Talk:Piston

Poorly worded introduction?
Am I the only one who noticed that the introduction is worded funny?

"In general, a piston is a lubricated sliding shaft that fits tightly inside the opening of a cylinder. Its purpose is to change the volume enclosed by the cylinder, to exert a force on a fluid inside the cylinder, to cover and uncover ports, or some combination of these. A rubber seal is sometimes used to keep the lubricate within the shaft. Due to the constant motion of the machine this seal wears quickly and should be replaced with every servicing. If the seal should break during usage there can be disastrous long lasting consequences for the machine."

If it is, is there a way to reword this? SniperWolf1564 10:57, 16 May 2007 (UTC)

I realize that this introduction was deliberately worded this way, however, I think it's informative while also humourous and should be left the way it is. -Sparky 00:32, 18 May 2007 (UTC)


 * I agree that the introduction was awful and I have re-written it. Biscuittin (talk) 11:09, 30 March 2008 (UTC)

Rewording is fine but redefining? This could have legal implications by patents for instance. In this version outside of "reciprocating engines, pumps and gas compressors" there are no pistons. What do you call an object that is driven through a long tube for instance by an expanding gas and possibly connected at its ends through a valve box to itself?

AdrianAbel (talk) 11:49, 29 April 2008 (UTC)

I noticed that restricted list of practical applications; added text to generalize it. Pistons are among the most-basic elements of mechanical design; somehow, the author didn't seem to realize that. One unusual example is the Airpot™, which has a precision graphite piston quite closely-fitted in precision-bore glass tubing. The fit is nearly gas-tight, yet the piston has notably-low friction. It's used in scientific and measuring instruments and other equipment of basically related construction. Another is the differential piston, part of the high-pressure "air-spring" recoil mechanism in the U.S. Navy 5-inch/38 caliber guns. Nikevich (talk) 01:59, 11 November 2010 (UTC)

Angular Moving Piston
Hello. Does anybody heard about a new kind of piston, connected to a shaft? Such piston have angular motion (rather than linear motion) and produces less friction to the chamber walls.

A while ago I saw a documentary (in Discovery Channel or BBC, doesn't fully remember) that shows a Japanese engine that uses such piston. I think it would enrich this article.

If anybody know piston specifications mail to me at : karthirevi@rediffmail.com (I did: Nikevich (talk) 01:59, 11 November 2010 (UTC))

The old windshield-wiper pneumatic motors used for windshield (windscreen, UK) wipers on earlier 20-Century cars had such pistons. These motors were powered by manifold vacuum, and stopped when the throttle was opened wide. Nikevich (talk) 01:59, 11 November 2010 (UTC)

Piston seizure
Is there no article on piston seizures in the English language WP (cause and effect)? In the German language WP, there is de:Kolbenfresser. --Abe Lincoln 15:07, 11 October 2006 (UTC)

timing
hello, could anyone tell me the length of time that a piston is still for between directions (from down back up ) and also is there a name for this. Thanks
 * Whilst the crank is turning the piston only stops instantaneously at the top and bottom of it's stroke. These are known as 'top dead centre' and 'bottom dead center' respectively.

The exact amount of time spent at top and bottom dead centre depends on the speed of rotation of the connecting crankshaft and the amount of play at the big and small ends. As long as the crankshaft is running at a continuous speed and any play in the big and small end is negligible why should the piston connected to it spend any more time at angle zero as at any other angel of its rotation?

AdrianAbel (talk) 12:05, 29 April 2008 (UTC)

More specifically, if the crankshaft is turning at 360 RPM which is slower than most internal combustion engines run at idle speed (usually between 400 and 800 RPM) it needs one second to traverse one degree.

AdrianAbel (talk) 10:50, 2 May 2008 (UTC)

I'd say that "dwell" is a term that could apply. Nikevich (talk) 01:59, 11 November 2010 (UTC)

Governing equations
I am attempting to model the flow in and out of a single piston cylinder arrangement. On the down stroke the pressure in the cylinder decreases and a one way valve opens to admit fluid into the cylinder, on the up stroke the other one way valve opens (and the first closes) as the piston “pushes” fluid out of the cylinder. I will firstly begin modeling assuming the fluid in the cylinder is incompressible but later as the model becomes more complex I will model using compressible theory gas theory. If any one has any information or knows where I can get any information on the basic formulations of the energy, continuity and momentum equations could you please email me at: 14107864@sun.ac.za Thank you Paul

Suggest physics and mechanical-engineering texts, handbooks, and/or courses. Sorry not to be of more help. Nikevich (talk) 01:59, 11 November 2010 (UTC)

Piston and plunger
I am an engineer and I can not believe what is happening here. I can not find a word about materials for piston, and than I tried plunger, and I discovered an engineering article there. Wow--Billy the lid (talk) 08:55, 27 December 2007 (UTC)


 * Hey Billy,

A new article for called "Piston pump" still needs to be made; at present it simply links to this article; so the redirect needs removing and text has to be added. I made an additional image for the types of piston pumps which can be added to that article: File:Piston pump types.png KVDP (talk) 09:25, 27 May 2010 (UTC)

