The front and rear racks on the Polaris Industries Sportsman 700 Twin all terrain vehicle (ATV) must be able to carry substantial loads at temperatures down to -25°F (-31.5°C).
Rather than use steel, with its attendant costs for forging, welding and painting, Polaris engineers turned to a Ticona Celstran® long fiber reinforced thermoplastic (LFRT) to gain a moulded part having high impact and flexural strength at low temperatures.
The racks on the Sportsman 700 Twin hold strapped-on cargo or serve as a mounting point for cargo boxes and accessories like sprayers and seeders.
The front rack, which measures 20 x 40 inches (51 x 102 cm), is rated for up to 100 lbs (45 kg). The rear one is rated at up to 200 lbs (90 kg) and has dimensions of 25 x 43 inches (63.5 x 109 cm).
Both rack systems are ribbed to reduce weight and build strength. They also have tie-down areas and are supported by painted steel members bolted to the main frame of the ATV.
The injection-molded racks are made of Celstran® PP GF40 02 LFRT, which contains 40 percent long glass fibers in a polypropylene matrix.
This grade has a notched Izod impact strength of 5.1 and 6.7 ft-lb/inch at 72°C and -40°C, respectively. It also has a flexural strength of 27,000 and 42,600 PSI at 72°C and -40°C, respectively.
The resin also resists wear and creep and processes well, and has high UV and chemical resistance so it weathers well and does not corrode.
“We looked at traditional short-fiber-reinforced plastics, some much more expensive than the long-fiber polypropylene we chose, but none had the low-temperature impact strength, toughness and the other properties we needed,” says Scott Ostroski, program leader for the Polaris Sportsman ATV product line. “The Celstran® LFRT racks passed our demanding durability tests, so we are sure they will withstand the rigors of sustained use in off-road vehicles.”
“This means, for instance, that they have the fatigue resistance to flex when carrying sandbags and other substantial loads as the ATV traverses rough terrain. The racks weigh less than if they were made of steel, and moulding them was far faster than forming them from steel. The plastic racks need no secondary steps after processing.”
Polaris also uses Celstran® LFRT instead of steel in the bumpers, racks, cargo boxes and footwells of its Sportsman 400, 500 and 600 and Magnum ATV lines. The grades used in these applications contain 10 to 40 percent long-glass fiber in polypropylene.
The Sportsman 700 Twin was named “ATV of the Year” in 2002 by ATV Magazine for its innovation, industry influence and consumer interest. It is powered by a liquid-cooled, four-stroke, twin engine and has a new frame and transmission and an upgraded independent rear suspension.