Feasibility of Adoption of Double-Crank Inversion of Four-Bar Chain as a Substitute for a Gear Box

Abstract

In this paper, a complete investigation with respect to the kinematic properties of double-crank inversion of a four-bar chain is presented. The observation from preliminary analysis of the coupler of the double-crank inversion shows that all points in the coupler plane trace a circular path with variable angular velocity. It is verified through graphical kinematic analysis, i.e., drawing mechanism configurations for its different positions in one cycle of operation of the mechanism that for a four-bar chain O1ABO2, where O1O2 = 15 cm (fixed link), O1A = 40 cm (input driving crank), AB = 35 cm (coupler), and BO2 = 50 cm (output crank), each point on the coupler plane has a specific band of variation of angular velocity and the points lying at a radius of 5 cm–8 cm from point A have its angular velocity variation band up to 8–12%. There are possibilities of tapping motion from various points on the coupler plane to get output shaft speed variation over a certain band.The above fact motivates the investigator to explore the complete range of such mechanisms. The outcome of this exploration may reveal a new design of gear box in which several output speeds could be available with a very low band of variation of angular velocity. There are many process units, for example, low capacity crusher, chopper, cutter, mixer, plastic shredders, etc., for which such a transmission can be used instead of gear box. The most important shortcoming of a presently available gear box that is manufacturing synchromesh and/or the gear itself can be overcome by adopting double-crank inversion.