What's the Deal with Torsion Springs Anyway?

Ever tried to open a door and wondered how it swings so smoothly? Or maybe you've pondered how a trailer ramp stays steady when loading heavy equipment. The secret behind these everyday wonders is the torsion spring! But why should you care about them? Well, if you're looking to design or fix anything that rotates or twists, understanding torsion springs is a game-changer. In this guide, we're going to dive into the world of custom torsion springs in a way that's easy to grasp. We'll break down the basics, walk you through designing one step by step, and even show you how to use nifty tools like Acxess Spring's Instant Spring Quote and Online Spring Force Tester to make your life easier. So, ready to become a custom torsion spring guru? Let's get rolling!

Understanding Torsion Springs

What Exactly Is a Torsion Spring?

In simple terms, a torsion spring is a spring that works by twisting or turning one leg while the opposite leg remains stationary. Unlike the springs you might find in a mattress or a pen (which compress or extend), torsion springs provide rotational force. Imagine twisting a rubber band around your finger and then letting it go—that twisting action and the force that comes from it is what a torsion spring does, but in a controlled and predictable way.

These springs are usually made by coiling wire tightly around a rod or arbor or coiled from a spring coiler. When you apply force to the ends (called legs), the spring twists, storing energy. When you let go, it releases that energy, returning to its original leg position. This twisting motion is what makes torsion springs super useful in applications where things need to rotate or pivot.

How Do They Work?

When you twist a torsion spring, it resists that twisting motion. Think of it like trying to twist a thin piece of sheet metal; it pushes back against you. This resistance is what creates torque—the rotational equivalent of linear force. The more you twist the spring, the more torque it provides to try and get back to its starting point.

Several factors affect how much torque a torsion spring can provide:

• Wire Diameter: Thicker wire means a stronger spring.

• Mean Diameter: The average diameter of the coils; larger diameters make the spring less stiff or weaker.

• Total Coils: More coils allow the spring to twist further in degrees but can reduce torque.

• Material Properties: Different materials have different strengths and flexibilities.

Materials

Torsion springs come in different materials depending on what they're needed for. Common materials include:

• Music Wire ASTM A228: This is a high-carbon steel that's super strong and flexible. It's great for indoor applications where corrosion isn't a concern. Music wire is often used in pianos and guitars, which speaks to its strength and flexibility.

• Stainless Steel 302 ASTM A313: Resistant to rust and corrosion, making it awesome for outdoor use or humid environments. If your spring will be exposed to the elements or moisture, stainless steel is a solid choice.

​​​​​​​

Phosphor Bronze A ASTM B159 and Beryllium Copper ASTM B197: These materials are ideal when you need electrical conductivity or non-magnetic properties. They are often used in electrical switches and connectors.

Key Things to Consider When Designing Torsion Springs

Designing a custom torsion spring isn't just slapping some wire into a coil and calling it a day. You've got to consider a few important factors to make sure your spring does what you want it to do and lasts as long as you need it to.

Load Requirements

First up, how much torque do you need? Torque is the rotational force, measured in inch-pounds per degree (in-lbs/Degree). Think about what the spring will be moving. Is it a lightweight cabinet door that needs just a gentle push, or is it a heavy-duty industrial gate requiring significant torque force? Knowing the required torque helps you determine the spring's specifications and ensures it will perform as needed without failing.

To calculate the required torque, you need to consider factors like the weight of the object being moved, friction in the mechanism, and any additional forces acting on the system. Getting this right is crucial because too little torque means the spring won't do its job, and too much could cause unnecessary wear or even damage other components.

Rotation Angle

Next, figure out how much the spring needs to twist—this is your deflection or travel, measured in degrees. Over-twisting or going past the maximum deflection can lead to a busted spring, and nobody wants that. Each material and spring design has a maximum safe deflection which is the rotation angle before the material yields or fails. Ensure the spring can handle the twist you need without overstressing it.

For example, if your application requires the spring to rotate 90 degrees (a quarter turn), you need to design the spring so that this amount of twisting doesn't exceed the material's elastic limit. Otherwise, the spring may not return to its original position, or worse, it could break.

Space Constraints

Check out the space where the spring will live. Measure the inner diameter (so it fits over any rods or shafts). Make sure your torsion spring’s inner diameter is bigger than the shaft or rod you will be placing it over, because when you twist the torsion spring legs the spring's inner diameter shrinks as you twist. It is very important to allow for at least 10% to 15% inner diameter clearance around the shaft or rod you will be placing the torsion over because if you don’t have enough clearance around the rod or shaft, the spring’s inner diameter will bind or bit down on the shaft when you twist the spring leg and then you will lose all the torque from your spring. Don't forget about the body length of your torsion spring. Make sure your torsion springs body length cavity is bigger than the body length of your torsion spring by at least one wire diameter. Why? Because the torsion spring's body length grows and increases when you twist the spring, one must allow more space inside the cavity where the torsion spring will be placed so the spring can work freely and not bind to any mating parts.  Space constraints can significantly impact your design choices. If you have limited room, you might need to opt for a spring with a reduced outside diameter to fit the space. Also, consider how the spring will be installed and whether there's enough room to assemble it without damaging the coils.

Environmental Factors

Is your spring going to brave the elements or chill indoors? Temperature, moisture, and exposure to chemicals can affect the material you should pick. For example, stainless steel is great for outdoor use because it resists rust, while music wire might corrode quickly in the same environment.

