The prime mover (PM) rotates the gear-reducer gears through a V-belt drive. The two most common PMs are electric motors and internal combustion (IC) engines. These considerations, as well as other factors, have been discussed in numerous publications. The characteristics of these engines are summarized here, and the detailed comparisons and field experiences have been published elsewhere. These test data should be requested and furnished to the purchaser from the manufacturer. The data should include the manufacturer's curves showing the torque, maximum brake HP, and the rated-brake HP vs. engine speed. These are important to know the speed range in which the engine would be able to operate. A general guide for installation and maintenance of gas engines is API RP 7C-11F,  which covers all three types of engines and includes a troubleshooting section.