offset axis for revolute as-built joint?

[ronmcgraw]

Hello all, I have a multi-joint hinge that moves a rotational axis "up and away" in outer space,  from where a traditional rotational axis would be.  I am trying to model a flush mount opening that uses this multi-joint hinge to determine its location to prevent the opening door from encountering an interference while performing the arc move.  I cannot figure out how to place the revolute axis away from an actual edge or face or pin etc... Is there a way to offset the axis?  Thank you in advance for any help you might provide!!

[jhackney1972]

You need to attach your model to explain what you desire.  

If you do not know how to attach your Fusion 360 model follow these easy steps. Open the model in Fusion 360, select the File menu, then Export and save as a F3D or F3Z file to your hard drive. Then use the Attachments section, of a forum post, to attach it. If needed, ZIP a F3Z file.

[ronmcgraw]

Thank  you John.  I have edited my original post to include the attachment.

[bwalker145 · Accepted solution]

Is this the motion you're trying to replicate? If so, all you need to do is fully constrain the appropriate hinge components to the floor and hatch (I used As-Built Joints for a quick fix); you already have the motion of the hinge prescribed in the existing joints. You can then set joint limits as needed.

Edit: Added file, joint limits not set in example.

[ronmcgraw]

wow! yes.  Thank you!  Just so I am clear and can learn from what you did... Like you said, I already set the joints in the hinges on seperate models and brought them into the model.  I pre set the limits of the hinges but it looks like those dont have any affect on the final model?  I also attempted to set rigid joints for the plate to the angle iron, centered and flat.  How did you get the plate to rotate on an arc and follow the hinges?  I didnt know how to put the axis in an arbritrary location for the plate to follow.  The problem I kept getting into was with regards to "ground to parent"...  I was getting alot of unexpected results when setting joints, the movements were very odd and off camber and some things like the latch, which I blanked out prior to attaching the model, would twist out of alignment when a different component was moved...  I will see if I can study what settings, grounds, joints etc.. that you have done.  Thank you so much!!!

[ronmcgraw]

I think I follow what you're saying.  I added the other hinge and only used constraints and was able to make it mimic the first hinge.  but.. I need to move the original hinge down .25" and cant figure out how to do that.  I have tried to edit the constraint but it moves the door instead of the hinge...

[bwalker145]

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@ronmcgraw wrote:

How did you get the plate to rotate on an arc and follow the hinges? I didnt know how to put the axis in an arbritrary location for the plate to follow.

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Sound like you figured this out, but just to answer: No offset joint location required for this example. Remember that your use and application of joints/constraints should mimic, when possible, how the real-world design will assemble & interact (Note: If you're familiar with GD&T, there are parallels in application). In this case:

1. The Hinge Lower Mounting Plate (A) will be secured to the Concrete Floor via some sort of fasteners, no motion allowed. I applied a rigid joint between these two components to reflect that relationship.

2. The Hinge Upper Mounting Plate (B) will be secured to the Hatch (either the frame or plate, I'm not sure your design intent) via fasteners, no motion allowed. I applied a rigid joint between these two components as well.

Remember that a Rigid Joint only forces a static relationship between the components involved, and does not otherwise restrict motion in the design as whole; you can rigidly join two components together, but they'll still be free to move about the design space until further constraints (rigid joint to origin, ground-to-parent, etc.) are applied. You have the Concrete Floor "ground-to-parent", causing it to act as the non-moveable anchor in your design (which is accurate to real-world).

The hinge linkages are what dictate/drive the motion of the Hatch. You accurately had the revolute joints applied to all of the hinge components, creating a connected & dynamic assembly. The final step was just to "attach" each end of the Hinge to the appropriate components. Since the Concrete Floor is anchored & non-movable, and the Hatch is connected to the other end of the Hinge, your are able to drive the motion/position of the Hatch with the Hinge.

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@ronmcgraw wrote:

I think I follow what you're saying.  I added the other hinge and only used constraints and was able to make it mimic the first hinge.  but.. I need to move the original hinge down .25" and cant figure out how to do that.  I have tried to edit the constraint but it moves the door instead of the hinge...

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I think you've got two main problems here, but should easy to fix:

1. Your first hinge is mated to the Hatch Plate, but the second hinge is mated to the Hatch Frame. You'll want these both to be mated to the same component, whichever one is correct for your design intent.

2. Your second hinge is not fully constrained to either the Concrete Floor or the Hatch; you can see both mounting tabs "slide" as you drive the motion. Try reapplying your constraints (either using the Constrain Components or Joint tools) to fully secure the mounting tabs to the appropriate components. Give these a try and let me know if you're still having issues.

Edit: Added a file with what I believe is your current design intent. It's not the cleanest as I didn't start completely over, but should give you some ideas. You can adjust the offsets in the constraints to play with the positioning of the hatch/hinges. I added a rest position of 0° to one of the hinge joints to ensure the assembly returns to 90°.