# How to animate a steam train on a track?

hey guys i need a little bit of help. hope you guys can help me out. So here’s my situation, hope you guys have seen a steam locomotive before, if not, well i have a video for you to look at to see what i am trying to achieve.

I need this for a school project. i know how to get the steam effect, i just want to try to get the wheel spin synchronized with the movement along the tracks. if you’ve ever seen a steam locomotive you know how complex they can be as a machine. any help is greatly appreciated. thanks.

-AJ

P.S. if i can achieve a doppler effect with the speaker object, that would be simply awesome

also just to clarify, i do know how to animate a steam locomotive’s wheels, drive train, and rods, i just don’t know how to synchronize them moving on the track. again, any help is greatly appreciated. thanks

-AJ

You will probably need to set up a driver (I can’t remember off hand how this is done but you could search for it) so that either the forward motion of the train drives the rotation of the wheels or vice versa. You calculate the circumference of the wheel and set the driver so that train will travel this distance during one rotation of the wheel.

math, i like math but my math classes make it a pain cuz everyone else gets bored

Here is a blend file of an easy example; if you move the cube along the x-axis the circle will rotate around the z-axis. The circle has a radius of 1 blender unit and thus a circumference of 2pi units. This circle has a driver on z-axis rotation and is parented to a cube, the movement of the cube will drive the rotation of the circle. Since a full rotation of the circle (360 degrees is 2pi radians) there is a 1 to 1 relationship between the movement of the cube along the x-axis and rotation of the circle around the z-axis. Thus in the generator panel you need only change the 1 to -1 to alter the direction of rotation. You just have to change the value of this 1 in relation to the diameter of your wheel.

driver.blend (388 KB)

hm, thanks alot i’ll have to test this on my animation. test animation video to follow hopefully. but also, by 2pi what do you mean? the radius is one blender unit so one blender unit equals 2pi units?

2pi means 2 x pi which means 2 x 3.142 = 6.28. So if the radius is 1 blender unit then the circumference of the wheel is 6.28 blender units

That’s a job for Copy Rotation and Transform Constraints.

sorry i’m using 2.5 not 2.49…

also another question. does a driver effect it if it’s following a curve? it is a train after all!

Come on, look at 2.5 has the same constraints too. Look first please.

yea i finally figured it out. thanks for your help everyone!

-AJ