Computer Aided Synthesis of a Four-Bar Mechanism For Soil Tilling

Abstract

A four-bar crank-rocker mechanism has been synthesized to loosen the soil over which a ridge could be formed for root crop plantation or loosen the soil over an area where the soil needs to be removed. The mechanism can loosen the soil up to a depth of 300mm below the soil surface. Synthesis started with a four-bar mechanism generating a symmetric pear shape coupler curve. A double effect loosening is obtained by the arrangement of the mechanism in a mirror image of itself so that the two mechanisms acting together at the same time can lift the soil over an area to a height of about 400mm and drop the soil over the same area over which it was lifted thus effecting further loosening. With a graphic interactive programme written in the C-language, the fixed points, circle points, lengths, and the coupler point of interest of the chosen mechanism were altered and the resulting coupler curve plotted. The process was repeated until a suitable coupler curve and acceptable dimensions and fixed points locations were obtained. Keywords : Computer synthesis, four-bar mechanism, fixed point, circle point, coupler, crank-rocker. Journal of the Ghana Institution of Engineers Vol. 5 (1&2) 2007: pp. 13-20