Hey Sebastian, are you subjecting the fiber to a longitudinal force when winding or are you winding it a round a static coil? If you are pulling by rotating the coil, I'd look at it as a static problem and first equate the torque of your motor and respective tangential force (longitudinal force in the fiber) with the force which "holds" the fiber on the other end (friction, clamping, etc.). This gives you the stress in the fiber. If ok I'd increase it until you reach a stress threshold, which I'd define somewhere within the linear-elastic regime of your material including a safety factor. If you have the longitudinal force, you have the torque and can calculate the revs per minute or fiber length per minute. If you want to take dynamic effects into account consider that the dynamic tensile strength is probably higher than the static one. I'd also check the strain rate dependency of the material. Hope that helps, Bernhard