The Ultimate Buyer's Guide for Purchasing volute spring

Springs are mechanical devices that pull, push, wind, support, lift, or protect. They are used mainly in mechanical assemblies to provide force—compressive, tensile, or torsion—where they can be used to lift engine valves, open die sets, or hold batteries in place, to name just a few examples. Springs are commonly wound from wire but can be machined from solid steel, built as cylinders, formed as bags, stamped from steel, or assembled from other springs. Ordinary wire springs exhibit a force whose magnitude increases linearly as the spring is pushed, pulled, or twisted. This linear behavior with respect to the displacement distance is known as Hooke’s law motion. Springs are often made to order using dedicated wire winding machines that can wind wire through a given number of turns over a specific length to produce the necessary force constant for the particular application.

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For a quick video overview of the types of springs outlined in this article, view this video below:

Different Types of Springs and their Characteristics

A variety of spring types are available, depending on the force or torque needed by the application and the operational conditions. The most common spring types include:

• Compression Springs
• Extension Springs
• Torsion Springs
• Constant Force Springs
• Belleville Springs
• Drawbar Springs
• Volute Springs
• Garter Springs
• Flat Springs
• Gas Springs
• Air Springs

Compression Springs

Compression springs are helically coiled wires designed to provide an opposing force when compressed. Under increasing load, the space between coils closes until the spring’s compressed length is reached when the coils touch. Key specifications include the spring rate, helix type, spring ends type, wire diameter, material, various diameters, and free length. Compression springs are used primarily in manufacturing applications, where a variable and opposing force is required between components. The ends can be open (left as cut) or closed (where the last coil is flattened against the adjacent coil to produce a more square end relative to the axis). Squaring the ends may also be achieved by grinding the surface of the last coil. Compression springs, commonly fashioned from wire, can also be machined for particularly demanding applications. Compression springs are often wound to order but are available in stock sizes and as assortment kits.

Extension Springs

Extension springs are helically coiled wires designed to provide an opposing force when stretched. Key specifications include the spring rate, helix type, spring ends type, wire diameter, material, and free and maximum extended lengths. Extension springs are used primarily in manufacturing applications where a variable, opposing force is required between two components. Many sizes, spring rates, and materials are available depending on the holding forces required. The ends are usually formed in the shape of a hook or loop and can also be custom-made. Different types of spring ends are used with extension springs, and many of these are standardized for specific applications, usually formed in the shape of a hook or loop, and can also be custom-made. You can learn more about these spring end options in our related guide on the extension spring end types.

Extension springs are typically fashioned from wire and are not self-limiting; they can be stretched beyond their limits and are thus limited to applications where failure isn’t a critical issue. Extension springs are often wound to order but are available in stock sizes and as assortment kits.

Torsion Springs

Torsion springs are helical or flat spiral coils or strips that apply or resist torque loads. Key specifications include the spring rate, spring end type, wire diameter, material, and torque rating at a known position. Torsion springs are used primarily in manufacturing applications as components for various motion controls. There are two basic types: helical (coil) torsion springs and spiral torsion springs. Helical torsion springs are available in compression or extension springs and act in a radial direction when applying torque rather than axially to produce tension or compression. Spiral torsion springs are wound as concentric spirals, usually from flat or rectangular stock. Many types of torsion springs are available, and applications range from clocks and watches to motion controls in automatic machinery. Torsion springs are often wound to order but are available in stock sizes and as assortment kits.

Our related guide on torsion spring design recommendations provides additional information concerning best practices to consider when designing torsion springs.

Constant Force Springs

Constant force springs are tightly wound bands of steel that resemble a roll of tape. A load forces the spring to contract, and when it is removed, the spring rebounds with a constant force. Constant force springs are found in clocks, wind-up toys, and similar devices.

Belleville Springs

Belleville springs, or washers, resemble a slightly tapered disc and, for this reason, are also known as disc springs. They are used in conjunction with fasteners like bolts for pre-tensioning purposes. Typically, a bolt is inserted in a Belleville spring and then attached to a substrate. Belleville springs are available in various material options, including 17-7 PH stainless steel, 301 stainless steel, beryllium copper, H13, Inconel®, phosphor bronze, ZC plated, and ZY plated.

