Dynamic Simulation - Calculate Cylinder force - over-constrained error?

[Sparky87]

Hi,

Having some problems with my Dynamic Simulation. I'm in a prestudy phase of an project and trying to quickly check how big cylinder needed to lift an lever arm. I'm trying to find the unknown force in the cylinder.

Problem is that I getting this error saying: "The meachanism is over-constrained by 1 degree":

 

I tried everything, I'm stuck. So I will be very thankful if someone could help me solve this problem?

Attached is the 3D-modell of the lever arm.

[JDMather · Accepted solution]

There are two parts reported missing from the files you attached - so I didn't spend a lot of time on this yet, but -

I would constrain such that the piston and the cylinder have a Prismatic Joint for the motion between the two. (rather than Cylindrical:3)

I would constrain such that there was a Point-Line Joint replacing the Cylindrical:4.

[Sparky87]

Hi, and thanks for your quick answer. Having some problems with the prismatic joints, I now I'am doing something wrong here but cannot figure it out... The cylinder and rod "explodes" and will not stick togheter? Would be happy if you could show some examples on my attached model?  

The attached model is only missing some simulation files not needed, and they are to big to attach here. To you have a functional model with after just skipping those simulation files?

[JDMather]

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@kristian.jacobsson wrote:

The attached model is only missing some simulation files not needed, ...

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No, I wrote that the assembly you attached is missing two part files.  I have no interest in the missing simulation files as they aren't relevant to solving the Joint problem.

See the attached assembly.

[Sparky87]

It should be ok now, please check the attachment?

[JDMather]

Not sure why you posted this assembly again.

Did you check the assembly I posted above in Dynamic Simulation Environment?

[Sparky87]

Sorry for that, this is very strange?! I sent this to an colleague for test before I posted it again, and it opens just fine!! How can that be...

But I have now checked the assembly you posted and I can now clearly see what I did wrong. Thanks alot!

One more thing, when I want to find the "Unknown Force" of that cylinder, then I use Jack and choose Prismatic joint, and then choose cylinderbracket edges on each side of the cylinder as reference? Is that correct?

[JDMather · Accepted solution]

You can use either the Prismatic Joint or the Revolution1 (number of degrees of revolution) as your reference.

I suspect you might need to calculate the number of degrees of revolution that give you the lift distance you need.

Whichever one you use - I like to set the initial position and then Right Click - Set Offset so that the initial position is set to zero.

I selected the end of the piston rod and the end of the hole in the cylinder as my Unknown Force - Jack reference points (use Select Other since these points are inside the assembly).

Select the reference joint you want to use (either Prismatic or Revolution) and how far you want it to move and the number of calculations.

In the above image I right clicked on the Prismatic position and set it as the graph reference.

File attached.

[Sparky87]

Thanks alot JDMather, you helped me out here