How to select gear ratio for a gear reducer?

Gear reducers are an essential part of mechanical power transmission systems, being used for speed and torque conversion. Selecting the right one for an application is a fairly straightforward process. The first step in selecting a gear reducer is to know the required torque and speed as well as the most suitable type of motor to use. Then, it can be determined if a gear reducer is needed in the particular case. If so, then the next step is to select the proper type and ratio.

So what does a gear reducer do? The most common benefits are that they can reduce speed, multiply torque, and solve inertia mismatching issues. For instance, to take speed reduction, the amount needed will depend on the type of motor used. That’s because some motors can operate at low speeds (less than 1,000 rpm, for instance) without the need for a gear reducer, while others cannot.

For speed reduction the gear ratio is calculated using the equation:

G = N_MOTOR / N_LOAD

where G is the gear ratio, and N is the angular velocity of the motor and the load.

The way gear reducers work is that they essentially multiply the output torque of the motor. So for instance, a small motor with a gear reducer may be less expensive and smaller than a larger motor without a gear reducer producing an equal amount of torque.

To calculate the required gear ratio when torque multiplication is needed, use the equation: