Theory of Machine
The Ackerman steering gear mechanism is preferred to the Davis steering gear mechanism, because

Both (A) and (B)
The Ackerman steering gear is most economical
Whole of the mechanism in the Ackerman steering gear is on the back of the front wheels
The Ackerman steering gear consists of turning pairs

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Theory of Machine
The displacement of the reciprocating roller follower, when it has contact with the straight flanks of the tangent cam, is given by (where r₁ = Minimum radius of the cam, r₂ = Radius of the roller follower, and θ = Angle turned by the cam from the beginning of the follower displacement)

(r₁ + r₂) (1 + cosθ)
(r₁ + r₂) [(1 - cosθ)/cosθ]
(r₁ - r₂) [(1 - cosθ)/cosθ]
(r₁ - r₂) (1 - cosθ)

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