Bicycle Chain

[Gene]

Ok, so I've been trying to figure out the best way to animate a chain and sprocket like on a bicycle, but I see no easy way to do this.

 

The easiest way I can think of is to use a path in a chor, and add a bone to each link in the chain that would follow the path.

 

Then, I guess I would have to constrain the path to the sprockets.

 

Please let me know if you have any better way to do this??

 

Oh, another question...why isn' it possible to add a path in an Action? Wouldn' this be useful?

 

Thanks,

 

Eugene

[ddustin]

Gene,

I have a model of a BMX bike that has a chain on it that goes around.

 

I got from somewhere else.

 

Interested?

[pwknox]

Eugene,

 

I have never attempted to animate a chain, but I do have an answer for the path in an action question.

 

A path is just a spline that you then constrain bones to. I have a model where I needed to constrain bones to a spline so I just added the spline to the model. The bones are constrained to this spline (rather than a path) in a relationship or action. The spline follows the model and does not render.

 

So, you have all the benefits of the path in the action. The only downside is that the spline is now part of the model not part of the action. The action would not then be re reusable without a matching spline in all models.

 

Oh, well. You only get half of what you asked for.

 

Phil

 

PS: I remember reading about someone animating a tank tread. A bike chain would be similar I think.

[Gene]

Hey Dave,

 

I think I have that Bike somewhere....was that the one from Animation Pit Stop?

 

I am going to give this a shot with a simple model before attempting anything big.

 

Phil,

 

Now that seems so obvious, I don't know why I couldn't make the connection...but you know how it goes when you've been staring at your model for a couple of hours...the other parts of your brain stop working.

 

Thanks Guys.

 

I will post my results...

 

Eugene

[ddustin]

Gene,

Yup I think I did get it from the pitstop.

 

The spline path sounds like it might work.

 

 

David

[Gene]

Well,

 

I tried the spline path, but I am obviously doing something wrong because the bones just don't line up the way I want and the bones go out of orientation.

 

So, I just went straight ahead and moved the each link to the next position forward (i.e. one link ahead) and then just repeated the action in a chor.

 

Chain

 

You'll notice that there is a slight jump in the chain, but that was just the way I positioned the bones on the last frame. I wasn't too picky since this was just a test.

 

I will have to figure out a more accurate (and easy) way to do this.

 

Thanks all,

 

Eugene

[jamagica]

I think the jump looks natural because there are ridges on the gears...

[ddustin]

Gene,

 

I agree there has to be an easier way.

 

If I understand you right, you moved each bone a certain amount then just repeated it to give the illusion the chain was rotating.

 

What I've struggled with in this area (I had to be specific as I struggle regularly ) is constraining a group of bones to a path or spline is that you need to set the ease for each bone to get the right spacing. Both at the beginning and end.

 

When I was doing the animation for the rolling machine, it took for ever to get the purple material to follow the path correctly. There were 42 bones in that material to get it to flow similar to the actual material. I also had a dwell portion where at a specific time in the animation, all the bones had their ease set to a specific value for 50 frames or so.

 

What you did looks great! When you apply it to your forklift model you won't be running in an oval. I don't pretend to understand this but couldn't you use some type of kinematic chain?

 

David

[Gene]

Hey Dave,

 

This was sort of for the forklift, but actually, I will probably just use an alternate method.

 

As for the Kinematic Chain...I am not sure really how these are used or what happens when they are applied.

 

I sort of remember them being used on character rigs to give bones a target or something like that.

 

Can anyone elaborate??? Might give me another option.

 

Thanks,

 

Eugene