Drawbar Springs

Drawbar springs are coil compression springs incorporating U-shaped wire forms that are inserted for use in extension applications. The drawbar spring combines the tension application of the extension spring with the positive stop feature of the compression spring. Key specifications include the free length, maximum spring deflection, and wire diameter. Drawbar springs are used primarily in applications where a tension-producing spring is required and when the self-limiting feature of compression springs is also needed. A typical use for a drawbar spring is supporting porch swings where the spring cannot be loaded past the point of failure due to the self-limiting property of the compression spring.

Volute Springs

Volute springs are flat metal strips wound together to form helical spirals typically used in compression applications. Key specifications include the intended application, diameter, stroke, material, and end attachment style. Volute springs are mainly used in applications where a compression spring requires a long fatigue life or high spring force repeatability. They come in various sizes depending on the application, force required, and materials. Some volute springs are single-ended, while others are double-ended. An easily recognizable use of the volute spring is the compression spring found in high-quality nail clippers or pruning shears.

Garter Springs

Garter springs are spring coils whose ends are joined to form circular springs, which provide a radial force in components that may contain a variable load. A common use of garter springs is in hydraulic, pneumatic, and radial shaft seals, providing a slight inward force on sealing lips.

Flat Springs

Flat springs are strips or bars of metal, or assemblies of such, formed to produce a repeatable counterforce when compressed or displaced and used for positioning or contacting. Key specifications include the intended application, flat spring type, and spring ends type. Flat springs are mainly used in applications where a repeatable counterforce is required to control motion or load by making contact and applying force. They are available in various sizes, material types, and mounting shapes. Some easily recognizable examples of flat springs are flat battery contacts, vehicle leaf springs, and counterbalances in sliding screen windows.

Gas Springs

Gas springs are mechanical devices consisting of a cylinder and a rod that use the pressure from a pre-charge of nitrogen or other inert gases to produce a force bias on a piston or rod. Key specifications include the intended application, stroke, compressed length, extended length, force, and features. Gas Springs are used primarily in the automobile industry for the raising and/or lowering of hoods or hatches. They are available in various sizes and stroke lengths depending on the application and load requirements. Other applications include seat height adjustments for office chairs.

Air Springs

Air springs are air-pressurized bellow or bladder-type devices of various shapes and sizes and are used for providing actuation, shock absorption, and vibration isolation. Key specifications include the intended application, type, style, physical dimensions, mounting type, and features. Air springs are used primarily in machine applications such as vehicle suspensions for shock absorption and machine mounts for vibration isolation. They are available in various types and sizes based on the load requirements and application. Other uses include lifting, compressing, tilting, etc. Air springs used for vibration isolation are also known as air cushions.

Other Springs

Springs that are assembled into components for particular applications are called spring assemblies. Springs used to protect hydraulic lines are called protective coil springs. Hydraulic springs use special hydraulic fluid in very short-stroke applications and are found in die springs. Box springs support the bed mattresses.

Applications and Industries Where Springs are Used

Compression springs are used more than extension springs in critical applications due to their self-limiting properties. A compression spring cannot be pushed past its breaking point, whereas an extension spring can be easily overloaded to the point of failure. But in many situations, extension springs are acceptable because the installation limits their travel range. Consider the many extension springs used in an automotive drum brake, which are critical applications.

Compression springs can be manufactured in various shapes besides the standard straight coil, including conical, barrel, and hourglass forms used in special applications. Compression springs, though usually made from round wire, can also be made from square or rectangular wires. They can also be manufactured in shapes other than round, rectangular coils. Extension springs also can be made in many shapes besides the basic coiled round wire.

An important consideration for both compression springs and extension springs is their ends. Coil springs are often used with seats, and grinding the ends flat allows them to be set fully into a seat. This is especially true of heavy-duty springs like those used in engine valve trains. Compression springs used for lighter-duty applications will often just be made with single extra loops at the ends, which lay flat compared with the spring helixes. Extension springs are available with many varieties of hooks and loops for their ends, which serve as attachments to posts, holes, etc. Often, the spring, if overloaded, will break at the hook, not the coil.

