February 15, 2009 The Tweel is an non-pneumatic Tire/WhEEL combo which offers an idiot-proof, no-maintenance, easily-retreadable tire for consumers and the holy grail for the military - a tire that can't be “shot out.” You won't see the Tweel on your sandmobile any time soon because it has noise, vibration, heat and wear problems at highway speeds, but its unique construction enables it to be specifically engineered with ideal characteristics for highly specialized low speed applications. The ultimate badge of credibility was bestowed on the design when it rolled down Pennsylvania Avenue on NASA’s Small Pressurized Lunar Rover prototype during the Obama presidential inauguration.
Despite the fact that Michelin has been supplying space shuttle tires for more than two decades, years, NASA's choice of Tweel-based technology in the development of new wheels for its lunar vehicles validates the claims Michelin has been making about the ability to engineer “designer properties” into its Tweel for specific applications.
NASA's testing and authentication procedures are among the most exacting known to man – it aims to deliver the very best people, procedures, materials and technologies for each space mission so in our mind, the design of the Michelin Lunar Wheel validates the Tweel's design. Sure, it has been demonstrated on a range of specialist machines designed for low-speed applications such as earthmoving and construction equipment and mobility aids, but evn the Tweel's appearance on Dean Kamen's Segway, Centaur and iBOT could have been a publicity-inspired gimmick. Their appearance on a Lunar Rover is most definitely NOT a gimmick.
The Michelin Lunar Wheel underwent testing in Hawaii from October 31 to November 13, 2008 as part of NASA’s lunar analogue testing and evaluation program. The terrain, rock distribution and soil composition of Hawaii’s Big Island provide a high-quality simulation of the lunar polar region.
Made of composite materials, the structurally supported tyre/wheel assembly was jointly developed by Michelin’s European and North American research centres and Michelin claims its Tweel technology will help meet NASA’s mobility needs for both manned and unmanned missions to the moon over the next decade.
Based on the Michelin Tweel®, the Michelin Lunar Wheel maintains flexibility and constant ground pressure, allowing the vehicle to move through loose soil and craters. In addition, it combines low weight and high load-carrying capacity, making it 3.3 times more efficient than the original Apollo Lunar Rover wheels. Its textile tread, developed in partnership with Clemson University and Milliken & Company, enables the rover to maintain traction at very low temperatures.
Tweel consists of a composite reinforced tread band, connected to a flexible (deformable) wheel via rectangular, polyurethane spokes. The resulting mechanical structure provides weight-carrying ability, shock absorption, ride comfort, rolling resistance and mass similar to pneumatic tires while adding suspension-like characteristics that greatly improve handling.
The Tweel automotive application, as demonstrated on the Audi A4 in the accompanying image library, is still definitely a concept for the future, but the company's decision to enter the market with lower-speed, lower-weight Tweel applications such as iBOT, Centaur and skidsteer. appears to have been the correct strategy. With the NASA relationship now validating the technology, the chances are that the Tweel will become a very important invention.
Several other airless tire initiatives are forging towards commercialization, most notably Amerityre and more recently, Resilient Technologies.