Analytical design of self-propelled rotor weeder based on crop morphological parameters

The rising labor costs and declining availability of manual labor in agriculture have intensified the demand for mechanized weeding solutions. This study presents the design and development of an adjustable self-propelled rotor power weeder suitable for inter-row cultivation in light to medium-textured soils. The power requirement was primarily calculated based on soil resistance, blade dimensions and operational speed. A specific draft value of 25 N/cm was adopted for sandy loam soils, resulting in a total draft force of 2000 N per rotor. The calculated power requirement for four rotors was 3.555 kW (4.75 hp), with an additional 0.031 hp required for the drive wheels, summing to a total of 4.78 hp. Accounting for power losses, a 5.36 hp engine was selected. The rotor shaft was designed for a maximum tangential force of 2033.89 N, leading to a moment of 25423.74 N-cm. The rotor shaft diameter was determined to be 19 mm for solid shafts and 21.5 mm for hollow square shafts. The L-shaped blade with a triangular peg tooth was selected and stress analysis revealed a maximum equivalent stress of 146.77 MPa, well within the material limit for mild steel. A gear reduction mechanism was designed to reduce engine speed from 130 rpm to 65 rpm, ensuring optimal rotor speed and operator comfort. The developed weeder offers improved efficiency, operator ergonomics and adaptability across varied crop row spacings, making it a suitable solution for sustainable weed management in small to medium-sized farms.