A self-propelled cart for transporting heavy loads of the type comprising: a chassis having, on top, a substantially horizontal loading deck on which the item to be transported rests; and a series of pivoting wheel assemblies that are located beneath the chassis , each with the capability of rotating, on command, about a respective reference axis (A); each pivoting wheel assembly comprising: a slewing bearing which is fixed to the chassis with the capability of rotating about said reference axis (A) ; a servo-motor which is adapted to rotate, on command, the slewing bearing about said reference axis (A) ; a horizontal axle which is located beneath the slewing bearing , is connected to the slewing bearing so as to rotate together with the latter, and is provided with at least two ground-resting wheels coaxial to one another; and an active suspension which is interposed between the horizontal axle and the slewing bearing , and is capable of varying, on command, the distance (d) between the plane on which the slewing bearing lies and rotates and the rotation axis (R) of the two wheels ; the horizontal axle of at least one of said pivoting wheel assemblies comprising: a central hub which extends between the two wheels of the axle coaxial to the wheel rotation axis (R) and is laterally connected to the slewing bearing via a hinge that allows the central hub to swing about a first axis (B) which is perpendicular to said reference axis (A) and is parallel and spaced from the wheel rotation axis (R); and an engine adapted to drive into rotation the wheels of the axle about the common rotation axis (R); wherein the engine is located outside of the central hub , is arranged parallel to the wheel rotation axis (R), is spaced beside the central hub , is supported by a transversal bracket that protrudes from the central hub on the opposite side with respect to the hinge , and is connected to the wheels of the horizontal axle via a transversal powertrain . each pivoting wheel assembly comprising: a slewing bearing which is fixed to the chassis with the capability of rotating about said reference axis (A) ; a servo-motor which is adapted to rotate, on command, the slewing bearing about said reference axis (A) ; a horizontal axle which is located beneath the slewing bearing , is connected to the slewing bearing so as to rotate together with the latter, and is provided with at least two ground-resting wheels coaxial to one another; and an active suspension which is interposed between the horizontal axle and the slewing bearing , and is capable of varying, on command, the distance (d) between the plane on which the slewing bearing lies and rotates and the rotation axis (R) of the two wheels ; the horizontal axle of at least one of said pivoting wheel assemblies comprising: a central hub which extends between the two wheels of the axle coaxial to the wheel rotation axis (R) and is laterally connected to the slewing bearing via a hinge that allows the central hub to swing about a first axis (B) which is perpendicular to said reference axis (A) and is parallel and spaced from the wheel rotation axis (R); and an engine adapted to drive into rotation the wheels of the axle about the common rotation axis (R); wherein the engine is located outside of the central hub , is arranged parallel to the wheel rotation axis (R), is spaced beside the central hub , is supported by a transversal bracket that protrudes from the central hub on the opposite side with respect to the hinge , and is connected to the wheels of the horizontal axle via a transversal powertrain . <EOS>