Friday, July 11, 2008

Reinventing the Wheel: Airless Tire

The military is trying to develop a tire for HumVees and other vehicles running on pneumatic tires, that cannot be punctured or shot out from under the vehicle. The "airless tire" is a project being worked on by the US DOD with the help of Resilient Technologies and the University of Wisconsin, Madison.
“You see reports all the time of troops who were injured by an IED or their convoys got stranded because their tires were shot out,” says Mike Veihl, general manager of Resilient. “There’s all sorts of armor on the vehicle, but if you’re running in the theater and get your tire shot out, what have you got? You’ve got a bunch of armor in the middle of a field.”

...The Wisconsin design breakthrough, first developed by Resilient’s in-house design and development team, takes a page from nature. “The goal was to reduce the variation in the stiffness of the tire, to make it transmit loads uniformly and become more homogenous,” Osswald says. “And the best design, as nature gives it to us, is really the honeycomb.”

...The patent pending Resilient design relies on a precise pattern of six-sided cells that are arranged, like a honeycomb, in a way that best mimics the “ride feel” of pneumatic tires. The honeycomb geometry also does a great job of reducing noise levels and reducing heat generated during usage - two common problems with past applications. “We definitely brainstormed,” says Foltz. “We wanted to create more of a matrix of cells within the tire, and it seemed kind of natural to go with the honeycomb’s hexagon shape. We tried some other shapes, such as diamond shapes, and they didn’t perform as well.” _Source
Honeycomb designs make sense for load distribution, but I suspect there is a better design waiting to be tried. A pneumatic tire distributes the load almost uniformly in continuously alternating tension-compression in the tire, distributed by the compressed air inside the tire.

This is the type of relatively simple engineering problem that computer models should be capable of handling. In terms of vehicle maneuverability, we may find that the pneumatic tire is not the best type of tire.

Interestingly, some of the same problems that need to be solved to design the best airless tire also need to be solved in the design of the modular seastead. The outer "rim" of the seasted needs to absorb the energy of the surrounding seas, protecting the sensitive living and working areas within.

Interesting work.

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