I’m trying to make a wheel rotate at variable speeds, so I thought the easiest way to do this is to add a driver to the x-rotation value and write an expression to increment it a certain amount each frame, like this:
self.rotation_euler[0] + 1
I also tried referencing the property in an input variable, but the wheel stays still either way. What am I doing wrong?
Drivers don’t work like that (at least as far as I know). Drivers are used to evaluate expressions, not to execute commands. You can make property A follow property B (or multiple ones) by specifying a formula how to compute A from B.
I’m not knowing what exactly your setup is. If it is just this single rotation value you need to animate, it might suffice to keyframe it directly (and if needed, tweak the curve in the graph editor).
If you want to increment something by each frame, use #frame, which returns the current frame value. If you want to increment more than 1 each frame, just multiply #frame by a constant, or edit the curve in the driver editor.