When designing extension springs, knowledge of a spring's capacity to bear loads is necessary. This article discusses the main load considerations affecting the functionality and lifespan of extension springs. We will look at how you can increase a spring's ability to bear loads by better choices of material and diameter. A usual problem is using a light-duty spring for heavy load conditions. This issue usually causes the spring to fail immediately. Involving these load considerations in your design plans can result in spring systems that last longer and safer engineering projects.

Load Bearing Capacity of Extension Springs

The load-bearing capacity of an extension spring, defined as the maximum force it can withstand before deforming or breaking, is a crucial parameter in spring design. The wire diameter, coil diameter, initial tension, and the number of active coils influence this factor.

Extension Spring Stress Analysis

Examining the load-bearing capacity of an extension spring is a primary step. Following this, a detailed stress analysis is performed to detect any areas of potential failure, aiding in the production of more resilient springs.

An area of focus during extension spring stress analysis is the portion of the spring under the highest stress, typically the interior of the spring body. Take a spring in a trampoline as an example. As the trampoline is utilized, the majority of the tension and resulting stress is positioned on the interior of the spring.

Important variables that factor into stress comprise the wire diameter, coil diameter, initial tension, and the number of active coils. All these components play roles in the overall load-bearing capacity of the spring. A spring made with a wider diameter wire can withstand higher stress owing to its sturdy structure. In addition, a spring with a larger coil diameter can distribute the load over a wider area, potentially reducing stress. However, increasing wire and coil diameter might heighten the spring's weight, which could be undesired in some applications where weight is a limiting factor.

Taking these interrelated factors and their impacts into account during extension spring design results in a product that possesses superior durability and is suited to its intended application.

Avoiding Overstretching and Breakage

Extension springs may overstretch if the forces exerted on them surpass the predetermined elastic limit. For instance, consider an extension spring integrated in a garage door system, designed to handle a 50kg load. If the actual weight of the garage door exceeds 50kg, overstretching might occur, potentially resulting in permanent distortion or failure of the spring. Manipulating the spring's elastic limit correctly requires a precise knowledge of load requirements.

Spring failure typically occurs under intense stress conditions. Routine checks for signs of wear and fatigue can aid in mitigating breakage. As an illustration, performing regular inspections when extension springs operate in machinery that manages substantial loads could identify potential issues before they lead to system failure.

Completing an in-depth stress analysis during the design phase can be advantageous. Let us take the previously mentioned extension spring, which is utilized in heavy-duty industry machinery. The machinery uses this spring to actuate a hatch, which operates 100 times per day. The crucial operation parameters such as the frequency and load should be considered in the stress analysis. Taking this step could help enhance the design of the spring, consequently minimizing the risk of failure due to overstress and overstretch.


Designing an extension spring requires detailed load considerations, including assessing the load-bearing capacity and conducting stress analysis accurately. It's essential not to overstretch the spring to prevent potential breakage. Engineers have identified that an overstretched spring could initiate mechanical failure and impact the application. Therefore, the precise application of these guidelines aligns with enhancing the performance of the design and simplifying the fabrication process.