetic energy generated from the rubber band releasing its elastic tension was not enough to power this model. Occasionally, with the right conditions, the propeller will move the car a few centimeters forward, but this process is not stable and makes this rubber band-powered car nowhere near its optimal functionality.
Of course, when building this model, some risks had to be taken, as the original design (idea taken from a YouTube video) was built out of a lightweight plastic bottle and a bottle cap to hold the propeller in place. Some creativity was required to find a way to hold the propeller in place, determine an optimal length and width to accommodate the wheel axles and rubber band length, etc. In this case, the risks did not resolve as they should have, making the design not work. However, I spent a good amount of effort into this project and I was still able to explain the conversion of energy by explaining the balance between mass and kinetic energy.