Abstract: An automatic transmission for mounting within the rear fork of a bicycle includes a plurality of pairs of constant mesh gears and a plurality of discs. Each disc is concentric with one of the gears in each pair and includes a notch for partially enclosing a centrifugally actuated pawl. The notches in adjacent discs face in opposite directions and all the discs but one include a spring for opposing the centrifugal force on each pawl to keep each pawl in a disengaged position. The one disc includes a spring for holding the pawl in an engaged position. The pawls are shaped to permit the bicycle to coast or freewheel.

Abstract: An automatic transmission having a plurality of driving gears which are individually and selectedly placed in driving engagement with a drive shaft dependent upon the speed of rotation of the drive shaft. The method of automatically engaging and disengaging the drive coupling between a drive gear and the drive shaft is such as to permit the drive shaft to free wheel whenever the rotation of the drive gear is retarded or stopped. The releasable coupling is achieved by centrifugally actuated pawls which selectedly engage in detent notches about the inner diameter of the drive gears and which pawls automatically retract and disengage from these notches when the drive gears are retarded or stopped.