What is Mechanism: Definition and 528 Discussions

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;
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. elisua

    Screws versus pins

    What is stronger and better for continuous movement? Screws or pins for a mechanical component made of titanium Ti-6Al-4V
  2. leonardo_alex

    Help with Moments in Mechanism

    I'm developoing one mechamical device, that we'll put two nutrunner in one gear. One spur gear will rotate the gear and put the nutrunner and one position. Each nutrunner will fix one bolt with 70Nm. I need put one motor in pinion, but i need consider the moments to define de size of the motor...
  3. G

    I How Does a Magnetic Repulsion Machine Work?

    Someone on a machining forum is proposing a curiosity machine. Imagine two magnets, constrained to move along one axis, set N to N. They will move apart. If you insert a piece of steel in the gap, the magnets will move towards it. The input of the machine will be a rotating toothed...
  4. Z

    Questions about motion control and the moment of inertia referred to a motor shaft

    hello take a mechanism driven by a DC motor in automation books you find transfer functions such as : G(s) = k1/s(s+k2) normally it s assumed that the moment of inertia referred to motor shaft is a constant the point is that in general it is not a constant take for example a slider - crank...
  5. Y

    Is it Possible to Overlubricate a Manual Ratchet?

    Is it possible to overlubricate a manual ratchet that you operate by hand? I'd imagine if you tried really really hard, you can add so much grease, that it would be so dense, that you couldn't rotate the ratchet, or if you used very thick grease that is like a block of cheese. Or that when you...
  6. tetris

    Engineering Static Vs Dynamic Force Analysis in Mechanism

    My understanding is that : Static Force Analysis carried out on objects in static or dynamic equilibrium, that is rigid bodies that are not moving or moving with zero acceleration therefore, does not take into account the inertia of the object Dynamic Force Analysis carried out on objects in...
  7. T

    I Is there any mechanism possible for the Big Brake?

    https://arxiv.org/abs/0705.1688 https://ui.adsabs.harvard.edu/abs/2014IJMPD..2350054P/abstract https://www.scientificamerican.com/article/time-s-end-will-be-the-end-of-endings/ According to these references they suggest that dark energy can suddenly change sign and causing the universe expansion...
  8. A

    Modeling an earthing switch for a High Voltage Impulse Generator

    Hi All, I am trying to model this mechanism for a project. It is a switch that uses a solenoid to break the contact by lifting the aluminium arm. I understand that there is most likely software out there that can do this but i would like to understand how to model this from first principals. I...
  9. D

    Translating reciprocating motion into a 45 degree rotation

    I'm trying to design a mechanism to translate reciprocating motion into a 45 degree rotation. Here's the idea: A pin will push against the part marked in red, causing part of the desired rotation. Then, when the pin is pulled back, its interaction with the blue part will complete a 45 degree...
  10. M

    Engineering Kinematic modelling of a mechanism (General Crank)

    Hi, I was wondering if you could help me with a job at the university that consists of the kinematic modeling of mechanism number 3 in the image attached to this message. I have to set up the constraint equations and then solve the position, velocity and acceleration problem. For now I would...
  11. A

    Engineering Drawing velocity polygon for a press mechanism

    Hello, I'm new to the forum, I want to ask help on this problem here, above is a press mechanism and I'm tasked to draw a velocity polygon based on this mechanism. The point of contact between the two gears is A and consider it as a swivel hinge (rotating but stay still), so I guess it's O2...
  12. N

    Help with this mechanism (acceleration with graphic method)

    Hi guys! I have problems with this mechanism...finding the aceleration with graphic method. I already have drawn the speed diagram and the values of all of them. But, i dont know if my aceleration diagram it is well drawn. I'm stuck especially when trying to plot and calculate the...
  13. T

    Model for Gravity -- What mechanism distorts space in the real case?

    Homework Statement:: Model for Gravity Relevant Equations:: Rg -Rg = G/(8pi*c^4)T The rubber table model for gravity can't quite translate to reality. One sees that a ball placed on the table distorts it, but this is due to it being in a uniform gravity field. Just what mechanism distorts...
  14. sHatDowN

    Vector sample problem -- Force components on a spring mechanism

    Determine the amount and type (tensile or compressive) of the spring force so that the resulting force is a vertical force. Also get the resultant force. i find 60N (compressive) and resultant forces is 10800 is that correct?
  15. B

    I Solar anomaly and the Antikythera Mechanism

    I'm building a replica of the Antikythera Mechanism; a device that was conceived and manufactured around 50BC. it is an orrery and amongst other things it shows the motion of the five known planets, the sun and the moon when viewed from the earth. I've managed to calculate the motion of the...
  16. P

    Chemistry Draw the mechanism of the reactions of steps 1 and 2

    Hi everyone! There is a task that I can't solve. Can you explain me how I have to draw the full mechanism? Draw the mechanism of the reactions of step 1 and 2. Indicate the product before step 3. (in step 2 also TMG =Tetramethylguanidine is given and instead of the protecting group DMT was...
  17. D

    Did my Android program crash because it lacks a delay mechanism?

