Monowheels have actually been around in one form or another since the 19th century. They began with an early bicycle design. After all, if something works with two wheels, could it also work with just one?
The first monowheel designs appeared as early as 1869. Several of these featured a seat for the rider with pedals connected to a small wheel, which was in turn connected to the outside wheel. The rider pedals the small wheel, and that drives the large wheel, creating motion. Even at that time, the monowheel was recognized as a difficult means of transportation: One publication remarked that the vehicle was "impracticable for ordinary mortals" (source: Museum of Retro Technology).
By the early 20th century, inventors were experimenting with monowheels powered by actual engines, including a 150cc single-cylinder engine prototype from 1910 that today sits in the Auto & Technik Museum in Germany. Some designers also built monowheels with airplane propellers up front to aid in steering. None of these designs ever became mass-produced.
In the 1930s, science magazines began featuring designs for car-like monowheels that were enclosed by metal and glass and could seat several people. One article even featured a monowheel tank equipped with a machine gun [source: Museum of Retro Technology].
For the next several decades, inventors would experiment with different monowheel designs -- although, arguably, not with the fervor that they had in the late 19th and early 20th centuries. By now, the drawbacks of a monowheel had been firmly established, and its practicality as an everyday vehicle for ordinary people was pretty much discounted.
But as you know, some ideas never die -- no matter how questionable they are. Up next, we'll look at monowheels today and concepts planned for the future.