The found present has like object an actuator to fluidodinamico drive, with compasses perfected of support of the pinion, of the type that comprises a body, inside of which is defined a substantially cylindrical room, which lodges, in flowing way, a brace of coaxial pistons, that they are furnitures to commando, from opposite parts, along the axis of such room. The pistons introduce a stelo to cremagliera, that it gears with a pinion, carried from a tree, that crosses the room cross-sectionally, in correspondence of an median zone. The specified tree is supported, in revolving way, around its axis, from the body of the actuator, by means of two compasses, that they are posizionate from opposite parts between they, regarding the pinion. The two compasses are realized in acetalica resin and a first compass is realized in two semicompasses, that they are pointed out, one to the other, in a plan of perpendicular connection to the axis of the tree, with interposed an estate organ. The compass introduces, instead, a opened ring-like development.