Editing Shock absorber (section)

==Types of vehicle shock absorbers==
[[File:Shock Absorbers Detail.jpg|thumb|Diagram of the main components of a twin-tube and mono-tube shock absorber]]
Most vehicular shock absorbers are either twin-tube or mono-tube types with some variations on these themes.

===Twin-tube===

====Basic twin-tube====
Also known as a "two-tube" shock absorber, this device consists of two nested cylindrical tubes, an inner tube that is called the "working tube" or the "pressure tube", and an outer tube called the "reserve tube". At the bottom of the device on the inside is a compression valve or base valve. When the piston is forced up or down by bumps in the road, hydraulic fluid moves between different chambers via small holes or "orifices" in the piston and via the valve, converting the "shock" energy into heat which must then be dissipated.

====Twin-tube gas charged====
Variously known as a "gas cell two-tube" or similarly named design, this variation represented a significant advancement over the basic twin-tube form. Its overall structure is very similar to the twin-tube, but a low-pressure charge of nitrogen gas is added to the reserve tube. The result of this alteration is a dramatic reduction in "foaming" or "aeration", the undesirable outcome of a twin-tube overheating and failing which presents as foaming hydraulic fluid dripping out of the assembly. Twin-tube gas charged shock absorbers represent the vast majority of original modern vehicle suspension installations.

====Position sensitive damping====
Often abbreviated simply as "PSD", this design is another evolution of the twin-tube shock. In a PSD shock absorber, which still consists of two nested tubes and still contains [[nitrogen]]<ref>{{Cite web |title=Nitrogen - Element information, properties and uses {{!}} Periodic Table |url=https://www.rsc.org/periodic-table/element/7/nitrogen |access-date=2024-11-18 |website=www.rsc.org}}</ref> gas, a set of grooves has been added to the pressure tube. These grooves allow the piston to move relatively freely in the middle range of travel (i.e., the most common street or highway use, called by engineers the "comfort zone") and to move with significantly less freedom in response to shifts to more irregular surfaces when upward and downward movement of the piston starts to occur with greater intensity (i.e., on bumpy sections of roads— the stiffening gives the driver greater control of movement over the vehicle so its range on either side of the comfort zone is called the "control zone"). This advance allowed car designers to make a shock absorber tailored to specific makes and models of vehicles and to take into account a given vehicle's size and weight, its maneuverability, its horsepower, etc. in creating a correspondingly effective shock.

====Acceleration sensitive damping====
The next phase in shock absorber evolution was the development of a shock absorber that could sense and respond to not just situational changes from "bumpy" to "smooth" but to individual bumps in the road in a near instantaneous reaction. This was achieved through a change in the design of the compression valve, and has been termed "acceleration sensitive damping" or "ASD". Not only does this result in a complete disappearance of the "comfort vs. control" tradeoff, it also reduced pitch during vehicle braking and roll during turns. However, ASD shocks are usually only available as aftermarket changes to a vehicle and are only available from a limited number of manufacturers.

====Coilover====
{{main|Coilover}}

Coilover shock absorbers are usually a kind of twin-tube gas charged shock absorber inside the helical road spring. They are common on motorcycles and scooter rear suspensions, and widely used on front and rear suspensions in cars.

===Mono-tube===
[[File:Ammo monotubo.gif|thumb|Hydraulic shock absorber monotube in different operational situations:<br>
1 ) Drive slow or adjustments open<br>
2 ) Like "1", but extension immediately after the compression<br>
3 ) Drive fast adjustments or closed, you can see the bubbles of depression, which can lead to the phenomenon of cavitation<br>
4 ) Like "3", but the extension immediately after the compression<br>
Note: The volume change caused by the stem is considered.]]

