Between the 1860s and the 1930s, inventors across the world kept returning to one of the strangest ideas in the history of transportation: a single giant wheel with the driver sitting inside it. Known as the monowheel, or monocycle, this vehicle was proposed again and again as the future of personal travel. It never became that. But the machines themselves, and the people who built and rode them, left behind a fascinating and peculiar chapter in engineering history.
A monowheel works differently from a unicycle. On a unicycle, the rider sits on top of the wheel. On a monowheel, the rider sits inside the wheel’s circumference, cradled within the rotating outer loop. The system functions like a giant ball bearing. The engine drives the outer wheel, while the inner frame — where the driver sits — stays relatively level due to gravity. The principle that keeps it upright is the same one that keeps a spinning gyroscope from falling over: as long as the wheel keeps moving, it resists tipping.
That stability, however, came with serious limits. Steering was extremely difficult. Braking was dangerous. If the machine accelerated or stopped too quickly, the rider would spin inside the wheel like a hamster on a running wheel — a problem engineers never fully solved. Contemporary observers called these vehicles “impractical for ordinary mortals,” and that description was not unfair.
The first known monowheel dates to 1869, created by a French inventor. It was pedal-powered, with a smaller wheel beneath the rider’s seat that drove the large outer wheel when the rider pedaled. That same year in the United States, Richard C. Hemming patented his own hand-powered design, which he called the “Flying Yankee Velocipede.”
Horse-drawn monowheel concepts also circulated during the late 19th century, with designers imagining the giant wheel being pulled or pushed by animals rather than engines.
As the 20th century began, inventors started replacing pedals and horses with engines. Gas motors and electric motors both found their way into monowheel frames. Italian inventor Davide Cislaghi built a motorized monowheel capable of reaching 40 mph by 1923, making it one of the more capable machines of the era.
The Italian monowheel tradition continued into the following decade. Cislaghi was still testing new designs by 1933, and another Italian inventor, M. Goventosa de Udine, pushed the concept to an extreme — building a single-wheel motorcycle that could reach an astonishing 150 kilometers per hour, or about 93 mph.
Other designers tried different approaches to the steering problem. Some attached airplane-style propellers to the front of their monowheels to help guide the vehicle. These designs were published in scientific magazines and drew public curiosity, but none of them went into production.
In 1917, French inventor D’Harlingue built his own monowheel, and Alfred D’Harling later developed what he called the “Aero-unicycle,” incorporating aeronautical thinking into the frame’s design.
Professor E.J. Christie took a completely different approach to scale. In 1923, he built a monowheel measuring 14 feet in diameter — a genuine monster of a machine that towered over a person standing beside it.
The Italian Motoruota, which appeared in a 1927 issue of Motorcycling magazine, represented another serious attempt to bring a motorized monowheel to public attention. Like its predecessors, it remained a curiosity rather than a commercial product.
By the early 1930s, the monowheel had found a new audience in popular science publications. Magazines ran illustrations of enclosed, car-like monowheels made of metal and glass that could seat up to three passengers. The concept seemed futuristic and exciting on paper.
The year 1932 became the high point of monowheel history, largely because of one man: Dr. J.A. Purves of Taunton, England. Purves believed the monowheel was the most simplified form of motorized transportation ever conceived. He built a vehicle he called the Dynasphere — a large, radial-tire-shaped machine that enclosed the driver within its rolling frame. Purves considered it a potential revolution in how people moved from place to place.
Purves tested the Dynasphere at Bream Sands near Weston-super-Mare in Somerset, England. He built two versions — one powered by petrol and a smaller one driven by electricity. Both were tested on the beach, where the flat, open terrain gave the machines the best possible conditions for a run.
The Dynasphere was also demonstrated at Brooklands, the famous racing circuit in Surrey. Crowds watched the machine roll around the track, reaching speeds of up to 30 mph. It was fast enough to impress onlookers, but that was about the extent of its appeal.
The Dynasphere had real problems that no amount of public enthusiasm could fix. It could carry only one additional passenger. Braking was unreliable. Steering remained as difficult as it had been on every monowheel before it. The vehicle struggled to gain the attention of manufacturers or investors, and Purves’s dream of revolutionizing transport faded quickly.
Other inventors tried to apply the monowheel concept to military use. Hugo Gernsback designed a “trench destroyer” — a large, weapon-equipped single-wheel vehicle meant for use in warfare. The Treffaswagen, a spherical tank armed with weapons, actually reached the trials stage, making it the only armed monowheel vehicle to be physically tested.
By 1935, the monowheel had shifted from an engineering proposition to a spectacle. Walter Nilsson rode his monowheel alongside a man on a penny-farthing bicycle — a pairing that captured just how much the monowheel had become a sideshow curiosity rather than a serious vehicle.
Some monowheels survived into museum collections. The Edison-Puton monowheel, for instance, is preserved today at the technical museum in Sinsheim, Germany, where visitors can see the design up close.
Below are additional historical photographs showing the range of monowheel designs across the decades — from early sketches and prototypes to the machines that were actually built and ridden.
