Mobile device including a system for transforming rotational motion of powered rotors into translational motion of the mobile device, comprising; - at least one pair of rotors (2, 3) mounted in coaxial relation with respect to a rotary shaft, each pair of said rotors (2, 3) being associated with at least one power plant for actuating rotation thereof in opposite directions through motion transmission and synchronisation means (6 to 9), and - each rotor (2, 3) of the pair including a mass subject to a gravitational force (2a, 3a) eccentrically disposed with respect to said rotary shaft, characterised in that; - the rotation paths of the two rotors (2, 3) of the pair overlap inside of each other, with their respective masses subject to a gravitational force (2a, 3a) disposed in alignment with each other on a central plane of rotation, in that, - the two masses subject to a gravitational force (2a, 3a) are arranged to be subjected to synchronised rotational motion, in opposite directions, describing circles with radii proportional to their respective masses, in such a manner that both masses subject to a gravitational force (2a, 3a) are susceptible of generating the corresponding centrifugal forces, said centrifugal forces being capable of compensation in a certain direction and capable of generating a back and forth translational movement of the mobile when both masses cross each other during rotation, and in that, - it comprises rotating wheels arranged for moving the mobile over a surface in a translational direction, said wheels including a conventional anti-rollback ring susceptible of limiting the back and forth translational motion of the mobile device in a single pulsating forward translational motion. - at least one pair of rotors (2, 3) mounted in coaxial relation with respect to a rotary shaft, each pair of said rotors (2, 3) being associated with at least one power plant for actuating rotation thereof in opposite directions through motion transmission and synchronisation means (6 to 9), and - each rotor (2, 3) of the pair including a mass subject to a gravitational force (2a, 3a) eccentrically disposed with respect to said rotary shaft, - the rotation paths of the two rotors (2, 3) of the pair overlap inside of each other, with their respective masses subject to a gravitational force (2a, 3a) disposed in alignment with each other on a central plane of rotation, in that, - the two masses subject to a gravitational force (2a, 3a) are arranged to be subjected to synchronised rotational motion, in opposite directions, describing circles with radii proportional to their respective masses, in such a manner that both masses subject to a gravitational force (2a, 3a) are susceptible of generating the corresponding centrifugal forces, said centrifugal forces being capable of compensation in a certain direction and capable of generating a back and forth translational movement of the mobile when both masses cross each other during rotation, and in that, - it comprises rotating wheels arranged for moving the mobile over a surface in a translational direction, said wheels including a conventional anti-rollback ring susceptible of limiting the back and forth translational motion of the mobile device in a single pulsating forward translational motion.