Pinion 1 rotates about fixed axis A and meshes with internal gear 2 which rotates about fixed axis B. The tooth profiles a of gear 2 are straight lines. The transmission ratio is i₁₂=ω₁/ω₂=n₁/n₂=z₂/z₁=2 where ω₁ and ω₂ are the angular velocities, n₁ and n₂ are the rpm and z₁ and z₂ are the numbers of teeth of pinion 1 and gear 2.
$2304$SG,3L$