Dynamical simulation shows a fast-moving ring
The panels above (the first is an animated GIF) show a 10 ps MM2-based molecular mechanics simulation of the rod and sliding ring (described here). The simulation starts with the ring positioned at the bottom of the rod. Electrostatic repulsion accelerates the ring upward and the rod downward, with the ring reaching a speed of 1.6 km/s relative to the rod (the speed of sound in the rod is ~16 km/s). This motion terminates in a collision of the ring with the knob at the top of the rod. Asymmetry in this collision twists the knob, setting the rod into strong transverse vibration as the ring rebounds downward at a reduced speed.
This model should be taken as merely qualitative in certain respects: The crude treatment of electrostatics makes the speed of the ring only approximate, and the MM2 model of bonding may fail to reveal structural damage that would occur during an actual collision. It should be emphasized that molecular machine systems proposed for molecular manufacturing make no use of such rings, speeds, or collisions. These extreme conditions merely illustrate how stiff structures respond to large forces and deformations, showing how greatly these structures differ from the floppy structures common in chemistry. When the shaft and ring are subject only to thermal motion, motions are small.