Pulleys 1 and 2 rotate about fixed axes A and B. Rotation is transmitted from pulley 1 to pulley 2 through crossed flexible link 3. Radii R̵₁ and R₂ of the pulleys are equal. The transmission ratio from pulley 1 to pulley 2 is i₁₂=ω₁/ω₂=n₁/n₂=-1 where ω₁, ω₂, n₁ and n₂ are the angular velocities and speeds (in rpm) of pulleys 1 and 2. The length of the flexible link is L=2πR+4R*arcsin(2R/d)+2*sqrt(d²-4R²) where d is the distance between axes A and B, and R=R₁=R₂.
$3480$SFL,4L$