IRVINE, CALIF. — A 27-pound thermoset Deere & Co. pre-production chassis captured awards as both the best agriculture, lawn and garden entry and the best single part in the SPI Structural Plastics '97 competition.
John Cerny Jr., a Deere plastics applications developer, sees a future for the fully tested design and use of sheet molding compound, although Deere has yet to find an appropriate application for the chassis, which was engineered using computer-aided design and manufacturing. The original concept focused on a rear-engine riding mower until that market diminished.
Other possible applications include lawn and garden tractor, golf cart, utility vehicle and even small electric-powered car, Cerny said in an interview at Structural Plastics '97 in Irvine.
The design reduced part count by 140 vs. an equivalent metal rider and produced a quieter ride. Virtually nothing can vibrate or come loose.
Quantum Composites Inc. of Midland, Mich., supplied its Quantum 8000 SMC material consisting of vinyl ester hybrid with a 64 percent fiberglass reinforcement. Conventional SMC material contains about 27 percent reinforcement.
Development work at the Deere & Co. technical center in Moline, Ill., began in 1991.
Hoegner's Tool & Die in Moline completed the mold and Bailey Corp.'s PreMix unit in Lancaster, Ohio, compression molded the chassis' 4-millimeter-thick walls using 400 tons of force in a four-minute cycle.
Deere conducted 300 hours of testing at a Florida facility and a separate 600-hour actuator test using hydraulic cylinders in an advanced design verification.
Cerny cited several ways to mass-produce the chassis cheaply: compression molding, injection molding, liquid composite molding or hand layup.
``Compression molding is cost-effective for mass production,'' he said.
``The integrated chassis and suspension system act basically as a spring'' and handle all structural stress, Cerny noted.
The structure is rigid but flexes throughout its length and width to absorb loads. A U.S. patent was issued in September 1996, protecting the design of the chassis as incorporating the suspension unit.
Two-piece injection molded ABS skins weigh a total of 8 pounds and serve aesthetic purposes only.
In early work, Deere conducted parallel development of this thermoset concept and, in Horicon, Wis., another involving thermoplastic.
For test purposes, three thermoset vehicles and 12 thermoplastic vehicles were built, but the downturn in the rear-engine riding mower market scuttled the thermoplastic idea.
``Both were functional and reliable, but the thermoplastic exhibited creep,'' Cerny said.