Apr 1, 2015
No More Flat Tires
A punctured tire is the definition of a bad day, but Michelin is taking some of the sting out as it announces the opening of its newest North American plant, which the company says is the first in the world dedicated to the manufacture of airless tires called "Tweels".
The Tweel is a combined tire and wheel that was introduced by Michelin as a concept in 2005. It consists of a molded-tread rubber band similar to that of a conventional tire mounted on a steel shear beam that acts as a contact patch. Between this and the hub is a series of energy-absorbing polyurethane spokes connected to an inner rim structure, which can be adjusted based on the expected loads with the tread also able to be customized.
According to Michelin, the Tweel lasts three times as long as conventional tires. Unlike conventional tires, the tread can be replaced without having to replace the entire unit, so there is less waste of material. In addition, since the design doesn't need to retain air, it can be made to shed water quickly, which reduces hydroplaning.
Since there's nothing to inflate, there's also no possibility of getting a flat.
That—along with the potential weight savings of combining tire and wheel—has led to plenty of airless-tire experimentation.
Both Bridgestone and Hankook have demonstrated their own airless-tire concepts. Hankook has also claimed NVH improvements because of the shock-absorbing qualities of its design.
Currently, Michelin is aiming its advanced airless radial tire at the agricultural and construction markets, which suffer from significant downtimes from punctures. However, the performance of the Tweel indicates that it has applications in many other fields.
Combining a tire and wheel into a single airless object has proven to be a popular concept, although it still hasn't gone mainstream. Michelin recently announced a new production version of what it calls a 'tweel,' but not for any automotive applications—just yet.
It will open a dedicated tweel-producing factory in Piedmont, South Carolina, this week. However these airless tires will be used on skid-steer loaders and certain models of John Deere lawnmower, not cars.
Potential benefits of the Tweel include not only the obvious safety and convenience of never having flat tires, but also, in automotive applications, the Tweel airless tire has the potential to be able to break a significant performance compromise that is inherent to pneumatic tires. Unlike a pneumatic tire, a Tweel can be designed to have high lateral stiffness while simultaneously having low vertical stiffness. This can be achieved because, in the design elements of a Tweel, the vertical and lateral stiffness are not inseparably linked and can thus be optimized independently.
Because the tread rubber around the outer circumference is replaceable when worn (as opposed to disposing of a whole worn tire), the potential environmental impact of a Tweel airless tire can be less than that of a conventional pneumatic tire.
Military testing has indicated that the Tweel deflects mine blasts away from the vehicle better than standard tires and that the Tweel remains mobile even with several spokes damaged or missing.