Centreless wheel
A centreless wheel or hubless wheel is a wheel that lacks a centre or hub, instead being supported and driven at the rim.
Design
Centreless wheels are toroidal in shape and have one or multiple bearings along the rim. Propulsion can be achieved in different ways, such as with gear teeth along the inner surface of the rim. They can be made lighter than solid and spoked wheels, resulting in better handling, and less rotational inertia. The lack of spokes or a traditional hub also allows for more space, which can be used to more easily package a hub motor.Centerless wheels were built and patented for monowheels by at least 1869 and were proposed to replace conventional wheels by at least 1890. Prototypes for multi-wheel vehicles were built by Franco Sbarro at least by 1989, and Paul Lew had started small-volume commercial sales by 1993.
The mass production of centreless wheels has not been pursued by many large companies due to their complexity, with their use mostly limited to small companies, limited run vehicles, concept vehicles, and scientific analyses.
Examples
''Black Hole'' Bicycle Wheel
The Wear and Tear Black Hole front bicycle centreless wheel and fork was designed with the goals of lighter weight and better aerodynamics than conventional wheels. It supported the rim with several small rollers, which reportedly wore out quickly - acceptable for a race-oriented product, but not practical for everyday use. The Black Hole was sold starting in 1993. Production was stopped after it was banned by the Union Cycliste Internationale, as the downsides meant it was not compelling for general use. One of the designers, Paul Lew, later developed improved lightweight aerodynamic wheels using hubs. Today, conventional wheel+fork assemblies are lighter than the Black Hole. It is unclear how modern aerodynamic wheels compare.''Tron: Legacy'' Light Cycle replica
One real-life example of hubless wheels are those used in the replica Tron: Legacy Light Cycle. The street-legal motorcycle was modelled after the vehicle from the film and sold through Hammacher Schlemmer. Its hubless wheels are made from former truck tires, and a chain-driven friction drum provides power and brake force.Designed "for casual cruising and slow ride-bys at shows", it consists of a fuel-injected Suzuki 4-stroke engine in a steel frame covered by a fiberglass body with electroluminescent wire lighting.