What is a Four Bar Linkage and How is it Used in Machine Mechanisms?

[rachelleteo]

anybody knows about 4 bar linkage??
there's a crank and slider mechanism and i need help... i would like to know more about the crank slider and what is it made of?? what is that slider made of?? roller?? 2 bars and a square metal?? help! thanks alot...

 

[brewnog]

If it's in a mechanics textbook, it doesn't matter. It's just a model, it means that the slider is allowed to slide but restrained in other directions of movement.

 

[rachelleteo]

emm.. no... what if it's not in the textbook... and i am suppose to make the slider out... do you or anyone have any ideas?? thanks... cos currently i am having my industrial attachment thingy and i am thinking of some machine improvements... and need to design something like that... and i do not know what that thing is actually like.. what i know is just the model and the drawing..

 

[brewnog]

Well I'm not sure I understand.

What are you making? Could you use a smoothed block and some polished surfaces? Perhaps a t-slide? Or just some rollers? If you provide more information we might be able to help!

 

[rachelleteo]

it is not easy to explain... emm... cos i am designing some improvements... and i just want to know how a crank slider work and how is it like(for the real) thing...
i am still designing and i need to know it just to visualise whether it can be fixed onto that machine or not... cos due there is some obstructions, i got to first visualise and see whether will it works..
thanks so much for your help...

 

[ceptimus]

A normal piston engine is an example of a crank slider. The piston is the slider. The fourth bar in a four bar linkage doesn't move - it is the frame that the other (moving) bars attach to.

 

[rachelleteo]

thanks so much for your help, ceptimus... so, is the piston hydraulic?? or pneumatic?? normally for a four bar linkage, a motor is attached to trigger it to move the bars, so for this crank and slider, it is the slider that is using a piston to move the rest of the bars??

 

[brewnog]

You're not making any sense.

A four bar linkage is just a simplification for a mechanism found in many machines, the piston engine is just one of them. In a car engine, the piston is powered by expanding gases being combusted. On something else, the mechanism may be hydraulically actuated, or driven by an electric motor, or by a big hamster wheel, whatever.


Show us your application and we'll show you how it works. Perhaps you have a motor turning your crank, perhaps you have a compressed source pushing a piston, all you've told us is that you're using a four-bar linkage!

 

[rachelleteo]

so the four bar linkage is a simplification for mechanism found in machines, i got what you mean. because what i have learned are those theories part of this four bar linkage and it doesn't tells me that it is the simplification for mechanism found in machines or maybe i didn't make good notice of it.

well, i don't have the application, because i am trying to design out and four bar linkage just come to my mind. what i am going to design is a mechanism that can flip parts (from die casting) when the part is being dropped from the top by a robot arm. i am still learning as i am an IA (industrial attachment) student and that is my task and that is also why i want to know more about this four bar linkage.

you get me now?