Materials for coil springs range from music wire to spring steel alloys. Some materials offer good corrosion resistance, relaxation resistance, electrical conductivity, etc. Generally, coil springs are stress-relieved after forming to remove any residual stresses imparted during manufacturing. For a more complete discussion on the different materials used in the manufacturing of springs, see our related guide on the types of spring materials.

Torsion springs look similar to compression and extension springs, but instead of applying force through a longitudinal axis, a radial force is applied opposite to the direction of the coil winding. The same material considerations apply to compression and extension springs. Ends are another consideration for torsion springs. The ends usually extend out from the body of the spring where they form lever arms. The orientation of these lever arms with respect to each other is a consideration. Another consideration is the handedness of the spring. Torsion springs wound as concentric spirals from flat stock are sometimes called spring motors because of their use in mechanical watches, windup toys, etc.

Drawbar, volute, and garter springs all rely on the mechanism of the coil spring to function. Flat springs are sometimes called leaf springs and are often custom-formed from flat spring steel for specific purposes. Many trucks and some automobiles use leaf springs for their suspensions.

Gas and air springs differ in their actuating methods from most mechanical springs discussed here. Instead of relying on the twist in a length of straight or coiled metal, gas, and air springs use pressurized gas to produce a spring effect.

Spring manufacturing is a heavily made-to-order business in that most manufacturers can make any spring you want based on a number of specifications, including wire diameter, number of coils, coil diameter, etc. A number of manufacturers publish catalogs of their stock springs, which cover a wide range of choices over a discrete range of dimensions and sizes.

Considerations When Choosing Springs

Spring rate is the fundamental consideration when selecting compression and extension springs. The spring rate (k) is the force per unit length of compression or extension. Some manufacturers group their stock springs in accordance with the spring rate, calling those with low spring rates “light duty” or similar to reflect their application to the low forces required by instruments, etc. Springs intended for high-force applications, e.g., in dies, might be grouped as heavy-duty or die springs.

Compression springs are often installed in holes over shafts or both, and they must be sized to work without binding in these situations. Extension springs are not usually constrained in this way.

A compression spring will also have a free and solid length based on the number of coils, the wire diameter, and the style of the ends.

Extension springs will have a free length measured over the span of the coils and the ends. Generally, they are designed with a maximum load to avoid overstretching and the resulting failure.

Torsion springs are concerned with the orientation of the two legs, and they are generally available in increments of 90 degrees of angular separation. Handedness is a critical factor as a torsion spring is meant to wind up under the application of the load.

Important Attributes

Spring Rate

The spring rate is generally constant for standard coil springs. It represents the force the spring will exert for each incremental length of compression (or extension) and is usually stated as lbs. per inch. Spring rates can be made variable with special designs.

Spring Ends Type

Compression springs can be left open, with the helix of the spring continuing to the end of the coils, but usually, they are finished in some way to provide full coils for seating the springs. For light gauge springs, the ends are typically closed and left unground. Heavier gauge strings will usually be closed and ground.

Extension spring ends are more varied. The most common is the crossover loop, formed by looping the coil ends from one side of the helix across the spring centerline to or near the opposite side. Machine ends are a variant, having more pronounced angles leaving the helix. Side loops are similar to crossover loops but emanate from the side of the coil rather than the middle. Extended round hooks leave the helix with a portion of straight wire before forming their loops. Extended square hooks do the same but end with squared-up hooks rather than loops. Again, these are the major variants, but end designs are myriad. Though not covered in this attribute, spring ends can also be in line, as seen in the top left, or opposite, as seen in the top right. You can learn more about these spring end options in our related guide on the extension spring end types.

Torsion spring ends can be equally varied, with the most popular styles being the short hook, hinge, straight offset, and straight torsion. Names for these ends may vary from manufacturer to manufacturer, but they usually provide illustrations to guide their selection.

