Machine Design

Car wash rolls on urethane elastomer

Solid urethane triples the life of rollers used in car-wash conveyor system at the Miracle Car Wash facility in Cranston, R.I.

Car-wash conveyor rollers made from a solid Durethane S urethane sport a 95 Shore A hardness, a tensile strength of 6.6 kpsi, an elongation of 400%, and an abrasion rating of 800 mg/1,000 cycles per Tabor Abrasion Index.

The rollers are a special formulation of Durethane S, a solid, open-cast, thermoset elastomer from MPC (Mearthane Products Corp.) also in Cranston ( The rollers sport good abrasion resistance, a high coefficient of friction, and play a key role in the facility's automated, roller-on-demand conveyor system.

The system engages the left rear tire as the car enters the car wash to move the vehicle along the conveyor. There are dozens of rollers on the conveyor, and they are under constant friction both from the tire and from the steel conveyor structure, says Miracle Car Wash owner and operator Ray DelGreco. "We've been running the Durethane rollers over a period of several years and they are the longest-lasting rollers I've ever used."

Traditional rollers, made from ultrahigh-molecular-weight poly-ethylene or thermoplastic urethane, needed replacing every six to eight months, reports Del-Greco, because of the harsh conditions that include salt, corrosive automotive fluids, and extreme cold in the winter.

Miracle tested several roller prototypes from a number of material formulations before finding the Durethane S. And although the new rollers cost roughly 10% more than the old ones, they last 18 to 20 months, says DelGreco. "This eliminates two maintenance cycles of up to 5 hr each. This savings in maintenance more than makes up for the higher roller costs," he says.

Durethane S urethanes can also be formulated with customized conductive properties to control static and for tribocharge management for use in such high shock-and-wear applications as bumpers for pneumatic tools.

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