What about a piston for a Pneumatic cylinder?
The introduction assumes that all pistons are reciprocating, hence implying that all are continuously moving. This is clearly wrong (see the first query on this talk page). What about the piston used in a Pneumatic cylinder? That article links here, but there is no suggestion here that a piston could be part of a linear actuator of some kind. -- EdJogg (talk) 13:15, 18 August 2010 (UTC)

Not so sure that reciprocating implies continuous motion. It does, however, imply that the reciprocating element moves in a straight line, has limited travel, and of necessity, reverses direction (not necessarily immediately) when it reaches the limit of its travel. Nikevich (talk) 01:59, 11 November 2010 (UTC)

Magnetic pistons?
I just deleted a discussion line about magnetically moving pistons, it seemed not serious, but then I started searching about the subject on the net and found lots of things. I'm wondering if it should not be mentioned in the article. —Preceding unsigned comment added by 70.187.173.135 (talk) 16:12, 30 October 2010 (UTC)

Pistons for rodless cylinders
Double-acting cylinders (usually, if not always pneumatic) do not necessarily have piston rods. It is likely to amaze people who know something of technology, but, there are several companies who make these, and they are a commercial success. I'm not sure about high-flux magnets installed into the piston that "couple" with external magnets (or just solid ferromagnetic pieces), but there are definitely rodless cylinders with a relatively-wide slot in the cylinder wall. A sealing strip prevents leakage, and the piston is relatively long -- maybe 3 or4 times its diameter. Piston rings (O-rings or other) are at both ends, and the center portion, as it moves, "peels" off the sealing strip, permitting the actuator to move through the slot. At the other end, an identical structure "re-applies" the sealing strip. There probably are wipers for the slot edges and the strip.

This topic should be part of an article (again, not checking) about rodless cylinders, better yet, part of an article about cylinders in mech. engineering in general. Nikevich (talk) 01:59, 11 November 2010 (UTC)

Re-cast this article?
A piston is only a part of an assembly correctly called a cylinder, in mechanical engineering. There should be (note below) an article describing such a device, and this article could (and probably should) be merged into it. A cylinder consists (typically) of Note: At this writing, my priority queue before I go to sleep is already about eight entries deep, so I'm not checking... Nikevich (talk) 01:59, 11 November 2010 (UTC)
 * The cylinder itself, nearly always having a cylindrical bore (in the geometrical sense)
 * Sometimes a piston rod (e.g. steam engine, hydraulic cylinder)
 * Some sort of seal[s], usually on the piston itself (piston rings) and piston-rod seal (if there is a piston rod)
 * Ports, often but not necessarily at one or both ends
 * Supports for mounting, of some sort.


 * This talk page is showing how much this article is lacking, but it requires some detailed study on someone's part to come up with a more comprehensive treatment. For now, it is still the product of many separate editors, with many knowledge gaps remaining. However, you are welcome to take on the task...:o)
 * -- EdJogg (talk) 13:55, 23 February 2011 (UTC)

Piston skirt?
This should be an article about a piston - not a piston engine. There should be explained the parts of a piston, for instance what is a "Piston skirt" etc. Is it called wall, skirt, mantle, mantel? no help from wikipedia.--173.170.92.3 (talk) 17:02, 20 January 2011 (UTC)

Two-stroke vs. four-stroke — text removed
The section "Internal combustion engines" has become a discussion of the merits and disadvantages of two-stroke and four-stroke engines, which has nothing to do with the pistons themselves. This discussion can be found elsewhere in other WP articles, and has no place here. Chris the speller  yack  16:49, 7 December 2011 (UTC)


 * Delete the whole article. There's barely a line in here that achieves any sort of encyclopedic standard. Andy Dingley (talk) 16:50, 7 December 2011 (UTC)

I didn't go that far (yet). But here is what I removed from the section in question: "There are two ways that an internal combustion piston engine can transform combustion into motive power: the two-stroke cycle and the four-stroke cycle. A single-cylinder two-stroke engine produces power every crankshaft revolution, while a single-cylinder four-stroke engine produces power once every two revolutions. Older designs of small two-stroke engines produced more pollution than four-stroke engines. However, modern two-stroke designs, like the Vespa ET2 Injection, utilise fuel injection and are as clean as four-strokes. Large diesel two-stroke engines, as used in ships and locomotives, have always used fuel injection and produce low emissions. One of the biggest internal combustion engines in the world, the Wärtsilä-Sulzer RTA96-C is a two-stroke; it is bigger than most two-storey houses, has pistons nearly 1 metre in diameter and is one of the most efficient mobile engines in existence. In theory, a four-stroke engine has to be larger than a two-stroke engine to produce an equivalent amount of power. Two-stroke engines are becoming less common in developed countries these days, mainly due to manufacturer reluctance to invest in reducing two-stroke emissions. Traditionally, two-stroke engines were reputed to need more maintenance (despite exceptions like the Ricardo Dolphin engine, and the Twingle engines of the Trojan car and the Puch 250 motorcycle). Even though the simplest two-stroke engines have fewer moving parts, they could wear out faster than four-stroke engines. However fuel-injected two-strokes achieve better engine lubrication, also cooling and reliability should improve considerably"

I left several sections for others to clean up. Chris the speller  yack  23:00, 7 December 2011 (UTC)

More off-topic text removed
Removed from "Drawbacks section": "To supply the fuel and remove the exhaust fumes from the cylinder there is a need for valves and camshafts. During opening and closing of the valves, mechanical noise and vibrations may be encountered. A two-stroke engine does not require valves, meaning it doesn't need a camshaft, making these engines faster and more powerful."

