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HOME
Radical new Tire Design
on it's Way?
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A radical new tire design by Michelin.
Could this be the next generation of
tires? These tires are airless and are scheduled to be out on the market very
soon. The tires are dubbed the "Tweel", because of the wheel being built
right into the tires' hub. This is looked upon as a disadvantage because
use of the Tweel takes no regard for wheel selection, you can only
use the wheels built into it.
Law enforcement probably will not like this concept
either. The bad news for law enforcement is that spike strips will not work on these tires.
This concept is what great R&D will do, and just think of the impact on existing technology:
The first automobile to use
air-filled tires was a race car built by André and Edouard Michelin in the
early 1890s. More than a century later, the French company founded by the
Michelin brothers is so identified with pneumatic tires that its mascot,
Bibendum, is a man made of little else.
Now, after decades spent persuading the world to ride on air, the company
has begun work on an innovation that could render the pneumatic tire
obsolete. Engineers at Michelin's American technology center are working
on what they call Tweel, a combined tire and wheel that would not go flat
because it contains no air.
Arriving at a conference room recently to explain the development project,
a research engineer, Bart Thompson, used the Segway Human Transporter that
he rode to the meeting to illustrate his points.
Aboard this self-balancing electric scooter, Thompson whizzed down the
hallway and out to the lobby, pirouetting among the benches and planters
to demonstrate the flexibility of the Tweel.
The Segway would be a small market for Michelin, the world's leading tire
maker, but it is an apt demonstration vehicle for the Tweel. The first
commercial use of the integrated tire and wheel assembly will be on the
stair-climbing iBOT wheelchair, another product developed by Dean Kamen,
the Segway's inventor. The
tire maker has high expectations for the Tweel. The concept of a
single-piece tire and wheel assembly is one that the company expects to
spread to passenger cars and construction equipment and aircraft.
The Tweel offers a number of benefits beyond being impervious to nails in
the road. The tread will last two to three times as long as current radial
tires, Michelin says, and when it does wear thin, it can be retreaded.
For manufacturers, the Tweel offers an opportunity to reduce the number of
parts, eliminating most of the 23 components of a typical new tire as well
as the costly air-pressure monitors that will soon be required on new
vehicles in the United States.
Manufacturers have devoted an increasing amount of attention to tires that
allow motorists to continue driving, at a reduced speed, for at least 100
miles, or 160 kilometers after a puncture. Several such designs are
available, providing peace of mind for travelers and cutting the need for
spare tires. Michelin sells them under the Pax name.
The Tweel, mounted on a car, is a single unit, though it actually begins
as an assembly of four pieces bonded together: the hub, a polyurethane
spoke section, a "shear band" surrounding the spokes and the tread band -
the rubber layer that wraps around the circumference and touches the
pavement.
While the Tweel's hub functions as it would in a normal wheel - a rigid
piece that attaches to the axle - the polyurethane spokes are flexible, to
help absorb road impacts. The shear band surrounding the spokes
effectively takes the place of the air pressure, distributing the load.
The tread is similar in appearance to a conventional tire.
One shortcoming of a tire filled with air is that the pressure is
distributed equally around the tire, both up and down as well as side to
side. That property keeps the tire round, but it also means that raising
the pressure to improve cornering - increasing lateral stiffness - also
adds up-down stiffness, making the ride harsher.
With the Tweel's injection-molded spokes, those characteristics are no
longer linked, holding the potential to improve handling response. The
spokes can be engineered to give the Tweel five times as much lateral
stiffness as pneumatic tires without losing ride comfort.
The Tweel is in its infancy - "version 1.0," Thompson said, and only one
set of car Tweels exists. A test drive in a Tweel-equipped Audi A4 sedan
on roads around Michelin's research center proved to be far less exotic
than the construction method or appearance would suggest. The prototype
Tweels are noisy, as Thompson warned they would be, because the spokes
vibrate. (Pictures above.)
Almost everything else about the Tweel is undetermined at this early stage
of development, from serious matters like cost to more frivolous questions
like the possibilities of chrome-plating.
Other uses - military vehicles, for example - would come before
automobiles, but Michelin's business projections accommodate the
possibility that the Tweel may not be an overnight success. This would be
nothing new for Michelin: The radial tire it invented in 1946 was not
widely accepted in the United States until the 1970s.
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