Mechanism Definition and 534 Threads

In engineering, a mechanism is a 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;
Belts and chain drives;
Cams and followers;
Linkages;
Friction devices, such as brakes or clutches;
Structural components such as a frame, fasteners, bearings, springs, or lubricants;
Various machine elements, such as splines, pins, or keys.The German scientist Franz Reuleaux defines machine as "a combination of resistant bodies so arranged that by their means the mechanical forces of nature can be compelled to do work accompanied by certain determinate motion". In this context, his use of machine is generally interpreted to mean mechanism.
The combination of force and movement defines power, and a mechanism manages power to achieve a desired set of forces and movement.
A mechanism is usually a piece of a larger process, known as a mechanical system or machine. Sometimes an entire machine may be referred to as a mechanism; examples are the steering mechanism in a car, or the winding mechanism of a wristwatch.
However, typically, a set of multiple mechanisms is called a machine.

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  1. Mayan Fung

    B Ice Skating Mechanism: Exploring the Real Science

    As far as I know, ice skating works because high pressure lowers ice melting point. A thin layer of water forms between the blades and the ice which greatly reduces the friction. Just now, I am reading a thermodynamic book. For the phase boundary between ice and water, dP/dT ~ 135bar/K...
  2. Grinkle

    I What is the mechanism behind Hawking radiation?

    I thought Hawking radiation was a virtual particle pair emerging from nothing, one particle falling into the event horizon and the other particle tunneling out of the event horizon. Then I read this - https://www.physicsforums.com/insights/vacuum-fluctuation-myth/ and now I think a virtual...
  3. I

    Can't find this exact reaction mechanism online -- Help please....

    Homework Statement Homework EquationsThe Attempt at a Solution Can't find this exact reaction mechanism online. Help? http://imgur.com/a/X9P7e I don't know what the mild oxidation does. Does it split the double bond into a ketone and aldehyde?
  4. FallenApple

    Mechanism For Oscillation of Cylinder

    Homework Statement [/B] Begin with a solid cylinder of mass M and radius R. A hole is bored through this cylinder with radius r < R/2, parallel to the axis of the cylinder and with the surface of the hole touching the cylinder’s axis. This modified cylinder then rolls on a horizontal surface...
  5. thunderstrike33

    Writing Vector Loops and Geometric Constraints for a Mechanism with a P1 Joint

    How would you write the vector loops and geometric constraints for this mechanism?
  6. Jimster41

    What causes oak trees to develop galls and how do they benefit the gall wasp?

    How does the Gall Wasp get an Oak tree to make these? http://ento.psu.edu/extension/factsheets/galls-oak https://en.wikipedia.org/wiki/Gall_wasp I am not able to find anything other than "induced by chemicals secreted by the wasp" more or less. I have been looking at these over the last six...
  7. szc

    Single Direction Applied Force Locking Mechanism

    Having trouble researching/discovering any locking mechanisms that engage with force in a linear direction and then allow the engagement to be released with force in the same applied direction. I don't know if it has been done, any help/findings would be greatly appreciated. The only technology...
  8. G

    Diamagnetism Mechanism: Questions Answered

    Friends! I have some things unclear about diamagnetism in matter.Please see attached picture.
  9. entropy1

    I The mechanism of entangled particles

    First let me ask this: Consider a pair of entangled photons fired at a respective detector after passing respective polarisation filters. If a photon passes a polarisation filter, is it in a superposition of having passed and not having passed? Is the measuring device (that detects the...
  10. Uriel

    How Does SPDC Happen? A Guide for Beginners

    I've been doing some reading about SPDC. I understand the wave mixing, the conservation laws, the coupled equations for the three fields (pump, signal and idle). But I can't find any good reference on how does the split happens? (how the two photons are created) Is it because photons of the...
  11. C

    Establishing equations for a worm screw mechanism

    Hey guys :) So I'm looking to form equations that I can apply a Laplace transformation to. The mechanism specifically is a trailer jack - it converts rotational motion to linear motion. And its high torque provides a mechanical advantage to lifting heaving loads. Can anyone help me form...
  12. O

    Can smaller bars be used in redesigning this lever mechanism?

