ABSTRACT
The lower part of the rotor-spun yarn from the doffing tube navel to the rotor groove is called the yarn arm. In rotor spinning, the lower end of the rotor-spun yarn is always directed toward the collecting surface of the rotor to be spliced and then combined with the fibers that are deposited in the rotor grooves. The yarn tension variability is dependent on the yarn mass variation, that is, count variation. The yarn arm inside the rotor is the distance from the navel to the collecting surface and is equal to the rotor radius. The calculation of the rotor-spun yarn's dynamic tension at the outlet of the doffing tube is dependent mainly on the centrifugal tension of the yarn arm inside the rotor—either straight or curved. In both cases, the calculations neglect both the air drag on the yarn arm and the Coriolis force.