Related Product Categories

Spring Washers are parts of fastening or alignment systems that apply premeasured forces and can serve as locking washers or as springs.

Sources

How to Determine Your Ideal Spring Rate When Buying coil springs

How To Calculate Spring Rates – How To Adjust And Tune Suspension Secrets

Coil Springs

Coil springs are the most common application of spring within motorsport. For reason why and some more information on coil springs make sure you check out our article “coil springs”.

There are two main ways to calculate spring rate. One is through calculations based upon looking at and measuring the spring. The other is by practical measurement. The practical measurement is the most accurate form when carried out with the correct equipment. Both ways are shown below.

The Calculation Route

The diagram below shows a coil spring along with the following important parameters that are required to calculate the spring rate.

The important parameters are:

L = Free Length of The Unloaded Spring (m)

G = Shear Modulus of Rigidity of Material

d = Wire Diameter (m)

D = Mean Diameter (m)

N = Number of active coils (an active coil sweeps one full circle)

Where:

Free length is the distance from the top face of the spring to the bottom face of the spring when no load is on it.

Shear modulus of rigidity is based upon the type of material that the spring is made from. The value can be found in the table below. All you need to find out is what material your spring is made from. If you are unsure the most common material is highlighted in bold in the table.

Material Shear Modulus of Rigidity (G) ANSI Spring Steel 79,300,000,000 Pa Cold Rolled Steel 75,000,000,000 Pa Stainless Steel 77,200,000,000 Pa

Wire diameter is the thickness of the coil metal which is most accurately measured with vernier callipers

Mean diameter is shown in the diagram and is the distance between centres of the coil spring. The easiest way to reach this number is with the below equation

Mean Diameter = Total Spring Diameter – Wire Diameter

The number of active coils still has uncertainty in the industry of how to apply an accurate number for a type of spring. The diagram below shows 4 common styles that a coil spring has at its ends.

Closed Ends

Closed and Ground Ends

Plain Ends Ground

Plain Ends

The industry standard to now is that a spring with closed ends or closed and ground ends has one inactive coil at each end meaning that two coils have to be taken off the total amount of coils for the “number of active coils” parameter.

However, springs with plain ends are considered to have no inactive coils so every single coil counts towards the “number of active coils” parameter.

Finally, springs with plain ends ground are considered to have half an inactive coil at each end meaning that a total of 1 coil is removed for the “number of active coils” parameter.

It is very important to understand how your springs are finished as the number of active coils parameter can have a large influence on the calculated spring rate.

The Equation

With your measurements complete it is time to calculate the stiffness of your coil spring with the equation shown below.

Therefore:

So using the example figures of:

G = 79.3GPa

d = 10.3mm

N = 6

D = 68.5mm

The Practical Method

If you have access to some load testing equipment then the practical method is the most accurate option to calculate your spring rate. A machine such as a Tinnius-Olsen shown below is the ideal piece of equipment for this test.  If you have access to one or something similar then insert your spring on the machine and compress it by 10mm. Record the force required to compress it at this point. Then compress the spring in stages of 10mm, recording the force required at each point. If the spring starts to become over-stressed towards the end of the test then do not keep compressing as it could damage the spring.

With all of your results in a similar format to the below example, convert all your millimetre readings to meters. Then divide the force required by the distance moved in each case. If all of the answers to this look similar then you have a constant rate spring. You can now add up all of the answers and divide it by the number of results to get the average reading which is your spring rate.

If the answers get progressively smaller or larger by a noticeable amount then you have a progressive rate spring. If this is the case for you it would be best to plot a graph of your results n excel tracing spring rate against mm of compression. This will be very important information to know when applying pre-load to your spring. Also, if you know how much your car lowers when it is sat on its wheels then you can calculate the static spring rate of your springs at ride height for future reference.

Leaf Springs

Calculating the spring rate for a leaf spring is much more complex than for a coil spring. This is due to the number of variables that can apply to leaf springs such as; leaf thickness, width and taper, end constraint variations or the load being applied off centre etc. Therefore the most accurate way to measure leaf spring stiffness is practically. However, for a close answer you can also use the calculation route where some approximations have to be made.

