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Designer's Corner

Designer's Corner

Wave-powered desalination

Seasonally arid islands, desert agriculture, and depleted coastal aquifers could all benefit from desalinated seawater--if only the cost per gallon were lower. The McCabe Wave Pump may change those economics by converting the kinetic energy of ocean waves into hydraulic power for reverse-osmosis desalination.

Each wave pump comprises twin power pontoons connected to a central inertial barge in a bell-crank and slider arrangement to drive hydraulic pressurizing pumps. A 40-meter, 250-kW Wave Pump operating in one-meter swells with a seven-second period could produce 100,000 gallons of potable water per day at an estimated 0.7 cent /gallon. Prototype testing in Ireland's Shannon River estuary is set to begin soon.

Prof. Michael McCormick, The Johns Hopkins University, Whiting School of Engineering, 113 Latrobe Hall, Baltimore, MD 21218, (410) 516-8728.

In Europe: Peter McCabe, Hydam Technologies Ltd., Sea Rd., Yellow Walls, Malahide, Co. Dublin, Ireland, +353-1-845-2920.

Flexible connector

This Heat Seal Connector simplifies wiring of flat-panel displays to printed-circuit boards. The flexible laminate consists of a PET base overlaid with copper traces in custom patterns and a tinted polymer top coat that covers all but the edges of the connector. Edge connections are made by a heat-curable adhesive covering the ends of the traces. Conductive particles uniformly suspended in the adhesive get squeezed between the connector traces and the panel leads when applied to make the electrical connection. Particles outside of the trace-lead area have no electrically conductive path.

The anisotropically conducting adhesive and copper traces permit lead pitches as fine as 8 mils. Cured adhesive is less prone to cracking than solder connections and delivers peel adhesion of 500 gm/cm minimum--better than solder.

Wanda Bishop, Electronic Products Div., 3M Austin Center, Bldg. A130-3N-25, 6801 River Place Blvd., Austin, TX 78726-9000, (512) 984-3672.

Linear servo actuator

Self-contained DXL-475 linear actuators deliver nearly 50 times the life of standard ball screws at their rated 2,000-lb thrust--that's 100 million inches of travel. A patent-pending threaded-roller design makes it possible.

The actuators use a rare-earth, brushless ac servo driving a hollow, internally threaded armature. As the armature rotates, the planetary-screw rollers propel the actuator rod linearly at speeds to 40 inches per second over strokes as long as 10 inches. The threaded rollers offer greater contact area than conventional ball- or roller-bearing designs, which translates into greater load-carrying ability, stiffness, and working life. Available in IP-65- or IP-67-compliant housings, the actuators include Hall-effect limit switches and connectors for analog or digital servo drives.

Kurt Schmitz, Emerson EMC, Emerson Electric Co., 1365 Park Rd., Chanhassen, MN 55317-8995, 1-800-FX-SERVO.

Greener fasteners

It's not a breakthrough but a heads-up: Using retaining rings in place of threaded fasteners where appropriate reduces scrap and hazardous-waste generation. In a recent demonstration, machining a shoulder and screw threads onto a .50-inch cold-rolled steel shaft to accept a washer-and-nut retainer generated 0.021 lbs of waste. Machining grooves to accept SH-50 retaining rings produced just 0.003 lbs of waste and used correspondingly less cutting fluid.

With a flat ring serving as the shoulder and a dished or "bowed" ring to take up end play, a proper ring-retention design accepts thrust loads to 550 lbs.

Craig Slass, Rotor Clip Co., Inc., 187 Davidson Ave., Somerset, NJ 08875-0461, (908) 469-7333.

TAGS: Materials
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