Embodiments of electric motor driven door or barrier opener with a manually operable drive for use in the event of a power failure are provided. The operator comprises a gear box drive connectable with an electric motor of said operator, said gear box comprising an output for drive coupling with said door to effect opening and closing of said door by said motor and a shaft that drive rotates when said motor rotates. The shaft carries a free wheeling manually rotatable drive wheel as said manually operable drive and useable in the event of power failure to effect manual drive rotation movement of said shaft to open and close the door via said gearbox. The manually rotatable drive wheel comprises at least one drive coupler mounted to move in a generally radially extending direction relative to a central longitudinal axis of said shaft so that manual rotation of said drive wheel in the event of a power failure will effect a movement of the at least one drive coupler in the generally radially extending direction to effect a drive coupling between said drive wheel and said shaft to input drive to said shaft to permit manual opening and or closing of said door.