Rigging Car wheel, local axis and child of

Question

I have been following this tutorial on how to rig a car wheel: Blender How to make a Tire Roll - Tutorial Constraints

I don't follow exactly the tutorial as I am using the local axis, so that I can drive my car in a straight line in all directions. The problem I am having is that when I try to Parent the "WheelRig" to "MainController", the wheel stops spinning. So I used the constraint "Child of", and the wheel spins almost as expected.

The problem I am having is that if you rotate the "MainController" say 130 degrees in the Z-axis, and move the "MainController" in the local x-axis, the wheel spins backwards.

If I unparent "WheelRig" from "MainController" and rotate the "WheelRig" as above it works.

So what can I fix this? Why isn't the wheel spinning if I just use "Set Parent to ..."?

I have uploaded the .blend-file to my Dropbox, so you can download and have a look. (Just close the login to dropbox if you don't have and account and you can download the file)

Wheel_Rig_v01.blend

Answer 1

In the Transformation constraint on the Tyre object change the Mix entry from Add to Replace.

Edit: Oops, just noticed that messes up the rotation around the z-axis. But you can use a Driver instead.

First remove or turn off the Transformation constraint.

In the 3D Viewport select the wheel(s) object. Then click the Item tab of the the tool-shelf panel (or N-panel). Right click the relevant rotation axis (x in this case) and choose Add Driver.

In the Driver window click on the driver (X Euler Rotation in this case). Then click on the Drivers tab of the N-pannel. Set the type of the driver to Scripted Expression. As the Expression write -var * 1.72787". As Driver Variable Type choose Transform Channel. As the object choose the WheelController (or MainController) Object. As Type choose X Location. As Space choose Local Space.

Now the wheels should rotate according to tot the orientation an direction of their controller object (while not rotating around a unwanted axis when the controller object does so; sorry for my initial advice)