A pair of bellows creates sealed passages between two high-pressure pumps and the Space Shuttle's power head, according to Mike Paytas of Pratt & Whitney in West Palm Beach, Fla. Paytas, project engineering manager for the Space Shuttle's main engine turbopump program, said the turbopumps began delivering liquid oxygen to the shuttle engines in 1995 and liquid hydrogen in 2001. The pumps replaced an earlier design in an effort to increase the number of flights between overhauls. The turbopumps last 10 missions between rebuilds.

The bellows maintain passageways for the gases, while accommodating thermal expansion and isolating the pumps from engine vibration. The machined bellows replace an earlier hydroformed version.

Aboard the Space Shuttle, a liquid hydrogen pump (left) and liquid oxygen pump (right) deliver their gases to the power head via machined bellows.

Hydrodyne of Burbank, Calif., machines the bellows from a single piece of metal, according to engineering vice president Jeff Bluen. There are no welds, even at the flanges. Machined bellows open a wider range of material possibilities than either formed or welded bellows can, Bluen explained. Material thickness through the tubular shell or the flat plate sections can be made wider or narrower to account for stress distribution and to be sure that the material stays within its non-yielding levels, he added.

Bluen mentioned another potential application for machined bellows. Because walls lend themselves to tight thickness control, the force that a bellows exerts can be governed precisely as well. Unlike a bolted seal, which pushes against the sealing material hardest under the bolts, a bellows seal exerts the same force around the entire circumference. Its flanges can thus be made lighter, Bluen said, an important consideration in aerospace applications.

NASA engineer John Vranish has been working on a way to convert oscillatory motion to continuous motion using flex wedges—a design he invented several years back. The original intent of his invention was to control friction through flexure.

NASA depends on brakes releasing when they're told to, Vranish said. It's quite a ride up into space to free a stuck brake on an actuator. And wedge brakes, while they hold well, don't always release according to formula. That's especially true if they're loaded. Sometimes, they can require 30 percent more or less force than predictions call for.

Contrast that with the bending in certain metals, which can be predicted with great accuracy, Vranish said. Those particular metals—beryllium copper is one—exhibit a "tiny hysteresis," he explained.

According to its inventor, NASA's flex wedges may help tame the oscillations that inhabit the realm of the very small. Micro, first, then MEMS, he said.

Instead of the solid body found on common wedges, the flex wedge relies on two thin arms to hold its twin shoes. The shoes mount perpendicularly to the arms. The arms meet midway between the shoes, where a third arm acts as an actuator to drive the wedge into its groove, or to withdraw it.

According to Vranish, the arms flex slightly when pulled, relieving the force of the shoes against the groove walls. The force required is always the same.

Though the arms are thin, they are strong in a direction normal to the shoes. They can be pushed upon mightily without failing, Vranish said. In that way, they can actually increase the holding power of the shoes, even to the extent that a brake can hold through a coat of molydisulfide—a lubricant perfect for space because it doesn't outgas in a vacuum.

Vranish is pursuing the conversion of oscillatory motion to continuous motion along a couple of fronts. At the Naval Surface Warfare Center in Bethesda, Md., Vranish has been working with research physicist Joseph Teter to compound the small stroke of powerful magnetostrictive devices into actuators that will go to greater lengths. According to Teter, the Navy has long wanted to eliminate hydraulics in its systems, to be rid of their many maintenance and environmental concerns. After prototyping a three-dimensional sprag clutch, which Vranish designed, the project team has begun seeking similar solutions based around flex wedges.

Meanwhile, researchers at Penn State University in support of the Defense Advanced Research Projects Agency are investigating the same application of flex wedges to minute piezoelectric drives, Vranish said.

Truck suspension maker Hendrickson International of Woodridge, Ill., has developed a way to replace the traditional leaf-spring suspension worn by most dump trucks with one employing a walking beam and springs of rubber and high-density thermoset material. According to marketing manager Sean Coleman, the suspension promises to improve the ride quality on certain Peterbilt and Kenworth trucks. Both companies signed exclusive agreements with Hendrickson.

Rubber plates stacked at an angle to the road provide both shear and compressive resistance. This is especially important for trucks in vocational service—dump trucks, logging trucks, and so forth—because they're driven empty half the time. Shearing forces on the rubber provide ride comfort; compressive forces stabilize loads.

Rubber elements on this truck suspension made by Hendrickson International soften the ride both coming and going, thanks to a variable spring rate.

Another element adds variable spring rate. A block of high-density thermoset material situated about halfway between the truck frame and the axle stays inactive unless the truck runs loaded. It then springs into action, so to speak, adding stability to the ride.

The suspension weighs in several hundred pounds lighter than traditional suspensions, Coleman said. That translates to money earned over the course of a typical dump truck's day, he added. If a trucker hauls at least 500 more pounds every run, and drives eight runs a day, he's carrying an extra two tons of payload a day.

Further savings come in the form of reduced maintenance, Coleman said. The design eliminates a center bushing that's normally a high-wear area. The conventional suspension might have to be rebushed three times in 10 years, Coleman said. Eliminating the center bushing crosses a step off the maintenance checklist.

A tire from Goodyear Tire & Rubber Co. of Akron, Ohio, out now in concept form, is designed especially for use on hybrid and electric vehicles. To reduce rolling resistance, the tire rides on a cushion of air pressurized beyond the level of ordinary designs.

The 22-inch tires also use a special tread whose leaflike pattern Goodyear molds from high-flexing, easy-rolling compounds. Narrow rim width and rounded sidewalls help counter the harsh ride that would otherwise accompany high inflation pressure.

The tires debuted with General Motors' introduction of the Autonomy skateboard chassis in January.

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