Machine Design

Plastic thrust washers take transmission torture

GM engineers chose a glass-fiber-reinforced grade resin for thrust washers in automatic transmissions.

Thrust washers act as spacers between metal components such as clutch housings and sprockets. AT-6130 HS polyphthalamide resin from Solvay Advanced Polymers LLC, Alpharetta, Ga., survives constant immersion in automatic transmission fluid and has an operating range of -40 to 150°C which is typical of automotive applications.

The resin washers resist the wear caused by high pressures and high relative velocities between rotating parts called pressure-velocity (PV) load. For example, in a typical transmission, the PV forces can reach 1 million psi-ft/min from rotational speeds of 6,000 rpm. AT-6130 has a heat deflection temperature of 276°C and is said to withstand heat better than nylon 6, 4/6, or 6/6.

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