Ex-NASA engineer and Youtube inventor Mark Rober has made a perfect rock-skipping robot. Not only can the robot perform impressively, but it can help you learn how to skip rocks better too. Rober built the robot by tweaking a clay pigeon thrower, creating wooden custom throwing arms and a base for stability. Once he built a prototype, his team of assistants (nieces and nephews) gave Skippa, the rock-throwing robot a makeover with spray paint and giant googly eyes, then brainstormed test variables for a perfect skip.
How do you achieve the perfect rock skip? The team narrowed it down to four variables: the wrist angle of the robot (the angle of the rock relative to the water), the arm angle of the robot (which changes the path of the rock), and the rocks used (variations in diameter and thickness). To create uniform controls for robot tests, Rober and his team made their own rocks out of unfired clay (the clay discs easily dried in the sun, and dissolved in water under 30 mins).
After the robot tested some unsuccessful skips, it began to shoot rocks tumbling across the water in over 60 skips per throw. Here’s the recipe Rober finally found for the perfect rock skip: the rock should hit at a 20 degree angle to the water, with a 20 degree path, and a higher throw for more energy. Flicking the wrist as much as possible will help the rock spin, which will help the rock stable. And finally, the most important factors for rock selection is a flat bottom, and finding a rock that’s heavy but not too big to handle.
When Rober’s amateur engineering team tested the principles they learned from the robot, they were quickly able to improve their skips from an average of three to 16 skips.