Designing torsion springs requires a focus on several factors including strength, weight, cost, and supply sources. For example, when designing a torsion spring for a garage door, the design must prioritize strength and accuracy to prevent malfunctions or safety issues. The parameters might vary depending on the specific use of the springs. This article provides guidance and suggestions on torsion spring design that can be beneficial in your project.

Weight vs Strength vs Cost Tradeoffs

Designing torsion springs involves considering the variables of weight, strength, and cost. Within the aerospace industry, the weight of a spring can influence the operation of a system. Lighter springs may have less strength and lower durability. As a result, materials that demonstrate higher strength, yet cost more, are often chosen.

The function of the spring determines how its weight, strength, and cost are optimized. For instance, the torsion springs in an airplane's landing gear focus on safety, which typically requires the use of materials that are strong, durable, and expensive. In a different scenario, the torsion springs in a clothespin aim for cost-effectiveness and therefore employ lighter, less costly materials.

Testing during the design stage enables engineers to consider materials that provide the right balance of weight and strength, consequently improving the spring's durability. An example might be the use of carbon fiber composites, noted for their high strength-to-weight ratio. Through thorough testing of various materials, design methods, and parameters, engineers can find the optimum balance among weight, strength, and cost, according to the specific requirements of the application.

Understanding Tolerances and Precision

Performance and reliability of a torsion spring directly relate to its tolerances and precision. Tight tolerances, despite appearing to be a good choice, can lead to elevated production costs and longer manufacturing time. Setting tolerances that ensure spring functionality without an unnecessary rise in costs or production duration is essential. For this, analysis of the spring's behavior under different operational conditions is required.

Take, for instance, a garage door torsion spring subjected to pressure, temperature changes, and cyclic loads. Understanding the spring's reactions under these conditions is necessary to determine suitable tolerances. Conducting tests like life cycle, load, and stress are methods to glean this understanding.

In a scenario where the stress test shows that the spring can endure high stress for an extended period but struggles with a steady increase in load, the tolerance levels need adjustment. This alteration would enhance the performance of the spring, without leading to an unnecessary increase in production costs or time.

This highlights the need to thoroughly analyze each application, as operational conditions play a part in deciding the suitable tolerance and precision levels for a spring.

Finding a COTS Spring

In some scenarios, the decision to use a commercially available off-the-shelf (COTS) spring can simplify the design process, reducing both its duration and cost. However, this can be a complex process when the wide array of catalogues and specifications do not provide a spring that aligns exactly with the application requirements. An example can be found in situations where applications have specific torque requirements. In these cases, a suitable COTS spring might not be readily available, putting engineers in a position to evaluate the advantages and disadvantages of working with an available COTS spring and potential performance variances.

Considering these issues, one potential solution might be to alter a COTS spring. This choice often emerges when a standard spring does not satisfy the required load or deflection criteria. Involving spring manufacturers at this stage can result in achieving desired outcomes. These manufacturers have the necessary knowledge and skills to guide engineers in choosing and adapting springs. For example, if a torsion spring with a unique coil diameter or leg arrangement is needed, manufacturers can change a COTS spring's specifications to meet this need in a precise manner.


Designing a torsion spring is complex and intricate process. This process requires careful analysis of numerous factors such as weight, strength, and cost while applying vital engineering principles. Setting the accurate tolerances is a substantial aspect of this design process as it requires an extensive understanding of the material's behavior under varying levels of stress. Also, finding a ready-made or Commercial off-the-shelf (COTS) spring that aligns with unique needs can be a difficult task.

Understanding these design challenges, using practical strategies, and having a systematic engineering approach helps in designing a torsion spring that aligns with specific needs. Material selection is an example of such a challenge. The track record has shown that even though high carbon steel is typically selected due to its remarkable yield strength and cost-effectiveness, stainless steel springs provide superior resistance to corrosion, hence extending the spring's lifespan.

Overcoming each of these hurdles eventually leads engineers closer to the goal of an effective torsion spring design. It is also beneficial to update and adjust the design to handle the changing demands and new challenges that may arise.