# Slider crank calculator

Calculating Torque of a Crank Mechanism. Hi, Im currently designing a small machine which uses a simple crank mechanism but my crank mechanism is not a typical one. My application:. Last edited: Nov 30, Related Mechanical Engineering News on Phys.

Simon Bridge Science Advisor. Homework Helper. Is it correct? How is the force reaction like so I can resolve it and calculate the torque? Simon Bridge said:. Yes - you have drawn one of them.

But I think you have your thinking backwards - you are driving the block from the wheel not the other way around - the block moves along a line so torque may not help much here.

The torque you need to apply to the shaft to drive the block will vary with time - depending on how you want the block or the wheel to move.

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You should be able to plot the position of the black against the angular position of the wheel. If you intend to crank the wheel at a constant angular speed, you can use that to find a position-time graph for the block. Who knows - how did you calculate this figure?

What were the conditions? Your last diagram appears to show an applied force on the block, but your description says the wheel is driving the block - which is it? If you push on the block like that diagram shows, the force is transmitted along the shaft. So the direction shown for force at the pivot between the wheel and the shaft is incorrect. There is not enough information: for instance, the torque will be different if you want the block to have a constant speed for part of it's motion, a constant acceleration, or perhaps you want to drive the wheel at a constant speed - or with a constant torque and you want the minimum torque for this.

Well your first problem is that the top of the wheel is higher than the shaft can go. The wheel diameter is 50, same as the length of the shaft, but the bottom of the wheel is well above the track the mass runs on. Use free body diagrams to work out how the torque turns into ma.

So it is going to get stuck. You must log in or register to reply here. Last Post Aug 25, Replies 3 Views 7K. Torque and power calculation for a crank wheel. Last Post Feb 26, The four-bar mechanism has some special configurations created by making one or more links infinite in length.

The slider-crank or crank and slider mechanism is a four-bar linkage with the slider replacing an infinitely long output link. This configuration translates a rotational motion into a translational one. Most mechanisms are driven by motors, and slider-cranks are often used to transform rotary motion into linear motion. In this project a slider crank mechanism shown below is simulated in Hyperworks by giving different inputs like angular velocity, force, BISTOP torque to the links.

These cylinders are then assigned to the respective bodies as shown above. The mass and inertia properties of the two bodies are then extracted from their associated graphic cylinders.

Joints are models of interconnections between components. A lower pair is an ideal joint that constrains contact between a point, line or plane in the moving body to a corresponding point, line or plane in a fixed body or another moving body.

These have physical analogies e.

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This completes the model building process for the slider-crank mechanism. The number of degrees of freedom can be verified by hand calculations in the following manner:. With the point C not being constrained by any joint, the mechanism starts to oscillate randomly which is evident from the video below. Since the system has 2 degrees of freedom, a joint which only provides 2 degrees of restrain needs to be added.

For this purpose an inline joint aligned to Global X axis is added at point C. The DOF of the system is still 0 as a system can only be constrained by adding joints, constraints or motion to the joint. This can be verified by going to the Check Model option.

An output is added between Body1 and Ground Body to measure the velocity of point P2. The mechanism was then simulated for 12 seconds. With Point C constrained by the inline joint, Body 0 rotates about Point 0 and point C behaves like a slider now.It is important to use the correct length of crank to ensure that your legs can work efficiently. You risk damaging your knees if you habitually use cranks which are too long, especially as you get older.

This length goes all the way to your hip joint and cannot be measured directly. Ask a friend to measure your height twice — first when you are standing upright against a wall, without shoes on, and second when you are sitting squarely against it. Then subtract one measurement from the other one, as shown below. Even shorter cranks may be required by disabled riders with restricted knee movement and by users of faired racing recumbents due to space restrictions.

Additionally, riders with very long legs may need shorter cranks on standard upright bicycles, to prevent their toes hitting the front wheel or their pedals hitting the ground when cornering.

Crank Length Calculation It is important to use the correct length of crank to ensure that your legs can work efficiently. Send this to friend Your email Recipient email Send Cancel.

The position, velocity, and the center of the rotary part is mm long.

