Links, joints, and kinematic chains and Their applications

 Linkage design:

 Linkages are the basic building blocks of all mechanisms

 All common forms of mechanisms (cams, gears, belts, chains) are in fact variations on a common theme of linkages.


• Linkages are made up of links and joints.

• Links: rigid member having nodes

• Node: attachment points

1. Binary link: 2 nodes

2. Ternary link: 3 nodes

3. Quaternary link: 4 nodes

Joint: a connection between two or more links (at their nodes) which allows motion; (Joints also called kinematic pairs).

Joint Classification

Joints can be classified in several ways:

1) By the type of contact between the elements, line, point, or surface.

2) By the number of degrees of freedom allowed at the joint.

3) By the type of physical closure of the joint: either force or form closed.

4) By the number of links joined (order of the joint).


A joint with more than one freedom may

also be a higher pair

• Type of contact: line, point, surface

• Number of DOF: full joint=1DOF, half joint=2DOF

• Form closed (closed by geometry) or Force closed

(needs an external force to keep it closed)


• Joint order

Joint order = number of links-1

Terminology of Joints

 A joint (also called kinematic pair) is a connection between two or

more links at their nodes, which may allow motion between the links.

 A lower pair is a joint with surface contact; a higher pair is a joint with point or line contact.

 A full joint has one degree of freedom; a half joint has two degrees of freedom. Full joints are lower pairs; half-joints are higher pairs and allow both rotation and translation (roll-slide).

 A form-closed joint is one in which the links are kept together form by its geometry; a force-closed joint requires some external force to keep the links together.

 Joint order is the number of links joined minus one (e.g. 1st orde means two links).


Comments

Post a Comment

Popular posts from this blog

The working Principle of the Hydraulic Crane

Image
 Hydraulic Crane:- A hydraulic crane consists of a central pedestal supporting a mast from which is attached a jib or ram. The jib can be raised or lowered to reduce or increase the radius of action of the crane. The mast can revolve about the vertical axis so that jib with load can be positioned anywhere in a circular area around the crane . Thus, both by lowering or raising the jib revolving around the pedestal,  the load can be moved to any place within the crane area action. there are two sets of pulleys include one which is stationary and the other which is moveable. The load is suspended by a wire rope that passes over a guide pulley fixed on the jib and on another end the wire rope is attached to the hydraulic jigger. The jigger consists of a fixed pulley. at the bottom end of the fixed cylinder is attached to a movable pulley. At the bottom end of the fixed cylinder is attached to a fixed pulley. The jigger is attached to the mast. The wire rope to the jigger passes ov...
Read more

Bernoulli's Equation In Irrotational Flow

Image
  Bernoulli's Equation In Irrotational Flow we have obtained Bernoulli’s equation       This equation was obtained by integrating the Euler’s equation (the equation of motion) with respect to a displacement ' ds'  along a streamline. Thus, the value of C in the above equation is constant only along a streamline and should essentially vary from streamline to streamline. The equation can be used to define relation between flow variables at point B on the streamline and at point A, along the same streamline. So, in order to apply this equation, one should have knowledge of velocity field beforehand. This is one of the limitations of application of Bernoulli's equation. Irrotationality of flow field Under some special condition, the constant C becomes invariant from streamline to streamline and the Bernoulli’s equation is applicable with same value of C to the entire flow field.  The typical condition is the irrotationality of flow field. Proof: Let u...
Read more

The Pelton wheel is an impulse turbine

Image
Pelton wheel  The  Pelton wheel is an impulse turbine. In the Pelton wheel, the pressure energy of water is fully converted into kinetic energy by passing water through the nozzle. This forms a high-velocity jet that is used for the driving wheel by changing its velocity on the buckets. A Pelton turbine consists of a rotor. On the periphery of the rotor are mounted equally spaced buckets that have either double hemispherical or double ellipsoidal shapes. Water is brought down from a high head source like a dam through a pipe system, Which is called a penstock. A nozzle is provided at the end of the penstock which converts the potential energy of high head water into a high-velocity water jet. The high-velocity water jet emerging from the nozzle impinges on the buckets of the Pelton wheel and it sets the wheel in Function of the casing of a Pelton turbine is.....  (i) to prevent the splashing of water;   (ii) to discharge water to tail race; and  (iii) to safegu...
Read more