Types of Extension Springs: Hook Ends, Materials & Uses

What Are Extension Springs?

Extension springs, also known as tension springs, are made from tightly wound coil wire. They are designed to absorb and store energy by resisting a pulling force or tension. Unlike compression springs, which compress under load, these tightly wound helical coils stretch when force is applied and return to their original shape when the force is removed. They are used in applications that require two components to be brought back together or tension to be maintained. Often, they feature hooks or loops at each end. 

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Extension Spring Mechanism

An extension spring works by resisting a pulling force, storing mechanical energy, and then releasing it to return to its original position. When at rest, with no external force, it is tightly coiled. When a pulling force is applied to the ends of the spring, it begins to stretch along its axis, which increases the distance between the coils. Extension springs have a set initial tension, and a higher initial tension creates a stronger spring.

As the spring stretches, it stores potential energy; this energy is proportional to the distance the spring is stretched and is governed by Hooke’s Law. When the external force is removed, the stored energy in the spring is released, causing the spring to contract. It pulls the attached components back toward each other, returns to its original length and releases the stored energy in the process.

Types of Extension Springs

Extension springs come in various types, each designed to meet specific requirements and applications. Understanding these different types can help you choose the right spring for your project.

Standard Extension Springs

Standard extension springs are pre-manufactured springs designed to meet common specifications. You will find standard springs available in a variety of common lengths, wire diameters, coil diameters and sizes. These springs typically come with standardised hooks or loops at the ends so that they can be easily attached to other components in a system.

Common Uses: 

• Automotive - throttle return mechanisms, trunk latches, brake systems.
• Industrial Machinery - conveyors, levers, and counterbalance systems.
• Consumer Products - garage doors and trampolines.

Precision Extension Springs

A precision extension spring is manufactured to very tight tolerances and specific design requirements to ensure high accuracy, consistency, and performance. These springs are often custom-designed and produced to meet the exact specifications needed for specialised tasks where standard springs may not provide the necessary precision or reliability.

Common Uses:

• Aerospace - control mechanisms, landing gear assemblies, and safety systems.
• Automotive: transmission systems, fuel injectors, and braking systems.
• Medical Devices: surgical tools, diagnostic devices, and implantable devices.

Custom Extension Springs

A custom extension spring is specifically designed and manufactured to meet specialised requirements that cannot be fulfilled by standard or off-the-shelf springs. These springs are tailored to precise specifications, including dimensions, materials, load capacities, and end configurations, to suit specific applications. They may also have special coatings and finishes to enhance durability and performance in harsh environments. 

Common Uses:

• Aerospace and Defense - aircraft, spacecraft and military equipment.
• Automotive - specialised suspension, engine and braking mechanisms. 
• Renewables - wind turbine blade pitch controls, hydroelectric dam gate systems

Heavy Duty Extension Springs

A heavy-duty extension spring is specifically designed to handle high loads and withstand significant stress. These springs are built to be robust and durable, making them ideal for applications that involve heavy machinery, large mechanical systems, or environments where the spring is subjected to intense forces and repetitive use. Typically, they are made from thicker wire and have large coil diameters, with strong end loops or hooks. 

Common Uses:

• Construction Equipment - cranes, bulldozers and excavators.
• Automotive - suspension systems, brake assemblies and engine components.
• Railway Applications - coupling systems, brake assemblies and suspension systems.

Types of Extension Spring Hooks

There are many types of extension spring hook and end types. Here are ten of the most common end types that we use in our expert, heavy-duty spring manufacturing process.

Round-End Hook

Round-end hooks are a common type of spring end featuring a simple circular loop formed at the end of the spring coil. This design provides a simple, durable attachment point, which supports a spring to connect securely to other components. 

V Hook

V Hooks are shaped like the letter "V" at the end of the spring, offering a solid and secure attachment point. They are helpful in applications that require a firm grip and stability, where the spring needs to resist movement and where precise positioning is needed. 

Closed German Loop

The closed German loop is a tightly wound loop that forms a small, nearly circular end. This design provides enhanced strength and durability, making it ideal for heavy-duty applications where the spring needs to withstand significant forces without the loop opening or deforming.

German Side Loop

The German side loop features a loop that extends sideways from the end of the spring. This allows for easier attachment in applications where the spring must connect to a component at a specific angle, providing versatility in design and installation.

Half German Hook

The half German hook is a variation of the German loop, where the loop is partially formed, creating an open-ended loop. This design is often used when quick attachment and detachment are required, offering a balance between security and accessibility.

