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Shock Absorber

 
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Shock absorber
 
 
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] A shock absorber in common parlance (or damper in technical use) is a mechanical device designed to smooth out or damp
Damping

Damping is any effect, either deliberately engendered or inherent to a system, that tends to reduce the amplitude of oscillations of an oscillatory system....
 shock
Shock (mechanics)

A mechanical or physical shock is a sudden acceleration or deceleration caused, for example, by impact, drop, kick, earthquake, or explosion. Shock is a transient physical excitation....
 impulse, and dissipate kinetic energy
Kinetic energy

The kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the mechanical work needed to accelerate a body of a given mass from rest to its current velocity....
.

Explanation
Shock absorbers must absorb or dissipate energy. One design consideration, when designing or choosing a shock absorber is where that energy will go. In most dashpot
Dashpot

A dashpot is a mechanical device, a damper which resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy....
s, energy is converted to heat inside the viscous fluid.






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Encyclopedia


] A shock absorber in common parlance (or damper in technical use) is a mechanical device designed to smooth out or damp
Damping

Damping is any effect, either deliberately engendered or inherent to a system, that tends to reduce the amplitude of oscillations of an oscillatory system....
 shock
Shock (mechanics)

A mechanical or physical shock is a sudden acceleration or deceleration caused, for example, by impact, drop, kick, earthquake, or explosion. Shock is a transient physical excitation....
 impulse, and dissipate kinetic energy
Kinetic energy

The kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the mechanical work needed to accelerate a body of a given mass from rest to its current velocity....
.

Explanation


Shock absorbers must absorb or dissipate energy. One design consideration, when designing or choosing a shock absorber is where that energy will go. In most dashpot
Dashpot

A dashpot is a mechanical device, a damper which resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy....
s, energy is converted to heat inside the viscous fluid. In hydraulic cylinder
Hydraulic cylinder

A Hydraulic cylinder is a mechanical actuator that is used to give a linear force through a linear stroke. It has many applications, notably in engineering vehicles....
s, the hydraulic fluid
Fluid

A fluid is defined as a substance that continually deforms under an applied shear stress. All liquids and all gases are fluids. Fluids are a subset of the Phase and include liquids, gas, Plasma physics and, to some extent, plasticity ....
 will heat up, while in air cylinders, the hot air is usually exhausted to the atmosphere. In other types of dashpots, such as electromagnetic
Electromagnetism

Electromagnetism is the physics of the electromagnetic field, a field which exerts a force on Elementary particles with the property of electric charge and which is reciprocally affected by the presence and motion of such particles....
 ones, the dissipated energy can be stored and used later.In smaller terms shock absorbers help cushion cars on uneven roads

Description


Pneumatic and hydraulic shock absorbers commonly take the form of a cylinder with a sliding piston
Piston

A piston is a component of reciprocating engines, pumps and gas compressors. It is located in a Cylinder and is made gas-tight by piston rings....
 inside. The cylinder is filled with a fluid (such as hydraulic fluid) or air. This fluid filled piston/cylinder combination is a dashpot
Dashpot

A dashpot is a mechanical device, a damper which resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy....
.

Applications


Shock absorbers are an important part of automobile
Automobile

An automobile or motor car is a wheeled motor vehicle for transportation passengers, which also carries its own car engine or motor. Most definitions of the term specify that automobiles are designed to run primarily on roads, to have seating for one to eight people, to typically have four wheels, and to be constructed principally f...
 and motorcycle
Motorcycle

A motorcycle is a Single track, two-wheeled motor vehicle powered by an Motorcycle engine. Motorcycles vary considerably depending on the task for which they are designed, such as Touring motorcycle travel, navigating Naked bike, Cruiser , Motorcycle sport and Motorbike racing, or off-road conditions....
 suspension
Suspension (vehicle)

Suspension is the term given to the system of spring , shock absorbers and Linkage that connects a vehicle to its wheels. Suspension systems serve a dual purpose ? contributing to the car's car handling and brake for good active safety and driving pleasure, and keeping vehicle occupants comfortable and reasonably well isolated from road no...
s, aircraft
Aircraft

An aircraft is a vehicle which is able to flight by being supported by the air, or in general, the atmosphere, of a planet. Examples include balloons, airplanes and helicopters....
 landing gear
Landing Gear

Landing Gear is Devin the Dude's fifth studio album. It was released on October 7 2008. It will be his first studio album since signing with the music label Razor & Tie....
, and the supports for many industrial machine
Machine

A machine is any device that uses energy to perform some activity. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work....
s. Large shock absorbers have also been used in structural engineering
Structural engineering

Structural engineering is a field of engineering dealing with the analysis and design of structures that support or resist structural loads. Structural engineering is usually considered a specialty within civil engineering, but it can also be studied in its own right....
 to reduce the susceptibility of structures to earthquake
Earthquake

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph....
 damage and resonance
Resonance

In physics, resonance is the tendency of a system to oscillate at maximum amplitude at certain Frequency, known as the system's resonance frequencies ....
.

