motor is described comprising a plurality of segments separated by radial grooves adapted to slidably house paddles each segment includes a surface external edge consisting of a convex portion joined to at least one concave abutment application_number US 79314110 A description with reference to the accompanying drawings and in particular to fig1 and 2 a surfacer 100 is shown comprising a pneumatic paddle motor 20 belonging to the known art motor 20 is equipped with a rotor 10 with paddles 40 eccentrically contained in a housing 60 adapted to activate a shaft 170 motor 20 is described in the introduction of the present application hereinafter a brief reminder of the activation of rotor 10 as depicted in fig2 is provided the compressed air flow from an inlet 70 enters in a milled channel 400 in the upper 140 and lower 150 heads fig1 thus triggering the rotation said channel 400 consists of a radial section 401 connected to inlet 70 and of a curved section 402 adapted to direct the air towards a housing 60 of a paddle 40 a self triggering rotor 1 according to the present invention for a pneumatic paddle motor 2 is seen in fig3 7 in particular in fig3 the self triggering rotor 1 activating a shaft 17 is denoted which comprises radial grooves 5 in which paddles 4 adapted to define rotor segments 50 are slidably housed.