Double German Loop

The double German loop features two loops at the end of the spring. This provides a stronger and more secure attachment point than other spring ends. This design is used in heavy-duty applications where additional strength and stability are needed and prevents the spring from detaching when a heavy load is applied. 

Extended German Side Loop

The extended German side loop is similar to the standard German Side Loop but with an extended length of end loop. In the diagram above, you will notice the loop end being two coils long rather than one, which allows for greater flexibility in attachment points. This end type is ideal for situations where springs need to be connected over a long distance or at a specific angle.

English Loop

The English loop is a classic, straightforward loop at the end of the spring, typically larger and rounder than the German loops. Typically, the loop is offset, which means it is not centred directly at the end of the spring but instead positioned on one side. This allows for easier attachment in applications where the spring needs to be connected to components that are not directly in line with the spring's axis

Extended Side Hook

The extended side hook features a hook that is raised up from the side of the spring, providing a more extended reach for attachment. This design is useful when the spring needs to be connected to a component at a distance or where flexibility in positioning is required.

Other End Types

Other end types include screw plugs and crew shackles. These are specialised end types used in applications requiring a more permanent or mechanically secure connection. Screw plugs allow the spring to be fastened securely into place, while crew shackles provide a robust and durable connection point that can handle heavy loads. 

Extension Spring Materials

Various materials can be used in the extension spring manufacturing process. These range from carbon steel, stainless steel, and alloy steel to non-ferrous metals and speciality materials. Let’s explore each of these in more detail.

Carbon Steel

Carbon steel is a popular material used in the manufacturing of extension springs due to its strength, durability, and cost-effectiveness. It is composed mainly of iron and carbon, offering a good balance of toughness and tensile strength. Carbon steel springs are commonly used in general-purpose applications but may require protective coatings to prevent rust and corrosion in more demanding environments.

Stainless Steel

Stainless steel is a highly corrosion-resistant material, making it ideal for extension springs used in harsh or moisture-rich environments. This material is known for its excellent strength, durability, and resistance to rust, making it a preferred choice in industries such oil and gas exploration, renewables and marine application

Alloy Steels

Alloy steels are used in extension springs when specific properties, such as increased strength, toughness, or resistance to wear and fatigue, are required. By adding elements like chromium, nickel, or molybdenum to the base steel, alloy steels can be engineered to perform in extreme conditions, including high-stress or temperature environments.

• Chrome Silicon

Chrome silicon is a high-performance alloy steel used in extension springs that require resilience and resistance to high temperatures. This material maintains its strength and elasticity even under repeated stress and exposure to high temperatures, making it ideal for applications in motorsport engines, heavy machinery, and other high-stress environments.

• Chrome Vanadium

Chrome vanadium is another high-strength alloy steel used in springs that must endure heavy loads and repeated cycles. Known for its excellent fatigue resistance, this material is commonly used in applications such as automotive suspension systems, industrial machinery, and tools that require superior durability.

Non-Ferrous Metals

Non-ferrous metals are used in extension springs when specific properties, such as resistance to corrosion, conductivity, or the need for non-magnetic materials, are required. These materials do not contain iron, making them ideal for specialised applications where the typical characteristics of steel are not suitable.

• Phosphor Bronze

Phosphor bronze is a non-ferrous alloy used for its excellent corrosion resistance, good electrical conductivity, and fatigue resistance. This material is commonly used in applications requiring precise mechanical properties and durability, such as electrical connectors, switchgear, and marine environments.

Contact us to discuss your requirements of heavy duty tension springs. Our experienced sales team can help you identify the options that best suit your needs.

• Beryllium Copper

Beryllium copper is a non-ferrous alloy known for its high strength, excellent conductivity, and non-sparking properties. Extension springs made from beryllium copper are often used in environments where electrical conductivity is essential, such as in electronics and aerospace, and in explosive environments where non-sparking materials are required.

Speciality Materials

Specialty materials are used in extension springs when extreme performance characteristics are needed, such as resistance to high temperatures, corrosion, or specific chemical environments. Often these materials are often more expensive and are used in highly specialised applications.

• Inconel

Inconel is a nickel-chromium alloy known for its exceptional resistance to high temperatures, oxidation, and corrosion. Extension springs made from Inconel are used in extremely demanding environments, such as aerospace, power generation, and chemical processing industries, where they must withstand severe thermal and corrosive conditions.

