Performance of a curved animal drawn tillage implement

The performance of animal drawn implements should be within the range of the pulling capacity of draught animals. The effects of design and operational parameters such as tail angle, side rake angle and radius of curvature of a curved soil tillage implement on horizontal and vertical forces have been investigated under laboratory conditions. Seven different wings of different radii of curvature (150, 200, 250, 300, 350, 400 and 450 mm) were designed. The range of tail angle used was between 32° and 54° and the range of side angle was between 40° and 65°. The effect of curvature on the horizontal force showed anomalous behaviour for different tail angles. For smaller tail angles (about 30° to 40°) the horizontal force decreased significantly with an increase of radius. For a tail angle of about 45°, the horizontal force decreased first with the increase of radius of curvature and then increased with further increase of radius. For tail angles greater than 50° the horizontal force increased with an increase of radius. The variation of the behaviour of radius and force relation is presumably due to the edge rake angle, since it varies with the radius. For larger radii, the effect of edge rake angle on the horizontal force is much more pronounced than the effect of radius on the horizontal force. For the vertical force (directed downward), it was observed that, for all tail angles used, the force increased significantly with a decrease of radius and this relation was described well by a third order polynomial equation. Variation of tail angle showed a significant effect on both horizontal and vertical forces. This is mainly due to an increase of normal compression forces and gravitational force when the tail angle is increased. For the range of tail angle used the horizontal force could be described by a trigonometric model. The effect of variation of side rake angle on the resulting forces for different speeds and radii was also investigated. Experimental investigation showed that variation of speed and radius affects the of side rake angle and force relation. The study recommends a combination of larger radius and smaller side rake angles for high speed operations to achieve a good penetration performance and reduced horizontal force. From the analysis made, a radius of about 275 mm was found to be an optimum for a curved implement. On the basis of the results obtained from the soil bin experiments and from the basic design of a conventional mouldboard plough and an ard type plough, a reversible animal drawn plough was designed