[[File:Ammortizzatore con serbatoio.jpg|thumb|left|Absorber with remote-reservoir connected rigidly, compared to most shock absorbers. It uses a diaphragm instead of a membrane, and does not contain a control valve for expansion of the pneumatic chamber.<br>
Description:<br> 
1) Sheath and gas tank <br> 
2) Stem <br> 
3) Snap rings <br> 
4) Plate bearing spring <br> 
5) Spring <br> 
6) End cap and preload adjustment <br> 
7) Cap gas, present in versions both with or without gas valve (inverted profile) <br> 
8) Mobile diaphragm <br> 
9) Pad switch (compression) <br> 
10) Wiper <br> 
11) Oil seal assembly, and shock seal <br> 
12) Negative buffer pad or limit switch (extension) <br> 
13) Piston with sliding blades and seal]]
The principal design alternative to the twin-tube form has been the mono-tube shock absorber which was considered a revolutionary advancement when it appeared in the 1950s. As its name implies, the mono-tube shock, which is also a gas-pressurized shock and also comes in a coilover format, consists of only one tube, the pressure tube, though it has two pistons. These pistons are called the working piston and the dividing or floating piston, and they move in relative synchrony inside the pressure tube in response to changes in road smoothness. The two pistons also completely separate the shock's fluid and gas components. The mono-tube shock absorber is consistently a much longer overall design than the twin-tubes, making it difficult to mount in passenger cars designed for twin-tube shocks. However, unlike the twin-tubes, the mono-tube shock can be mounted either way—it does not have any directionality.<ref>{{Cite web|url=http://www.thyssenkrupp-bilstein.de/en/produkte/1-rohr-daempfer.php|title=thyssenkrupp Bilstein - Entwicklung / Produkte - Konventionelle Dämpfer - 1-Rohr-Dämpfer (deCarbon-Prinzip)|website=www.thyssenkrupp-bilstein.de|language=en|access-date=2017-07-13}}</ref> It also does not have a compression valve, whose role has been taken up by the dividing piston, and although it contains nitrogen gas, the gas in a mono-tube shock is under ''high'' pressure (260-360 [[pounds per square inch|p.s.i.]] or so) which can actually help it to support some of the vehicle's weight, something which no other shock absorber is designed to do.<ref name="carley">{{Citation| last =Carley| first =Larry| title =Monotube shocks-- don't absorb shocks, but...| newspaper =Brake and front end magazine| date =February 2008| url =http://millingtoncentralhs.scsk12.org/~jkasper/Site/Homework_handouts_files/Shocks%20Monotube.pdf| archive-url =https://web.archive.org/web/20140102200021/http://millingtoncentralhs.scsk12.org/~jkasper/Site/Homework_handouts_files/Shocks%20Monotube.pdf| archive-date =2014-01-02| url-status =dead| access-date =1 January 2014}}</ref>

Mercedes became the first auto manufacturer to install mono-tube shocks as standard equipment on some of their cars starting in 1958. They were manufactured by [[Bilstein Shock Absorbers|Bilstein]], patented the design and first appeared in 1954s.<ref>Shelton, p.24 and p.26 caption.</ref> Because the design was patented, no other manufacturer could use it until 1971 when the patent expired.<ref name="carley"/>

=== Spool valve ===
Spool valve dampers are characterized by the use of hollow cylindrical sleeves with machined-in oil passages as opposed to traditional conventional flexible discs or shims.<ref>{{Cite news|url=http://blog.caranddriver.com/from-f1-to-baja-multimatics-clever-spool-valve-dampers-explained/|title=From F1 to Baja: Multimatic's Clever Spool-Valve Dampers Explained|access-date=2017-07-19|language=en-US}}</ref> Spool valving can be applied with monotube, twin-tube, or position-sensitive packaging, and is compatible with electronic control.<ref>{{Cite news|url=http://www.caranddriver.com/features/automotive-dampers-explained-how-6-common-types-work-feature?src=socialflowTW&mag=cdb&dom=tw|title=Damper and Awe: 6 Types of Automotive Dampers Explained - Feature|access-date=2017-07-19|language=en}}</ref>

Primary among benefits cited in [[Multimatic]]’s 2010 patent filing is the elimination of performance ambiguity associated with flexible shims, resulting in mathematically predictable, repeatable, and robust pressure-flow characteristics.<ref>{{cite patent|title=Hydraulic damper spool valve|pubdate=2014-08-12|url=http://www.google.com/patents/US8800732|inventor-last=Holt|inventor2-last=O'Flynn|inventor3-last=Tomlin|inventor-first=Laurence J.|inventor2-first=Damian|inventor3-first=Andrew|country=US|number=8800732 B2}}</ref>

===Remote reservoir/piggy-back===
An extra tube or container of oil connected to the oil compartment of the (main) shock via a flexible pipe (remote reservoir) or inflexible pipe (piggy-back shock). Increases the amount of oil a shock can carry without increasing its length or thickness.

===Bypass shock===
Allows each section of suspension travel to have an independent suspension tune. Bypass shock, double bypass shock, triple bypass shock etc. Triple bypass would have a separate set of suspension tuning controls for each of its three sections of suspension travel: initial travel, mid-travel, full-travel.<ref>{{Cite web |title=Byass Shocks Part 1 – AccuTune Off-Road |url=https://accutuneoffroad.com/articles/byass-shocks-part-i/ |access-date=2024-06-14 |language=en-US}}</ref>