Many people may remember spending a day by a body of water and learning how to skip rocks. There was always that one kid who made what seemed like dozens of skips. Meanwhile, most everyone else was debating whether a half skip counted. In reality, most of the time was spent searching for just the right rock.
While some people may still be able to get a few skips in, they might prefer to take a lesson from something unexpected. Mark Rober, a former NASA engineer and popular YouTube star and inventor, has built a robot that can skip rocks with precision consistently and can possibly even teach people how to perfect their stone-skipping skills.
“I made a robot—or, I suppose, more of a machine, but robot sounds way cooler—that could skip rocks really well,” Rober said. “Or, at least, it did eventually. We really just made it to have built-in adjustable parameters like wrist angle and arm angle so we could do experiments to find the best settings for a perfect rock skip.”
Rober’s quirky concept soon turned into something much more. He started by tweaking a clay pigeon thrower by building custom wood throwing arms and a stable base. His assistants—his nieces and nephews—gave life to the robot with some googly eyes and spray paint. The real challenge was figuring out how to make “Skippa” perfectly skip a rock.
The testing starting point came down to determining what variables needed to be considered for Skippa to work. Rober and his team focused on wrist angle, the rock’s angle relative to the water; arm angle, which can change the rocks trajectory; and the rocks themselves. The team created their own rocks made of unfired clay to ensure uniform controls.
Though initially there were some unsuccessful throws, Skippa soon was able to achieve 60 skips per throw. Rober discovered the formula for perfection required the rock coming into contact with the water at a 20 degree angle with a 20 degree trajectory. A higher throw was required for additional energy.
Additionally, skipping stone perfection requires flicking the wrist as much as possible for rock stabilization and, something that hasn’t changed over time, finding the right rock. It needs to be just the right weight and have a flat bottom.
After learning from the robot, Rober’s testing team was able to go from an average of around three skips per throw to 16. Check out Skippa in action here working to master the perfect skip.
Interested in more robotic innovations? Check out Chicago Engineers Building a River Cleaning Trash Robot and “Blind” Robot Can Climb Stairs and Traverse Rough Terrain.