The Calculation Route

There are two main types of leaf spring within automotive applications. They are “single leaf parabolic” and “laminated leaf spring”. The latter is more common in modern applications. Images below display the different types.

Single Leaf Parabolic

Laminated Leaf Spring

Two equations apply for leaf springs. One is the bending stress formula to ensure that maximum load will not over stress the material. The other is the spring stiffness. This is the figure that is important for further calculations. The equations for a single leaf parabolic spring are:

And:

Where:

L = Half the overall length of the longest leaf spring (m)

F = Force applied at each mounting point to the chassis (usually half the load applied at the axle point) (m)

b = Leaf spring width at the centre point (m)

t = Vertical depth of the leaf spring at the centre point where it mounts to the axle (m)

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E = Youngs modulus for the material (Pa) (see table below)

X = Spring displacement vertically (m)

The equations for a laminated leaf spring vary slightly and are:

And:

Where:

L = Half the overall length of the longest leaf spring (m)

F = Force applied at each mounting point to the chassis (usually half the load applied at the axle point) (m)

b = Leaf spring width at the centre point (m)

n = number of leaves stacked

n’ = number of leaves directly at the spring ends

t = Vertical depth of the leaf spring at the centre point where it mounts to the axle (m)

E = Youngs modulus for the material (Pa) (see table below)

X = Spring displacement vertically (m)

Youngs Modulus Table for Common Materials

Material Youngs Modulus (E) ANSI Spring Steel 207,000,000,000 Pa Cold Rolled Steel 186,000,000,000 Pa Mild Steel 210,000,000,000 Pa

The Practical Route

The more accurate route to measure the stiffness of your leaf springs is to test them practically if you have the correct load application equipment. To test the load you need to disconnect the axle form the spring and move it away from directly below the spring. Next, a load needs applying using a device that will measure the amount of load being applied in Newtons of force. The leaf spring needs to be deflected in steps of 10mm increments with the force required to move the spring being recorded. For each step the force can be divided by the displacement to give the spring rate using the below equation. If the numbers have a large variation and increase each time after the below equation has been used then the spring has a progressive rate and a graph should be plotted in excel to show what rate is present at each point of displacement as this will be more accurate than using an equation.

Where:

F = Force applied (N)

x = Amount of displacement (m)

How to Convert Metric to Imperial

If you would rather have your spring rates in terms of pounds and inches then you can use the below conversion equation to change the result form newtons per meter into pounds per inch.

Likewise if you wish to convert pounds per inch into newtons per meter then input the pounds per inch value where it says example below and I will produce the newtons per meter answer.

How to Add Spring Rates for Multiple Springs

There are two configurations that multiple springs come in. One is springs in series and one is springs in parallel. A car can be considered to have springs in parallel because if you look at the front axis of a car each wheel as its own spring acting on the front of the vehicle making a total of two springs working side by side. This makes them parallel.

Springs in Series

A few examples are shown below of when a spring can be considered in series.

When two springs or more are put on top of each other, the combined spring rate always becomes less than that of the softest spring. This is because you have effectively added even more coils to the softer spring (N) which reduces overall spring rate. The spring rate for each individual spring must first be known before the below equation can be used to calculate the total spring rate of the springs in series. If two springs are being used in series then the below equation can be used:

Where:

K total = Combined spring rate

K1 = bottom spring rate

K2 = Top spring rate

If more than two springs are in series then the next spring up can keep being added to the equation for all the springs; for example in the case of 4 springs stacked on top of each other the equation would be like the below:

Springs in Parallel

Springs in parallel can be achieved in a few ways as well. The images below show a few examples of when springs can be considered in parallel.

Springs are said to be in parallel when they always share a load. The composite rate of parallel springs is much easier to calculate than springs in series as the spring rates are simply added together. The equation below can be used to calculate the overall effective spring rate of the parallel springs:

And so on.

Before the release of part 2 next week please also read “How to Adjust and Tune Anti-Roll Bars” for information on how to calculate anti-roll bar spring rates.

Spring Rate: What Is It and How Is It Calculated?

