In Iraq and elsewhere, improvised explosive devices (IEDs) pack a double-deadly whammy: They can kill when they explode, and then they turn surviving soldiers into sitting ducks when Humvee tires blow out. Conventional Humvee tires need a certain amount of air pressure, but also may include so-called "run-flat" inserts that wrap around the tire's rim to keep it from going completely flat when the tire's surface is ruptured. The U.S. Army, however, is looking for an alternative that can keep its vehicles running faster and farther than a run-flat donut after an attack.

To keep troops from being stranded and easily ambushed on the battlefield, the Army is working with researchers to develop tires for their Humvees that can better withstand roadside attacks. One such  design comes from Resilient Technologies, LLC, based in Wausau, Wisc., and the University of Wisconsin–Madison's Polymer Engineering Center. With a four-year, $18-million grant from the Pentagon, Resilient is working to create a "non-pneumatic tire" (NPT) technology, called that because it doesn't require air.

The NPT looks like a circle of honeycombs bordered by a thick black tread. "There's a lot of space for shrapnel to pass through," says Ed Hall, Resilient Technologies's director of business affairs. "Even if you remove 30 percent of the webs, the tire will still work."

Resilient is now working to deliver to the Army Research Lab a prototype wheel that the Army would be able to manufacture on its own. "The Army Research Lab approached us, saying that flats on Humvees made them susceptible to attack," Hall says. "We looked at a lot of non-pneumatic designs before coming up with a polymeric web."

Resilient says it's too early to say how much the tires will cost or even which polymers they're using, because they're still in the prototype phase. (The company installed a set of 37-inch (94-centimeter) NPTs on a Wausau-based National Guard Humvee to test them in April.) Although the military is hoping to put these tires in use as soon as possible, Resilient has no plans for a consumer version right now. It may be a decade or more before an NPT makes spare tires a relic of the past: that's how long Michelin says it will be before its airless "Tweel" comes to market. In the meantime, the Tweel is more likely to show up on small construction vehicles.

And for those of you wondering why all tires aren't simply made out of solid rubber, some construction vehicles use them on sites with debris that can easily shred a pneumatic tire, but solid tires give an incredibly rough ride, generate a lot of heat, and might be even worse if a piece came off during an explosion, because it could not easily be repaired. The NPT's  honeycomb structure is designed to support the load placed on the tire, dissipate heat and offset some of these issues.

View a slide show of Resilient's technology

6 Comments

1. 1. Magician 07:28 PM 8/11/08

   This is nothing new. Michelin's Tweel proved the concept in 2006 or earlier. http://www.michelin.com/corporate/actualites/en/actu_affich.jsp?id=17448&lang=EN&codeRubrique=4&actu=true

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2. 2. Magician 07:30 PM 8/11/08

   This is nothing new. Michelin's Tweel proved the concept in 2006 or earlier.
   
   http://www.michelin.com/corporate/actualites/en/actu_affich.jsp?id=17448&lang=EN&codeRubrique=4&actu=true

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3. 3. Phoolio 10:51 PM 8/11/08

   this seems like a no brainer but the tire needs sidewalls to prevent mud, rock or whatever from filling and unballancing the tire.

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4. 4. BlueFire 03:50 AM 8/12/08

   From solid tires to tires with tubes to tubeless tires to semisolid tires. Hmmm... next step back to solid tires of some sort?

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5. 5. Magician in reply to Phoolio 09:36 AM 8/12/08

   I agree. Perhaps they're initially targeting vehicles that won't require well-balanced tires. I did see a video of prototype Tweel mounted on an Audi sedan few years back; not sure how this will do in snow. For all I can see, whole thing can turn into an ice-solid piece of rock each morning :)

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6. 6. karlchwe 03:43 PM 8/12/08

   I can see how the design creates a compressible tire that works like a pneumatic tire, deforming under load and springing back. That is what creates a softer ride and allows the tire to conform to rough terrain.
   
   
   But I don't see how the tire transmits torque to the ground. If you can imagine the tire tread being held stationary, and a motor trying to turn the hub, you can imagine there might be some slop there. I.e., the hub might turn a bit before the tread starts turning.
   
   
   That also means that plastic web has to be flexible, but certain components (perhaps the "spoke" members) have to resist stretching. Is there some kind of fiber embedded in the plastic?

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