Three minutes to understand the basic concepts and selection calculations of reducers

Release Time：

2025-03-23

Just like a car shifting gears and climbing hills, the gearbox can convert the high-speed rotation of the motor into low-speed high torque output. For example, if a motor rotates 1500 revolutions per minute and is "processed" by a reducer, the output end may only rotate 30 revolutions, but the force can lift hundreds of pounds of weight!

Three minutes to understand the basic concepts and selection calculations of reducers
What is a gearbox?

In simpler terms, a gearbox is a "speed reducer and power amplifier".

Composition of gearbox

We have learned what a gearbox is, and now let's take a closer look at the components of a gearbox. It mainly consists of three parts

1. Gear set: Like a bicycle gearbox, gears of different sizes bite to change the speed.

2. Bearings: Precision components that make rotation smoother.

3. Box: Generally made of metal material, it protects the internal components.

Five step selection method for gearbox

1. Check the usage of the load

Stable load: such as conveyor belts, fans, etc

Impact load: Stamping machine, crusher

2. Formula for calculating load torque

Required torque T=9550 x motor power (kW) ÷ output speed (r/min)

Case: A 0.75kW motor needs to output 30r/min

Torque T=9550 × 0.75 ÷ 30 ≈ 239N · m

3. Determine the reduction ratio

Speed ratio i=motor speed (input speed) ÷ required output speed (output speed)

(Common speed ratios range from 5-100, and special models can reach 10000:1)

4. Verify the power meter

Refer to the manufacturer's parameter table and select the model with a bearing capacity ≥ calculated value, leaving a safety margin of torque × 1.2~1.5 times

5. Measure installation dimensions

Confirm whether the flange form (flange type, shaft mounted type), installation size, and shaft diameter match the equipment

Practical Cases

Scenario: Select a mixer with a reducer motor power of 5.5kW, a speed of 1440r/min, a required mixing shaft speed of 60r/min, and a load torque of 800N · m.

1. Reduction ratio i=1440/60=24 → Select standard value 25

2. Theoretical output torque=9550 × 5.5/60 ≈ 880N · m

3. Actual torque requirement 800 × 1.5=1200N · m

4. Choose a gear reducer (efficiency 95%) with a rated torque of ≥ 1200N · m for the model

Guide to Avoiding Pits

Environmental factors

Choose heat-resistant oil seals for high temperature environments

Waterproof type is required in damp environments

Dust often uses fully sealed structure

Maintain cold knowledge

Oil must be changed after 200 hours of operation!

Choosing the wrong type of grease=white maintenance

Money saving trap

Some platforms offer low-priced recycled refurbished gears, which may have a lifespan less than 1/10 of the genuine product