A wheel is a wheel, right? We sorted wheels out way back in the caveman times or something, and we have only improved on them since then by making them rounder — except that isn’t quite true. Wheel technology is still very much in development, and we’re not just talking about improved tire rubber. If you want proof of that, look no further than the famous Omniwheels and Mecanum wheels that seem to defy physics. Maker’s Muse has 3D-printed some pretty strange wobbly wheel toys in the past and wanted to find out if they’re suitable for robots. To test that, he built this little four-wheel drive robot and equipped it with a variety of unusual wheels.
The first wheel type demonstrated, dubbed the “Wobbly Wheel,” may look familiar if you’ve seen videos from Maker’s Muse in the past. These have a very odd shape that seems like it shouldn’t even be able to roll at all, because that shape looks like a ellipse if you’ve viewing it perpendicular to one of the flat sides. But it is all a matter of perspective and those flat sides are not parallel to the direction of travel. In actuality, the entire tread surface of the wheel is the same distance from the center hub, so they roll perfectly well. The other unusual design, nicknamed the “Prongle Wheel,” is shaped like a hyperbolic paraboloid—or a Pringles chip. Like the Wobbly Wheel, it looks like it shouldn’t roll, but can thanks to the fact that the tread surface is actually a cylinder.
Those two wheel designs were put up against two other, more conventional, designs. The first was a simple disk, which is basically the quintessential wheel. The second looks like the paddle on a steamboat. It is important to note that Maker’s Muse ensured that all four wheels had roughly the same surface area on the tread. The wheels were attached to a remote control, 3D-printed rover robot, with each wheel getting its own gear motor. The wheels were tested on carpet with a load cell to see how much traction they could achieve on a low-friction surface, and then were given a real world test on a sandy beach. The plain disk wheels performed the worst in both scenarios, and could barely move the robot in the sand. From there, the Wobbly Wheels came in third, the Prongle Wheels came in second, and the paddleboat-esque 8 Spoke Wheels claimed gold. That was likely due to each wheel’s ability to “bite” into the sand (and carpet) in order to gain traction. This information may not be particularly useful to you, but it is interesting to see outlandish wheel designs and how they can actually outperform traditional designs.