    Hi everyone I modified some code that originally displayed a toast when the screen was pressed and held. The original code used onTouchListener with a relative layout, but I changed it to a button instead. I think I've copied it correctly, but my program crashes when the button is clicked. I...
  18. Al-Layth

    Mechanism Ideas for: Rotary Action-input Pump?

    I'm trying to come up with a design for a handheld pump that will be used to suck diesel from a car's fuel tank. There's definitely going to be a pipe dipping into the fuel tank, and there's definitely going to be a human manually operating the pump. I'm trying to think of a mechanism that...
  19. DaveC426913

    Misc. Repairing recliner couch mechanism

    Bought this recliner couch DC (During Covid). Left side was opened while the Roomba was underneath and that has caused some misalignment so that now it doesn't open all the way anymore. It doesn't close all the way either, but that's hardly noticeable. I've finally gotten the courage to flip it...
  20. C

    What is the mechanism behind Quantum Entanglement?

    What is the mechanism behind Quantum Entanglement? Why do only subatomic particles exhibit Quantum Entanglement?
  21. D

    Designing a Geneva Mechanism: Overcoming Challenges

    (note: I never studied engineering, but I think I have a good math (and slight physics) background. I'm mentioning this not so you'll go easy on me - if I don't understand something, I'm sure I'll figure it out or find someone to help me decode what you're saying. I'm mentioning this in the...
  22. L

    Scotch yoke mechanism movement equation

    Hi, I am not an engineer and sorry in advance if I am not correct with the terms. I design out of curiosity this Scotch yoke mechanism (left image) based on a scheme (right image). I looked for some equations to find if there is a relation between the R0 , R to R0 distance (which changes...
  23. mktsgm

    What is the underlying physiological mechanism of itch?

    What is the dermatological condition called severe itch or urticaria? What is its underlying pathophysiological mechanism? While a simple scratch may be a compulsory reflex, it may reward a pleasurable experience. How it is different from an itch, which is considered a pathological condition...
  24. Alfredomaximun

    How can the degrees of freedom of a mechanism be obtained?

    Summary: ##M=3\left(n-1\right)-2j_1-j_2## Hi, I'm trying to get the degrees of freedom of a can crusher. So substituting I get ## \begin{array}{l}M=3\left(n-1\right)-2j_1-j_2\\ n=5\\ j_1=5\\ M=3\left(5-1\right)-2\cdot 5-0\\ M=2\end{array} ## And I would think it would be 1
  25. Leo Liu

    The mechanism of bendable headrest of seats on airplane

    When I flew on a plane not long ago I started wondering about how flexible headrest works. This kind of headrest is reliable and still holds up well after several years of constant bending. I speculate it employs the same design as gooseneck lamp, but after some Google digging I cannot seem to...
  26. V

    Mechanism of mechanical transverse wave in solids

    I am not sure, but below is my attempt. In solids the force between adjacent atoms/molecules is very strong. So, when a part of the solid medium is displaced perpendicular to the solid medium like a rope, the atoms/particles in the medium just ahead of the displaced part will tend to bring the...
  27. Euan12345

    How Do You Calculate Spring Properties for Effective Landing Gear Design?

    Summary:: I am making a landing gear mechanism, and am struggling to mathematically model it, the aim is to find the required properties for the spring for it to work. Hi can you help me with a problem, I am making a landing gear mechanism and am struggling to model it mathematically. The aim...
  28. J

    Question about the mechanism of a fishing rod

    Hello I would love to know how a fishing rod mechanism works. How is the wire always taut? I mean I guess it's a spring. Is it possible to get a consent form from someone? I can not understand how the spring works there Thank you
  29. P

    A Why is the Higgs mechanism needed?

    Here's my current understanding of mass terms. For scalar fields, a mass term flows under RG to larger values in the IR. This implies having mass values in the theory is unnatural because it has to be fine tuned at the UV level to get the correct observed mass at low energy (the term I think...
  30. mmcnaught831

    How to translate force into upward hinging motion between two panels?

    Pictured below are two hinged panels that can rotate upward to form an upside-down V. In position 1, the panels are lying flat. In position 2, the panels have folded together and the joined edge is raised up. Normally, in order to actuate this hinging motion, one would need to manually lift the...
  31. berkeman

    Medical What is the mechanism of using EMDR for treating PTSD?

