Ring Collision Problem

First of all, thanks to all the helpful people on these forums. I have solved so many problems just by using the easy search button.

Now for my question: For a school project we have to make a “roller coaster” and I was going to use blender to do a simulation of it. It’s a washer going around a wire track. I have the washer and track, but I’m having troubles with the collisions between the washer and wire. The washer seems to always bounce and never stop. At first I couldn’t even get it over the first hill, but I’ve tweaked settings and managed to make it work. Now when it rests before the loop, it just sits there and bounces, which isn’t very realistic at all. Half the time the wire is going through the middle of the washer too.

I have the collision bounds as triangle mesh, have the friction down all the way to 0, and have restitution at 0 for both. The setting that I’ve noticed seems to make the most difference is “Margin” in advanced settings under the physics tab, so if anybody could explain exactly what that does, it would be great. All the blender documentation is too old to help lol.

I have attached a .blend file so you can look at it. As a side note: I know that the lighting and materials are terrible, but I’m going to worry about those after I get the actual animation to work.


rollercoaster.blend (187 KB)

You could use logic bricks to make it gain velocity when you press a key. A real roller coster (As far as I know) does not use collisions. Also make sure that actor is enabled and that you are not using a static object.

I dont know alot about the margin, but I will check out the blend when I get back from school.

A little tip:

In the Game menu, check Show Physics Visualization and you will see how the physic engine deal with the objects ( this way you will see the problems in the file ), also as Sunjay03 stated, you shouldn’t use collision, try for example to disable the collision and use an IPO to play the “simulation”…

If you need an example just ask…

Hope this helps you, :slight_smile:
Cya =)

Sorry, I should have made myself more clear. It’s not an actual roller coaster, it’s just a washer going through a wire.
Thank you PadrePioX. I checked the “show physics visualization” and I was able to see that it was recognizing my wire about a unit off, disabled Compound for the bounds and it was fixed. And for my washer, it thought the washer was bigger than it actually was supposed to be. Apparently there’s a minimum size or something for rigid bodies, because after I scaled everything up, I was able to get the washer the size that I wanted it to be. I’m not sure if there’s a better way, but it works. Now I’m just having trouble getting it to fall realistically, because it seems to stay the same speed now.

When you scale objects use always Ctrl+A to apply the scale or the physic bounds will get scaled in a bad way; also for the speed you could use a motion actuator, using a local linV, take a look at the .blend…

Hope this helps you, :slight_smile:
Cya =)


rollercoaster.blend (182 KB)

Thanks for telling me how to apply the scale, that makes sense now. Thanks for all your help, I’ve got it figured out now.

Nice, if you need other help just ask :slight_smile:

Good Luck,
Cya =)