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What is a Helical Spring?

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  • Written By: Paul Scott
  • Edited By: R. Halprin
  • Last Modified Date: 27 September 2016
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A helical spring is a coiled mechanical device which stores and releases energy to absorb impacts or shock and to resist either compression or pulling forces between objects. It is typically cylindrically shaped and features varying numbers of coils according to its intended use. The wires used to manufacture helical springs are generally specially tempered after their construction to give the spring its compression characteristics. The tags or ends of the wire may either be cut flush with the coils or extend beyond the spring axis as attachment points. Helical springs are generally used in several distinct applications.

A helical spring is typically a cylinder shaped spring with any number of progressive coils. Helical springs may also be cone shaped according to their intended use but still follow the same basic progressive coil design. These springs are usually formed around steel jigs while the wire is still annealed or soft, then tempered or hardened to produce the resilient, resistive qualities of the finished spring. With extended use the tempering may be degraded to the point where the helical spring stretches or sags and no longer functions. Depending on the financial implications, a worn spring may either be replaced or re-tempered to restore its original characteristics.

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Helical springs are generally used in two different applications. The first is the role of compression spring which offers resistance to forces moving two components towards each other. Typical applications are car suspension and mattress springs. Compression springs typically have their ends trimmed in such a way that they lie flush with last coils on each end allowing for easy mounting.

The second common use for the helical spring is as a tensioning element. Springs used in this role resists forces moving two objects away from each other. A couple of common tension spring applications include spring scales and automatic door closers. The ends of a tension spring extend beyond the axis of the spring and are typically equipped with a loop to allow for fastening.

The helical spring may also be used in applications where the energy stored in a compressed spring imparts percussive impact. These applications typically see the percussive work piece pulled back against the spring tension then released to strike another object. This cycle may be completed in a single action or the striker may be locked in place with the spring under tension for later use. Common examples of these uses include firearm firing pins, detonators on anti-personal ordinance, and automatic center punches.

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anon327546
Post 6

A chip clip is a torsion spring.

anon263338
Post 5

I would like to know why we use mostly the helical/coil spring in most applications.

One reason I found was it takes in both tensile and compression loads. Please share if there are any more reasons for the wide use of helical springs. --Sud

stl156
Post 4

@Emilski - Interesting question. While a Slinky couldn't really put any outward force on something, you have to consider the tension springs that the article talks about. If you let a Slinky hang down and put a weight on it, the toy would be trying to pull the weight upward. That's the same idea behind a spring scale.

As for plastic springs, they certainly aren't very common. I am almost positive that I have seen them in some type of kid's toy, though. I figure they just aren't used because metal is probably similar in price, and will last much, much longer.

Does anyone know what the name of the springs are that are used in things like chip clips? Instead of the spring pushing or pulling on the ends, it has the two loose wires being pushed, and the force of the spring compressing causes the jaws to close.

Emilski
Post 3

I think my favorite type of spring would probably have to be the Slinky. I can't count how many of those toys I went through when I was a kid. Would it really count as a spring, though?

Whenever there is no force on it, it just coils back together. It could never really put any force on anything, could it?

The Slinky got me to thinking about something else, too. Could you make a spring out of plastic that was actually used in some sort of device? It seems like you would be able to, but I can't think of anything I have ever seen that used a plastic spring. Can anyone else think of anything?

kentuckycat
Post 2

When they are manufacturing springs, how do they get every one of the coils the perfect distance apart? I'm sure that a machine does the work, but it seems like there would have to be some type of guide to make sure that the coils are the same distance apart. If they weren't the same distance apart then you would end up with a spring that was crooked and useless once you took it off of the cylinder.

cardsfan27
Post 1

When I started reading this, I expected the springs to be more in a helix shape like we think of DNA. I guess in principle, the normal springs we use have the same shape, they are just compressed more.

I have always wondered, what exactly makes a spring stop being "springy"? The article says the spring gets degraded, but how? Do the molecules in the metal of the spring slowly get pushed out of place every time the spring is pushed down until the spring is useless? Otherwise, what happens?

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