Extension springs are a simple yet underrated components in many systems across our daily lives. This guide aims to simplify the selection process of the suitable extension spring for your requirements, thus aiding you in accomplishing your projects. Important aspects to consider are weight capacity and stretch limits, because exceeding a spring's capacity can impact the safety of your design.

What is an Extension Spring?

Extension springs are devices created for storing and releasing energy. An extension spring elongates when an external load is applied.

Such springs are typically found in systems that need a pulling force. For instance, in a garage door system, the extension springs accumulate energy while the door is being lowered. This stored energy assists in offsetting the weight of the door during lifting. Similarly, in a trampoline, the act of jumping stretches extension springs, causing energy to be stored and then released to propel the jumper upward.

Another instance of extension spring usage is in washing machines. Here, they are employed to maintain stability during operations like the spin cycle. The selection of an appropriate spring depends on various parameters including machine specifications and load requirements. Essential factors like spring size, strength, and required extension length are to be taken into account by engineers for ensuring proper machine operation.

Extension springs can be applied in a wide variety of mechanical contexts. Engineers will need to align the properties of the spring to the specific mechanical requirements.

Extension Spring Physics

An extension spring displays a particular response when an external force is applied. Its length changes in relation to the exerted force, a concept derived from Hooke's law. According to Hooke's law, the degree of extension or compression of a spring has a direct relationship with the applied force. Importantly, an extension spring will return to its original length once the force is removed, assuming the force did not exceed the spring's elastic limit - meaning, it did not cause permanent deformation of the spring.

The retraction trait inherent in extension springs is used in devices requiring an element to reset itself. A trampoline serves as a suitable example, where extension springs pull the fabric mat back to its original shape after a person jumps on it, contributing to a consistent bounce.

Incorporating knowledge of extension springs in engineering tasks is crucial when in the design or selection stages. Different designs necessitate springs with unique characteristics based on the operating requirements of the mechanism. For instance, an extension spring in an aircraft's landing gear would need to possess considerable tensile strength and durability due to the high forces it would face during landing. Conversely, a spring in a letter scale indicator that resets the scale might need to be lighter and less sturdy. Selecting a spring that doesn't match the requirements could result in subpar product performance or even significant damage. As such, a thorough analysis of the mechanical needs of the project, combined with a solid understanding of a spring's behavior, will aid in choosing a suitable spring.

Important Factors in Extension Spring Selection

Selecting an extension spring involves certain specifications and requirements linked to the intended product's operation and safety.


Progressing in extension spring selection involves gaining knowledge of the basics and understanding the physical laws associated with these components. It's important to consider specific elements when making a selection, tailored to your individual requirements. Complete knowledge of extension springs, including properties such as spring rate, initial tension, and material type will make your selection process easier. For example, stainless steel springs provide resistance to corrosion, suitable for environments prone to rust. It's necessary to prioritize quality, as compromises could result in issues, particularly in regards to safety.