Design Knowledge Intermediary
Toy cars, scaling model helps scientists understand how tires drive over sand
"Think of bulldozers, excavators, all these things that need to manipulate and move granular material around," researcher Ken Kamrin said. "These aren’t really optimized."
Thanks to a new scaling law, scientists can study the physics of tires traveling across sand by analyzing toy car models.
Researchers used scaling laws to study air flow across airplane wings, testing miniature jets in wind tunnels, but this is the first time scaling laws have been developed for studying sand as a transportation medium.
To scale air flow models, physicists look to scaleable equations that describe how air behaves -- specifically how it acts on an air foil at varying speeds. Similarly, researchers at MIT focused on arithmetic describing granular flow. The resistive force theory includes several equations that describe the resistive force acted on a moving object by a granular medium.
To test their scaling law, researchers 3D-printed a large and small version of two wheel shapes, lug and cylindrical, and drove them across a bed of sand in the lab. Lug wheels are designed to dig out pockets of sand as they drive, preventing slippage, while cylindrical wheels move more smoothly across the sands surface, preventing sinkage.

- www.upi.com