Constant Force Spring
Definition - Constant force springs will deflect proportionally to the amount of force placed on it, based on the spring’s rate. Also known as a linear spring.
There are two types of constant force springs; Extension and Compression. The springs do the exact opposite from each other. One is meant to be pulled by its hooks while the other is compressed. This article will be based on constant force compression springs but you may read about constant force extension springs here.
Constant force compression springs will deflect/compress under a load. The distance between its original position/free length and its loaded height is the distance traveled. This dimension along with the load you’ll be placing on your spring will help you determine the constant force your spring will need to have.
Why is it important to know the required spring rate? You spring’s rate is your spring’s force expressed in units of force per 1 unit of measurement. This specification is determined by your spring’s dimensions depending on how tight and stressed, or how loose and light, they are. The more stressed your spring is, the stronger it will be but it will also be stiffer thus losing elasticity.


To calculate your compression spring’s required constant, you must divide the amount of force you’ll be using by the amount of travel it should compress under that load. The formula is as follows:
Rate = Load ÷ Travel
k = F ÷ x
Once you’ve done these calculations, you may use our spring calculator to design a compression spring that’ll meet your spring constant requirements. You can adjust your spring’s physical dimensions to meet the force and elasticity you need. Maybe adjusting one dimension will make your spring super strong yet super stressed thus not letting you get the elasticity you need. Then you must adjust another dimension to make the spring a bit lighter and remove some stress. Adding coils or partial coils helps out a lot when it comes to having a strong, yet soft compression spring.

