topic Re: Joint Trouble (not arthritis) in Fusion Design, Validate & Document Forum

Joint Trouble (not arthritis)

MrBradB — Thu, 19 May 2022 01:10:07 GMT

I inserted a scissor jack file from McMaster-Carr. I converted all of the bodies to components, named them and ordered them in the browser. I then turned on Capture History.

I began creating the joints that would allow the jack to move. I started with the arms, going from the base to the saddle. So far so good. I created a basic handle for turning the screw and I can't get that to work. I used a simpler example (I *think* I found it in the AutoDesk Gallery). The example used 2 motion links. I can get 1 to work but not the other.

Hopefully someone can show me what I'm doing wrong. I did this as a challenge to get comfortable with using joints. I'm mostly happy with the outcome thus far. None of the armature joints have set limits at this time. The was going to be the next step.

Thanks in advance,

Brad

Re: Joint Trouble (not arthritis)

hamid.sh. — Thu, 19 May 2022 02:14:42 GMT

I changed two joints from Slider to Cylindrical, so threaded rod can both rotate and slide in threaded pins, added a Motion Link (1 rotation = 1 pitch of thread which I think is 0.0625") and fixed handle to rod. I think in reality handle is two components with a revolute joint between them (Grab Handle to Body2). My changes are highlighted below:

It's hard to drive this model by mouse so I used Motion Study, though even with that there are only 100 frames so some steps are lost when I rotate 10 revolutions (10 * 360°):

Re: Joint Trouble (not arthritis)

davebYYPCU — Thu, 19 May 2022 02:14:43 GMT

Yeah there's a problem. Takes a while to figure it out.

The motion link works, for what it does, but is not supposed to work that way.

You need to set up a little differently.

The Revolve Joint is not correct. The handle and the Threaded rod, are currently a slip joint, turning the threaded rod, has nothing driving the handle, (if there was a grub screw locking these together, then the motion Links would not work.)

The simple fix, change the handle revolve to rigid.

Make a Revolve for the Threaded Rod, on the same Axis of the Slider joint of one Threaded Pin.

Delete the current Motion Link.

Make a Motion Link for the Slider and Revolve, for both Threaded Pins.

A bit harder to set up, is Step 2 above, making that one a cylindrical Joint, and controlling the turn to pitch ratio.

Might help....

Re: Joint Trouble (not arthritis)

MrBradB — Thu, 19 May 2022 20:43:48 GMT

Thank you both for your replies. This is the most complex joint system I have attempted to date.