Many applications take advantage of constant torque spring motors. If you want to use them, there are several things to consider.

This guide collects several critical topics, it summarizes all you need to know about constant torque spring motors, let dive in right now!

  1. What’s constant torque spring motors.
  2. Constant torque spring motors assembly.
  3. Functionality and Applications.
  4. Design.
  5. Features.
  6. Multiplying the Load.
  7. Frequently asked questions.

What’s Constant Torque Spring Motors

Constant torque spring motors result from a combination of two or more constant torque springs, the springs are steel strips that are prestressed.

They are the assemblies that are made up of springs and drums and are easy to generate bigger retractable force.

Constant Torque Spring Motors Assembly

Constant torque springs motors form when the spring coils onto a smaller storage drum. The terminal end Is then backwound and secured onto a larger output drum.

The spring portion on the output drum is known as the “winding portion”, you can assemble the springs in single or multiple configurations.


Single spring configuration


Multiple spring configuration

Natural decoupling is possible in multiple spring configurations. It helps in eliminating torque loss in the setup.  Due to this, the motor delivers a specific torque. It also operates at high efficiency.

Functionality and Applications

The functionality of your constant torque spring motors depends on the designs. The springs can vary in sizes.

Therefore, they make it suitable to use in multiple applications.

We strongly suggest that you consult with YongSheng expert early enough in the design phase, these will be greatly convenient for the further assembly process.

Constant torque springs are wildly used in these applications as below:

  1. Cord retractors
  2. Counterbalancing
  3. Retrieving and returning applications
  4. Drive motors
  5. Cordless window blinds

The springs have a high turn design making them ideal for counterbalancing applications. When they turn entirely, the springs exert a constant torque. You are also guaranteed high torque levels. This is due to their compact nature and high efficiency.

There are two ways you can connect constant torque springs motors.  If connected in the same direction, it is called an A-type motor. If connected in reverse, it is called B type motor.  See the below illustrations.

A-type-constant-torque-spring-motor B-type-constant-torque-spring-motor

Design of Constant Torque Spring Motor

The design of your constant torque spring motor plays a big part in the efficiency of your application. The factors you should consider are:

  1. The shaft – includes the inner and outer diameter.
  2. The working height where the load is applied.
  3. Load capacity. The load capacity is due to the application.
  4. Material, we usually apply stainless steel or high carbon steel as the spring’s raw material.


Type A and type B constant torque spring motor have some similarities. These include

  1.  Easy to assemble and operate.
  2. Almost constant torque force
  3. A high number of turns

However, Type B has higher torque levels than type A.

Stretching the spring on the storage drum guarantees constant torque. The spring always wants to regain its original state. Movement of the output drum induces a constant torque.

Multiplying The Load

Multiplying the load ensures that you can increase the load force. You are also sure of higher torque and longer life. Multiple springs share the load force, discharging constant torque against the load force.


The number of springs in a single unit motor determines the force produced.  Some applications require a higher amount of force. For this, you need to use a higher number of springs for the motor.

You can select our standard constant torque spring motor designs. Moreover, you can request customization if your application requires unique springs.

Frequently Asked Questions

  1. What material is used in making constant torque spring motors?

Constant torque spring motors use type 301 stainless steel. It is wound up and delivered in coils. It helps with mounting onto motor drums.

  1. How to attach constant torque spring motors to a storage drum?

The spring is wound tightly on two drums. Next, set up by winding it on from the first drum towards the second. The curvature then reverses.

  1. What is the working mechanism for Constant torque spring motors?

Force exerts onto the drum, which will lead the spring to unwind around the shaft. The storage drum will generate counterpart force. When mounted, the springs will retract when a force is applied. Applications can, therefore, take advantage of the resistant force generated.