a thermoplastic endless belt has a smooth outer surface substantially free of discontinuities and an inner surface with a plurality of teeth at a given belt pitch . the teeth are adapted to engage a pulley with circumferentially spaced sheaves at a pulley pitch greater than the belt pitch . the belt is slightly stretchable so that the pulley can drive the endless belt when engaging the teeth within a range of load on the belt . means are provided to minimize friction between the belt and the drive pulley . also , a position limiter ensures that the driven tooth stays engaged optimally with the drive sheave .