Six-bar Linkage
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mechanics Mechanics () is the area of physics concerned with the relationships between force, matter, and motion among Physical object, physical objects. Forces applied to objects may result in Displacement (vector), displacements, which are changes of ...
, a six-bar linkage is a mechanism with one degree of freedom that is constructed from six links and seven
joint A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...
s. An example is the Klann linkage used to drive the legs of a walking machine. In general, each joint of a linkage connects two links, and a binary link supports two joints. If we consider a hexagon constructed from six binary links with six of the seven joints forming its vertices, then the seventh joint can be added to connect two sides of the hexagon to form a six-bar linkage with two ternary links connected by one joint. This type of six-bar linkage is said to have the Watt topology.An animation o
a six-bar linkage with the Watt topology.
/ref> A six-bar linkage can also be constructed by first assembling five binary links into a
pentagon In geometry, a pentagon () is any five-sided polygon or 5-gon. The sum of the internal angles in a simple polygon, simple pentagon is 540°. A pentagon may be simple or list of self-intersecting polygons, self-intersecting. A self-intersecting ...
, which uses five of the seven joints, and then completing the linkage by adding a binary link that connects two sides of the pentagon. This again creates two ternary links that are now separated by one or more binary links. This type of six-bar linkage is said to have the Stephenson topology. The Klann linkage has the Stephenson topology.


Watt six-bar linkage

Watt's parallel motion generator consists of the four-bar linkage that has a coupler curve that traces an approximately straight line trajectory, combined with a parallelogram linkage that copies this straight line movement to a desired location. This configuration of six bars and seven joints has two four-bar loops.


Stephenson six-bar linkage

The six-bars and seven joints of the Stephenson linkage comprise one four-bar loop and one five-bar loop. It has two ternary links that are separated by a binary link. This means the two ternary links are not connected to each other by a joint as in the case of the Watt topology. The Stephenson has three forms depending on the link that is selected as the frame, which are denoted Stephenson I, II and III.


See also

*
Mechanism (engineering) In engineering, a mechanism is a Machine, device that transforms input forces and movement into a desired set of output forces and movement. Mechanisms generally consist of moving components which may include Gears and gear trains; belt drive, ...
*
Linkage (mechanical) A mechanical linkage is an assembly of systems connected so as to manage forces and Motion, movement. The movement of a body, or link, is studied using geometry so the link is considered to be Rigid body, rigid. The connections between links ...
* Five-bar linkage


References


External links


A six-bar straight-line linkage in the collection of Reuleaux models at Cornell University

Mechanism animations including the Klann linkage

Example of a six-bar function generator that compute the angle for a given range.

Animations of six-bar linkage for a bicycle suspension.

A variety of six-bar linkage designs.

Lecture on the design of six-bar and eight-bar linkages

Article about patents and six-bar linkages
{{Linkages Linkages (mechanical)