Speed reducers consist of a set of gears, shafts and bearings that are
factory mounted in an enclosed lubricated housing. Speed reducers are
available in a broad range of sizes, capacities and speed ratios. Their
job is to convert the input provided by a prime mover into an output of
lower RPM and correspondingly high torque. AGMA defines speed reducers
as "units operating at pinion speeds below 3,600rpm or pitch-line
velocities below 5,000fpm. They are of substantial construction, combining rigidity with strength. They offer a corrosion resistant surface. They virtually eliminate backlash and friction. They also have high stiffness. They are designed to optimize speed, increase torque, and improve the performance and precision of a system's mechanical components.
Speed reducers come in two varieties: base mounted and shaft mounted. The shaft-mounted type, in turn, has two variations. One is truly shaft mounted, in that it is supported entirely by the input shaft of the drive machine, with torque reaction absorbed by a special link. The other is mounted to the driven-machine housing so the input shaft does not absorb reducer weight or torque reaction.
Speed reducers are used in manufacturing industry, rolling stock, aircraft industry, mechatronics, robotics and instrumentation.