Differential motion simulation

[SpringHalo]

I'm attempting to make a tank differential system similar to this one and figured out how to get the gear modeling application in NX, and how to work it, but now I'm struggling with the motion simulation. I'm sure the two driving gears are supposed to be revolute, and the outer gear should be revolute jointed to the center, but I can't figure out how to get the pinion gears working so that they:
A. interact with the driving gears (through the gear function)
B. rotate around their own axes while rotating around the outer gear's axis
I'm thinking it has something to do with revolute linking the outer and pinion gears together, but when I do that, the gear function no longer works.

Any insight as to why this is happening is appreciated!

 

[Toost]

You are making "the major beginners mistake", trying to setup all at once.
When defining mechanisms, do it one link/ joint at a time and test each joint/link ( if possible) before adding the next.
For example, the "outer" link in your part is a link and it has a revolute joint connected.
This means that the "outer" takes part in the simulation solving, but since it is allowed to spin freely, ( nothing driving or controlling it) it only adds to the overall degrees of freedom and the result is that the solver might return a message similar to "not yet solvable". -There are too many degrees of freedom.
I.e if you would drive one of the "spurs", should then the "outer" turn or not at this stage when nothing controls the "outer" ?
I hope you see my point here, delete the "outer" link and it's joint, delete 3 of the 4 pinion links / joints, then make 1 Spur drive 1 pinion which drive the other spur whilst the "outer" is static.
When that works, then it's time to define the "outer" as a link+ joint.
When the entire mechanism is working, you can add the other three pininons which aren't really necessary for the CAE mechanism but are necessary in the real differential because of the loads.


I will play around with the model.


Regards,
Tomas

 

[SpringHalo]

I figured out the problem; the origins of the two linked pieces of the revolute joint (the fixed bit) have to be at the exact same point, and the revolute joints both need to be with respect to the same object (so the two spurs need to "revolve" around the outer bit even if they aren't touching)

Thanks!