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What is a Dashpot?

A dashpot is a mechanical device that dampens motion through viscous friction, providing resistance to sudden starts or stops. Often found in machinery and vehicles, it ensures smooth operation and prolongs equipment life. Curious about how a dashpot can enhance your system's performance? Discover the intricate workings and diverse applications of this unsung mechanical hero in our detailed exploration.
Keith Koons
Keith Koons

A dashpot is a mechanical device that applies friction to an object in order to restrict the velocity of its movement. This process is normally accomplished by means of a spring and some type of internal lubricant that applies resistive pressure that counters the force generated from the object when it is placed in motion. There is also normally an adjustment present on a dashpot to set the amount of counterforce during operation. The main idea behind the installation of a dashpot is to prevent parts from slamming together at high rates of speed and causing senseless damage.

One of the most common examples of a dashpot system can be found installed on doors within homes and businesses throughout the world. The device allows the door to open unimpeded, but once released, it will close very slowly due to the internal spring that counters the natural pull of gravity. This type of option is especially popular on doors with elaborate glass panes that could become cracked or broken if the object slammed shut with too much force—it is also implemented on relatively inexpensive models as well to ensure that they close properly. To better understand the physics behind a dashpot spring, individuals can try applying force to the door while it is closing to understand how much resistance the relatively simple device can provide.


There are essentially two types of dashpots commonly available; linear and rotary. The above example describes a linear dashpot since the counterforce is applied in a single preset direction. This type of system is popular within hundreds of everyday items ranging from electronics that have external moving parts to the shock absorbers installed within automobiles, like a carburetor dashpot. Rotary dashpots work a bit differently in that their resistive motion is in a circular pattern, and they can often be found within machinery that is required to turn rapidly. An eddy current damper is another example of a less popular type of dashpot that works off of magnetic fields.

The implementation of dashpots on modern machinery ensures that precision can be controlled even when extreme amounts of force are generated by rapid movement. Without this type of technology, many household and industrial items would require maintenance much more often since internal parts would unintentionally collide much more frequently. Linear and valve dashpots can be constructed for relatively little money, yet typically provide an effective counterbalance lasting several years or even decades.

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Discussion Comments


@Mammmood - That’s bad, but there are worse fates in life – like your shock absorbers failing.

I drove for years with bad shock absorbers, because I tend to be one of those people who puts off car repairs until I have no choice.

Finally it got to the point where I had no choice. The bumps over the pot holes were especially jarring and at times I felt like the whole chassis of the car was about to fall apart.

When I changed the shock absorbers the difference was night and day. I should have done it sooner. There’s no telling how much additional wear and tear I put on the car by waiting as long as I did.


There is nothing more annoying than having a storm door with a broken dashpot. I know, because I had one.

I had removed it when moving so that I could haul my large refrigerator through the door. It didn’t fit through the door frame with the storm door in place.

I must have done something wrong when trying to put the door back, because the spring mechanism in the dashpot was broken, and it no longer worked.

The door swung open and shut fine, but there was no resistance. That meant there was a sudden slam every time it shut. I thought that I could live with that for awhile, but no way. It got to the point where I thought the neighbors would complain, so I buckled down and bought a new dashpot unit.

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