Vehicle suspension


In a vehicle, it reduces the effect of traveling over rough ground, leading to improved ride quality
Ride quality

Ride quality refers to the degree of protection offered vehicle occupants from uneven elements in the road surface, or the terrain if driving off-road....
. Without shock absorbers, the vehicle would have a bouncing ride, as energy is stored in the spring and then released to the vehicle, possibly exceeding the allowed range of suspension
Suspension (vehicle)

Suspension is the term given to the system of spring , shock absorbers and Linkage that connects a vehicle to its wheels. Suspension systems serve a dual purpose ? contributing to the car's car handling and brake for good active safety and driving pleasure, and keeping vehicle occupants comfortable and reasonably well isolated from road no...
 movement. Control of excessive suspension movement without shock absorption requires stiffer (higher rate) springs, which would in turn give a harsh ride. Shock absorbers allow the use of soft (lower rate) springs while controlling the rate of suspension movement in response to bumps. They also, along with hysteresis
Hysteresis

A system with hysteresis can be summarized as a system that may be in any number of states, independent of the inputs to the system. To be exact, a system with hysteresis exhibits path-dependence, or "rate-independent memory"....
 in the tire itself, damp the motion of the unsprung weight
Unsprung weight

In a ground vehicle with a suspension , the unsprung weight is the mass of the suspension, wheels or Caterpillar tracks , and other components directly connected to them, rather than supported by the suspension....
 up and down on the springiness of the tire. Since the tire is not as soft as the springs, effective wheel bounce damping may require stiffer shocks than would be ideal for the vehicle motion alone.

Spring
Spring (device)

A spring is an Elasticity object used to store mechanical energy. Springs are usually made out of hardened steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealing steel and hardened after fabrication....
-based shock absorbers commonly use coil spring
Coil spring

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....
s or leaf spring
Leaf spring

Originally called laminated or carriage spring, a leaf spring is a simple form of spring , commonly used for the suspension in wheeled vehicles....
s, though torsion bars can be used in torsional
Torsion (mechanics)

In solid mechanics, torsion is the twisting of an object due to an applied torque. In circular sections, the resultant shear stress is perpendicular to the radius....
 shocks as well. Ideal springs alone, however, are not shock absorbers as springs only store and do not dissipate or absorb energy. Vehicles typically employ both springs or torsion bars as well as hydraulic shock absorbers. In this combination, "shock absorber" is reserved specifically for the hydraulic piston that absorbs and dissipates vibration.

Structures


Applied to a structure such as a building
Building

In architecture, construction, engineering and Real estate developer the word building may refer to one of the following:# Any man-made structure used or intended for supporting or sheltering any use or continuous occupancy, or...
 or bridge
Bridge

A bridge is a structure built to span a gorge, valley, road, Rail tracks, river, body of water, or any other physical obstacle, for the purpose of providing passage over the obstacle....
 it may be part of a seismic retrofit
Seismic retrofit

Seismic retrofitting is the modification of existing built environment to make them more resistant to seismology, ground motion, or soil failure due to earthquakes....
 or as part of new, earthquake resistant construction
Earthquake engineering

Earthquake engineering is the study of the behavior of buildings and structures subject to seismic loading. It is a subset of both structural engineering and civil engineering....
. In this application it allows yet restrains motion and absorbs resonant energy
Resonance

In physics, resonance is the tendency of a system to oscillate at maximum amplitude at certain Frequency, known as the system's resonance frequencies ....
, which can cause excessive motion and eventual structural failure
Structural failure

Structural failure refers to loss of the Structural load-carrying capacity of a component or member within a Architectural structure or of the structure itself....
.