### Crank Length Calculation

The all acceleration generated by a slider-crank mechanism during variables that are used to solve this question is given in the operation can be determined analytically. The variations of nomenclature. Mathematics In the question that can be shown in the Figure 1.

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We are link with it in the reciprocating pump and compressor, in [1] Eben C. Cobb,Slider — Crank Mechanism for with the input rotation is changed to reciprocating motion of the Demonstration and Experimentation MQP piston.

Meriam, L. Kraige, J. Bolton,Engineering I preferred a internal combustion engine as my reference Mechanics of Dynamics, p. The crankshaft is held in place relative to the engine block by main bearings, which allow it to rotate. Bulkheads in the crankcase form a half of every main bearing; the other half is a detachable cap.

## Piston motion equations

In some cases a single main bearing deck is used rather than several smaller caps. A connecting rod is connected to offset sections of the crankshaft the crankpins in one end and to the piston in the other end through the gudgeon pin and thus transfers the force and translates the reciprocating motion of the pistons to the circular motion of the crankshaft.

I firstly solve the question with my analytical knowledge from the lecture and and I got from some research. I started the writing a MatLab code to get the plots. MatLab code corrects the solutions this is why because it was an important part of the project. Melis HUNT for her help and support throughout my project.

Search titles only. Search Advanced search…. Log in. Forums Engineering Mechanical Engineering. JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. How to calculate the torque of slider crank? I know it can be a simple question for Mechanical Engineering majors, but I am an Electrical Engineering major and have very little knowledge in Mechanical Engineering.

I am working on a project related to slider crank systems and really need to know this.

It would be great if you could tell me which book introduces slider crank torque calculation too. Related Mechanical Engineering News on Phys. Homework Helper. Welcome to PF! So calculating torque isn't really engineering, it's geometry. You need a book on geometry, or on trigonometry, or maybe on the elements of vectors particularly the cross product. I know it can be a simple question for Mechanical Engineering majors Last edited: Feb 14, Not nearly as simple as one 1 would like to think!

We've got a very similar mechanism that we need to determine the applied thrust to overcome a known torque across some degrees or so of crank rotation with an added twist. How does that affect the equations above? If it matters, the slider will be offset to the right of the crank pivot AND offset far enough to allow the slider to pass over and beyond the crank pivot and continue to the "dead mans" position and then continue to travel to rotate the crank back fifteen 15 to thirty 30 degrees or so.

Pretty sweet actually So we already have any and all angles we could ever dream of, just can't quite get out of the "brain dead" mode to find the solution, especially don't know quite what to do with the offset. Oh yeah, almost forgot.

We're in real life here in real time here, so we'll need to consider friction of slider as well both knuckles joints Any thoughts around a similar solution to this? You must log in or register to reply here. Related Threads on How to calculate the torque of slider crank? Calculating torque required to drive crank and slider.

Last Post Oct 1, Replies 15 Views 10K. Calculating Torque of a Crank Mechanism.

Last Post Dec 1, Replies 4 Views 30K.PMKS returns quick and accurate results for the position, velocity, and acceleration of rigid bodies connected as planar mechanisms. The PMKS term refers to a calculator - a compiled dynamic library e.

This calculator can be accessed: 1 through an Excel macro, 2 through. This can always be found at the Persistent URL Unlike commercial tools, PMKS is pure kinematics, which is a good thing in that you do not need to specify masses, or stiffnesses. We have shown in technical papers that the approach is quicker and more accurate than other approaches.

Furthermore, a novel approach to analyzing non-dyadic mechanisms has been developed which gives unprecedented results see examples in rightmost column of examples table. The implementation is lightweight and runs completely within the browser as a Silverlight application.

You can download two small files and run it locally: the webpage pmks. As such it makes certain simplifications or predictions to quicken the drafting process. When the main page is opened, you will see a single pendulum moving counter-clockwise at the center of the screen, like in the following screenshot.

Let us consider the various components of this page. Once a joint is fully specified as a new row in the table, it will appear in the main window.

