Figure 2. Trajectories of the flagellar tip of the E. coli model at selected phases, showing the filament motion consisted of two types of rotation: spin and revolution, which resulted in precession.

The filament moved gradually to a more horizontal direction (tilt angle θ = π/2 rad) with time (from a to c). The time interval between (a) and (b) was ~0.2 sec, and ~0.1 sec between (b) and (c), by assuming a motor torque of T_m = 10³ pN∙nm and fluid viscosity of μ = 10⁻³ Pa∙s. The time scale of the tilt angle change was much longer than that of one spin rotation and one revolution rotation.