Types of shock absorbers

There are several commonly-used approaches to shock absorption:
  • Hysteresis
    Hysteresis

    A system with hysteresis can be summarized as a system that may be in any number of states, independent of the inputs to the system. To be exact, a system with hysteresis exhibits path-dependence, or "rate-independent memory"....
     of structural material, for example the compression
    Physical compression

    Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. The opposite of compression is tension ....
     of rubber
    Rubber

    Natural rubber is an elastomer?an Elasticity_ hydrocarbon polymer?that was originally derived from a milky colloidal suspension, or latex , found in the sap of some plants....
     disks, stretching
    Stretching

    Stretching is a form of physical exercise in which a specific skeletal muscle is deliberately elongated to its fullest length in order to improve the muscle's felt elasticity and reaffirm comfortable muscle tone....
     of rubber bands and cords, bending
    Bending

    In engineering mechanics, bending characterizes the behavior of a structural element subjected to an external Structural load applied perpendicular to the axis of the element....
     of steel
    Steel

    Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.14% by weight , depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese, chromium, vanadium, and tungsten....
     spring
    Spring (device)

    A spring is an Elasticity object used to store mechanical energy. Springs are usually made out of hardened steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealing steel and hardened after fabrication....
    s, or twisting of torsion bar
    Torsion spring

    A torsion spring is a spring that works by Torsion or twisting; that is, a flexible Elasticity object that stores mechanical energy when it is twisted....
    s. Hysteresis is the tendency for otherwise elastic
    Elasticity (physics)

    In physics, elasticity is the physical property of a material when it deforms under stress , but returns to its original shape when the stress is removed....
     materials to rebound with less force than was required to deform them. Simple vehicles with no separate shock absorbers are damped, to some extent, by the hysteresis of their springs and frames.


  • Dry friction
    Friction

    File:Friction alt.svgFriction is the force resisting the relative lateral motion of solid surfaces, fluid layers, or material elements in contact....
     as used in wheel brake
    Brake

    A brake is a device for applying a force against the friction of the road, slowing or stopping the motion of a machine or vehicle, or alternatively a device to restrain it from starting to move again....
    s, by using disks (classically made of leather
    Leather

    Leather is a material created through the tanning of rawhides and skins of animals, primarily cattlehide. The tanning process converts the putrescible skin into a durable, long-lasting and versatile natural material for various uses....
    ) at the pivot of a lever, with friction forced by springs. Used in early automobiles such as the Ford Model T
    Ford Model T

    The Ford Model T was an automobile produced by Henry Ford's Ford Motor Company from 1908 through 1927. The Model T set 1908 as the historic year that the automobile came into popular usage....
    , up through some British cars of the 1940s. Although now considered obsolete, an advantage of this system is its mechanical simplicity; the degree of damping can be easily adjusted by tightening or loosening the screw clamping the disks, and it can be easily rebuilt with simple hand tools. A disadvantage is that the damping force tends not to increase with the speed of the vertical motion.


  • Solid state, tapered chain shock absorbers, using one or more tapered, axial alignment(s) of granular spheres, typically made of metals such as nitinol, in a casing. ,


  • Fluid
    Fluid

    A fluid is defined as a substance that continually deforms under an applied shear stress. All liquids and all gases are fluids. Fluids are a subset of the Phase and include liquids, gas, Plasma physics and, to some extent, plasticity ....
     friction, for example the flow of fluid through a narrow orifice (hydraulics), constitute the vast majority of automotive shock absorbers. An advantage of this type is that using special internal valving the absorber may be made relatively soft to compression (allowing a soft response to a bump) and relatively stiff to extension, controlling "jounce", which is the vehicle response to energy stored in the springs; similarly, a series of valves controlled by springs can change the degree of stiffness according to the velocity of the impact or rebound. Specialized shock absorbers for racing purposes may allow the front end of a dragster to rise with minimal resistance under acceleration, then strongly resist letting it settle, thereby maintaining a desirable rearward weight distribution for enhanced traction. Some shock absorbers allow tuning of the ride via control of the valve by a manual adjustment provided at the shock absorber. In more expensive vehicles the valves may be remotely adjustable, offering the driver control of the ride at will while the vehicle is operated. The ultimate control is provided by dynamic valve control via computer in response to sensors, giving both a smooth ride and a firm suspension when needed. Many shock absorbers contain compressed nitrogen
    Nitrogen

    Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
    , to reduce the tendency for the oil to foam
    Foam

    The most general definition of foam is a substance that is formed by trapping many gas bubbles in a liquid or solid. It can also refer to anything that is analogous to such a phenomenon, such as quantum foam....
     under heavy use. Foaming temporarily reduces the damping ability of the unit. In very heavy duty units used for racing and/or off-road use, there may even be a secondary cylinder connected to the shock absorber to act as a reservoir for the oil and pressurized gas. Another variation is the Magneto rheological damper
    Magneto rheological damper

    A magnetorheological damper or magnetorheological shock absorber is a shock absorber filled with magnetorheological fluid, which is controlled by a magnetic field, usually using an electromagnet....
     which changes its fluid characteristics through an electromagnet
    Electromagnet

    An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric Current . The magnetic field disappears when the current ceases....
    .


