Spring Rate: What Is It and How Is It Calculated?

What is spring rate and why is it beneficial to fully understand how it’s calculated? Here is a helpful guide on everything you need to know in order to produce quality products.

Spring Rate: What Is It and How Is It Calculated? - KB Delta

A spring is an elastic object that possesses mechanical energy. Springs are made majorly from steel, and are used in our everyday activities. Springs can be found in watches, vehicles pens, toys, CD players, and so on.

Basically, spring rate, also referred to as spring constant is the amount of weight needed to compress a spring by one inch. Spring rate can also be defined as the estimation of the amount of force needed to compress a spring to a specific distance. The unit of measurements of spring rate is N/m or Ibf/in i.e. force divided by distance.

The spring rate of a spring is the change in the force applied divided by the change in diversion of the spring.

There are various types of springs, let’s see some types of spring since we know what a spring and spring rate are.


Types of Spring

Classification based on the load force applied, we have the:


  • Tension or extension spring
  • Compression spring
  • Torsion spring
  • Constant spring
  • Variable spring and,
  • Variable stiffness spring


Classification based on their shapes:


  • Flat spring
  • Machined spring
  • Serpentine spring and,
  • Garter spring


Classification based on how common they are:


  • Cantilever spring
  • Coil or helical spring
  • Volute spring
  • Hairspring or balance spring
  • Leaf spring and,
  • V-spring


Other classifications include:


  • Belleville spring
  • Constant-force spring
  • Gas spring
  • Ideal spring
  • Mainspring
  • Wave spring and so on.


Most springs obey Hooke’s law, as long as they are not compressed or stretched beyond their elastic limit. Hooke’s law states that the force with which the spring pushes back is linearly proportional to the distance from its equilibrium length.

F= -kx

Where x is the displacement factor, k is the spring constant or rate; the higher the spring constant, the stiffer the springs.

F is the resulting force vector.


How to Calculate Spring Constant

To calculate the spring rate you start by compressing the spring about 20% of the available distance of the spring and measure the height and the load, this can be named (for better understanding) height 1 and initial load in (lbs/inch) or (N/mm). At that point, compress the spring about 80% and measure the height, which can be named height 2 and the final load.

Spring rate = final load – initial load/height 1 – height 2

Most springs are moderately linear, which implies you would get a similar spring rate from the condition regardless the distance.

A few springs are non-linear, which normally implies the spring gets stiffer as you compress it. A way this could be possible is by changing the coil space, with the goal that the coils begin to contact each other as you compress. Another route is for the spring to compress and afterward experience an extra spring. This expands the spring rate since the spring is now doubled acting to the force.


Factors That Affects Spring Rate

There are three major factors that affects spring rate:


  • Wire diameter: when the wire diameter increases, the spring constant increases too. A thicker wire will make the spring constant become stronger and even difficult to deflect.
  • Spring diameter: increase in the spring diameter will lead to decrease in the spring rate.
  • Number of coils in the spring: the higher the number of coils, the lower the spring constant.


Spring Rate: What Is It and How Is It Calculated? - KB Delta


Theory of Springs

In classical physics, a spring can be viewed as a gadget that stores expected vitality, explicitly flexible possible vitality, by stressing the bonds between the molecules of a versatile material.

Hooke’s law of flexibility expresses that the expansion of a versatile bar (its enlarged length less its casual length) is directly corresponding to its strain, the power used to extend it. So also, the withdrawal (negative augmentation) is relative to the pressure (negative strain).

This law really holds just around, and just when the deformation (expansion or withdrawal) is little contrasted with the bar’s general length. For disfigurements past as far as possible, nuclear bonds get broken or reworked, and a spring may snap, clasp, or for all time distort. Numerous materials have no plainly characterized versatile breaking point, and Hooke’s law cannot be seriously applied to these materials. Besides, for the super-elastic materials, the direct connection among power and relocation is suitable just in the low-strain locale.

Hooke’s law is a numerical outcome of the way that the expected vitality of the pole is a base when it has its casual length.

Conclusively, spring is an aspect of physics which is a basic part of the human life. So when deciding to buy that car, consider the spring rate as you would consider other factors. Springs should be compressed around 25-30% when supporting the vehicle’s weight. The softer the spring rate, the easier the ride while the stiffer the spring rate, the firmer the ride. Spring rate is majorly based on the Hooke’s law as long as the elasticity level is not exceeded.

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