Velocity diagram for 4 bar linkage

In summary: In the sum VBA+VCB+VDC=0, all three velocities are relative to B, so they are all drawn from B.In summary, the conversation discusses the concept of velocity in a linkage system, focusing on the first three images provided. The first image shows the origin and the direction of velocity for Vao and Vdo. The second image shows the velocity of C relative to B, while the third image shows the velocity of D relative to C. The conversation also mentions the confusion about the direction of Vcb and the location of the blue axis in the first image. Ultimately, the individual is seeking a clearer explanation of this topic and asks for a recommended resource.
  • #1
jb101_
1
0

Homework Statement



http://photouploads.com/images/017db8.png
http://photouploads.com/images/eebec7.png
http://photouploads.com/images/f472e6.png

Homework Equations


v= rω

The Attempt at a Solution


I don't really have much of an attempt. I missed this lecture so I am completely confused on how to do these questions. I can't really find something online that explains the method from start to end in layman's terms. In the first image above, I'm assuming O stands for origin? Where is the origin in this image? Why is Vao = Vdo = 0?

Why is Vcb in the direction indicated? If link AB is being pulled to the ''left'', then surely link BC is also pulled to the ''left'' therefore Vcb should also be in this (left) direction?

Why are the blue axis drawn at the A end rather than the B end?

For the second image, why is it Vba + Vcb + Vdc = 0, surely the last term should be Vcd as this is written just 2 lines above it?

For the third image, I really don't understand the whole velocity space. Why are o, a and d in the same spot?

Perhaps it would be better if someone could link me to a clear explanation of this topic? I tried to search online but didn't yield anything simple.

Sorry for the lack of explanation but really confused and have been on this for hours now.

Cheers
 
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  • #2
I don't think it matters where O is, it's just a way of stating that A and D are fixed.
VCB is the velocity of C relative to B. Consequently it is orthogonal to BC. It doesn't matter which way it is drawn. If it turns out to be the other way then its value will be negative.
In each link-specific diagram, the axes are drawn at the 'local' origin. E.g. in the second such diagram, the velocity of C relative to B is considered, so for that purpose B is the origin.
VDC is the velocity of D relative to C. VDC=-VCD.
 

Related to Velocity diagram for 4 bar linkage

1. What is a velocity diagram for 4 bar linkage?

A velocity diagram for 4 bar linkage is a graphical representation of the velocities and directions of movement of the different links in a 4 bar linkage mechanism. It helps to visualize the speed and direction of movement of the links at different positions in the mechanism.

2. How is a velocity diagram for 4 bar linkage drawn?

A velocity diagram for 4 bar linkage is typically drawn by using the principle of relative velocity. The velocities of the different links are plotted on a common scale and their direction of movement is shown with arrows. The point of intersection of the velocity vectors represents the instantaneous center of rotation for that position in the linkage.

3. What are the applications of a velocity diagram for 4 bar linkage?

A velocity diagram for 4 bar linkage is used in various engineering applications such as in the design of machines and mechanisms, robotics, and in the study of motion and kinematics. It can also be used to analyze and optimize the performance of existing 4 bar linkage mechanisms.

4. What are the key components of a velocity diagram for 4 bar linkage?

The key components of a velocity diagram for 4 bar linkage are the velocity vectors for each link, the direction of movement of each link, and the instantaneous center of rotation for each position in the mechanism. It also includes the fixed pivot points and the moving pivot points for the links.

5. How does a velocity diagram for 4 bar linkage help in understanding the motion of a mechanism?

A velocity diagram for 4 bar linkage provides a visual representation of the velocities and directions of movement of the different links in a mechanism. This helps in understanding the motion of the mechanism and identifying any potential issues or areas for improvement. It also aids in determining the required input velocities for specific outputs of the mechanism.

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