    In a Facebook post recently by a friend of mine who is a very experienced Firefighter Paramedic FF/P (and currently a Captain at our local FD), he mentioned that EMDR had helped him a lot to deal with the traumatic events that Fire and EMS deal with. Several other FFs chimed in that EMDR...
  32. mktsgm

    Mechanism of asymptomatic Covid infections

    How we may explain or understand the absence of symptoms in an asymptomatic Covid patient? Which following scenario may explain asymptomatic infection more clearly? A highly efficient innate immunity arm takes care of the infection without the need for intervention from the adaptive arm as...
  33. D

    My weird geneva mechanism doesn't work. Looking for suggestions

    Two things that I think I should say before I describe what I did: First, I do not have any physics-related background (but I have a degree in CS, and I'd like to think I have a good enough grasp on math to be able to understand equations describing motion of objects). So please forgive me if...
  34. M

    Equation for the angular position of a slider crank mechanism

    Hi! I would like to know how I could define an equation for α with given the two lengths of the rods and angle theta (θ). I sketched the situation below, the problem arises when the rod Lab has pasts the 180 degrees. Like to hear.
  35. mktsgm

    What are the mechanisms of immune response after Covid vaccination?

    As the Covid vaccines become more prevalent worldwide, the hospitalization and mortality rates are coming down hearteningly. Actually, what happens after vaccination? 1) Vaccination causes the production of antibodies. So when later infection happens, the antibodies are up and ready to bind...
  36. F

    Opening mechanism for a bicycle kickstand

    Hey Guys, I found this thread about the proper size dimension of a torsion spring for upholding a kickstand in the right position. I have to develop a kickstand for my Omnium Cargo bike. I have been thinking about using the same choice of spring type for my product, but I've also been...
  37. J

    Inclined plane FBD for latch mechanism

    I apologize if this is the wrong area to post this in, I've never posted on thisforum before. I'm trying to form a FBD of a mechanism that uses linear motion to actuate a pin in a transverse direction. I've attached the general idea in a picture where the pin is free to move up and down. In...
  38. S

    Mechanism that engages when turning both ways, but releases when not driven

    I have an application in mind with a hand crank mechanism that will usually not be engaged to a trugh shaft so it can freewheel, but as soon as you start turning the hand crank in either direction it should engage with the shaft. And i want it to be silent (no mechanical ratchets) and with...
  39. duchuy

    Chemistry Methylation of glucose (mechanism)

    Hi, I don't understand why this correction would be a nucleophile substitution? From what understand : The O atoms in the cyclic glucose acts as nucleophiles. ICH3 is also a nucleophile due to the presence of iodine's "non bonding electron pairs" (sorry I don't know the right term for this), and...
  40. subatomicprincess

    Question about Slider Crank Mechanism problem

    I have attached my attempt. The only thing I keep getting wrong is the direction of V_(D/B). I know it is perpendicular to r_(BD) but, I never know if it is going upwards or downwards. In this case, I thought it was going downwards but when I checked the answer key, it had said it is going...
  41. P

    Kinematic diagram of a gear mechanism

    Can anyone help me with a kinematic analysis for the mechanism attached below? I need the outline of the mechanism, its notes and the necessary formulas to find out the transmission ratio and the rest of the values.
  42. K

    Finding the torque required for telescopic cable mechanism

    Summary:: I am designing a linear telescopic system that gets elevated with a step motor, but in order to find the compatible motor, I need to work out the torque that is required for the elevation. I have uploaded my CAD model to this thread with how cables are connected. Could someone please...
  43. I

    Chemistry Reaction Mechanism of Cl2 and CHCl3

    I think the answer is both A) Cl and B) CCl3, since both are produced and used up. The correct solution is only A). Could anyone explain why? Thanks.
  44. brotherbobby

    Brake mechanism in a car and pressurised oil

    (I must confess I couldn't get far, owing mostly to the term "an average distance (of 12 cm) from the axis". Axis of the (peached coloured) wheel at the center with the arrow pointing down? Is the arrow the location of the "axis" of the wheel? Let me see.) Objective : To find the oil pressure...
  45. K

    Engineering Mobility of the Mechanism, Chebychev–Grüblerv Formula

    For question J) I've got 9 number of links, 10 number of joints and 1 higher pair ( assuming that there is a slippage), substituting these values in the Chebychev–Grübler's formula gives me the mobility of 1. For question H) I've got 7 number of links, 9 number of joints substituting these...
  46. naviakam

    How Does Compressing Fully Ionized Gas Accelerate Ions to High Energies?

    Fully ionized gas, if compressed to a cylinder of mm scale, collapses rapidly and accelerates the e/ions to very high energies (MeV). The temperature in the compressed gas is around 100 eV. What could be the possible acceleration mechanism?
  47. Y

    Torque calculation for a new loading mechanism

    I'm designing loading mechanism of new machine and need to know what the torque will be. Here is the sketch of my mechanism. Distance from centre of shaft to the top of loading table is 200mm. Distance from the centre of mass of workpiece to centre of the shaft 50 mm. Max load is 400 kg. Weight...
  48. FEAnalyst

    Quick return mechanism stress analysis

    Hi, I wonder how to approach stress analysis of quick return mechanism used in shaper machines (see the diagram below): The first issue is: which moment in the working process of this mechanism should be used for analysis (when will the mechanism experience largest loads)? So far I assumed...