Big wheeled bikes are very stable, due to the gyroscopic effect of the large wheel. But small wheeled bikes take up less space and are very manoeuvrable. The Lunartic is a bike design submitted for a Dyson Award that tries to combine the benefits of both.
The designer writes:
Belt drives are clean and maintenance free and a hubless wheel creates a whole new space, as well as an intriguing aesthetic. The combination of these features is a new balance of ride quality, space saving, style and convenience. Moving the working parts back, inside the rear wheel shortens the wheel base but maintains large wheel performance and there is no sacrifice to conventional geometry.
The hubless wheel is driven by a toothed track inside the wheel. Given that the spokes of a conventional wheel are an incredibly light and sophisticated way of holding a wheel's shape and giving it strength, one wonders what one gains by eliminating them. Perhaps having all of the greater weight of the hubless wheel on the outside increased the gyroscopic effect and adds to the stability. Or maybe it just looks really cool.
But the designer says it serves a purpose:
There is the possibility for more use of the hubless space, to house the front wheel if folded, as luggage storage or with an edited mechanism, complete housing of the whole drive system.
Perhaps. More at James Dyson Awards