What is spring rate and why is it beneficial to fully understand how it’s calculated? Here is a helpful guide on everything you need to know in order to produce quality products.

A spring is an elastic object that possesses mechanical energy. Springs are made majorly from steel, and are used in our everyday activities. Springs can be found in watches, vehicles pens, toys, CD players, and so on.

Basically, spring rate, also referred to as spring constant is the amount of weight needed to compress a spring by one inch. Spring rate can also be defined as the estimation of the amount of force needed to compress a spring to a specific distance. The unit of measurements of spring rate is N/m or Ibf/in i.e. force divided by distance.

The spring rate of a spring is the change in the force applied divided by the change in diversion of the spring.

There are various types of springs, let’s see some types of spring since we know what a spring and spring rate are.

Types of Spring

Classification based on the load force applied, we have the:

Tension or extension spring

Compression spring

Torsion spring

Constant spring

Variable spring and,

Variable stiffness spring

Classification based on their shapes:

Flat spring

Machined spring

Serpentine spring and,

Garter spring

Classification based on how common they are:

Cantilever spring

Coil or helical spring

Volute spring

Hairspring or balance spring

Leaf spring and,

V-spring

Other classifications include:

Belleville spring

Constant-force spring

Gas spring

Ideal spring

Mainspring

Wave spring and so on.

Most springs obey Hooke’s law, as long as they are not compressed or stretched beyond their elastic limit. Hooke’s law states that the force with which the spring pushes back is linearly proportional to the distance from its equilibrium length.

F= -kx

Where x is the displacement factor, k is the spring constant or rate; the higher the spring constant, the stiffer the springs.

F is the resulting force vector.

How to Calculate Spring Constant

To calculate the spring rate you start by compressing the spring about 20% of the available distance of the spring and measure the height and the load, this can be named (for better understanding) height 1 and initial load in (lbs/inch) or (N/mm). At that point, compress the spring about 80% and measure the height, which can be named height 2 and the final load.

Spring rate = final load – initial load/height 1 – height 2

Most springs are moderately linear, which implies you would get a similar spring rate from the condition regardless the distance.

A few springs are non-linear, which normally implies the spring gets stiffer as you compress it. A way this could be possible is by changing the coil space, with the goal that the coils begin to contact each other as you compress. Another route is for the spring to compress and afterward experience an extra spring. This expands the spring rate since the spring is now doubled acting to the force.

Factors That Affects Spring Rate

There are three major factors that affects spring rate:

Wire diameter: when the wire diameter increases, the spring constant increases too. A thicker wire will make the spring constant become stronger and even difficult to deflect.

Spring diameter: increase in the spring diameter will lead to decrease in the spring rate.

Number of coils in the spring: the higher the number of coils, the lower the spring constant.

Theory of Springs

In classical physics, a spring can be viewed as a gadget that stores expected vitality, explicitly flexible possible vitality, by stressing the bonds between the molecules of a versatile material.

Hooke’s law of flexibility expresses that the expansion of a versatile bar (its enlarged length less its casual length) is directly corresponding to its strain, the power used to extend it. So also, the withdrawal (negative augmentation) is relative to the pressure (negative strain).

This law really holds just around, and just when the deformation (expansion or withdrawal) is little contrasted with the bar’s general length. For disfigurements past as far as possible, nuclear bonds get broken or reworked, and a spring may snap, clasp, or for all time distort. Numerous materials have no plainly characterized versatile breaking point, and Hooke’s law cannot be seriously applied to these materials. Besides, for the super-elastic materials, the direct connection among power and relocation is suitable just in the low-strain locale.

Hooke’s law is a numerical outcome of the way that the expected vitality of the pole is a base when it has its casual length.

Conclusively, spring is an aspect of physics which is a basic part of the human life. So when deciding to buy that car, consider the spring rate as you would consider other factors. Springs should be compressed around 25-30% when supporting the vehicle’s weight. The softer the spring rate, the easier the ride while the stiffer the spring rate, the firmer the ride. Spring rate is majorly based on the Hooke’s law as long as the elasticity level is not exceeded.

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