    Hello everyone, I am currently doing an internship and I am working on a part that opens and closes using a pneumatic cylinder as you can see bellow Here is a force diagram I would like to redesign this in order to use a cylinder with a shorter stroke and perhaps a slightly bigger diameter...
  13. MeesterDave

    I in working out forces in a real mechanism

    I have a mechanism that controls the movements of multiple assemblies in the X Y and Z directions. The mechanism has been built and suffers from a wobble on a fast X travel. We have a few suggested solutions but it would obviously be a good idea to get some calculation to help prove a solution...
  14. Daniel Barco

    Where can i find the design criteria of this mechanism

    i need I need to design this mechanism, but have not found the design criteria or how, someone could show me how or where to look. I need to design the mechanism that puts the lid to the product. but not with pneumatic actuators. in the following videos you can see how it works:
  15. C

    Help with design for moving a box

    Hi, I'm trying to design a contraption for a project that will move an item/box up and to the side. I have a picture of what it should look like and how it should look like but I need help with the mechanics of it. The box's starting position is In the ground and under a slap of metal or wood...
  16. T

    Hills Hoist Mechanism: Understanding the Function and Assembly | Explained

    Firstly, am struggling to wrap my head around exactly how the mechanism for a traditional 'hills hoist' (as seen below) clothesline functions. The handle can be turned in order to raise the clotheslines but from my googling, the mechanism is different to what I was expecting. Would be...
  17. W

    What Is the Correct Name for This Animatronic Eye Mechanism Part?

    Hello All. I'm searching for this part and also have video footage of it in motion. I cannot find it to finish the eye mechanism because I don't know what it's called. Can anyone tell me what it is? I would greatly appreciate it. Even companies dealing in such parts as well as metal...
  18. R

    Mechanism for height adjustment of rotating body

    Hi, I am trying to build (or at least conceptually) design a diy autonomous lawnmower. I want to add an automated grass cutting height mechanism. I have never worked with lawnmowers but through basic googling know that most lawnmowers have simple mechanisms in wheels to change cutting height...
  19. Alistair McCheyne

    Slider Crank Mechanism Magnitude and Direction

    https://scontent-lhr3-1.xx.fbcdn.net/v/t34.0-12/13181084_10156883800920486_1357045350_n.jpg?oh=a39d7777f01c4aa06301c4f3d740de1e&oe=57301DBC Hi I am currently studying design engineering and my lecturer has left just before an exam. I really don't know how to find the magnitude and direction of...
  20. T

    Design a Crank Mechanism: Solutions & Equations

    I want to design a crank mechanism. I found this page on Wikipedia https://en.wikipedia.org/wiki/Piston_motion_equations Relating from this diagram, is x the max stroke of the piston ?, or is it PO-(max stroke of piston) ? And why is l^2 = r^2 + x^2 - 2*r*x*cos(A) Shouldn't it be, l^2 =...
  21. K

    Design a automatic locking mechanism for two concentric cylinders

    How much force required to pull the actuator pin from the solid cylinder Weight of the solid cylinder is 15kg And angle of inclination 30 , Coefficient of friction 1.5
  22. T

    Can a Swash Plate Mechanism be Adapted for Radial Displacement Along a Spoke?

    This is a hard one to describe and I couldn't think of a better tittle, sorry. My aim has been for a while to create a mechanism which allows me to move an object (i.e a washer or something) in or out radially along a spoke of a wheel. However I have some restrictions which have made me scrap...
  23. C

    Higgs Mechanism and Lorentz transformation of currents

    Homework Statement Consider the Higgs mechanism lagrangian, $$\mathcal L = (D_{\mu} \phi)^* (D^{\mu} \phi) -\mu^2 (\phi^* \phi) - \lambda (\phi^* \phi)^2 - \frac{1}{4}F_{\mu \nu}F^{\mu \nu},$$ with ##F_{\mu \nu} = \partial_{\mu} A_{\nu} - \partial_{\nu} A_{\mu}## and ##D_{\mu} = \partial_{\mu}...
  24. B

    Reaction mechanism for ketone and vinyl lithium

    Homework Statement What is the product of 1-bromo-3-propanone treated with vinyl lithium? Homework EquationsThe Attempt at a Solution I know that the carbonyl is attcked by the organolithium but I am having a hard time understanding how it attaches to the carbonyl since it is sp2 hybridized...
  25. D

    Mechanism for extinction by scattering?

