The green and orange cams have different Archimedean profiles (pitches p1 and p2, p1 = 2.p2). The green one is input.
Two cams rotate in opposite directions with different speeds, like in a drive of two gears of different tooth numbers.
Transmission ratio = 1/2.
Pitch of the Archimedean profile must be big enough to prevent possible jam.
A spiral spring can be used instead of the weight.