Rotor Spinning
The rotor groove runs at a quarter of a million g. That is what holds the fibres in it.
— tpm
Rotor speed divided by delivery speed
The twist relationship is exact for the yarn in the rotor, but the wound yarn carries slightly less because of the false twist introduced by the navel and doffing tube - measured twist on the package typically runs a few per cent below the calculated value, and the difference varies with navel type. Peripheral speed and centrifugal acceleration are taken at the rotor groove diameter, which on a real rotor is slightly larger than the nominal diameter quoted. Production assumes continuous running at the stated efficiency and excludes piecing after ends down, rotor cleaning cycles and package doffing. The diameter-to-fibre-length check uses a single fibre length; where the length distribution has a long upper tail, size the rotor against the upper percentile rather than the mean.
Rotor Spinning Twist, Peripheral Speed & Production Window — free, with the formula and a worked example, at Textile School.