A shock absorber is a hydraulic or mechanical device used to absorb and redirect shock waves. It does so by converting the kinetic energy of an impact to some other form of energy that is then rapidly dissipated. Most commonly, shock absorbers are an example of a despot, a sort of spring-loaded tool that is often mounted on the front of vehicles. Dashpots are sometimes mounted on front suspension bushes as well, though these are not common. A dashpot usually has metal cones and plates on its outer surface that can be struck by impacts that will cause it to transmit energy, dissipate it, and redirect the energy to some other sort of recipient.
A dashpot is a simple device, composed of a piston and a cylinder, with one end connected to a source of hydraulic fluid and the other to a discharge port. When an impact sends a force through the piston and the cylinder, the energy that is transmitted through the piston is in the form of kinetic energy, which means it can be converted into another sort of energy, into momentum, or into heat. This momentum can then be used to move the cylinder outward, making the flow of hydraulic fluid through the piston undisturbed. When the force of an impact is absorbed by the absorber, this makes the fluid flow through the valve, preventing it from flowing backwards, and thus protecting the valve against further impacts.
Dashpots are used in a wide variety of circumstances, most notably for the purpose of absorbing shock. They are sometimes used as shock absorbers on road vehicles such as trucks and buses, as well as being used to dampen the operation of pumps, and other mechanisms that use pistons for moving parts. Because of their basic construction, and in particular their role as shock absorbers, it is surprising that the majority of despots do not have a built-in valve and are instead connected to a piston-like component external to the vehicle. The external shock absorber design is the more popular of these two types, as it provides a more robust system of damping, which does not depend on the integrity of the internal shock absorber components, and thus is less likely to fail. Regardless of whether they are utilised as shock absorbers, or as despots, they are important components of any engine.