Hi Alex,
If it is a circle, a center Null could be the Parent and it rotated anything below it. With the Rotation angle, anything can be defined.
Does this that sounds good? I’m happy to check out the simplest solution for that.
Here is an example file, with two speed calculations, as the inner and the outer wheel have a different distances to travel. I made the wheels large to show the effect. The radius of the inner wheel is connected to the outer. Just adjust the radius [disc.out] and the P.Y (P.Y for both – in and out, but you can as well connect those)
Scene file [01]
https://www.amazon.com/clouddrive/share/Fpo8rnwd1j8MQNfbif50ms9T5r2O6ItbOWo1gBZWZkk
A very simple set up, yet my favorite is based on the length of the MoSpline. Even an back and fore will affect the rotation of the wheel perfectly.
Scene file [11]
https://www.amazon.com/clouddrive/share/t10XG0oORp31v1I4tzpAfZUAHKDp3ILkBSlpaxntruN
To have an un-even track, here is an example: [21]
https://www.amazon.com/clouddrive/share/JQJT6JTOZH20H96NOu19V4XAmNxFe2FSwCJ62yMZyk4
To keep a vehicle normally on a track, I do it with a target tag, whereby the target is a position (Null) in distance on the same spline, and the up vector is the parallel spline (Another Null). If the track is a closed spline, the Null that is a little bit ahead, needs a different Offset, instead of 0% to 100, it needs 5% to 100% to 5%, example here: (move one of the circles to see the effect how it really works)
https://www.amazon.com/clouddrive/share/DXdaK8KONAQnEbvLYLyLsrPdKbW9ksynLJ1YSbJoGAh
If the file was more an example, please advice what details are needed.
Cheers
Edited 10:10pm PST