When Robert Thomson invented the pneumatic tire over 150 years ago, a rubber doughnut filled with air was only one of several ideas he was working on. It seemed like a great idea but he wasn’t sure that it was possible to keep the air contained within the tire. Other designs he had involved filling his proposed tire with resilient substances such as sponges and even horsehair. Those seemed to be a better idea because substances such as those don’t leak out easily. The object of all of this, of course, was to have a tire that absorbed road shocks and thus provided a comfortable ride for the riders in the carriage (Remember: this was before automobiles). So, even though the pneumatic tire had yet to be perfected, research 150 years was being put into tires that weren’t inflated by air.
Airless tires on the Moon
Fast forward to the space age. Despite over 100 years of success with pneumatic tires on automobiles, the concept of an airless tire appeared once again. This time, however, it was for use on the Moon. Yup, in the 1970s, NASA’s Lunar Rover was outfitted with four 9-by-32-inch tires consisting of steel-mesh toroids attached to aluminum hubs – no air involved. The treads were made of V-shaped titanium which undoubtedly were considered the best type of tread for driving around on moon dust, a substance that is profoundly different than pavement.
Back on Earth, the Tweel was developed
Perhaps gaining some momentum from the Lunar Rover design, the concept of an airless tire became a serious concept once again in 2005 when Michelin designed the “Tweel.” The Tweel consisted of a thin rubber tread band reinforced by a composite-plastic belt and supported by dozens of V-shaped polyurethane spokes. Introductory performance claims versus conventional pneumatic radials were actually impressive. Studies showed that they were capable of two to three times the tread life of conventional tires and five-times-better lateral stiffness. Frankly, the Tweel seemed like the answer to every handling engineer’s dreams. Despite the advantages, though, Michelin didn’t move forward with the Tweel.
Dutchess Chrysler Jeep Dodge of Poughkeepsie, NY explains that Bridgestone presented their own airless tire concept at the 2011 Tokyo Motor Show. Mimicking the Tweel, the airless Bridgestone consists of a thin rubber tread supported by flexible thermoplastic spokes and a rigid aluminum hub. Inner and outer spokes run in opposite directions to provide vertical support without twisting.
Airless tires are still years away
Despite plenty of R&D, non-pneumatic tires are realistically a decade away. Beyond their performance, two things will propel them toward acceptance: Tire companies must address the recycling of such tires and, of course, expense. The new wheels must be cost competitive with the old technology or the industry will likely stay with what is standard and familiar. After all, over 100 years of pneumatic tires has resulted in a product that is consistent and affordable.
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