Talk:Four-bar linkage

Revisions to this article
I am not sure what a "stub class" article may be, but I have made some revisions to this article that I believe help to explain four-bar linkages more clearly. Prof McCarthy (talk) 06:04, 27 June 2011 (UTC)
 * Yes, the article is much more informative. No longer stub. The external links in the lede should be put below, but the article can mention such and indicate where animations are used to clarify linkage function.Rgdboer (talk) 21:57, 27 June 2011 (UTC)

Incomprehensible
This article is nearly incomprehensible. I have a doctorate in biophysics, and a master's in computer engineering, yet I have no idea what the four bars are in the slider crank. I also do not see any relationship between the slider crank, and the design of four bar linkages. It is found as a set of three subheadings under that subsection, and this makes no sense to me. Nick Beeson (talk) 23:32, 10 May 2014 (UTC)


 * Yeah, I've got to say, I'm not really sure how the slider stuff relates to the four-bars. Maybe there's some mathematical similarity somehow (way beyond me), but it's never even mentioned.  HCA (talk) 22:02, 11 May 2014 (UTC)


 * Would one of you be responsible for the split proposal on that section? Because it is absolutely a good idea.--Martin BerkaT&#124;C 18:12, 2 August 2014 (UTC)


 * I am a mechanical engineer and I know what this stuff is.Slider crank chain or single slider-crank chain is made when one prismatic pair of four bar chain mechanism is replaced by a revolute pair.And the article Slider crank chain should not be merged with four bar chain mechanism as both are different types of mechanism and they must be split.Thank youPraveen.ujjain (talk) 05:02, 1 February 2015 (UTC)


 * The term four-bar linkage refers to a one degree-of-freedom mechanical system constructed from four links or bars and four joints, that may be hinges or sliders. If all of the joints are hinges, the shape of the linkage is a quadrilateral.  However, if one of the joints is a slider, then two bars of the linkage and the base that supports the slider form a triangle.  This leads to the question of where is the fourth bar in a slider-crank linkage.  This is answered by recognizing that each bar of a four-bar linkage is a physical body that supports two joints.  And each joint has two sides one each on the two links that it connects.  For a hinged joint there is an axle attached to one side and a bearing attached to the other.  This is true for a sliding joint as well, where there is a straight side on one side that engages a straight side on the other.  Apply this to a piston in an internal combustion engine to recognize that the straight side of the piston is one side of a sliding joint, and the straight side of the cylinder in the engine block is the second side of this joint.  Thus, the piston, connecting rod, crank and engine block are the four bars of the slider-crank linkage that is central to the operation of an engine.  I hope this is helpful. Prof McCarthy (talk) 17:55, 1 February 2015 (UTC)

March 18, 2018 additions
User:Salix alba please consider including in this present article of the content below - now removed. Please also attend the companion Slider-crank linkage.

I am copying User:Prof McCarthy who is an expert in the field and contributed extensively in the past to this article.

Applications

 * Pumpjack
 * Door closer
 * Pantograph (four-bar, two degrees of freedom, i.e., only one pivot joint is fixed.)
 * Crank-slider, (four-bar, one degree of freedom)
 * Double wishbone suspension
 * Watt's linkage and Chebyshev linkage (linkages that approximate straight-line motion)
 * Biological linkages
 * Part of Bicycle suspension
 * Part of fordable steps and fordable chairs
 * Part of some gear shift linkages
 * Part of some steam engines

Cited paper makes mistakes on generalised inverses
This article cites a conference paper connecting the involutory ring of dual numbers to the problem of designing certain spatial linkages of RCCC type. In the introduction, the article claims that one-sided inverses of matrices are the same as Moore-Penrose inverses. It then says that one-sided inverses are unique. In general, one-sided inverses of matrices are far from unique, as demonstrated by the matrix $$(1,0)^T$$, which admits the set of matrices $$\{(1,x) \mid x \in \mathbb C\}$$ as all its left inverses. I feel like this needs to be pointed out. --Svennik (talk) 17:14, 2 February 2024 (UTC)

More diagrams of exotic 4-bar linkages with a single sliding component?
I'm not sure the diagrams of a crank-driven slider at the end are exhaustive of linkages of type PRRR, RPRR, RRPR and RRRP. Simple, legible diagrams would be really, really helpful here. --Svennik (talk) 17:18, 2 February 2024 (UTC)
 * If you know of additional or better diagrams, or you are able to create them, feel free to be bold and add them. ~Anachronist (talk) 21:58, 2 February 2024 (UTC)
 * I've added two diagrams: One of them I copied to the top from further down the page. [EDIT] Found a more appropriate diagram for slider-crank. --Svennik (talk) 17:09, 4 February 2024 (UTC)