Help assembling hydraulic cylinder

[nickenglish8]

Hello all and thanks in advance for any help.   I am trying to create a visual for a project I am working on that needs a hydraulic cylinder connected to a moving arm.  I have created some joints in the assembly to try and see how the arm will move has the cylinder moves in and out.  However, when I try and make the last joint, I get and error/ warning.  I am not sure why it will not let me create the last "revolute" joint and have them all tied in together.  Could anyone take a look at the file and see what my issue is?  Thanks!

[TheCADWhisperer · Accepted solution]

@nickenglish8 

Are all of your sketches fully defined?

Are there any unresolved issues highlighted in your Timeline?

Does Ctrl b (CMD b on Mac) return any Warnings?

Are your components lined up?

See Attached file...

Anytime you are tempted to use Move command - you should STOP and ask questions first.

Move is sometimes the right move (pun intended), but usually not.

Anytime you are tempted to use Capture Position - you should STOP and ask questions first.

[nickenglish8]

THANK YOU!! So, I see now that the brackets at the bottom are not lined up with the brackets at the top.  I assume this is because I "moved" them at some point.  This is why it would not allow my assembly?  You have it working correctly even though it is still misaligned.  Is this because of where you made the "joint point" on the outsides of the bracked and cylinder?  I was trying to do the joint in the center of both faces. 

How do you know when to use "move" ?  Should I use "move" to realign the components?

Thanks so much!! 

[TheCADWhisperer]

---

@nickenglish8 wrote:

 You have it working correctly even though it is still misaligned.  Is this because

---

I used Cylindrical Joint rather than Revolution Joint.  Cylindrical Joint has a Rotational and Translational degree of freedom.

---

@nickenglish8 wrote:

How do you know when to use "move" ?  Should I use "move" to realign the components?

---

Don't use Move.  Ask questions at any time you are even tempted to use Move.  There is almost always a better way.

Use Joints to align components.

Sidebar Discussion:

Joint theory becomes very complex if you start to get into Dynamic Simulation analysis (Fusion 360 does not have this functionality - so is a bit of a side-road discussion).

Two Revolution Joints would actually over-constrain the system.

In the real world we cannot manufacture perfect parts.

There has to be clearance between moving parts to permit them to move.

Therefore the piston can actually twist a bit in addition to the translation and rotation because of the clearance between the pin and the hole at the end.

[nickenglish8]

I have been working at it, but I am still struggling some.  I have added my second cylinder, and it works to some degree, but I am having to use cylindrical joint instead of revolute because I assume something is out of line, but I can't figure it out.  The motion is still not working as it should in the real world, but I'm not sure how to resolve the issue.  

The cylinders do move the arms as i expect, but these are hydraulic cylinders that hold still while they are not being activated.  If you move the parts around on my design, One cylinders motion will allow the other hydraulic cylinders ram to be pulled out or pushed in.  This would not happen in the real world as one cylinder would hold its position as the other moved.  I don't know how to fix this.  I can't ground them as they still need to move, but they need to hold when they are not "activated".  

Thanks for the help!!