To form an actuator and pump of a compressed air type motion accumulating device producing compressed air by driving a pump by the braking force of a bicycle storing the compressed air in a tank and when necessary, converting the compressed air in the tank to a drive force into a rear wheel hub storage structure so as to simplify the appearance reduce the weight, and improve the bicycle assemblage of the motion accumulating device, to enable the driving force adjustment, and to provide an effective pump operation.

This device comprises a hub having a bottomed cylindrical fixed casing and a flanged cylindrical part fitted rotatably to each other and a core bar for tightening both thereof. A pump device a clutch device, and a valve device are stored in a space formed of the fixed casing and the hub so as to be connected to the spokes of a bicycle through a flange, and a free- wheel is provided between the hub and the clutch device.