Abstract: A back-stopping device rotor assembly is coupled to a motor shaft to rotate therewith and include a pair of L-shaped flyweights pivotably mounted to a channel crossbar, on respective sides of a motor shaft, which crossbar rotates at right angles to the shaft axis. The flyweights are pivotably mounted to the crossbar at points closer to their end facing the motor housing at positions regularly spaced from the shaft while extending parallel to the shaft, with the motor rotor at rest. A bracket mounted on the motor housing to one side of the shaft supports a stop relative to the shaft borne device rotor such that when the motor rotates at high acceleration in a first forward direction, the flyweights pivot during initial rotation to positions such that their ends proximate to the stops sweep through a stop recess and do not impact the stop. Low acceleration, backward rotation of the motor shaft up to a maximum of 180.degree.