Types of mechanism in mechanical engineering
Before we explore types of mechanism, we will learn about mechanism. A mechanism is a device or process that produces a desired effect, often involving the interaction of multiple parts in a defined sequence to achieve a particular outcome. Mechanisms can be found in various fields including physics, engineering, biology, and economics, and can be used to explain how things work or to design and create new systems. Mechanical mechanisms refer to devices that use physical components to transmit and control motion. Some common types of mechanism include:
- Levers: These are simple machines that use a pivoting point, or fulcrum, to magnify or change the direction of force.
- Pulleys: These are systems of wheels and ropes or belts used to change the direction or magnitude of a force.
- Gears: These are toothed wheels that mesh with one another to transmit power and change torque or speed.
- Cams: These are rotating devices that use a unique shape to produce reciprocating or oscillating motion.
- Linkages: These are systems of interconnected rods and pivots that transmit motion between different points.
- Screws: These are helical devices that convert rotary motion into linear motion or vice versa.
- Sliders and Cranks: These are linear or rotary components that convert linear and rotary motion, respectively.
These are just a few of the many different types of mechanism that exist. The specific type of mechanism used in a given application depends on the requirements of the system and the desired outcome.
If a number of bodies assembled in such a way that the motion of one body causes constrained and predictable motion to other bodies, then it is called mechanism. On another side, a machine is a mechanism or a combination of the mechanism. In addition to imparting motion to other parts, the machine also converts available mechanical energy into desired work. Let us dig more into mechanism and types of mechanism in mechanical engineering.
Types of mechanism in mechanical engineering
Simple mechanism
All mechanism having four links are the simple mechanism. This is basic of all types of mechanism.
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Four-bar mechanism
As the name implies, it has four links and so it is a simple mechanism. In addition to 4 links, it also consists of 4 turning pairs.
Crank: A link which can completely rotate around its joint
Rocker: A link which can partially rotate around its joint
As per Grashof’s law
S + l <= P + Q
where S is the shortest link
l is the longest link
P, Q are other links adjacent to the shortest link
Case 1 : if S + l < P + Q
S is fixed: Double crank mechanism
P and Q fixed: Crank-rocker mechanism
l is fixed: Rocker-rocker mechanism
Case 2 : if S + l = P + Q
Case2a: All links have different length then it is same as case 1
Case2b: S = P and l = Q : This results parallelogram linkage crank-crank mecahnism
Deltoid linkage
S is fixed: crank-crank mechanism
Also called as kite mechanism
l is fixed: crank-rocker mechanism
Case 3 : if S + l > P + Q
Here Grashof’s law is not satisfied, so it is a rocker-rocker mechanism
Inversion of the 4-bar mechanism
- Crank-crank mechanism: Example- coupling rod of a locomotive
- Crank-rocker mechanism: Example- Beam engine
- Rocker-rocker mechanism: Example – Watt’s indicator
Inversion of slider crank mechanism
- First inversion: Reciprocating engine/compressor
- Second inversion: Whitworth quick return mechanism
- Third inversion: Crank & slotted lever mechanism, the oscillating cylinder mechanism
- Fourth inversion: Hand pump, bull engine
Inversion of double-slider crank mechanism
- First inversion: Elliptical trammel
- Second inversion: Scotch yoke mechanism
- Third inversion: Oldham coupling
Approximate straight line mechanism
- Watts indicator
- Grasshopper mechanism
- Scott-Russel mechanism
Exact Straight line mechanism
- Hart mechanism
- Peculiar mechanism
Compound mechanism
A mechanism which has more than 4 links is called compound mechanism
Summary
These are the most common and basic types of mechanism in mechanical engineering.
Also read : Types of constraint in mechanism
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