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Plastics Take Sports to New Peaks

DN Staff

August 28, 1995

11 Min Read
Plastics Take Sports to New Peaks

On land or in the water, plastics continue their thrust into the sports and recreation industry. Even the thundering hooves of thoroughbred racing horses benefit from plastics, as affirmed by the three winners of this year's "Triple Crown" races.

In the summer, plastics and composites form the basis for new designs of golf clubs, skateboards, in-line skates, and a myriad of water-sport activities, as they continue to replace metal components, particularly structural parts. Let's take a look at some recent innovative examples.

Water world. When the weather turns hot, sports lovers turn to water activities. And there's one sport that can literally give its users an invigorating lift--air chairing. Unlike water skis or kneeboards, the Air Chair, made by RBM, San Bernardino, CA, requires little athletic ability, since it is ridden from a seated position. However, it still provides big-time thrills, allowing anyone to criss-cross waves or, on a more professional scale, perform acrobatic maneuvers.

Bob Woolley, the designer, has tweaked the concept for a decade in the course of developing a hydrofoil that works. One only has to look at the design to dismiss the notion that this is just a big ski or wakeboard with a seat bolted to the top. It comes in two parts, the blade assembly and strut, and the board. The smaller rear blade, which has two fins in the bottom, and the strut are cast as a single piece with a large front blade bolting to the assembly, all of which consist of 6061 aircraft-grade aluminum. The strut extends to the board, attaching at the seat base with a quick-release pin and a wing nut.

The board measures 52 inches long by 12 inches wide. And here's where the benefits of plastics and composites come in. The Air Chair is laid up with a foam core and unidirectional glass. The bottom features a keel and two tunnels on each side.

However, it's the seat that forms the most critical part of the chair. "It holds everything together," says Woolley. "If it fails, the whole system fails." To make certain that doesn't happen, Woolley turned to Capron(R) 8234G HS nylon 6 molding compound from AlliedSignal Plastics, Morristown, NJ.

"This is a 40% glass-filled nylon with excellent structural integrity," explains Keith Rosen, vice president engineering for McCawley Precision Machine Corp., Kent, WA, the molder. The material exhibits high strength (29,000 psi), rigidity (1.36 million psi), and heat deflection temperature (410F) properties, while resisting creep under load. "It also performs much better than nylon 6/6 when it comes to surface treatments,"Rosen adds, "making it an excellent replacement for metal."

Better boating. Boating enthusiasts will appreciate the durable features of Minn Kota electric boat motors from JWA Inc., Mankato, MN, that take anglers to the fish using key components made of DuPont Zytel(R) nylon resins. Injection molded propeller, mounting brackets, and depth adjustment assemblies of the glass-reinforced material not only meet the manufacturer's standards for reliability, good looks, and low cost, but "provide the ideal balance of toughness, fatigue resistance, strength, appearance, and molding productivity," says Dennis Starner, JWA's director of quality.

The patented propeller stays 100% weed-free at all motor speeds, according to Starner. The glass-reinforced Zytel provides stiffness and strength to deliver full motor power and efficiency, coupled with the toughness to resist cracking and nicking.

Key structural components also consist of Zytel. The motors attach to the boat transom with a tilt-adjustable bracket assembly. It involves two molded parts joined by a high pin and metal clamping bolts with molded-on handles. The depth adjustment assembly includes a molded collar and a tensioning bolt with a molded handle.

If you have to work on a marine motor or its propeller, it might be wise to use a wrench made from a long glass-fiber-reinforced polypropylene composite. Quicksilver Marine Parts & Accessories, the Fond du Lac, WI-based subsidiary of Mercury Marine, selected the Verton(R) PDX-M-87242 material, a product of LNP Engineering Plastics, Exton, PA, for the Prop Wrench.

