Drawbar Springs
Drawbar springs derive their namesake from a clever built-in feature called the drawbar that gives the helical coil spring a unique geometry while adding valuable functionality. The drawbars are two formed-loop wire pieces that fit through the helical coils' center. Each end protrudes at the opposite end of the helical coils and is looped around the outside of the coils, and the protruding wire ends are bent upwards to capture the component within the spring. In this way, the drawbars form a hard stop on both ends of the coil to prevent separation of the helical coils beyond the spring’s free length.
The working drawbar spring load is applied loop at the protruding ends of the drawbars. In this way, a drawbar spring is designed to absorb tension loads, as the loop configuration converts tension loads at the ends of the drawbar spring into a load that compresses the helical coils of the spring together. Minus the drawbar component, drawbar springs are very similar to traditional helical coil compression springs, but the drawbar changes their functionality entirely. They function like extension springs and can handle much higher loads without failure.
In this way, drawbar springs prevent the separation and catastrophic failure of the spring during an overload situation. They are designed to maintain load and structural cohesion, even when the spring has fractured.
The World's Largest Selection of Stock Springs, Plus Custom Build-to-Spec
Century Spring is proud to offer thousands of drawbar springs in a wide selection of materials and sizes available to ship today. We provide all the CAD files you need for stock drawbar springs, which are available for immediate download so you can determine how your spring will fit your application before purchasing!
We have also designed and manufactured numerous custom drawbar springs for applications across numerous industries.
Custom Drawbar Spring Manufacturing Capabilities
We proudly offer state-of-the-art manufacturing equipment to deliver high volumes of custom drawbar springs. We have cutting-edge CNC compression self-monitoring and coiling machinery to manufacture custom sizes and styles to fit any design envelope. We also provide complete prototyping and tooling assistance services.
We are ready to partner with you in all stages of development, from initial concept to procurement, to help you develop drawbar springs engineered to withstand the most demanding environments.
Don’t waste another minute; reach out to our experts today!
Quality Materials
Drawbar springs are generally composed of High Carbon or Stainless Steel; however, we stock many quality specialty materials for your custom component needs.
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Drawbar Spring Information & Resources
Drawbar Springs Characteristics
Drawbar springs have many of the same characteristics as helical coil compression springs.
The Drawbar Wire Size is the thickness of the metal used to form the helical coils.
Finally, you should know the Maximum Load rating on the drawbar springs. Drawbar springs offer inherent protection against an overload situation. However, knowing when your drawbar spring may become overloaded is critical to verify that this won’t be a frequent operating condition in your mechanism.
How to Select a Drawbar Spring
We offer a range of in-stock drawbar springs for many applications. When shopping for drawbar springs, it’s important to consider the general geometric properties identified above in conjunction with the Spring Rate.
The drawbar spring’s spring rate measures the resistance of the drawbar spring to compression forces. It is formally defined as the load (measured in lb.) required to compress the spring 1” inch. The spring rate is a function of the wire diameter, the number of coils, and the outer diameter of the coils.
In short, the larger the force required to compress the spring a given distance, the larger the spring rate. To illustrate the principle of spring rate further, engineers design with a known load that the spring must be able to absorb. You can use spring rate and spring size to calculate the deflection under design loading conditions. This information lets you easily determine whether such a spring will meet your space envelope design requirements and allowable deflection envelope.
Material Types and Benefits
Drawbar springs are commonly fabricated from high-carbon steel such as music wire or stainless steel, which are specified when additional corrosion resistance is required for an application. At the same time, a material such as spring steel is ideal for high-loading applications.
You can browse our interactive drawbar spring catalog by material to purchase a stock drawbar spring today!
If you can’t find the exact material you’re looking for, we have a stock supply of specialty alloys, including chrome silicon steel, nickel, and copper-based alloys, available to support you if you need a rapid turnaround on a custom spring design project.
Dimensions Measurement Guide
You can obtain all of the relevant dimensional properties of your drawbar spring by using calipers to measure at the following locations:
- Place the large outside jaws of the calipers on the outer surface of the helical coils of the drawbar spring to measure the Outer Diameter (OD). Record this measurement from the wire loop folded over the outside of the coils.
- Place helical coils between the caliper’s large outside jaws to read the Free Length dimension. Take care to read the measurement of this dimension without compressing the spring. Record this measurement inside the drawbar spring's wire loops to measure only the spring's helical coils.
Hold the spring vertically and place the large outside jaws on a drawbar that protrudes from the ends of the spring to measure the Drawbar Wire Size dimension. Record measurements at a few locations and both ends of the spring.