Chris the speller  yack  23:07, 7 December 2011 (UTC)

Please remove following nonsence
Quote:

'''These engines typically use crosshead pistons. The main piston has a large piston rod extending downwards from the piston to what is effectively a second smaller-diameter piston. The main piston is responsible for gas sealing and carries the piston rings. The smaller piston is purely a mechanical guide. It runs within a small cylinder as a trunk guide and also carries the gudgeon pin. Because of the additional weight of these pistons, they are not used for high-speed engines'''

Unquote

There is no machinery part named crossheead piston, such thing does not exist. Crosshead is not smaller diameter piston, it is not even circular, it is straight line bearing consisting of shoe and guide. There is no another gudgeon pin, and best of all is last comment. Crosshead is mounted on engines where trunk system can not perform the task of annulating side forces well enough. Side forces in engines grow with size of piston and its weight, therefore crossheads can be found on engines with large bore, mainly with bore over 300-400 mm. (MAN is world leading manufacturer of crosshead engines, starts from 350 mm) — Preceding unsigned comment added by 93.137.29.202 (talk) 11:01, 9 May 2013 (UTC)

history
Shouldn't there be a subsection regarding the history of the piston/cylinder invention, particularly pertaining to steam engines, and preceded by the motion of automatic safety valves (for limiting boiler pressure)? Cesiumfrog (talk) 12:54, 7 January 2014 (UTC)


 * There should be a whole article here, where at the moment we have almost nothing. The invention of the steam engine piston (Papin 1690, although some claim Huygens; also the Russians have a doubtful claim that Polzunov was the first with a workable piston actuated by steam pressure rather than atmospheric pressure against a condensed vacuum) is relatively simple and the gradual development of its seal is the interesting part. The development of the machinery for machining an accurate cylinder is by far the most important and complex aspect - we could have a whole article on that alone. Safety valve, which AFAIK has relatively little direct connection to the piston's history, is a much more complete article than piston. Andy Dingley (talk) 13:13, 7 January 2014 (UTC)

What about the CONCEPT of "a piston".
Why does the article focus mainly on pistons such as found in engines? A PISTON is a very basic concept, used in many things, and in many different forms. It ought to focus on what the CONCEPT of a "piston" is, and how it works, and THEN cover various examples of applications, such as internal combustion engines. I mean, it says that "a piston is sealed with piston rings". No. A piston as used in an reciprocating engine uses piston rings. A syringe forms a seal using a tight-fitting rubber piston. The gas piston in my AK47 uses little "gas trap" cutout-rings to slow and stop the gas during the short time that its pressurized, as does the spigot-type grenade launcher on my Yugo SKS (another form of piston, in which the piston stays stationary and the CYLINDER gets launched along with the grenade). In fact, a bullet being propelled down a gun barrel can be considered a piston of sorts. Some pistons don't use any form of seal at all, because they can be loose fitting. Shock absorbers, pneumatic door closers, cake decorating tools, nerf guns, these things all have pistons in them, in different forms. A shock aborber piston is highly complex, containing precisely balanced valves to control the flow of fluid through them.

This article is like saying: "The definition of a lever: A lever is a device used to operate a pump jack. Levers can come either fixed to the jack, or can be detachable. Sometimes they have rubber handles. Some floor jacks have release devices built into the lever so the user can release the pressure simply by turning the lever slightly". Sure, that is all perfectly true, but it doesn't come close to actually explaining what a LEVER is (i.e. a simple machine that works by amplifying the applied force). A lever is a simple machine, a basic fundamental thing that is used in thousands of shapes and forms, on countless applications. Either we ought to have an article about PISTONS, including a section about "reciprocating engine pistons", or there ought to be an article about PISTONS, linking to a different article on "Engine pistons".

Also, not sure if someone is trying to be funny, but for some reason they decided to add Flamethrower and Knurling to the "See Also" list, neither of which is remotely related to pistons. I've removed them, along with a link to Rocket engine nozzle which claimed that "a rocket nozzle acts as a piston" (para), which is dumb, because even if one wanted to pretend that a rocket somehow operated on a piston principle (i.e. by the action of pressure, rather than the reaction to the acceleration of the escaping gases), the rocket nozzle would be the CYLINDER, and the gas stream would be the "piston". Anyway, I removed it because it was wrong on both counts.

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