"The structural composite gives us the required strength, and has a specific gravity low enough so that it floats," says Mike Karls, project engineer. "There were several polymers, such as acetal and nylon, that we eliminated because their specific gravity was too high. We also found that standard unfilled and short glass-fiber-reinforced polypropylenes couldn't withstand the 50-55 ft lbs of torque we desired."

Injection molded in bright yellow, the wrench is easy to spot, even when it lands in the water. "This patented wrench is the first to be made out of a composite, and the first to float," adds Karls.

Hydrodynamics. Snorkeling enthusiasts should check out what its makers claim to be the "future of snorkeling." The DiVaire snorkel, produced by DiVaire Inc., Walled Lake, MI, incorporates six patents in a design said to be technologically advanced and hydrodynamically styled for comfort and durability.

"Before our snorkel, 'sophisticated' snorkeling equipment really had not progressed much beyond a tube to take in air and clear out water," says Ben Delphia, the snorkel's designer and DiVaire president.

Conventional snorkel tubes trap air and water in the tube when submerged, and, after surfacing, they leave behind carbon dioxide that is inhaled with fresh air. Over time, the CO2 build-up can cause headaches and fatigue.

The DiVaire snorkel eliminates that problem by letting fresh air enter through the top of the snorkel, which is curved downward to discourage water entry. Used air in the system is expelled, with the help of the internal deflector and fluid pump, through a side exhaust valve located just above the water line. The valves work in two ways to keep water out: the top valve seals shut when the snorkeler submerges so no water can enter; the one-way side valve only allows air and water out.

To help make the design work, Delphia turned to an electromagnetic welding process from Ashland Chemical Co.'s Specialty Polymers & Adhesives Div., Norwood, NJ, to achieve air-tight bonding at the snorkel's main seam and intake valve. And it enlisted soft thermoplastic elastomers (TPEs) from GLS Corp., Cary, IL, for the mouthpiece and air intake/exhaust system diverter.

"About a year ago, when I began to consider different ways to bond the snorkel, I looked at Ashland's Emaweld(R) process, as well as sonic welding. I eliminated sonic welding because it could not provide a smooth surface finish and had a potentially higher reject rate. The Emabond Systems gave me a perfect seal, and one that does not mar the aesthetically pleasing high-gloss finish of the snorkel."

Delphia incorporated GLS' Dynaflex(R) TPEs for injection molding of the snorkel components. Delphia found that silicones typically used were too hard for comfort. "An hour of clamping down on a silicone mouthpiece is a sure way to end up with jaw fatigue," he adds.

What Delphia wanted was a material with a softer durometer and that is recyclable. "I found the Dynaflex materials ideal," he says. "It's almost like having bubble gum in your mouth."

No matter where you go today it's hard not to see someone on in-line skates or skateboards. Once again, plastics and composites help bring these sports to new heights.

Now, skateboarders can say goodbye to sloppy turning geometry, poor steering control, and sluggish axle rebound with a "breakthrough" truck design from Seismic Skate Systems, Inc., Rockford, IL. Dan Gesmer, Seismic president, designed the truck to supply the power and steering sensitivity he found lacking in conventional trucks. Making the breakthrough possible, he feels, is LNP's Verton RF EM-HS long glass-fiber-reinforced, heat-stabilized 6/6 nylon composite.

Gesmer chose the material because it provides the right balance of strength and abuse resistance, and "it is very lightweight," he adds. "The composite is lighter than aluminum alloys and has greater toughness than short glass-fiber-reinforced polyamides."

Built into the Verton composite body is a computer-designed progressive-rate spring system integrated with a "rock-steady" 45o steering geometry. The progressive spring system is based on complex mathematical models and advanced theories of skateboarding bio-dynamics. Says Gesmer, "This is what allows you to make sharp turns with total control and no wobbliness, even at higher speeds. There are no dead spots, just a totally smooth response."

With in-line skates, stopping can be as critical as rolling. That's why First Team Sports, Inc., Mounds View, MN, designed the Disc Brake System (DBS) for its Ultra-Wheels(R).

