I imagine the red gear is the one backed with a motor rotating at a constant speed. Which would explain why it never slows down or speeds up. The blue one is b

I imagine the red gear is the one backed with a motor rotating at a constant speed. Which would explain why it never slows down or speeds up. The blue one is being entirely driven by the red. It slows down because moving 2 notches at a greater diameter requires less rotation than moving 2 notches at a lesser diameter. It then speeds up because moving 3 notches at a lesser diameter requires more rotation than moving 3 at a greater diameter.