I'm trying to make an odometer that behaves like a real mechanical odometer. Each dial needs to advance one number when the previous dial makes a full roatation. Setting each dial with an incrementally smaller spin modifier means the dials are constantly moving, which I don't want.

The attached file shows what I'm trying to do and what I've been able to do so far, but getting there is a pain in the butt. The dial on the right is constrained to "shaft" in the Motion tab with at -180° to start, then rotated to 0° at 15 keyframes, then rotated to +180° at 30 keyframes to achieve a full 360-degree rotation. The next dial is keyframed to move 36 degrees  when the previous dial makes a full rotation.

Does anyone have a better way of doing this, or know an easy way to loop each dial once I've keyframed a full rotation? I'm sure there's a good reason Carrara only works in 180 degrees, but right now I can't think of it. I'm about to lose my mud here!

Thanks in advance!