Reducing downtime is an important factor for OEMs in the heavy-duty equipment industry; as such, many have begun offering airless tires on their machinery. Michelin North America Inc. first introduced its X TWEEL airless radial tire in 2012 for compact construction applications. Since then, it has been expanding the applications and available sizes of the tire (see sidebar below).
Earlier this year, the company announced its X TWEEL airless radial tire would now be available for the UTV market, as well as a factory option on all CASE Construction Equipment skid steer loaders.
The MICHELIN X TWEEL SSL All-Terrain version, which is available on CASE skid steer loaders, is designed for rugged off-road working conditions and use in industries such as construction, landscaping and agriculture. Because it is an airless tire, there is no need to worry about the risk of getting a flat tire in these types of harsh operating conditions. “The market demand for Michelin X TWEEL SSL continues to increase,” said Justin Brock, Michelin Construction Segment Marketing Manager in North America in the press release announcing the partnership with CASE. “More and more end users are searching for solutions that reduce downtime. The TWEEL SSL provides the users this solution, without compromising key deliverables including traction, operator comfort and machine productivity.”
For the new 26 in. (66.04 cm) MICHELIN X TWEEL UTV airless radial tire, the company says it performs like a pneumatic radial tire but offers the durability and high damage resistance of an airless tire. The tire’s advanced spoke technology dampens the ride to help improve operator comfort while also providing lateral stiffness for cornering and side-hill stability.
The lack of air in these tires virtually eliminates downtime. In addition to there being no risk of flats, there is no need to check or maintain air pressure, worry about over or under inflation situations, idle time is reduced as well as the need to change out equipment due to an issue with the tire.
“It’s all about uptime,” says Olivier Brauen, Vice President of Michelin Tweel Technologies, a division of Michelin North America Inc., in regards to the benefits of airless tires. “Every minute has a price, and [customers] don’t want to be stopped.”
The composition of an airless tire
Brauen says the TWEEL concept came about from Michelin’s engineers envisioning future vehicles being driven without a flat due to a loss of air. “When the engineers started working on this premise, they were still designing a structure that looked like a regular pneumatic tire,” he explains. “What they discovered was that because they didn’t need to seal in the air pressure, they could change the configuration of the tire and in doing so the concept of the TWEEL—a tire and wheel assembly—was born.”
The MICHELIN X TWEEL is composed of a ridged hub connected to a shear beam by means of flexible, deformable, highly resistant polyresin spokes and a thread band which all function as a single unit, explains Brauen. “The polyurethane spokes absorb the energy and then give it back which allows the machine to be stable without hopping,” he says. “The stability improves the operator’s productivity.”
In addition, the spokes transfer the load around the circumference of the tread band, enabling the TWEEL to provide radial pneumatic-like performance with good shock absorption and reduced impact on the operator, equipment and work surface.
Equipment such as loaders, backhoes, telehandlers and other industrial and construction equipment often do not have adequate suspension, he says. The spokes on the TWEEL can absorb the impacts of these machines, making for a more comfortable operator experience.
Brauen also notes that Michelin’s proprietary technology gives the company the ability to optimize the contact patch of the tire beyond what is capable with a radial tire. “The TWEEL Airless Radial Tire is a top loaded tire meaning that it performs similar to a bicycle tire or a suspension bridge,” he says. “The spokes disburse the forces all the way around the tire radially much the same way air does in an air-filled tire. The tire’s construction pulls the spokes downward and from the outside of the structure to implicate the shear beam. It hangs the load from the top and creates a large footprint which ends up being a very low contact pressure footprint providing good traction and mobility.”
Conversely, he says other types of tires which don’t have air in them—such as foam filled or solid tires—carry the load from the hub to the contact patch and are thus called bottom loaders. This design results in high contact pressure which leads to poor traction and footprint.
In September of 2017, The Goodyear Tire & Rubber Company introduced its airless turf tire, the TurfCommand with DuraWeb Technology. Development of the tire came about as part of the company’s strategy to develop maintenance-free technologies.
