Pneumatic motors are used only in the mining industry and, despite this relatively narrow area, in their production there is an economically unfavorable multiplicity of models with the same operating parameters, but different sizes of the active part (rotors, pistons). For example, G I. Petrovsky plant (Donetsk SNH) serially produces gear pneumatic motors type BSH2-1-5 and PSH-7A with the same operating characteristics (pressure 3.5 kg/cm^2, power 7 hp, compressed air flow rate 6.,8-7 m3/min), but different sizes of rotors: the first has a rotor width of 150 mm and inter-center distance of 100, 75 mm, the second respectively 120 and 145.3 mm. Darasun plant (Chita SNH) and the Communist Plant (Krivoy Rog) serially produced also identical in operating characteristics (5 kg / cm^2; 10 hp; 10 m3 / min) piston engines DR-10 and MP-5. But the diameter and stroke of pistons in the DR-10 engine is 101X62 mm, and MP-5 POX 80 mm. These are not single examples.