Winners in the plastic bearing design contest sponsored by East Providence, RI-based igus (http://rbi.ims.ca/3847-512) and announced at the National Design Engineering Show last month, include pivot-housing bearings on a roller coaster, a pick-arm bearing in a potato seed planter, and slides to move a two-axis test-tube tray plus bearings for a three-axis probe to position and dispense fluids in immuno assays.
Top prizewinner ($5k) in the First North American Plastic Bearing Design Contest, or manus (derived from Latin for hand or courage and initiative), was Six Flags Magic Mountain Engineers' use of a plastic flange bearing on its X roller coaster. These bearings function under various G loadings to pivot wheel bogies that turn seats in excess of 360 degrees in a vertical planeóall while the 70-ft long, 30-ton trains carrying the seats ride alongside, rather than on top of or below, the rail structure carrying the cars.
Engineers chose the flange bearings to increase the roller coaster's reliability with longer service life and reduced costs due to less frequent maintenance.
Harriston Industries' second place entry ($1k) uses an iglideģ plastic bushing to give its potato-picker arm bearing 500-600 percent increased life, while costing 70-80 percent less (see Designer's Corner, p24). Harsh conditions the bearing faces include high abrasive volcanic ash concentrations in Washington and Oregon. In Maine and the Canadian Maritimes, high salt content in the air caused the original oil-impregnated brass bushings with graphite plugs to corrode and seize.
Nova Biomedical's use of fixed and self-aligning plastic bearing slides and bushings in immuno-assay equipment captured third place ($1k). Here, a two-axis tray operates in an incubated environment, which requires highly repeatable and accurate positioning to ensure precise optical measurements. A three-axis probe depends on plastic linear rail bearings to move precisely to dispense fluids in test tubes within the tray for absorption colorimitry reactions.
The plastic bearings' minimal service and long life at elevated temperature,
with periodic exposure to salt water, were vital in their selection for this
Top Good Turns: Six Flags engineers used
a plastic flange bearing on the X coaster to pivot bogey wheels that allow
seats to rotate more than 360 degrees under high G
Bottom: Good Earth: Plastic bearings
thwart corrosion and wear on Harriston Industries Potato planter.