A Coil spring, also known as a helical spring, is a mechanical device, which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces. They are made of an elastic

Elasticity (physics)

In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform or distort is removed. The relative amount of deformation is called the strain....

 material formed into the shape of a helix

Helix

A helix is a type of smooth space curve, i.e. a curve in three-dimensional space. It has the property that the tangent line at any point makes a constant angle with a fixed line called the axis. Examples of helixes are coil springs and the handrails of spiral staircases. A "filled-in" helix – for...

 which returns to its natural length when unloaded.

Coil springs are a special type of torsion spring

Torsion spring

A torsion spring is a spring that works by torsion or twisting; that is, a flexible elastic object that stores mechanical energy when it is twisted. The amount of force it exerts is proportional to the amount it is twisted. There are two types...

: the material of the spring

Spring (device)

A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...

 acts in torsion when the spring is compressed or extended.

Metal coil springs are made by winding a wire around a shaped former - a cylinder is used to form cylindrical coil springs.

Variants

The two usual types of coil spring are:

• Tension coil springs, designed to resist stretching. They usually have a hook or eye form at each end for attachment.
• Compression coil springs, designed to resist being compressed. A typical use for compression coil springs is in car
  Čar
  Čar is a village in the municipality of Bujanovac, Serbia. According to the 2002 census, the town has a population of 296 people.-References:...
  
   suspension systems
  Suspension (vehicle)
  Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose — contributing to the car's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants...
  
  .

Degradation

Many types of coil spring are wound in an annealed

Annealing (metallurgy)

Annealing, in metallurgy and materials science, is a heat treatment wherein a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces conditions by heating to above the recrystallization temperature, maintaining a suitable temperature, and...

 (soft) condition and then tempered

Tempering

Tempering is a heat treatment technique for metals, alloys and glass. In steels, tempering is done to "toughen" the metal by transforming brittle martensite or bainite into a combination of ferrite and cementite or sometimes Tempered martensite...

 to achieve their strength as a spring. Over time, this tempering can be lost and the spring will sag because it can no longer withstand the loads applied. Such springs can be re-set by annealing, returning to their original length (or deliberately setting them to a different length) and then re-tempering. Damage to springs, such as using oxy-acetylene

Oxy-fuel welding and cutting

Oxy-fuel welding and oxy-fuel cutting are processes that use fuel gases and oxygen to weld and cut metals, respectively. French engineers Edmond Fouché and Charles Picard became the first to develop oxygen-acetylene welding in 1903...

 to cut the end off a car suspension spring to lower a vehicle's ride height

Ride height

Ride height is the amount of space between the base of an automobile tire and the underside of the chassis; or, more properly, to the shortest distance between a flat, level surface, and any part of a vehicle other than those parts designed to contact the ground...

, can destroy the tempering in localised areas of the spring.

External links

• Helical Spring by Sándor Kabai, The Wolfram Demonstrations Project.
• glossary by McAllister Industries, a manufacturer
• Institute of Spring Technology
• Spring Manufacturers Institute
• How to make springs (tutorial by Dave Silberstein)
• "You Spring From Morning To Night" , April 1949, Popular Science article on the basics of steel coil springs manufacturing