    Let's say you have a monochromatic laser beam directed towards a light sensor. As you move the sensor away from the laser, the intensity read by the sensor will decrease because of scattering on air molecules (extinction). Since intensity is proportional to the square of the E-field amplitude of...
  26. S

    Designing a Tilting Mechanism for Air Hose, Locking Methods and Resources

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  27. N

    Discovering the Mobility of the Pictured Mechanism: Analysis and Insights

    I need to find the mobility of the pictured system I have labeled the 5 links with black numbers and the 6 joints with red letters for convenienceAttempt at a solution: I know the mobility equation is M = 3(N-1) – 2(J1) – J2 + R, where N = number of links, J1 is the number of 1 DoF Joints, J2...
  28. P

    Shaft and Pin Size of Slider Crank Mechanism

    Hi all, I am working on a slider crank mechanism for moving an object of about 100 kg back and forth 30 mm at about 600 rpm. I plan to attach the connecting rod onto a flywheel that act as a crank, or attach to a pulley (in case need to use a transmission system to reduce input speed, increase...
  29. M

    Velocity-Based Time Dilation: Teen's $400k Video Correct?

    Put simply, is the explanation for velocity-based time dilation toward the end of this video correct? http://www.iflscience.com/physics/teenager-wins-400000-his-video-explaining-einsteins-theory-relativity Considering he won $400k in an international science video competition, you would hope...
  30. V

    Microwave tube mechanism of heating

    Hello, first of all, I understand, how microwave tube works but I'm interesting in how exactly the microwave heat up a things? What's the matter inside. I have heard about increasing energy of molecules of water by polarization them by micro-wave. But I have got a plate which is not from...
  31. S

    Crank Slider mechanism analysis

    Homework Statement For the mechanism shown, analytically find A) Velocity B) Acceleration. Of All points (B, C, D, E and G) The lengths of all links are given in the photo. It has to be solved using the analytical velocity and acceleration method. I've attempted so far deriving the equations...
  32. thegreengineer

    Slider crank mechanism problem

    Before starting I want to say that this topic is from a subject I'm taking called vector mechanics. The subtopic dealt is called kinematics of rigid bodies. Homework Statement The wheel rotates around an axis. This point of reference of the center of the wheel is labeled as "A". This wheel...
  33. A

    Mechanism of tautomerisation in AgCN and AgNC?

    Can anyone give a detailed mechanism for the tautomerization in AgCN and AgNC and is the same possible in KCN and KNC ??
  34. Raymond Potvin

    B Diffraction of light, the mechanism

    Hi everybody, At wiki, I was astonished to read this about diffraction of light : "In Quantum Mechanics, it is a remarkable fact that the mechanism of diffraction is based on radiating particles of a medium, while quantum mechanical waves have no transmitting medium. As being part of the...
  35. M

    Disconnector Operating Mechanism

    Information : CS11G Manual operation or CJ6B motor operated , for GW4F-145 type dis-connectors, Hi Friends, i am very confused, about dis connectors , if these are Off Line operated then what is the use of Motor operated ? 2nd , if motor operated mechanism is installed then controls of that...
  36. K

    Is the Higgs mechanism a gauge transformation or not?

    I asked this question to PhysicsStackExchange too but to no avail so far. I'm trying to understand the way that the Higgs Mechanism is applied in the context of a U(1) symmetry breaking scenario, meaning that I have a Higgs complex field \phi=e^{i\xi}\frac{\left(\rho+v\right)}{\sqrt{2}} and...
  37. whitsona

    Foucault Pendulum: How important is release mechanism?

