A Modified Design for λ-Type Double-Cranks to Approximate a Straight Line

Abstract

Double-cranks containing a Chebyshev-dyad are investigated for their use as a straight-line mechanism. The three available design degrees of freedom have been used for the optimization of the minimum transmission angle, for the minimization of the maximum deviation and for the length L of the straight-stretch in the coupler curve. The resulting double-cranks are shown to have deviations that are about half as large as for those in which the coupler point lies on the extension of the coupler. For any maximum deviation, the length L of the straight-stretch also appears to be about 1.5 times as long as the one obtained when Ball’s point lies at the base of the design. A graph showing the maximum deviation as a function of L allows the designer to pick his choice mechanism. A table also will be of help to find accurate dimensions of the mechanism that yields a given deviation or a given length L of the straight part in the coupler curve.