ST. LOUIS — The innovative application of reaction injection molded polyurethane to encapsulate a snowshoe's tubular aluminum frame and traction cleats has yielded more than a durable product offering greater functionality at a lower cost.
Last week it also earned its designer — tiny Eikon Product Realization Inc. of Burlington, Vt. — the first IDSA/Plastics News Design Award.
Molded by Milfoam Corp. of Hamden, Conn., for Tubbs Snowshoe Co. of Stowe, Vt., the product was a double winner at the SPI Structural Plastics Division conference, held March 29-April 1 in St. Louis. Part of Tubbs' new Trekker series, the snowshoes also won the Recreation & Leisure category in the meeting's new-product design competition.
The snowshoe's design and execution impressed many at the event, including the five-person jury of plastics and design professionals who selected it for the new design award from a field of 67 parts entered into the overall competition.
The 3-year-old Eikon consists of just two individuals — co-founders Mike Garman and Thomas Powers. The two worked closely with Tubbs and urethane molder Milfoam to develop the Trekker shoes.
Eikon used the three-dimensional computer-aided-design program called SDRC Ideas, as well as Protogenic's rapid prototyping system, to produce a full-size prototype model in 1996. They used the prototype to solicit input from all involved parties very early in the process.
``All contributed ideas and we made changes that optimized the design,'' Garman said.
``It was 90 percent their work,'' Tubbs President Ed Kiniry said of the design effort.
Tubbs sells the RIM shoes for about $100 a pair, compared with the $150 models they aim to replace; high-end snowshoes can cost $225 a pair.
These products are targeted at the recreational hiker or winter walker, a fast-growing outdoor sports market, according to Kiniry. The U.S. market for metal snowshoes has soared from 8,000 pairs in 1990 to a projected 220,000 pairs this year.
Kiniry believes ``the opportunity exists for half-a-million pairs in the U.S. alone within three to five years,'' with about 40 percent of that being for products in the $100 price range. North America — for which Tubbs claims nearly a 45 percent market share — accounts for about one-third of global demand for such products.
Tubbs in 1906 started offering wood snowshoes with laced rawhide decking, and eight years ago introduced metal-framed shoes with a thermoplastic sheet decking made of nylon 12. In 1996 it brought out models with PVC-coated nylon decking, but plans to replace the PVC-coated shoes with the new RIM products, which Kiniry described as ``twice the shoe.''
Milfoam President Doug Pfenninger said, ``What's really neat about it is the utilization of RIM [polyurethane] as a membrane,'' which improved all the necessary properties of a snowshoe while adding structural strength. ``You really couldn't mold this product at these wall thicknesses with any other process other than RIM.''
But the real production savings come in reduced post-molding and assembly operations. The Tubbs snowshoes with thermoplastic decking require insertion of some 15-20 rivets to attach the die-cut sheet to the aluminum frame. Use of Bayer Corp.'s Bayflex 110-25 elastomeric urethane RIM system to encapsulate most of the frame in a single, 15-second shot, eliminates the need for those rivets.
``One of our goals was to cut the labor required to produce a snowshoe,'' said Tubbs research and development engineer Francis Mahoney.
Each new RIM shoe requires only 15-20 minutes of hand finishing, compared with the hour needed for riveted models.
The only negative is that, at 5.1 pounds per pair, the shoes are a couple pounds heavier than their predecessor, Kiniry said. Though this is a bigger issue in consumer perception than in performance, he said, ``We need to find ways, working with Bayer, to use fillers to get the weight down.''
Milfoam inserts the tubular aluminum frame into a machined aluminum mold, and shoots the liquid PU into the mold where it quickly cures into wall thicknesses of three-quarters of an inch down to 0.115 inch. The toe axle, a drawn aluminum alloy, is molded into the urethane, as are the tirelike treads on the bottom of the snowshoe.
At full production, which began last November, Milfoam can do about 140 shots in an eight-hour shift, said Pfenninger, whose 40-employee firm generates about $2 million in sales annually.
Mahoney said Tubbs has applied for a patent on the encapsulation process as it relates to this product.
The biggest production challenge, meanwhile, had to do with lack of uniformity of the tubular frames. ``We went through two or three sources, and ended up with a source in Canada,'' Pfenninger said, noting that the nominal thicknesses of the PU material offer virtually no margin for variation in the specifications of the bent frame.
Once the molding cycle is done, Tubbs has only to add the binding assembly with four rivets and brand the shoe using hot stamping.
Among Tubbs' objectives for this product were long-term durability and flexibility at very low temperatures.
Engineer Mahoney had his own, unique methods for testing the products for these properties. For one, he strapped 20-pound weights onto four different showshoe models and dragged them behind his pickup truck for a mile over Vermont's gravel roads. The Trekker PU shoe proved the most durable by far.
Then, to test the urethane's low-temperature performance, Mahoney stashed some Trekker snowshoes in freezers for three days at minus 40° F, then beat on them with a hammer. They passed the test.
Plastics News, in conjunction with the Great Falls, Va.-based Industrial Designers Society of America, sponsored the new award, which is to be presented annually at the Structural Plastics Division meeting. The award, featuring interlocking arches of clear, cast plastic and anodized, machined aluminum on a laser-etched aluminum base, was manufactured by General Pattern Inc. of Blaine, Minn.