• Elgiloy

Elgiloy is a cobalt-chromium-nickel alloy known for its outstanding corrosion resistance, high strength, and excellent fatigue properties. Extension springs made from Elgiloy are reliable and durable and are often used in harsh environments, including medical devices, chemical processing, and oil and gas applications.

• Titanium

Titanium is a lightweight, high-strength material with excellent corrosion resistance. Titanium springs are valued for their high strength-to-weight ratio and their ability to withstand extreme environments, though they are more expensive and challenging to work with compared to other materials. This material is used in aerospace, medical, and marine applications.

Extension Spring Uses

Heavy-duty extension springs can be used in many industry applications. Below, you will find specific examples of how they are used in various industries.

Construction Equipment

Heavy-duty extension springs are used in construction machinery such as excavators, cranes, and bulldozers. They are used to manage tension in control cables, counterbalance heavy attachments, and absorb shocks from moving parts. These springs help maintain stability and ensure smooth operation under the strenuous conditions typical of construction sites, such as heavy loads, vibrations, and repeated cycles of use.

Quarry & Mining Equipment

Heavy-duty extension springs are used in quarry and mining machines such as crushers, conveyors, rock crushers, drill rigs and vibrating screens. These springs manage tension and provide the necessary force to keep belts and other components in alignment. They also support machinery in operating efficiently under heavy loads and harsh environmental conditions. Plus, they absorb shock loads and vibrations, which protects equipment from damage during the processing of heavy and abrasive materials.

Motorsports

Heavy-duty extension springs are used to manage the extreme forces experienced in motorsports. They are used in suspension systems to control the rebound of shocks, in throttle return mechanisms for precise control, and in braking systems to ensure reliable performance under high stress. These springs withstand the intense conditions of high-speed racing, including rapid accelerations, sharp turns, and frequent impacts, while maintaining integrity and performance.

Fishing & Agriculture

Heavy-duty extension springs are used in fishing and agriculture equipment such as nets, traps, ploughs, and harvesters. In fishing, they are used to maintain tension in nets and traps, ensuring proper closure and operation. In agriculture, these springs help manage the movement of heavy machinery components, such as seeders and sprayers, and assist in the opening and closing of gates and hatches. They are robust enough to withstand exposure to harsh outdoor environments and regular mechanical stresses.

Renewable Energy Applications

Heavy-duty extension springs are used in systems such as wind turbines and solar tracking mechanisms. In wind turbines, they help maintain tension in the cables and control systems that adjust the blade pitch. This supports operation and stability under varying wind conditions. In solar panel tracking systems, they assist in moving the panels to follow the sun, which optimises energy capture. Specialised materials may be used so that they are resistant to environmental factors like temperature fluctuations, moisture, and corrosion. 

Leading Heavy Duty Extension Springs

There are many types of extension springs, which can be manufactured using various materials and end hook types, depending on the application. At Lesjöfors, we are leading specialists in custom spring design and can support you to find resilient, durable and reliable spring solutions for your custom needs. Our expert engineers will work alongside you to design and develop heavy-duty springs that meet your required specifications. Plus, our high-quality prototype and sample service enables you to test your spring in a real-time environment so that you can feel confident stepping forward into the manufacturing process.

Want to find out how we can support you with your custom spring design?

Enquire About Springs

Springs are essential components in various mechanical systems, providing elasticity and absorbing energy. Whether it’s in automotive suspension systems or mattresses, springs find applications in numerous industries. However, what sets a spring apart as truly exceptional? In this article, we will explore the key qualities that define a high-quality spring.

1. Material Quality

The first and foremost quality of a good spring lies in the material it is made of. Springs are typically manufactured using materials like steel, stainless steel, or alloys. The choice of material depends on the specific application and desired characteristics. For instance, stainless steel springs offer excellent corrosion resistance, making them suitable for outdoor or marine environments. Regardless of the material, a good spring should have high tensile strength, good resilience, and fatigue resistance to ensure longevity and reliable performance.

To further enhance the material quality, manufacturers may opt for specialized alloys or heat treatment processes. These techniques can improve the spring’s performance by increasing its strength, durability, and resistance to environmental factors. By carefully selecting the appropriate material and employing advanced manufacturing techniques, a high-quality spring can be created that meets the demanding requirements of various applications.

2. Durability and Longevity

Durability is a primary quality to consider when evaluating a good spring. Springs are subjected to repetitive loading and unloading cycles, which can lead to fatigue and eventual failure if the spring is not designed to withstand such stress. A high-quality spring should exhibit excellent fatigue life, ensuring optimal performance over an extended period.