From the main window, the coordinates can be manipulated by clicking and dragging on the purple for translation or pink for rotation arrows see below. Note: you do not have to catch the moving link! You manipulate the unfilled icon that appears at the initial location. This means that you could make the same mechanism many different ways.

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Updates via pmksim Planar Mechanism Kinematic Simulator PMKS returns quick and accurate results for the position, velocity, and acceleration of rigid bodies connected as planar mechanisms. Examples Here are some of the mechanisms created to date. Figure 2: A close-up of the icons that can be clicked and dragged with the mouse.A slider-crank linkage is a four-link mechanism with three revolute joints and one prismatic, or sliding, joint.

Velocity Analysis - Slider Crank Mechanism

There are also two methods to design each type: graphical and analytical. The displacement of the end of the connecting rod is approximately proportional to the cosine of the angle of rotation of the crank, when it is measured from top dead center TDC. So the reciprocating motion created by a steadily rotating crank and connecting rod is approximately simple harmonic motion :. Technically, the reciprocating motion of the connecting rod departs from sinusoidal motion due to the changing angle of the connecting rod during the cycle, the correct motion, given by the Piston motion equations is:.

This difference becomes significant in high-speed engines, which may need balance shafts to reduce the vibration due to this " secondary imbalance ". The mechanical advantage of a crank, the ratio between the force on the connecting rod and the torque on the shaft, varies throughout the crank's cycle.

The relationship between the two is approximately:. One way to calculate this angle is to find out when the Connecting rod smallend piston speed becomes the fastest in downward direction given a steady crank rotational velocity. Piston speed x' is expressed as:. For example, for rod length 6" and crank radius 2", numerically solving the above equation finds the velocity minima maximum downward speed to be at crank angle of Then, using the triangle sine lawit is found that the crank to connecting rod angle is At these points in the crank's cycle, a force on the connecting rod causes no torque on the crank.

Therefore, if the crank is stationary and happens to be at one of these two points, it cannot be started moving by the connecting rod. For this reason, in steam locomotiveswhose wheels are driven by cranks, the connecting rods are attached to the wheels at points separated by some angle, so that regardless of the position of the wheels when the engine starts, at least one connecting rod will be able to exert torque to start the train.

An in-line crank slider is oriented in a way in which the pivot point of the crank is coincident with the axis of the linear movement. The follower arm, which is the link that connects the crank arm to the slider, connects to a pin in the center of sliding object.

This pin is considered to be on the linear movement axis. Therefore, to be considered an in-line crank slider, the pivot point of the crank arm must be in-line with this pin point. With an in-line crank slider, the motion of the crank and follower links is symmetric about the sliding axis. This means that the crank angle required to execute a forward stroke is equivalent to the angle required to perform a reverse stroke. For this reason, the in-line slider-crank mechanism produces balanced motion.

This balanced motion implies other ideas as well. Assuming the crank arm is driven at a constant velocitythe time it takes to perform a forward stroke is equal to the time it takes to perform a reverse stroke. The graphical method of designing an in-line slider-crank mechanism involves the usage of hand-drawn or computerized diagrams.

These diagrams are drawn to scale in order for easy evaluation and successful design. Basic trigonometrythe practice of analyzing the relationship between triangle features in order to determine any unknown values, can be used with a graphical compass and protractor alongside these diagrams to determine the required stroke or link lengths. When the stroke of a mechanism needs to be calculated, first identify the ground level for the specified slider-crank mechanism.

This ground level is the axis on which both the crank arm pivot-point and the slider pin are positioned.

Draw the crank arm pivot point anywhere on this ground level. Once the pin positions are correctly placed, set a graphical compass to the given link length of the crank arm. Positioning the compass point on the pivot point of the crank arm, rotate the compass to produce a circle with radius equal to the length of the crank arm.

This newly drawn circle represents the potential motion of the crank arm. Next, draw two models of the mechanism. These models will be oriented in a way that displays both the extreme positions of the slider. Once both diagrams are drawn, the linear distance between the retracted slider and the extended slider can be easily measured to determine the slider-crank stroke. The retracted position of the slider is determined by further graphical evaluation.

Now that the crank path is found, draw the crank slider arm in the position that places it as far away as possible from the slider.

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