A circular cam whose centre is offset from shaft O₁ rocks a red roller arm. Changing eccentricity e changes the motion. Compare it with the translating plate-cam follower to see two different outputs from rotation.
At 1×, 15 rpm takes 4 seconds per cycle. Playback scale changes elapsed time only, not the motion relationship. Drawing scale stays fixed during playback.
Change blue values → use the button to return to the drawing
R, d, L: 1–10,000 mm; 0.1 ≤ e < R; 0.1 ≤ r ≤ R (mm). Require d > R+e+r+1 mm, |L−(R+r)| < d−e and d+e < L+R+r. Speed: 0.1–3,000 rpm.Blue cam centre E orbits shaft O₁ and pushes the green roller. The red arm rocks about O₂; its roller position is solved to remain tangent to the cam.
Parameters are cam radius R, eccentricity e, roller radius r, arm length L and pivot spacing d. E = (e cos φ, e sin φ), O₂ = (−d, 0). Roller centre B is the upper intersection of |B − O₂| = L and |B − E| = R + r; contact is E + R(B − E)/(R + r). Ideal planar motion assumes maintained contact. Dimensions must permit intersection throughout the cycle and keep the pivot outside the cam. Springs, gravity, contact forces, separation, friction, roller spin and manufacturability are not calculated; high-speed contact is not guaranteed.
