Shock absorbers, linear dampers, and dashpots provide absorption of shock and smooth deceleration in linear motion applications.

These devices work by applying an opposing force that is proportional to the velocity of the moving object — the faster the velocity, the greater the force applied in the opposite direction. This decelerates the object slowly and smoothly preventing large shock forces. They are commonly used with springs to provide a resistance to change in location. Providing a rebound force keeps an object in its original location after initial force is gone. This force can be generated in different ways.

Shock absorbers typically contain both a fluid or mechanical dampening system and a return mechanism to the unengaged position. Shock absorbers are usually manufactured with compression springs to help absorb and dampen the force. They use valved or ported cylinders to absorb kinetic energy and use it to push hydraulic fluids through small openings creating heat within the fluid. Shock absorbers vary from small device applications to large industrial and civil engineering uses.

Linear dampers is an inclusive term that can be applied to many forms of dashpots and shock absorbers. They are typically used for devices designed primarily for reciprocating motion attenuation rather than absorption of large shock loads.

Dashpots are typically distinct in that while they use controlled fluid flow to dampen and decelerate motion, they do not necessarily incorporate an integral return mechanism such as a spring. Dashpots can operate in either a linear fashion or rotational and resist motion using either fluid friction or electromagnetics. Dashpots are often relatively small, precise devices used for applications such as instrumentation and precision manufacturing.

Function

Dampening devices may be mechanical (e.g., elastomeric or coil spring), or rely on a fluid (gas, air, hydraulic), which absorbs shock by allowing controlled flow from outer to inner chamber of a cylinder during piston actuation. The piston rod is typically returned to the unloaded position with a spring.

Specifications

The absorption or damping action can be compression or extension. Important parameters to consider when searching for shock absorbers, linear dampers, and dashpots include: 

Absorber stroke, or spring stroke, is the difference between fully extended and fully compressed position. It defines the maximum linear travel.

Important physical specifications to consider when searching shock absorbers, linear dampers, and dashpots include: 

• Cylinder diameter or maximum width, referring to the desired diameter of housing cylinder

• Rod diameter refers to the desired diameter of extending rod

Mounting

Mounting options ensure the unit fits into an existing application. Mounting choices include:

• Ball and socket
• Rod end
• Clevis
• Eyelet
• Tapered ends

• Threaded

• Bumper or rod ends unattached

Material

When selecting a body material it is important to consider weight and corrosion concerns. If the unit will be exposed to water and air a material like stainless steel maybe better than carbon steel. If weight is a concern factor, aluminum or some plastics are appropriate.
 

Features

Common features for shock absorbers, linear dampers and dashpots include:

Adjustable configuration allows the user to fine tune desired damping, either continuously or at discrete settings.

Standards

Shock absorbers, linear dampers, and dashpots must adhere to standards and specifications to ensure proper design and functionality. For example, ADS RS199 which defines standard diameters of shock absorbers and jack cylinders and KS R 4019, which is used for telescopic shock absorbers. 

Image Credits:

Enertrols, Inc. | Festo Corporation | Stabilus