    I built just a long pendulum in my house in order to start looking at a simple Foucault pendulum "prove the Earth moves" event at the science museum I'm helping to start here in Pensacola. It gave me a nicely reliable movement that seemed to show the pattern I was looking for. Every time, it...
  38. A

    Mechanism to move things around

    Hi. I am working on a project that requires moving a small camera on a platform in a linear fashion. I have a rectangular board and this camera need to move from one end to the other controlled by an arduino or something similar. I don't even know how to begin to approach this problem. I am...
  39. W

    Vertical alignment mechanism on eccentric shaft

    What would be the appropriate mechanism such that when the eccentric circle is rotating about the larger center circle the table stays horizontal? The large circular is the driver (its continuously rotating)
  40. Y

    Mechanics, degree of freedom question

    Homework Statement Calculate the DoF (mobility) of the following system: Homework Equations [/B] M = 3(L-1) - 2J1 - J2 (where L = number of links, J1 is the number of full binary joints and J2 is the number of half joints. The Attempt at a Solution I am very confident about there being...
  41. L

    What is the definition of the degrees of freedom in a kinematic chain?

    As I know, when a link in a kinematic chain is fixed, the kinematic chain will become a mechanism. And, I only know the definition of the DOF of a mechanism. Is there the definition of the DOF of a kinematic chain ?
  42. stevebenson

    Help identifying this pivoting joint mechanism

    Hello all, I need help identifying the following pivoting joint, and also coming to an understanding of how this particular joint works and is designed... Thanks for your help!
  43. A

    Totally Hypothetical, probably incorrect, Shock Wave Generation Mechanism

    So I was sitting around pondering about forces, and I found myself thinking about shock-waves. Whether they're caused by supersonic travel, or explosions, the pressure at the front of the wave-bow shock pressure is a force. So I started thinking of a way to generate them without having to go...
  44. Richard Roberts

    RichRoberts44/9_00596_24_zpsjjn45ocm.jpg[/URL]Help with Sliding Plate Mechanism

    Hi all, I was wondering if anyone had any ideas on something I'm struggling with at the moment. In the attached picture I have a sliding plate that needs to travel as shown. I have a motor mounted in the position on the picture and due to limited space its the only position available. I had...
  45. S

    Offset crank slider mechanism connecting rod analysis

    Homework Statement A) Determine the value of the angle θ (measured from vertical) when the angular velocity of link AB a maximum. B) What is the maximum angular velocity of link AB. Homework EquationsThe Attempt at a Solution This is a part of a bigger question. I've managed to answer all...
  46. D

    Feasibility and Advantages of Variable Wing Area Concept in UAV/RC Aircraft

    Hey guys!, this is my final year aeronautical engineering project that me and my group are going to work on! we have this concept of producing a roll in an uav/RC aircraft by reducing the area of the wing on one side while keeping the other side area constant or increasing it(gradually) and...
  47. Glurth

    Describe the mechanism in GR causing *Space* expansion

    From what I have read, it sounds like GR predicts that under certain conditions, space itself will expand. If this is incorrect, please just let me know and ignore the below. While I don’t know the math involved in GR, I can understand explanations of how gravity distorts space-time, to alter...
  48. E

    What are the different types of release mechanisms for gliders?

    Hello, I ran a search online and found some examples of Nichrome and Ring and Hook based mechanisms, but i don't have enough experience to make an intelligent decision for my project. Does anyone have a good source of information for these things? Thanks.
  49. graceless9

    Mechanism to move a platform at a constant velocity

    Hi all, I'm new here on Physics Forums and can't wait to delve into some juicy topics! I have a very practical problem that I need help with. I am doing a home project where I want to move a platform on wheels (loaded to a maximum of 70kg) in a 1.5m long straight line across the floor at a...
  50. D

    Hip joint torque in walking mechanism

    Hi everyone, I am making a hexapod ( six legged walking mechanism ) which walking by keeping 3 alternate legs in air and other 3 on ground, pushing the body ahead, also known as tripod gait. The basic structure of model and one leg are shown in the pictures. I want to calculate the torque...
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