train carriage on curve

Hi, I’m having issues with animating a train.
See attached diagram
The bogies (b) follow the path exactly and the straight line distance between them is constant because the carriage body © is a fixed length. So when following a bend the distance along the curve is increased (black line) but the c remains the same. How do I fix it so I can animate the position of the front bogey and the rear one will be at the correct distance behind?

This was asked before but with no apparent solution: is there a way with the new animation features?



I think you need to model each bogey (i never knew they were called that!) as separate objects constrained to follow the path orientation. Then the right combination of parenting should do it, where either the front bogey is the master (Parent the boxcar to the front bogey. Parent the back bogey to the box car.) or the box is the master (the box follows the path, and the bogeys are the child of the box), or some combo. But you want the back bogey constrained to follow the path, and not just be a child or copy rotation of the front, otherwise it will jump the tracks.

thanks for your prompt answer, still can’t get it to work tho’- any other work arounds?


I’ve been trying to accomplish this task as well. I know it’s been a while since the thread got started, but hopefully you can still remember your thinking when you made the suggestion.

I know that both ‘bogies’ need to have path constraints so they don’t jump the track. However, how is that possible while also allowing them to be parented to the box? At that point Blender would be getting conflicting information regarding the position/rotation for them; one from the path and one from the box.

I’m sure there’s a way to accomplish this, but so far everything I’ve tried falls apart.

You could use this car rig and adapt it.

PS: I thought those were called “trucks” not “bogeys”?

Not sure what you will use it for, but I animated a robot on a track the other day, and used an action constraint. Paths didn’t work like I wanted them to. I would reccomend animating the bogeys and making a bone that moves forward be the action constraint target.

I would suggest having an armature going between the bogies. You can then parent the body to the armature.