Dynamic Simulation - Ball on Track

[RobJV]

Hi,

Within dynamic simulation, I am trying to have a ball follow a track made of (2) rods,  I can do it if the rods are straight but I do not know how to properly apply joints to allow the ball to follow the tracks when they are turning.  Are there some tips on how to accomplish this?  I need to do this within dynamic simulation because I also hope to add a chain and sprockets with a ball holder to bring the ball back up to the top.

I am very experienced with Inventor but using dynamic simulation is somewhat new to me and I am not sure I can accomplish this.

Thanks,

Rob

[JDMather]

Can you attach the assembly here?

Have you tried a Spatial joint and 3D Contact joints?

Define Gravity.

http://forums.autodesk.com/autodesk/attachments/autodesk/78/295240/1/Loop%20d%20Loop.gif

[RobJV]

I have tried all 3 of those things at different times but obviously not correctly.  I will attach my assembly.  Please note that the track is not correct and is not realistic - only used to try to get the ball to follow for a little while.  (I know that is not fully constrained.)

Thanks for taking a look.

Files are INV 2013.

[henderh]

Hi Rob,

  We had a discussion about a similar model here: 3D-Contact-and-Spatial-Joints-Challenge

  As JD said, you'll need a spatial joint between the ball and the track to set up the degrees of freedom of the mechanism.  Add a 3D contact with some friction, apply gravity and it should get you going.

  I've attached an R2013 quick mockup simulation to illustrate. 

Thanks! -Hugh

[JDMather]

I will not have access to my 2013 machine until tomorrow, but a couple of things -

You only need one Spatial joint to get the ball out of the Grounded group and into the Mobile Group with 6 degrees of freedom.

Why did you create the ball from a cylinder rather than revolve a half circle or better yet, use the Sphere command?

You will need a little rotational velocity or at least a slight downward ramp to the track to start the ball moving, otherwise gravity pulls it straight down - and there it will sit when it hits the track.

Also you need the 3D Contact.

Well, I see Hugh posted an example while I was typing.

[henderh]

Sorry Guys, I didn't hit refresh before I posted

I added some initial velocity and a 3D contact to your assembly.  It seems like the curvature of the track is too sharp to keep the ball captive.

Best regards, -Hugh

[RobJV]

I will take a look - thanks for the example!

[RobJV]

Hi JD,

I understand the slight downward section of the track being needed - I was just going to adjust gravity angle to get the ball moving in the meantime.  (The track is not correct - just did quickly to get something going.)  I know about revolving and sphere - felt like being different and if I did not do that you would not be able to ask me any typical JD questions. 🙂

I am going over Hugh's example right now and will post more if I need more info on what exactly was selected for the two objects.

Thank you guys!