If the spring will be exposed to extreme temperatures, you need to select a material that maintains its properties under those conditions. Some materials become brittle in cold temperatures or lose strength when it's hot. Chemical exposure can also degrade certain materials, so if the spring will be near corrosive substances, choose a material that can handle it.

Step-by-Step Guide to Designing a Custom Torsion Spring

Ready to dive into the design process? Let's break it down step by step.

Define What You Need

Start by jotting down all your requirements:

• Required Torque (M): How much rotational force do you need? For example, 9 in-lbs.

• Required Degrees of Travel (θ): How far will the spring need to twist? Maybe 120 degrees.

• Space Limitations: What's the maximum outer diameter (OD) and inner diameter (ID) you can work with? Also, consider how long the spring can be and the length of the legs.

Designing a custom torsion spring might sound complicated, but with the right tools and a clear plan, it's totally doable. Let's walk through the process using Acxess Spring's Instant Spring Quote and Online Spring Force Tester.

Step 1: Input Specifications

First, gather all the specifications for your custom torsion spring:

• Outer Diameter (OD): 0.500 inches

• Wire Diameter (WD): 0.080 inches

• Leg Length: 0.920 inches

• Number of Coils (N): 10 coils

• Required Torque:  8.8 inch-pounds (in·lb)

• Required Degrees of Travel : 120 degrees

• Material: Music Wire

EnEnter these custom parameters into the Instant Spring Quote tool on the Acxess Spring website.

Step 2: Obtain Results

After inputting the specifications, the Instant Spring Quote designs a custom torsion spring with the exact dimensions you need. It automatically generates the part number AT080-500-10000-MW-RH-0920-N-IN, which matches your requirements.

Step 3: Test the Spring

Now, navigate to the Online Spring Force Tester to simulate the torque required for your specific rotation angle.

Formula to Use:

Torque (M)=Spring Rate (k)×Rotation Angle (θ)

According to the blueprint for custom part number AT080-500-10000-MW-RH-0920-N-IN, let's assume the Spring Rate (k) is 0.07409 in·lb/Deg.

Now, calculate the torque:

Torque (M) = 0.07409 in-lb/Deg × 120 degrees ≈ 8.8908 in

Step 4: Analyze Results

The simulation shows that approximately 8.89 inch-pounds of torque are needed for a 120-degree rotation, which matches your required torque.

This means the designed torsion spring meets the specifications needed for your application, whether it's a door hinge, a lever mechanism, or any device requiring controlled rotational force.

Testing Your Torsion Spring Design

So you've got your custom torsion spring all planned out—awesome! But before you jump into production, it's crucial to make sure your design actually works the way you expect. Testing your custom torsion spring design is like taking a car for a test drive before buying it. You want to catch any issues early on to save time, money, and headaches down the road.

Why Testing Matters

Imagine spending time and resources to manufacture your spring, only to find out it doesn't provide enough torque or, worse, it breaks after a few uses. Not cool, right? Testing helps you:

• Validate Performance: Ensure the spring provides the required torque and handles the specified rotation angle.

• Check Material Limits: Confirm that the stress on the spring doesn't exceed what the material can handle.

• Verify Key Parameters: Test for Spring Rate, Maximum Torque, and Maximum Travel to ensure your spring meets all design specifications.

• Identify Design Flaws: Spot any issues with dimensions, coil spacing, or other factors that could affect performance.

• Save Money: Prevent costly mistakes by catching problems before manufacturing.

Adjusting Based on Test Results

• If Spring Rate is Off:

  • Too Low: Increase wire diameter, decrease the outer diameter or reduce the number of coils in your spring.  

  • Too High: Decrease wire diameter, increase outer diameter or increase the number of coils in your spring.

• If Maximum Torque is Too Low:

  • Decrease the number of coils.

  • Increase wire diameter.

  • Reduce the outer diameter.

• If Maximum Travel is Insufficient:

  • Increase the number of coils to allow more rotation without exceeding stress limits.

  • Adjust to a larger outer diameter  if space allows.

  • Increase the wire diameter to gain travel.

Wrapping It Up

Designing the perfect custom torsion spring might have seemed like climbing a mountain at first, but look at you now! You've learned about the key factors that go into a successful design, from load requirements and rotation angles to space constraints and environmental considerations. You've also seen how handy tools like Acxess Spring's Instant Spring Quote and Online Spring Force Tester can make the whole process smoother than a freshly oiled hinge.

Final Tips for Success:

• Don't Rush the Process: Good design takes time. Double-check your calculations and make adjustments as needed.

• Leverage Technology: Tools like the Instant Spring Quote and Online Spring Force Tester are there to help—use them!

• Seek Expert Advice: If you're ever in doubt, don't hesitate to reach out to professionals who can offer guidance.

• Stay Curious: The world of springs is vast and fascinating. Keep learning, and you might discover even more efficient or innovative solutions.

Your Next Steps:

• Start Designing: Head over to Acxess Spring's Instant Spring Quote and start inputting your specs.

• Test and Iterate: Use the Online Spring Force Tester to validate your design.

• Prototype if Possible: Order a small batch. Nothing beats seeing your design in action.

• Finalize and Order: Once you're satisfied, move forward with confidence.

So go ahead, embrace your newfound spring-savvy skills! Whether you're fixing up something at home, designing a new product, or just satisfying your curiosity, you've got the tools and knowledge to make it happen.

Ready to get started? Visit Acxess Spring's Instant Spring Quote to begin designing your custom torsion spring. And don't forget to test your design with the Online Spring Force Tester to ensure everything works just right.