Gravity Experiment Simulation

[billjenkins]

Is this type of gravity experiment possible with dynamic simulation?

http://www.youtube.com/watch?v=NGZ6odGcn-E&NR=1&feature=endscreen

I made the cone ramp and double cone but the cone either goes the wrong way or only moves a few inches in the correct direction and then gets stuck. I’m using 3D Contact Joints and Spatial Joints and Gravity Force.

Version = Inventor Pro 2009

Thanks,

Bill

[JDMather]

Attach your assembly here.

[billjenkins]

Thanks!

Bill

[billjenkins]

Did the .IAM  open for you?

Thanks,

Bill

[jingyi.liu]

Hi Bill

I tested your model by Inventor 2013, it should be ok to simulate the motion, but you need to take care of belows:

• there is no need to add joint like spatial:2, spatial:3 and 3D Contacts:5, they are redundacies;
• move your Cone to a appropriate postion,or you can adjust the property of planar:1
• set friction value of 3D contact, otherwise, the cone will slide down rather than roll down.

[billjenkins]

Hello Jingyi,

I deleted the extra 3D Contact and Spatial Joints. I experimented with the Planer 1 properties by selecting Enable Joint Torque of dof 1(R) and I also played with the other two dof tabs. I didn't know what number to use or also what option to select. You narrowed the issue down for me but I need some specific settings for Planer 1 properties if you would please.

You mentioned the position of the cone and suggested that I place the cone in the proper location. It is in the correct location and the cone should move -- up -- the incline ramp.

I also would appreciate links to good dynamic simulation tutorials. I have been successful simulating some pretty complicated stuff but many times I get stuck with the simplest things. I know I need a much better understanding of inserting joints and forces like friction and …

Thanks,

Bill

[jingyi.liu]

Hi Bill

You are welcome.

As you have pointed out, you can move the cone up to the inclined ramp, then the gravity will make it run down. Of course you can adjust its position by setting planar1 property, but i prefer to move the cone in assembly environment, it's much easier.

For 3D contact, you can try to set the friction value to 0.1, then set the time to simulate and internal steps, for 3D contact simulation, it's time consuming, so be patient.

About DS tutorial, I knew little except Inventor help, you can send me email and I will let you know when I find something useful. (jingyiDOTliuATautodeskDOTcom)

[billjenkins]

Hi Jingyi,

I have the 3D Contact to .1 for friction and no settings for Planar 1. As soon as I start the simulation the cone goes away. Gravity is set to 386.220472440945 in/s^2. I don’t think gravity is making the cone fall but instead I think I have a conflict. 

When I first tried the simulation it did stay on the ramp but the movement would stick and about half the time it would move in the wrong direction down the ramp. The cone starting point is at the low end of the ramp and then it should move (up) to the high end of the incline as the video in the first message demonstrates. Of course the CG or center of the cone will descend as the cone moves towards the wider opening of the ramp. It’s an interesting paradox that I bet some other Inventor users would like to try plus it would really show off Inventor’s capabilities if it can do it. 

Since the cone immediately disappears, I wonder if I should bring the parts into a new assembly file and or if I should give up. Ha! From the start I was skeptical if I could set it up correctly and if dynamic simulation could do this type of physics simulation. It seems that I’m asking a lot of the program but I simply don’t know the limits of realism that dynamic simulation can do.

It’s not a big deal but I will try any suggestions you may think of. I’ll give it a few days then I’ll just check the “Accept As Solution” option.

Thank You,

Bill

[jingyi.liu · Accepted solution]

Hi Bill

Could you check the settting of simulation player, especially the final time and number of images (steps), I guess your i steps are so small, the cone has dropped down through the ramp during the internal time, and 3D contact doesn't take effect at all.

[JDMather]

---

jingyi.liu
I'm not sure you are following the intent of the design experiment.

[billjenkins]

Good News!

I looked at the time and steps and found 30 seconds and 15 images. I have no idea how images was set at only 15. I changed the numbers to 15 seconds and 1500 images and the simulation works smooth and takes a very short time to complete. Below are a few other changes I made to the original assembly and settings to achieve the proper movement.

1. I modified the ramp to an incline of 2.5 degrees. 
2. I changed the thickness of the ramp sides from .0625” to 1” and added a full round over fillet to the top edge.
3. I changed Gravity to only 70.000in/s^2.
4. I used .1 friction on the 3D contact.
5. I did not input any settings into the Planar standard joint.

Changes 3, 4 and 5 were definitely required but I’m not sure if the first two changes made any difference. I don’t use dynamic simulation enough to really understand the logic but I’m always amazed when I finally get a smooth realistic end result.

I know the gravity setting is not realistic but at least it works without any extra forces. I guess if I had the properties of the cone set correctly then I could increase gravity back to the default number and probably decrease the time but like I said I really need to watch some dynamic simulation training videos.

Before I check the “accept as solution” I want to make a quick video and post the link here. I sure do appreciate the help.

Bill

[billjenkins]

I made a short video of the simulation.

http://www.youtube.com/watch?v=bO1Kbyk5oPA

Thanks again,

Bill