Design of Seeder in Relation to the Physical and Frictional Properties of Black Gram Varieties

Physical and frictional properties of black gram seeds play an essential role in designing a seeder in order to decide cell size, shape, thickness of metering disc and material, inclination of seed hopper. The present study aimed to determine the physical and frictional properties of black gram seeds of three varieties viz., VBN 6, ADT 5 & T9. Length, breadth, thickness, roundness, thousand seed weight, geometric mean diameter, sphericity were evaluated for designing metering disc of seeder. Bulk density, true density, angle of repose, coefficient of restitution and coefficient of static friction were evaluated for designing seed hopper of seeder. Cell diameters and thickness of the seed metering discs were designed based on the maximum breadth and length of seeds. Seed flow through the various components of the seeder were affected by both roundness and sphericity. Roundness of VBN 6, ADT 5 and T9 were 0.52, 0.49 and 0.51 respectively, while sphericity in the natural rest position of these seeds were 0.85±0.05, 0.85±0.06 and 0.85±0.04 respectively. The slope of the seed hopper was fixed at 30⁰, which is moderately higher than the average angle of repose of seeds for ensuring free flow of seeds. Mild steel sheet of material grade Fe 410 and 18 gauge i.e., 1.214mm thickness was selected for seed hopper in reference to the coefficient of static friction to other materials (Al, GI, SS & wood). In addition, the inner bottom surface of the seed hopper from where the seed enters into metering disc was imbedded with 3mm thick rubber sheet as its coefficient of restitution was lower than mild steel sheet of same thickness at different heights. It was observed that the average coefficient of restitution values of three varieties (VBN 6, ADT 5 & T9) were 4.2, 2.8, 2.8, 2.9, 2.9 & 2.1 times lower in rubber sheet compared to MS sheet at the heights of 50, 100, 150, 200, 250 & 300 mm respectively.