  • Compression of a gas, for example pneumatic shock absorbers, which can act like springs as the air pressure is building to resist the force on it. Once the air pressure reaches the necessary maximum, air dashpots will act like hydraulic dashpots. In aircraft
    Aircraft

    An aircraft is a vehicle which is able to flight by being supported by the air, or in general, the atmosphere, of a planet. Examples include balloons, airplanes and helicopters....
     landing gear air dashpots may be combined with hydraulic damping to reduce bounce. Such struts are called oleo struts (combining oil and air) .


  • Magnet
    Magnet

    A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials and attracts or repels other magnets....
    ic effects. Eddy current
    Eddy current

    An eddy current is an Electricity phenomenon discovered by France physics L?on Foucault in 1851. It is caused when a conductor is exposed to a changing magnetic field due to relative motion of the field source and conductor; or due to variations of the field with time....
     dampers are dashpots that are constructed out of a large magnet inside of a non-magnetic, electrically conductive tube.


  • Inertia
    Inertia

    File:192447main 017 law of inertia.oggInertia is the resistance of an object to a change in its state of motion. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the Motion of matter and how it is affected by applied forces....
    l resistance to acceleration, for example prior to 1966 the Citroën 2CV
    Citroën 2CV

    The Citro?n 2CV is an economy car produced by the France automaker Citro?n from 1949 to 1990. It is considered one of their most cultural icon cars....
     had shock absorbers that damp wheel bounce with no external moving parts. These consisted of a spring-mounted 3.5 kg (7.75 lb) iron weight inside a vertical cylinder and are similar to, yet much smaller than versions of the tuned mass damper
    Tuned mass damper

    A tuned mass damper, also known as an active mass damper or harmonic absorber, is a device mounted in structures to prevent discomfort, damage, or outright structural failure caused by vibration....
    s used on tall buildings


  • Composite hydropneumatic devices which combine in a single device spring action, shock absorption, and often also ride-height control, as in some models of the Citroën
    Citroën

    Citro?n is a France automobile manufacturer, founded in 1919 by Andr? Citro?n, it was the world's first mass-production car company outside of the USA....
     automobile.


  • Conventional shock absorbers combined with composite pneumatic springs with which allow ride height adjustment or even ride height control, seen in some large trucks and luxury sedans such as certain Lincoln
    Lincoln (automobile)

    Lincoln is a brand of Ford Motor Company. Founded in 1917 by Henry M. Leland and acquired by Ford in 1922, Lincoln has manufactured vehicles since the 1920s....
     and most Land Rover automobiles. Ride height control is especially desirable in highway vehicles intended for occasional rough road use, as a means of improving handling
    Car handling

    Car handling and vehicle handling is a description of the way wheeled vehicles perform transverse to their direction of motion, particularly during cornering and swerving....
     and reducing aerodynamic drag by lowering the vehicle when operating on improved high speed roads.


  • The effect of a shock absorber at high (sound) frequencies is usually limited by using a compressible gas as the working fluid and/or mounting it with rubber bushings.


See also

  • Strut
    Strut

    A strut is a structural component designed to resist longitudinal Physical compression. Struts provide outwards-facing support in their lengthwise direction, which can be used to keep two other components separate, performing the opposite function of a tie ....
  • Strut Bar
    Strut bar

    A strut bar, strut brace, or strut tower brace is a mostly aftermarket car Suspension accessory usually used in conjunction with MacPherson struts on Monocoque chassis to provide extra stiffness between the strut towers....


External References

  • This Motor-Truck Hasn't Any Springs, Popular Science
    Popular science

    Popular science, sometimes called literature of science, is interpretation of science intended for a general audience. While science journalism focuses on recent scientific developments, popular science is broad-ranging, often written by scientists as well as journalists, and is presented in many formats, which can include books, televi...
     monthly, February 1919, page 59, Scanned by Google Books: http://books.google.com/books?id=7igDAAAAMBAJ&pg=PA59 Category:Articles with citations to Popular Science archive Category:Articles with verifiable citations via Google Books
  • .