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# How do I use mates/relations to simulate rolling down a curved ramp?

Member Posts: 11 EDU
edited February 13
Hi, sorry if a similar question has been posted before. I'm working on a project where I send a vehicle down a ramp and try to stop as close as possible to a target point decided on the day of the competition. I've created the vehicle I plan to use but I'm still designing the ramp in Onshape.

One possible issue I thought of was the front of the vehicle (a wooden dowel) scraping the ramp due to the extreme "slope/rate of change" on the ramp. I want to know if there's a way to mate the vehicle to the ramp with a slider/planar? It's a curved surface so it's a bit different from similar things I've worked on. If the "mate" is possible, can I animate the car rolling down to check for any interferences (and is there something like interference detection for an animation?)?.

The whole situation looks something like this:

I'd also be open to taking any math-heavy solutions, I know with some geometry and heavy calculus this is definitely solvable. Thanks in advance to anybody who can help out!
"And now here is my secret, a very simple secret: it is only with the heart that one can see rightly, what is essential is invisible to the eye." - Antoine de Saint-Exupery, The Little Prince

## Answers

• Member Posts: 322 PRO
edited February 15
To get the general motion down, try using a single curved face. Make the front wheel & the back wheel tangent to that single curved face.

I'm not sure about spinning the wheels or animation if they are tangent to a curved surface.

Edit:
See below.

• Member Posts: 322 PRO
Try this something like this for the animation: Automated Ramp
• Gear relationship between each of the wheels
• Tangent relationship between the two of the wheels and the ramp
• Planar relationship between the side of the wheels and the side of the ramp, to keep things lined up.
• Tangent relation between the automation rod ant the body
• Gear relationship between the automation rod and the wheels

• Member Posts: 11 EDU
Try this something like this for the animation: Automated Ramp
• Gear relationship between each of the wheels
• Tangent relationship between the two of the wheels and the ramp
• Planar relationship between the side of the wheels and the side of the ramp, to keep things lined up.
• Tangent relation between the automation rod ant the body
• Gear relationship between the automation rod and the wheels
Thanks for the response! I tried what you did and got up until the automation rod. However, I encountered some errors when doing the gear relationship between the animation rod and wheels.

Do you know why that is and how to fix it? Thanks for all the help so far!
"And now here is my secret, a very simple secret: it is only with the heart that one can see rightly, what is essential is invisible to the eye." - Antoine de Saint-Exupery, The Little Prince
• Member Posts: 322 PRO
I don't see what the problem could be from the pics. If you want, you can link share the document and I will take a closer look. The assembly constraints can be fickle.
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