Try our Spring Calculator to automatically get key design data based on your spring’s measurements.
Applications and Industries
Where Drawbar Springs Are Used
Drawbar springs are excellent choices for applications that require a mechanism to stay in place for safety reasons, even under overload conditions. Additionally, because of the loop configuration, they are used in tension applications because their design serves to apply a tension load at the loop ends into a compression load at the helical coils. The drawbar configuration makes them ideal for use in high-load tension applications because the drawbar is stronger than the hook ends of a traditional extension spring. This also makes drawbar springs well-suited to absorb high shock and dynamic load profiles.
For example, a great drawbar spring application would be a trunk or door latch in automotive equipment. Drawbar springs are great for personnel and cargo bay doors within aerospace assemblies. Additionally, drawbar springs can be used in safety-critical medical devices that directly support a patient's full weight, such as wheelchairs or hospital bedding.
Case Studies: Industry-Specific Applications
Common applications of drawbar springs are consumer products that require additional operational safety. For example, drawbar springs are commonly used in front porch swings to support the weight of the occupants on the swing because even if the spring is damaged and breaks, the drawbar springs prevent the swing from collapsing, preventing injury.
FAQs About Drawbar Springs
Do I need a custom drawbar spring?
Standard springs are readily available in various sizes and specifications. However, if you determine that you need a custom-designed spring that we do not carry in stock, call us today at 800-237-5225 or fill out our Custom Quotation Form today!
What material should I choose?
In short, consider your application's mechanical loads, corrosion resistance, and temperature requirements. For example, consider a high-strength alloy if your application sees high loads or deformations. At the same time, you may want a stainless steel spring if corrosion resistance is paramount. Additionally, advanced Nickel-based alloys may be appropriate for use in applications that experience very high temperatures.
What typical tolerances can I expect on my drawbar springs?
Spring tolerances depend heavily on the exact spring type and geometry. As such, we have performed extensive empirical studies, which we have used to develop tolerance equations for different manufacturing techniques. We have combined these with the best industry standards to create general tolerance ranges for springs commonly employed in the Aerospace and Defense industries. However, these calculations can be very involved, so we have integrated them into our design and manufacturing automation software.
However, if you contact our design team today, we will gladly walk you through these calculations to provide general tolerance values for your spring type and geometry!
Why Choose Century Spring
Our Commitment to Quality and Service
Century Spring is a quality-first, ISO 9001 and AS9100D certified, industry-leading spring supplier specializing in stock and custom springs. We are the most trusted name in spring manufacturing and offer products and expertise to serve every corner of the drawbar spring market.
Our dedicated custom spring development and customer support teams help you navigate critical design criteria such as size, material, surface finish, and end type to find your application's optimal spring solution.
Our experienced product engineers, knowledgeable product quality team, and skilled manufacturing personnel always deliver the highest quality products to you faster than our domestic and international competitors. Our springs are always made in the USA.
We offer rapid delivery on over 40,000+ in-stock designs available to ship today. We are committed to getting products to you as quickly as possible because we understand your design scheduling constraints.
Visit us today to discover how our commitment to quality and customer satisfaction vastly improves your product design process!
Innovation and Customization in Spring Manufacturing
We bring extensive design for manufacturability (DFM) expertise to your project. We also have dedicated, high-speed machines that can quickly scale high-quality spring production processes to large part volumes.
We also have cutting-edge computational equipment simulation and testing techniques, such as CNC compression self-monitoring and coiling machinery. These capabilities enable us to deliver durable, reliable products across many custom sizes and styles. Our manufacturing services also include complete prototyping and tooling assistance.
Our team will work directly with you to create, refine, and optimize spring designs to fit specific tolerance, performance, and use case conditions. We are ready to partner with you to solve your most pressing design challenges.
Get In Touch
Contact Information
Contact us directly today, and allow our experts to resolve all your questions and guide you to one of our in-stock spring anchors that will fit your application. We can also guide you to one of our in-stock drawbar springs that will fit your application.
If you need immediate assistance, you can always reach us at our dedicated phone line to speak directly with our team: 800-237-5225.
Request a Quote and Consultation
We can also help you evaluate custom drawbar spring options and determine whether a custom design suits your application better.
Simply Request a Custom Quotation so we can partner with you to customize a spring design for your unique application.
Once we hear from you, our design team will follow up with a quote for a custom solution and be happy to answer any follow-up questions you may have.