Durable thermoplastic ski-on-wheels takes on tough trails

GateSkate Inc. (Richland, Wash.) has created a new sport with its TrailSkate, an all-terrain inline skate that is, in effect, a ski on wheels. Equipped with 80-psi air-filled tires fore and aft, the TrailSkate is designed to travel over a range of surfaces, including asphalt, dirt, gravel, grass and mountain trails. Its ski-like platform has a low center of gravity that reportedly delivers greater stability than traditional inline skates. GateSkate credits the help of DuPont (Wilmington, Del.) in fabricating a flexible, composite chassis for the TrailSkate, which could withstand repeated forceful loading under the user's full weight. The chassis is injection molded with Dupont's Zytel HTN, a high-performance, long glass fiber-reinforced polyamide resin intended to replace both metals and thermosets. The material reportedly offers improved fatigue performance and impact resistance, retains mechanical properties such as strength and stiffness in hot/humid climates and also provides chemical resistance in hostile environments. With assistance from DuPont, a moldflow analysis was completed to help with the injection molding. Zytel HTN is one of several Zytel compounds available in different grades, most reinforced with short glass fibers. The HTN grade used for the TrailSkate is reinforced with fibers several times longer than those used in standard short-glass reinforced thermoplastics, improving impact resistance and surface appearance.

The chassis, 53-cm/21-inches long, has wall sections ranging in thickness from about 5mm to 13mm (0.2inches to 0.5 inches), with one skate weighing 2.7 kg/6 lb. The mold design was critical in producing functional, durable parts, leading DuPont specialists to conduct mold flow analysis and recommend a gate location. When the design went into production in China, DuPont recommended a larger gate to enhance fiber orientation and suggested improvements in venting that ensured complete mold fill. When GateSkate decided that the original molder could not meet its quality needs, DuPont recommended a replacement, Excelight Ltd. The Hong Kong-based composites fabricator now molds the chassis.

According to GateSkate, Zytel HTN offered a 50 percent cost savings compared to the thermoset composite chassis used on an earlier production model. Each TrailSkate is equipped with a one-hand-operated hydraulic brake. A pair of TrailSkates retails for $349 (USD).