[Ether]

Equation of track: radius(θ) = a+1 + sin(θ)

"a" is the distance from the pivot to the "dimple" in the curve.

Attached figure "eqn.png" shows track curve for a=0.2

If you make "a" larger, say a=1, you can get a track with virtually no dimple (it may slide a bit smoother). See figure "no dimple.png"