Discussion: “Synthesis of 4-Bar Linkages Adjustable for Several Approximate Straight-Line Motions of a Coupler Point” (Beaudrot, C. B., 1969, ASME J. Eng. Ind., 91, pp. 172–178)

Closure Although each of the three design procedures will yield a mechanism for the chosen specifications, there are several factors that must be considered before the derived mechanism can be deemed useful. First, if the crank length is inordinately short when compared with the other links or with the distance from A to C, then large torque multiplications can occur if a load is to be placed at C. Second, if the minimum transmission angle becomes prohibitively small, then force transmission through the mechanism becomes inefficient. Third, since the straight-line paths are only exact for the initial design position, their quality and length for crank rotation are not immediately known. Finally, the mode of operation of the mechanism may turn out to be either crank-lever, double-lever, or drag link in the different adjustment positions. However, since oidy a few coupler points corresponding to positions near the original crank location will trace the desired approximate straight line, full rotation of the crank is not essential to its generation.