The patented system offers a brake that will stop skaters easier, faster, and smoother than existing brake-pad systems, according to company engineers. Not unlike brake designs used in cars, the DBS is activated by applying heel pressure to the roller brake located just behind the fourth wheel.

The concept comprises three brakes in one. As the skater applies pressure on the external "roller" brake, it causes friction against the road. At the same moment, the internal "disc" and "drum" brakes apply pressure against the DBS' vertical and horizontal rotation surfaces. This causes the brake to roll slower. The external roller brake grabs the road; the internal brakes slow down the rotation. All together, the effect is controlled resistance to rolling and deceleration.

The DBS' brackets are made from die-cast magnesium, the fasteners from steel, the plugs from aluminum, the springs from stainless steel, and the critical brake wheel from a phenolic with rubber molded on the outside.

Slicing golf-club costs. By reorganizing plant operations into manufacturing cells and installing induction-curing equipment, the Wilson Sporting Goods Co., Tullahoma, TN, achieved big savings in production time and improved part quality in assembling irons, woods, and putters.

A majority of the clubs have graphite shafts and aluminum or stainless-steel heads. These materials provide a strength and stiffness that protect the clubs against multidirectional stresses, including torque, tension, compression, and flex. Epoxy adhesives systems from Ciba-Geigy Corp.'s Formulated Systems Group, East Lansing, MI, give the clubs added impact resistance and durability.

Wilson ships golf-club shafts and heads from its other manufacturing facilities to Tullahoma for assembly. Here, bonding club components is a three-step procedure: adhesive application, induction curing, and part inspection. Wilson technicians position the club head on an automated dispenser that applies a bead of mixed two-component epoxy adhesive (Ciba-Geigy's Araldite(R) AV-138/HV-998 and AW-l06/HV953 systems) into the cavity at the top of the part. The shaft is in- serted into the head and the two components induction cured.

Wilson developed its induction-curing system to meet its specific assembly operations, including a variety of curing temperatures required by the different substrates being bonded. The curing equipment functions by setting up a magnetic field that quickly heats the club head to about 300 to 400F. At this temperature, the adhesive cures in less than 15 seconds to bond the shaft into the head. The club is then ready for inspection, polishing, and packaging.

There's also a "cure" for recreational golfers who have problems with distance and accuracy. To help overcome such handicaps, one manufacturer turned to Owens-Corning's S-2 Glass(R) fiber for its golf-club shafts. In contrast to ultra-stiff, all-graphite shafts, the S-2 shafts, or those that incorporate the fiber with other materials, flex as the club is swung. This flex action is said to offer golfers more distance and better accuracy; while some golfers like the softer feel the shaft provides.

"It's a simple case of energy transfer," says Don Kibbie, marketing director for Fort Pierce, FL-based Fiber Speed International, Inc. "The S-2 Glass fiber club does a better job of releasing energy generated from the backswing into the ball at the point of impact. This 'squaring up' of the club head compensates for lack of speed in the swing among recreational golfers."

Finally, if you like to bet on horse races, it might pay to find out what kind of shoes the horses are wearing. Thoroughbreds equipped with "athletic shoes for horses," developed and marketed by Chuck Gonsalves of the JAKS Co., Glendora, CA, came up winners at the Kentucky Derby (Thunder Gulch), Belmont Stakes (Thunder Gulch), and the Preakness (Timber Country).

Called No-Vibes, the aluminum shoes absorb shock with a layer of Isodamp C-100 vinyl supplied by EAR Specialty Composites, Indianapolis, IN. Gonsalves, a retired aerospace engineer, used his knowledge of shock and vibration isolation to develop the racing horseshoe.

And, like Gonsalves, more and more sports equipment manufacturers are hitting it big with plastics and composites. A visit to your local sports equipment outlet will verify how these materials have exploded on today's sports scene.

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