“Zero-turn-radius mowers are often operated in challenging terrain, and Goodyear wanted to develop technology for those difficult conditions to push our depth of understanding and development,” says Michael Gerowitz, New Ventures Leader – Non-Pneumatic Tire Programs at Goodyear. “The Goodyear TurfCommand tire offers our end users maintenance-free and puncture-resistant performance, and excellent ride quality.” 
While the TurfCommand tire can be punctured, machine operation can continue with minimal upkeep required.The Goodyear Tire & Rubber Company
Like the MICHELIN X TWEEL, the Goodyear TurfCommand cannot lose air and therefore eliminates the chance of downtime due to a tire puncture. Gerowitz says while the tire can be punctured, machine operation can continue with minimal upkeep required.
Goodyear’s DuraWeb Technology is a thermoplastic-based connecting structure that is part of the tire’s support assembly. It takes the place of the ply and sidewall which makes up the pneumatic cavity on a traditional tire. “A tire is a top-loaded, weight-bearing product, meaning the weight of the vehicle is transmitted through the axle and supported by the top of the assembly, while the tire’s footprint that contacts the ground is under compression,” explains Gerowitz. “DuraWeb Technology allows us to achieve those dynamics consistently with the top section under tension, and footprint under compression, as it moves in operation. The benefits are that we have replaced the pneumatic cavity and can operate without the typical air pressure supporting the assembly.”
The thermoplastic connecting structure of the tire provides a combination of stiffness and flexibility to carry heavy loads and at the same time maintain a smooth ride and reduce turf wear. TurfCommand’s spokes become taut as the load of the vehicle is transferred to them during vehicle operation while inversely, the area under that load goes into compression, allowing the tread package to absorb and envelop bumps and other minor obstacles.
In addition, TurfCommand features a constant spring rate that does not change with load which works in tandem with the repeating offset pattern of the DuraWeb structure to enable the tire to move over obstacles and not transmit negative forces back to the rider, says Gerowitz.
TurfCommand was developed exclusively for Bad Boy Mowers’ Outlaw XP zero-turn radius mower. Goodyear worked together with Bad Boy Mowers to ensure it was designed to the correct operating speeds and end users’ needs. The two companies also worked together on the development trials and field testing.
While developed for a specific machine type, Gerowitz says the company is always evaluating how this technology could benefit other applications and vehicle segments.
“The commercial release of this turf tire is an important step in our efforts to develop airless tire technology for a range of applications,” said Christopher Helsel, Goodyear’s Chief Technology Officer in the press release announcing the introduction of the tire. “As we look to a future where ridesharing and autonomous vehicles become mainstream, the demand for lower maintenance, longer lasting tires will continue to increase.”
The VISION concept tire is an airless, rechargeable and organically-composed tire which represents Michelin's vision for the future of tires.Michelin North America Inc.
Creating a longer lasting tire such as the TWEEL also aids sustainability efforts—the longer a tire lasts, the longer it stays out of a landfill. Michelin’s TWEEL product for turf applications has a 3,000-hour lifespan, enabling it to last the life of a mower, says Brauen, and possibly even be moved to a new machine if a customer wants. The tire’s longevity is due to the premium grade products Michelin uses as turf is relatively gentle on tire wire; the structure of the tire also helps ensure longevity.
Sustainability is an important aspect to Michelin. At its Movin’On Summit 2018, the company announced its plans to manufacture all tires using 80% sustainable materials and have 100% of all tires be recycled by 2048. Developing longer lasting products like TWEEL is one of the ways Michelin is working toward this goal.
Like Goodyear, Michelin is also continuing to evaluate applications in which its airless radial tire technology can be utilized. Brauen says load and speed are usually a factor for determining types of machinery and applications. He notes there is a research program going in mining applications, and that more industrial applications are being evaluated.
“The more we progress, the more opportunity we see,” he concludes.
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