Manufacturers achieve durability and longevity by incorporating careful design considerations, material selection, and proper heat treatment processes during manufacturing. These factors contribute to enhancing the spring’s ability to withstand repeated stress and maintain its performance characteristics over time. By investing in a durable spring, you can minimize the risk of failure and ensure consistent performance in your mechanical systems.

3. Precision Manufacturing

Precision manufacturing is crucial for producing high-quality springs. Springs with consistent dimensions and tolerances ensure uniform performance and compatibility within the intended system. Advanced manufacturing techniques, such as computer numerical control (CNC) machining, ensure precise coiling, forming, and shaping of the spring.

In addition to precise manufacturing techniques, close attention to detail during the production process minimizes defects and ensures consistent quality across production batches. By employing stringent quality control measures, manufacturers can guarantee that each spring meets the specified standards and performs reliably under expected working conditions. This consistency in manufacturing results in springs that can be trusted to deliver optimal performance in diverse applications.

4. Customization and Adaptability

Different applications require different types of springs with varying specifications. A good spring manufacturer should offer customization options to meet specific needs. Whether it’s the size, shape, or material composition, the ability to tailor the spring to precise requirements is a hallmark of a reliable spring supplier.

Customization allows for optimizing springs based on load requirements, space constraints, or environmental factors. Manufacturers can design springs that provide the necessary support, resilience, and load capacity for a particular application. By considering the specific needs of your system and working with a manufacturer that offers customization options, you can ensure enhanced performance and overall system efficiency.

Some customization options may include the ability to modify the spring’s dimensions, such as its length or diameter, to accommodate specific spatial constraints. Manufacturers may also offer a range of materials to choose from, each with its own set of characteristics. By tailoring the spring to your exact requirements, you can maximize its effectiveness and ensure optimal performance in your application.

5. Load Capacity and Resilience

The load capacity and resilience of a spring are critical factors to consider. A good spring should be able to support the required load without deforming excessively or losing its elasticity. The spring’s design and the material used should be chosen to withstand the anticipated load conditions.

Manufacturers determine the load capacity and resilience of a spring through careful engineering and material selection. By accurately assessing the expected loads and stresses, they can design springs with the appropriate dimensions and strength to handle these demands. Additionally, the spring should exhibit resilience, meaning it can return to its original shape after being compressed or stretched. This quality ensures that the spring can effectively absorb and dissipate energy, allowing for smoother operation and minimizing the risk of damage or failure.

6. Corrosion Resistance

Depending on the application, a spring may be exposed to harsh environmental conditions, chemicals, or moisture, which can lead to corrosion. A high-quality spring should possess excellent corrosion resistance to ensure its longevity.

Manufacturers achieve corrosion resistance by selecting suitable materials, such as stainless steel or specialized coatings, which provide a protective barrier against corrosion. Stainless steel springs, for example, exhibit exceptional resistance to rust and corrosion, making them ideal for applications that involve exposure to moisture or corrosive substances. By choosing a corrosion-resistant spring, you can ensure its reliability and avoid premature failure due to environmental factors.

7. Consistent Performance

Consistency in performance is a key quality of a good spring. The spring should exhibit predictable behavior and maintain its performance characteristics over time. Variations in performance can lead to system inefficiencies, reduced productivity, or even safety hazards.

To ensure consistent performance, reliable spring manufacturers conduct stringent quality control measures. These measures include testing for load capacity, resilience, and fatigue life to guarantee that each spring meets the specified standards. By adhering to strict quality control protocols, manufacturers can provide customers with springs that consistently deliver the expected performance, even under demanding conditions.

In conclusion, a good spring possesses key qualities such as material quality, durability, precision manufacturing, customization options, load capacity, resilience, corrosion resistance, and consistent performance. By considering these qualities when selecting a spring, you can ensure optimal performance, longevity, and reliability in your mechanical systems. Whether you are designing a suspension system for a vehicle or selecting a spring for a mattress, prioritizing these qualities will lead to the best possible outcome.

Are you interested in learning more about custom coil springs for cars? Contact us today to secure an expert consultation!

FAQ

1. What is the most important quality of a good spring?

• The material quality is the most important quality of a good spring.

1. How can durability and longevity be achieved in a spring?

• Durability and longevity can be achieved through careful design considerations, material selection, and proper heat treatment processes during manufacturing.

1. Why is precision manufacturing crucial for producing high-quality springs?

• Precision manufacturing ensures consistent dimensions and tolerances, resulting in uniform performance and compatibility within the intended system.

1. Why is customization and adaptability important in a spring manufacturer?