Graduate student Ackeem Ngwenya has combined the 6000 year-old wheel with modern materials to develop a new type of all-terrain wheel assembly that switches from narrow to wide tread at the turn of a screw. His Roadless wheel system, while envisioned for rural applications in his native Malawi, has the potential to be as big a change to road (and off-road) transport as was the introduction of anti-lock braking.
We've all done it. Before embarking on a long driving trip on smooth-surfaced interstate highways or other roads of national importance, we'll raise the tire pressure to boost the gas mileage a bit. Stuck in the snow, mud, or sand? Let some pressure out of the tires to increase the contact area, while at the same time increasing the chances that the now floppy tire will grab hold. However, the benefits of trying to change the aspect ratio of a tire by simply changing pressure are rather minor, and often associated with a significant loss in tire lifetime.
The Roadless wheel system attempts to throw out the limitations of a pneumatic tire by substituting a tread material wrapped around a pair of rod networks attached by an axle. The rods are adjusted using a mechanism reminiscent of a scissor jack.
When the disks on which the rods are mounted are far apart, the wheel takes the form of a wide tire of small diameter. When the disks are moved close together, the wheel becomes a narrow tire of large diameter. The proximate rods from the two disks are mutually attached to a fixed bearing (light blue circle).
The tread of the wheel must be sufficiently compliant to adapt to the changing aspect ratio of the wheel, so is likely to be some form of elastomer.
Alternately, the wheel can include compliant members that directly form the shape and supporting mechanism for the tread, which can then be as simple as a sheet of rubber.
The video below tells the story of Roadless, and also shows more clearly how it adjusts to varying terrain. There are a host of variations of this basic idea, whose genesis was to make it easier for people living in rural Malawi to more easily deliver their goods to market. It does not seem likely that this concept will stop there.