Gear Reduction. A familiar term to many, but what does it actually mean?

Gear Reduction. A familiar term to many, but what does it actually mean?

On the surface, it may seem that gears are being “reduced” in quantity or size, which is partially true.  When a rotary machine such as an engine or electric motor needs the output speed reduced and/or torque increased, gears are commonly used to accomplish the desired result.  Gear “reduction” specifically refers to the speed of the rotary machine; the rotational speed of the rotary machine is “reduced” by dividing it by a gear ratio greater than 1:1.  A gear ratio greater than 1:1 is achieved when a smaller gear (reduced size) with fewer number of teeth meshes and drives a larger gear with greater number of teeth.

Gear reduction has the opposite effect on torque.  The rotary machine’s output torque is increased by multiplying the torque by the gear ratio, less some efficiency losses.

While in many applications gear reduction reduces speed and increases torque, in other applications gear reduction is used to increase speed and reduce torque.  Generators in wind turbines use gear reduction in this manner to convert a relatively slow turbine blade speed to a high speed capable of generating electricity.  These applications use gearboxes that are assembled opposite of those in applications that reduce speed and increase torque.